EyeLink Clinical and Oculomotor Eye-Tracking Publications
EyeLink clinical and oculomotor research publications up until 2022 (with some early 2023s) are listed below by year. You can search the publications using keywords such as Saccadic Adaptation, Schizophrenia, Nystagmus, etc. You can also search for individual author names, and limit searches by year (choose the year then click the search button). If we missed any EyeLink clinical or oculomotor articles, please email us!
2023 |
Lara Koch; Norbert Kathmann; Benedikt Reuter Lack of speeded disengagement from facial expressions of disgust in remitted major depressive disorder: Evidence from an eye-movement study Journal Article In: Behaviour Research and Therapy, vol. 160, pp. 1–11, 2023. @article{Koch2023, Acute major depression is characterized by specific abnormalities in the way emotional material is attended to. In late stages of stimulus processing, clinically depressed and dysphoric individuals show difficulties to disengage attention from emotionally negative material. It is unclear, however, whether aberrant disengagement is a transitory attentional phenomenon tied to depressive symptoms, or whether it constitutes a more stable disposition that outlast the symptomatic episode. To address this issue, the current study examined 39 currently euthymic individuals previously affected by major depression (RMD) and 40 healthy control participants reporting no lifetime psychopathology (ND). We used a gaze-contingent eye tracking paradigm designed to separately assess the attentional components of engagement and disengagement when viewing facial expressions of sadness, disgust and happiness. Never-depressed healthy participants, but not remitted euthymic individuals, showed speeded disengagement from facial expressions of disgust. We propose that the lack of this distinct acceleration in previously depressed but fully remitted individuals might reflect an attentional disposition that carries over to euthymic phases of the disease. On the other hand, a tendency to disengage quickly from areas in the visual field that convey social disdain could potentially act as a protective, possibly mood-stabilizing bias in resilient individuals. |
Josefine Waldthaler; Alexander Sperlich; Aylin König; Charlotte Stüssel; Frank Bremmer; Lars Timmermann; David Pedrosa In: NeuroImage: Clinical, vol. 37, pp. 1–11, 2023. @article{Waldthaler2023, While deep brain stimulation (DBS) in the subthalamic nucleus (STN) improves motor functions in Parkinson's disease (PD), it may also increase impulsivity by interfering with the inhibition of reflexive responses. The aim of this study was to investigate if varying the pulse frequency of STN-DBS has a modulating effect on response inhibition and its neural correlates. For this purpose, 14 persons with PD repeated an antisaccade task in three stimulation settings (DBS off, high-frequency DBS (130 Hz), mid-frequency DBS (60 Hz)) in a randomized order, while eye movements and brain activity via high-density EEG were recorded. On a behavioral level, 130 Hz DBS stimulation had no effect on response inhibition measured as antisaccade error rate, while 60 Hz DBS induced a slight but significant reduction of directional errors compared with the DBS-off state and 130 Hz DBS. Further, stimulation with both frequencies decreased the onset latency of correct antisaccades, while increasing the latency of directional errors. Time-frequency domain analysis of the EEG data revealed that 60 Hz DBS was associated with an increase in preparatory theta power over a midfrontal region of interest compared with the off-DBS state which is generally regarded as a marker of increased cognitive control. While no significant differences in brain activity over mid- and lateral prefrontal regions of interest emerged between the 60 Hz and 130 Hz conditions, both stimulation frequencies were associated with a stronger midfrontal beta desynchronization during the mental preparation for correct antisaccades compared with DBS off-state which is discussed in the context of potentially enhanced proactive recruitment of the oculomotor network. Our preliminary findings suggest that mid-frequency STN-DBS may provide beneficial effects on response inhibition, while both 130 Hz- and 60 Hz STN-DBS may promote voluntary actions at the expense of slower reflexive responses. |
Arthur Pabst; Zoé Bollen; Nicolas Masson; Pauline Billaux; Philippe Timary; Pierre Maurage An eye-tracking study of biased attentional processing of emotional faces in severe alcohol use disorder Journal Article In: Journal of Affective Disorders, vol. 323, pp. 778–787, 2023. @article{Pabst2023, Background: Social cognition impairments in severe alcohol use disorder (SAUD) are increasingly established. However, fundamental aspects of social cognition, and notably the attentional processing of socio-affective information, remain unexplored, limiting our understanding of underlying mechanisms. Here, we determined whether patients with SAUD show attentional biases to specific socio-affective cues, namely emotional faces. Method: In a modified dot-probe paradigm, 30 patients with SAUD and 30 demographically matched healthy controls (HC) were presented with pairs of neutral-emotional (angry, disgusted, happy, sad) faces while having their eye movements recorded. Indices of early/automatic (first fixations, latency to first fixations) and later/controlled (number of fixations, dwell-time) processes were computed. Results: Patients with SAUD did not differ from HC in their attention to angry/disgusted/sad vs. neutral faces. However, patients with SAUD fixated/dwelled less on happy vs. neutral faces in the first block of stimuli than HC, who presented an attentional bias to happy faces. Limitations: Sample-size was determined to detect medium-to-large effects and subtler ones may have been missed. Further, our cross-sectional design provides no explanation as to whether the evidenced biases precede or are a consequence of SAUD. Conclusions: These results extend the social cognition literature in SAUD to the attentional domain, by evidencing the absence of a controlled attentional bias toward positive social cues in SAUD. This may reflect reduced sensitivity to social reward and could contribute to higher order social cognition difficulties and social dysfunction. |
Rony Lemel; Lilach Shalev; Gal Nitsan; Boaz M. Ben-David Listen up! ADHD slows spoken-word processing in adverse listening conditions: Evidence from eye movements Journal Article In: Research in Developmental Disabilities, vol. 133, pp. 1–15, 2023. @article{Lemel2023, Background: Cognitive skills such as sustained attention, inhibition and working memory are essential for speech processing, yet are often impaired in people with ADHD. Offline measures have indicated difficulties in speech recognition on multi-talker babble (MTB) background for young adults with ADHD (yaADHD). However, to-date no study has directly tested online speech processing in adverse conditions for yaADHD. Aims: Gauging the effects of ADHD on segregating the spoken target-word from its sound-sharing competitor, in MTB and working-memory (WM) load. Methods and procedures: Twenty-four yaADHD and 22 matched controls that differ in sustained attention (SA) but not in WM were asked to follow spoken instructions presented on MTB to touch a named object, while retaining one (low-load) or four (high-load) digit/s for later recall. Their eye fixations were tracked. Outcomes and results: In the high-load condition, speech processing was less accurate and slowed by 140ms for yaADHD. In the low-load condition, the processing advantage shifted from early perceptual to later cognitive stages. Fixation transitions (hesitations) were inflated for yaADHD. Conclusions and implications: ADHD slows speech processing in adverse listening conditions and increases hesitation, as speech unfolds in time. These effects, detected only by online eyetracking, relate to attentional difficulties. We suggest online speech processing as a novel purview on ADHD. What this paper adds?: We suggest speech processing in adverse listening conditions as a novel vantage point on ADHD. Successful speech recognition in noise is essential for performance across daily settings: academic, employment and social interactions. It involves several executive functions, such as inhibition and sustained attention. Impaired performance in these functions is characteristic of ADHD. However, to date there is only scant research on speech processing in ADHD. The current study is the first to investigate online speech processing as the word unfolds in time using eyetracking for young adults with ADHD (yaADHD). This method uncovered slower speech processing in multi-talker babble noise for yaADHD compared to matched controls. The performance of yaADHD indicated increased hesitation between the spoken word and sound-sharing alternatives (e.g., CANdle-CANdy). These delays and hesitations, on the single word level, could accumulate in continuous speech to significantly impair communication in ADHD, with severe implications on their quality of life and academic success. Interestingly, whereas yaADHD and controls were matched on WM standardized tests, WM load appears to affect speech processing for yaADHD more than for controls. This suggests that ADHD may lead to inefficient deployment of WM resources that may not be detected when WM is tested alone. Note that these intricate differences could not be detected using traditional offline accuracy measures, further supporting the use of eyetracking in speech tasks. Finally, communication is vital for active living and wellbeing. We suggest paying attention to speech processing in ADHD in treatment and when considering accessibility and inclusion. |
Marcello Maniglia; Kristina M. Visscher; Aaron R. Seitz Consistency of preferred retinal locus across tasks and participants trained with a simulated scotoma Journal Article In: Vision Research, vol. 203, pp. 1–9, 2023. @article{Maniglia2023, After loss of central vision following retinal pathologies such as macular degeneration (MD), patients often adopt compensatory strategies including developing a “preferred retinal locus” (PRL) to replace the fovea in tasks involving fixation. A key question is whether patients develop multi-purpose PRLs or whether their oculomotor strategies adapt to the demands of the task. While most MD patients develop a PRL, clinical evidence suggests that patients may develop multiple PRLs and switch between them according to the task at hand. To understand this, we examined a model of central vision loss in normally seeing individuals and tested whether they used the same or different PRLs across tasks after training. Nineteen participants trained for 10 sessions on contrast detection while in conditions of gaze-contingent, simulated central vision loss. Before and after training, peripheral looking strategies were evaluated during tasks measuring visual acuity, reading abilities and visual search. To quantify strategies in these disparate, naturalistic tasks, we measured and compared the amount of task-relevant information at each of 8 equally spaced, peripheral locations, while participants performed the tasks. Results showed that some participants used consistent viewing strategies across tasks whereas other participants' strategies differed depending on task. This novel method allows quantification of peripheral vision use even in relatively ecological tasks. These results represent one of the first examinations of peripheral viewing strategies across tasks in simulated vision loss. Results suggest that individual differences in peripheral looking strategies following simulated central vision loss may model those developed in pathological vision loss. |
Siobhan M. McAteer; Anthony McGregor; Daniel T. Smith Oculomotor rehearsal in visuospatial working memory Journal Article In: Attention, Perception, and Psychophysics, vol. 85, pp. 261–275, 2023. @article{McAteer2023, The neural and cognitive mechanisms of spatial working memory are tightly coupled with the systems that control eye movements, but the precise nature of this coupling is not well understood. It has been argued that the oculomotor system is selectively involved in rehearsal of spatial but not visual material in visuospatial working memory. However, few studies have directly compared the effect of saccadic interference on visual and spatial memory, and there is little consensus on how the underlying working memory representation is affected by saccadic interference. In this study we aimed to examine how working memory for visual and spatial features is affected by overt and covert attentional interference across two experiments. Participants were shown a memory array, then asked to either maintain fixation or to overtly or covertly shift attention in a detection task during the delay period. Using the continuous report task we directly examined the precision of visual and spatial working memory representations and fit psychophysical functions to investigate the sources of recall error associated with different types of interference. These data were interpreted in terms of embodied theories of attention and memory and provide new insights into the nature of the interactions between cognitive and motor systems. |
Elle Van Heusden; Christian N. L. Olivers; Mieke Donk The eyes prefer targets nearby fixation: Quantifying eccentricity-dependent attentional biases in oculomotor selection Journal Article In: Vision Research, vol. 205, pp. 1–11, 2023. @article{Heusden2023, An important function of peripheral vision is to provide the target of the next eye movement. Here we investigate the extent to which the eyes are biased to select a target closer to fixation over one further away. Participants were presented with displays containing two identical singleton targets and were asked to move their eyes to either one of them. The targets could be presented at three different eccentricities relative to central fixation. In one condition both singletons were presented at the same eccentricity, providing an estimate of the speed of selection at each of the eccentricities. The saccadic latency distributions from this same-eccentricity condition were then used to predict the selection bias when both targets were presented at different eccentricities. The results show that when targets are presented at different eccentricities, participants are biased to select the item closest to fixation. This eccentricity-based bias was considerably stronger than predicted on the basis of saccadic latency distributions in the same-eccentricity condition. This rules out speed of processing per se as a sole explanation for such a bias. Instead, the results are consistent with attentional competition being weighted in favour of items close to fixation. |
Monja Hoven; Alejandro Hirmas; Jan Engelmann; Ruth Holst The role of attention in decision-making under risk in gambling disorder: An eye-tracking study Journal Article In: Addictive Behaviors, vol. 138, pp. 1–10, 2023. @article{Hoven2023, Gambling disorder (GD) is a behavioural addiction characterized by impairments in decision-making, favouring risk- and reward-prone choices. One explanatory factor for this behaviour is a deviation in attentional processes, as increasing evidence indicates that GD patients show an attentional bias toward gambling stimuli. However, previous attentional studies have not directly investigated attention during risky decision-making. 26 patients with GD and 29 healthy matched controls (HC) completed a mixed gambles task combined with eye-tracking to investigate attentional biases for potential gains versus losses during decision-making under risk. Results indicate that compared to HC, GD patients gambled more and were less loss averse. GD patients did not show a direct attentional bias towards gains (or relative to losses). Using a recent (neuro)economics model that considers average attention and trial-wise deviations in average attention, we conducted fine-grained exploratory analyses of the attentional data. Results indicate that the average attention for gains in GD patients moderated the effect of gain value on gambling choices, whereas this was not the case for HC. GD patients with high average attention for gains started gambling at less high gain values. A similar trend-level effect was found for losses, where GD patients with high average attention for losses stopped gambling at lower loss values. This study gives more insight into how attentional processes in GD play a role in gambling behaviour, which could have implications for the development of future treatments focusing on attentional training or for the development of interventions that increase the salience of losses. |
Yiru Huang; Zitian Liu; Zidong Chen; Zongyi Zhan; Le Gao; Jingyi Hu; Yanyan Wu; Fang-Fang Yan; Daming Deng; Chang-Bing Huang; Minbin Yu Visual crowding reveals field- and axis-specific cortical miswiring after long-term axial misalignment in strabismic patients without amblyopia Journal Article In: Investigative Ophthalmology & Visual Science, vol. 64, no. 1, pp. 1–11, 2023. @article{Huang2023, PURPOSE. Inspired by physiological and neuroimaging findings that revealed squint- induced modification of cortical volume and visual receptive field in early visual areas, we hypothesized that strabismic eyes without amblyopia manifest an increase in critical spacing of visual crowding, an essential bottleneck on object recognition and reliable psychophysical index of cortical organization. METHODS. We used real-time eye tracking to ensure gaze-contingent display and examined visual crowding in patients with horizontal concomitant strabismus (both esotropia and exotropia) but without amblyopia and age-matched normal controls. RESULTS. Nineteen patients with exotropia (12 men, mean ± SD = 22.89 ± 7.82 years), matched normal controls (7 men, mean ± SD = 23.07 ± 1.07 years) participated in this 21 patients with esotropia (10 men, mean ± SD = 23.48 ± 6.95 years), and 14 age- study. We found that patients with strabismus without amblyopia showed significantly larger critical spacing with nasotemporal asymmetry in only the radial axis that related to the strabismus pattern, with exotropia exhibiting stronger temporal hemifield crowding and esotropia exhibiting stronger nasal hemifield crowding, in both the deviated and fixating eyes. Moreover, the magnitude of crowding change was related to the duration and degree of strabismic deviation. CONCLUSIONS. Using visual crowding as a psychophysical index of cortical organization, our study demonstrated significantly greater peripheral visual crowding with nasotemporal asymmetry in only the radial axis in patients with strabismus without amblyopia, indicating the existence of hemifield- and axis-specific miswiring of cortical processing in object recognition induced by long-term adaptation to ocular misalignment. |
Carmen Julia Coloma; Ernesto Guerra; Zulema De Barbieri; Andrea Helo; Carmen Julia; Ernesto Guerra; Zulema De Barbieri; Andrea Helo Article comprehension in monolingual Spanish-speaking children with developmental language disorder: A longitudinal eye tracking study Journal Article In: International Journal of Speech-Language Pathology, pp. 1–13, 2023. @article{Coloma2023, Purpose: Article-noun disagreement in spoken language is a marker of children with developmental language disorder (DLD). However, the evidence is less clear regarding article comprehension. This study investigates article comprehension in monolingual Spanish-speaking children with and without DLD. Method: Eye tracking methodology used in a longitudinal experimental design enabled the examination of real time article comprehension. The children at the time 1 were 40 monolingual Spanish-speaking preschoolers (20 with DLD and 20 with typical language development [TLD]). A year later (time 2), 27 of these children (15 with DLD and 12 with TLD) were evaluated. Children listened to simple phrases while inspecting a four object visual context. The article in the phrase agreed in number and gender with only one of the objects. Result: At the time 1, children with DLD did not use articles to identify the correct image, while children with TLD anticipated the correct picture. At the time 2, both groups used the articles' morphological markers, but children with DLD showed a slower and weaker preference for the correct referent compared to their age-matched peers. Conclusion: These findings suggest a later emergence, but a similar developmental trajectory, of article comprehension in children with DLD compared to their peers with TLD. |
2022 |
Lisa Kunkel genannt Bode; Anna Sophie Schulte; Björn Hauptmann; Thomas F. Münte; Andreas Sprenger; Björn Machner Gaze-contingent display technology can help to reduce the ipsilesional attention bias in hemispatial neglect following stroke Journal Article In: Journal of NeuroEngineering and Rehabilitation, vol. 19, pp. 1–15, 2022. @article{KunkelgenanntBode2022, Background: Hemispatial neglect results from unilateral brain damage and represents a disabling unawareness for objects in the hemispace opposite the brain lesion (contralesional). The patients' attentional bias for ipsilesional hemispace represents a hallmark of neglect, which results from an imbalanced attentional priority map in the brain. The aim of this study was to investigate whether gaze-contingent display (GCD) technology, reducing the visual salience of objects in ipsilesional hemispace, is able to rebalance this map and increase awareness and exploration of objects in the neglected contralesional hemispace. Methods: Using remote eye-tracking, we recorded gaze positions in 19 patients with left hemispatial neglect following right-hemisphere stroke and 22 healthy control subjects, while they were watching static naturalistic scenes. There were two task conditions, free viewing (FV) or goal-directed visual search (VS), and four modification conditions including the unmodified original picture, a purely static modification and two differently strong modifications with an additional gaze-contingent mask (GC-LOW, GC-HIGH), that continuously reduced color saturation and contrast of objects in the right hemispace. Results: The patients' median gaze position (Center of Fixation) in the original pictures was markedly deviated to the right in both tasks (FV: 6.8° ± 0.8; VS: 5.5° ± 0.7), reflecting the neglect-typical ipsilesional attention bias. GC modification significantly reduced this bias in FV (GC-HIGH: d = − 3.2 ± 0.4°; p < 0.001). Furthermore, in FV and VS, GC modification increased the likelihood to start visual exploration in the (neglected) left hemifield by about 20%. This alleviation of the ipsilesional fixation bias was not associated with an improvement in detecting left-side targets, in contrast, the GC mask even decreased and slowed the detection of right-side targets. Subjectively, patients found the intervention pleasant and most of the patients did not notice any modification. Conclusions: GCD technology can be used to positively influence visual exploration patterns in patients with hemispatial neglect. Despite an alleviation of the neglect-related ipsilesional fixation bias, a concomitant functional benefit (improved detection of contralesional targets) was not achieved. Future studies may investigate individualized GCD-based modifications as augmented reality applications during the activities of daily living. |
Haiyan Wang; Matthew Walenski; Kaitlyn Litcofsky; Jennifer E. Mack; M. Marsel Mesulam; Cynthia K. Thompson Verb production and comprehension in primary progressive aphasia Journal Article In: Journal of Neurolinguistics, vol. 64, pp. 1–18, 2022. @article{Wang2022d, Studies of word class processing have found verb retrieval impairments in individuals with primary progressive aphasia (Bak et al., 2001; Cappa et al., 1998; Cotelli et al., 2006; Hillis, Heidler-Gary, et al., 2006; Hillis, Oh, & Ken, 2004; Marcotte et al., 2014; Rhee, Antiquena, & Grossman, 2001; Silveri & Ciccarelli, 2007; Thompson, Lukic, et al., 2012) associated primarily with the agrammatic variant. However, fewer studies have focused on verb comprehension, with inconsistent results. Because verbs are critical to both production and comprehension of clauses and sentences, we investigated verb processing across domains in agrammatic, logopenic, and semantic PPA and a group of age-matched healthy controls. Participants completed a confrontation naming task for verb production and an eye-tracking word-picture matching task for online verb comprehension. All PPA groups showed impaired verb production and comprehension relative to healthy controls. Most notably, the PPA-S group performed more poorly than the other two PPA variants in both domains. Overall, the results indicate that semantic deficits in the PPA-S extend beyond object knowledge to verbs as well, adding to our knowledge concerning the nature of the language deficits in the three variants of primary progressive aphasia. |
Mahboubeh Habibi; Wolfgang H. Oertel; Brian J. White; Donald C. Brien; Brian C. Coe; Heidi C. Riek; Julia Perkins; Rachel Yep; Laurent Itti; Lars Timmermann; Christoph Best; Elisabeth Sittig; Annette Janzen; Douglas P. Munoz Eye tracking identifies biomarkers in $alpha$-synucleinopathies versus progressive supranuclear palsy Journal Article In: Journal of Neurology, vol. 269, pp. 4920–4938, 2022. @article{Habibi2022, Objectives: This study (1) describes and compares saccade and pupil abnormalities in patients with manifest alpha-synucleinopathies ($alpha$SYN: Parkinson's disease (PD), Multiple System Atrophy (MSA)) and a tauopathy (progressive supranuclear palsy (PSP)); (2) determines whether patients with rapid-eye-movement sleep behaviour disorder (RBD), a prodromal stage of $alpha$SYN, already have abnormal responses that may indicate a risk for developing PD or MSA. Methods: Ninety (46 RBD, 27 PD, 17 MSA) patients with an $alpha$SYN, 10 PSP patients, and 132 healthy age-matched controls (CTRL) were examined with a 10-min video-based eye-tracking task (Free Viewing). Participants were free to look anywhere on the screen while saccade and pupil behaviours were measured. Results: PD, MSA, and PSP spent more time fixating the centre of the screen than CTRL. All patient groups made fewer macro-saccades (> 2◦ amplitude) with smaller amplitude than CTRL. Saccade frequency was greater in RBD than in other patients. Following clip change, saccades were temporarily suppressed, then rebounded at a slower pace than CTRL in all patient groups. RBD had distinct, although discrete saccade abnormalities that were more marked in PD, MSA, and even more in PSP. The vertical saccade rate was reduced in all patients and decreased most in PSP. Clip changes produced large increases or decreases in screen luminance requiring pupil constriction or dilation, respectively. PSP elicited smaller pupil constriction/dilation responses than CTRL, while MSA elicited the opposite. Conclusion: RBD patients already have discrete but less pronounced saccade abnormalities than PD and MSA patients. Vertical gaze palsy and altered pupil control differentiate PSP from $alpha$SYN. |
Christoph Helmchen; Philipp J. Koch; Gabriel Girard; Norbert Brüggemann; Björn Machner; Andreas Sprenger NPTX1-related oculomotor apraxia: An intra-hemispheric disconnection disorder Miscellaneous 2022. @misc{Helmchen2022a, Oculomotor apraxia (OMA) is a rare and heavily disabling neurological disorder causing severe difficulties in the initia- tion and maintenance of voluntary eye movements when the head is stationary. If patients try to initiate saccades, they are grossly delayed and hypometric (stair-case). .. The aim of this study was to test competing pathophysiological hypotheses by functional and structural MRI, stating that OMA is related to either abnormal (i) inter-hemispheric or (ii) intra-hemispheric connectivity between the FEF and related oculomotor structures (oculomotor network) or (iii) both mechanisms. |
Mariana M. Gusso; Kate L. Christison-Lagay; David Zuckerman; Ganesh Chandrasekaran; Sharif I. Kronemer; Julia Z. Ding; Noah C. Freedman; Percy Nohama; Hal Blumenfeld More than a feeling: Scalp EEG and eye signals in conscious tactile perception Journal Article In: Consciousness and Cognition, vol. 105, pp. 1–14, 2022. @article{Gusso2022, Understanding the neural basis of consciousness is a fundamental goal of neuroscience, and sensory perception is often used as a proxy for consciousness in empirical studies. However, most studies rely on reported perception of visual stimuli. Here we present behavior, high density scalp EEG and eye metric recordings collected simultaneously during a novel tactile threshold perception task. We found significant N80, N140 and P300 event related potentials in perceived trials and in perceived versus not perceived trials. Significance was limited to a P100 and P300 in not perceived trials. We also found an increase in pupil diameter and blink rate and a decrease in microsaccade rate following perceived relative to not perceived tactile stimuli. These findings support the use of eye metrics as a measure of physiological arousal associated with conscious perception. Eye metrics may also represent a novel path toward the creation of tactile no-report tasks in the future. |
Nicole X. Han; Miguel P. Eckstein Gaze-cued shifts of attention and microsaccades are sustained for whole bodies but are transient for body parts Journal Article In: Psychonomic Bulletin & Review, vol. 29, pp. 1854–1878, 2022. @article{Han2022, Gaze direction is an evolutionarily important mechanism in daily social interactions. It reflects a person's internal cognitive state, spatial locus of interest, and predicts future actions. Studies have used static head images presented foveally and simple synthetic tasks to find that gaze orients attention and facilitates target detection at the cued location in a sustained manner. Little is known about how people's natural gaze behavior, including eyes, head, and body movements, jointly orient covert attention, microsaccades, and facilitate performance in more ecological dynamic scenes. Participants completed a target person detection task with videos of real scenes. The videos showed people looking toward (valid cue) or away from a target (invalid cue) location. We digitally manipulated the individuals in the videos directing gaze to create three conditions: whole-intact (head and body movements), floating heads (only head movements), and headless bodies (only body movements). We assessed their impact on participants' behavioral performance and microsaccades during the task. We show that, in isolation, an individual's head or body orienting toward the target-person direction led to facilitation in detection that is transient in time (200 ms). In contrast, only the whole-intact condition led to sustained facilitation (500 ms). Furthermore, observers executed microsaccades more frequently towards the cued direction for valid trials, but this bias was sustained in time only with the joint presence of head and body parts. Together, the results differ from previous findings with foveally presented static heads. In more real-world scenarios and tasks, sustained attention requires the presence of the whole-intact body of the individuals dynamically directing their gaze. |
Nina M. Hanning; Heiner Deubel The effect of spatial structure on presaccadic attention costs and benefits assessed with dynamic 1/f noise Journal Article In: Journal of Neurophysiology, vol. 127, pp. 1586–1592, 2022. @article{Hanning2022a, Already before the onset of a saccadic eye movement, we preferentially process visual information at the upcoming eye fixation. This “presaccadic shift of attention” is typically assessed via localized test items, which potentially bias the attention measurement. Here, we show how presaccadic attention shapes perception from saccade origin to target when no scene-structuring items are presented. Participants made saccades into a 1/f (“pink”) noise field, in which we embedded a brief orientation signal at various locations shortly before saccade onset. Local orientation discrimination performance served as a proxy for the allocation of attention. Results demonstrate that 1) the presaccadic attention shift is accompanied by considerable attentional costs at the presaccadic eye fixation and 2) saccades are preceded by shifts of attention to their goal location even if they are directed into an unstructured visual field, but the spread of attention, compared with target-directed saccades, is broad. We conclude that the absence or presence of saccade target objects markedly shapes the distribution of presaccadic attention and likely the underlying (space-based or object-based) cortical control mechanism. Our findings demonstrate the relevance of an item-free approach for measuring attentional dynamics across the visual field. |
Nina M. Hanning; Marc M. Himmelberg; Marisa Carrasco Presaccadic attention enhances contrast sensitivity, but not at the upper vertical meridian Journal Article In: iScience, vol. 25, no. 2, pp. 1–11, 2022. @article{Hanning2022b, Visual performance has striking polar performance asymmetries: At a fixed eccentricity, it is better along the horizontal than vertical meridian and the lower than upper vertical meridian. These asymmetries are not alleviated by covert exogenous or endogenous attention, but have been studied exclusively during eye fixation. However, a major driver of everyday attentional orienting is saccade preparation, during which attention automatically shifts to the future eye fixation. This presaccadic attention shift is considered strong and compulsory, and relies on different neural computations and substrates than covert attention. Thus, we asked: Can presaccadic attention compensate for the ubiquitous performance asymmetries observed during eye fixation? Our data replicate polar performance asymmetries during fixation and document the same asymmetries during saccade preparation. Crucially, however, presaccadic attention enhanced contrast sensitivity at the horizontal and lower vertical meridian, but not at the upper vertical meridian. Thus, instead of attenuating performance asymmetries, presaccadic attention exacerbates them. |
Frauke Heins; Markus Lappe Flexible use of post-saccadic visual feedback in oculomotor learning Journal Article In: Journal of Vision, vol. 22, no. 1, pp. 1–16, 2022. @article{Heins2022, Saccadic eye movements bring objects of interest onto our fovea. These gaze shifts are essential for visual perception of our environment and the interaction with the objects within it. They precede our actions and are thus modulated by current goals. It is assumed that saccadic adaptation, a recalibration process that restores saccade accuracy in case of error, is mainly based on an implicit comparison of expected and actual post-saccadic position of the target on the retina. However, there is increasing evidence that task demands modulate saccade adaptation and that errors in task performance may be sufficient to induce changes to saccade amplitude. We investigated if human participants are able to flexibly use different information sources within the post-saccadic visual feedback in task-dependent fashion. Using intra-saccadic manipulation of the visual input, participants were either presented with congruent post-saccadic information, indicating the saccade target unambiguously, or incongruent post-saccadic information, creating conflict between two possible target objects. Using different task instructions, we found that participants were able to modify their saccade behavior such that they achieved the goal of the task. They succeeded in decreasing saccade gain or maintaining it, depending on what was necessary for the task, irrespective of whether the post-saccadic feedback was congruent or incongruent. It appears that action intentions prime task-relevant feature dimensions and thereby facilitated the selection of the relevant information within the post-saccadic image. Thus, participants use post-saccadic feedback flexibly, depending on their intentions and pending actions. |
Christoph Helmchen; Björn Machner; Andreas Sprenger; David S. Zee Monocular patching attenuates vertical nystagmus in Wernicke's Encephalopathy via release of activity in subcortical visual pathways Journal Article In: Movement Disorders Clinical Practice, vol. 9, no. 1, pp. 107–109, 2022. @article{Helmchen2022, Downbeat nystagmus (DBN) is common in ataxia syndromes and usually related to cerebellar flocculus dysfunction. Persistent and disabling DBN commonly occurs in B1 deficient Wernicke's encephalopathy (WE) causing a functional cerebellar disorder.1 Here we describe a new, unusual phenomenon in a WE patient who has had severe vertical oscillopsia for years due to an incapacitating DBN: oscillopsia and his nystagmus is markedly attenuated when he covers one eye and views monocularly. We propose this is a new clinical sign of emerging activity in subcortical visual pathways. |
Christoph Helmchen; Björn Machner; Janina Gablentz; Andreas Sprenger; David S. Zee Downbeat nystagmus is abolished by alcohol in nonalcoholic Wernicke encephalopathy Journal Article In: Neurology: Clinical Practice, vol. 12, no. 5, pp. E129–E132, 2022. @article{Helmchen2022b, Background and ObjectivesLesions of the cerebellar flocculus cause enduring downbeat nystagmus (DBN) with unrelenting oscillopsia. Unlike most patients with DBN, the flocculus is structurally spared in nonalcoholic Wernicke encephalopathy (nWE) with chronic DBN. The objective was to study the effects of alcohol in nWE.MethodsWe recorded eye movements of a unique patient with nWE under controlled alcohol consumption who said his oscillopsia disappeared with a few drinks of alcohol.ResultsHis DBN was markedly diminished by alcohol (by 77.4%), although he remained alert with normal saccades.DiscussionThis striking observation may be caused by the differential effect of alcohol on the perihypoglossal complex and the paramedian tract neurons, which control the level of activity in the flocculus, with opposite (inhibition and excitation, respectively) effects. The finding suggests new ideas about the treatment and pathophysiology of DBN with a structurally intact cerebellum. |
S. N. Hof; F. C. Loonstra; L. R. J. Ruiter; L. J. Rijn; A. Petzold; B. M. J. Uitdehaag; J. A. Nij Bijvank The prevalence of internuclear ophthalmoparesis in a population-based cohort of individuals with multiple sclerosis Journal Article In: Multiple Sclerosis and Related Disorders, vol. 63, pp. 1–7, 2022. @article{Hof2022, Background: Internuclear ophthalmoparesis (INO) occurs in 15–52% of individuals with multiple sclerosis (MS) and is reliably detected by infrared oculography. Methods for diagnosing INO with infrared oculography and the association between INO and MS characteristics need confirmation. We aimed to describe INO prevalence and the clinical characteristics of individuals with MS and INO in a population-based cohort of individuals with MS born in the year 1966 (Project Y). Methods: Previously described thresholds for the versional dysconjugacy index (VDI), assessed with standardized infrared oculography, were used to detect INO in participants of project Y. Clinical characteristics, visual functioning and complaints were compared between individuals with MS with INO and individuals with MS without INO. Results: Two-hundred-twenty individuals with MS and 110 healthy controls were included. VDI values exceeding the threshold for INO presented in 53 (24%) individuals with MS and 19 controls (13%). INO was associated with male sex, greater disability, worse cognition and worse arm function in individuals with MS. There was no association with disease duration, visual functioning or complaints. Conclusions: INO is prevalent among individuals with MS aged fifty-three and related to clinical characteristics of MS. INO was more frequently detected in healthy controls than previous studies, implying that oculography based diagnosis of INO requires further refinement. |
Alex J. Hoogerbrugge; Christoph Strauch; Zoril A. Oláh; Edwin S. Dalmaijer; Tanja C. W. Nijboer; Stefan Van der Stigchel Seeing the Forrest through the trees: Oculomotor metrics are linked to heart rate Journal Article In: PLoS ONE, vol. 17, no. 8, pp. 1–12, 2022. @article{Hoogerbrugge2022, Fluctuations in a person's arousal accompany mental states such as drowsiness, mental effort, or motivation, and have a profound effect on task performance. Here, we investigated the link between two central instances affected by arousal levels, heart rate and eye movements. In contrast to heart rate, eye movements can be inferred remotely and unobtrusively, and there is evidence that oculomotor metrics (i.e., fixations and saccades) are indicators for aspects of arousal going hand in hand with changes in mental effort, motivation, or task type. Gaze data and heart rate of 14 participants during film viewing were used in Random Forest models, the results of which show that blink rate and duration, and the movement aspect of oculomotor metrics (i.e., velocities and amplitudes) link to heart rate–more so than the amount or duration of fixations and saccades. We discuss that eye movements are not only linked to heart rate, but they may both be similarly influenced by the common underlying arousal system. These findings provide new pathways for the remote measurement of arousal, and its link to psychophysiological features. |
Lijuan Huang; Yunyu Zhou; Wencong Chen; Ping Lin; Yan Xie; Kaiwen He; Shasha Zhang; Yuyu Wu; Ningdong Li Correlations of FRMD7 gene mutations with ocular oscillations Journal Article In: Scientific Reports, vol. 12, no. 1, pp. 1–10, 2022. @article{Huang2022a, Mutations in the FERM domain containing 7 (FRMD7) gene have been proven to be responsible for infantile nystagmus (IN). The purpose of this study is to investigate FRMD7 gene mutations in patients with IN, and to evaluate the nystagmus intensity among patients with and without FRMD7 mutations. The affected males were subdivided into three groups according to whether or not having FRMD7 mutations and the types of mutations. Fifty-two mutations were detected in FRMD7 in 56 pedigrees and 34 sporadic patients with IN, including 28 novel and 24 previous reported mutations. The novel identified mutations further expand the spectrum of FRMD7 mutations. The parameters of nystagmus intensity and the patients' best corrected visual acuity were not statistically different among the patients with and without identified FRMD7 mutations, and also not different among patients with different mutant types. The FERM-C domain, whose amino acids are encoded by exons 7, 8 and 9, could be the harbor region for most mutations. Loss-of-function is suggested to be the common molecular mechanism for the X-linked infantile nystagmus. |
Todd E. Hudson; Jenna Conway; John-Ross Rizzo; John Martone; Liyung T. Chou; Laura J. Balcer; Steven L. Galetta; Janet C. Rucker In: Clinical and Translational Neuroscience, vol. 6, pp. 1–12, 2022. @article{Hudson2022, Number and picture rapid automatized naming (RAN) tests are useful sideline diagnostic tools. The main outcome measure of these RAN tests is the completion time, which is prolonged with a concussion, yet yields no information about eye movement behavior. We investigated eye movements during a digitized Mobile Universal Lexicon Evaluation System (MULES) test of rapid picture naming. A total of 23 participants with a history of concussion and 50 control participants performed MULES testing with simultaneous eye tracking. The test times were longer in participants with a concussion (32.4 s [95% CI 30.4, 35.8] vs. 26.9 s [95% CI 25.9, 28.0] |
Shao-Chin Hung; Marisa Carrasco Microsaccades as a long-term oculomotor correlate in visual perceptual learning Journal Article In: Psychonomic Bulletin & Review, pp. 1–15, 2022. @article{Hung2022, Human perceptual learning, experience-induced gains in sensory discrimination, typically yields long-term performance improvements. Recent research revealed long-lasting transfer at the untrained location enabled by feature-based attention (FBA), reminiscent of its global effect (Hung & Carrasco, Scientific Reports,11(1), 13914, (2021)). Visual Perceptual Learning (VPL) is typically studied while observers maintain fixation, but the role of fixational eye movements is unknown. Microsaccades – the largest of fixational eye movements – provide a continuous, online, physiological measure from the oculomotor system that reveals dynamic processing, which is unavailable from behavioral measures alone. We investigated whether and how microsaccades change after training in an orientation discrimination task. For human observers trained with or without FBA, microsaccade rates were significantly reduced during the response window in both trained and untrained locations and orientations. Critically, consistent with long-term training benefits, this microsaccade-rate reduction persisted over a year. Furthermore, microsaccades were biased toward the target location prior to stimulus onset and were more suppressed for incorrect than correct trials after observers' responses. These findings reveal that fixational eye movements and VPL are tightly coupled and that learning-induced microsaccade changes are long lasting. Thus, microsaccades reflect functional dynamics of the oculomotor system during information encoding, maintenance and readout, and may serve as a reliable long-term physiological correlate in VPL. |
Saad Idrees; Matthias Philipp Baumann; Maria M. Korympidou; Timm Schubert; Alexandra Kling; Katrin Franke; Ziad M. Hafed; Felix Franke; Thomas A. Münch Suppression without inhibition: How retinal computation contributes to saccadic suppression Journal Article In: Communications Biology, vol. 5, pp. 1–23, 2022. @article{Idrees2022, Visual perception remains stable across saccadic eye movements, despite the concurrent strongly disruptive visual flow. This stability is partially associated with a reduction in visual sensitivity, known as saccadic suppression, which already starts in the retina with reduced ganglion cell sensitivity. However, the retinal circuit mechanisms giving rise to such suppression remain unknown. Here, we describe these mechanisms using electrophysiology in mouse, pig, and macaque retina, 2-photon calcium imaging, computational modeling, and human psychophysics. We find that sequential stimuli, like those that naturally occur during saccades, trigger three independent suppressive mechanisms in the retina. The main mechanism is triggered by contrast-reversing sequential stimuli and originates within the receptive field center of ganglion cells. It does not involve inhibition or other known suppressive mechanisms like saturation or adaptation. Instead, it relies on temporal filtering of the inherently slow response of cone photoreceptors coupled with downstream nonlinearities. Two further mechanisms of suppression are present predominantly in ON ganglion cells and originate in the receptive field surround, highlighting another disparity between ON and OFF ganglion cells. The mechanisms uncovered here likely play a role in shaping the retinal output following eye movements and other natural viewing conditions where sequential stimulation is ubiquitous. |
Uday K. Jagadisan; Neeraj J. Gandhi Population temporal structure supplements the rate code during sensorimotor transformations Journal Article In: Current Biology, vol. 32, pp. 1010–1025, 2022. @article{Jagadisan2022, Sensorimotor transformations are mediated by premotor brain networks where individual neurons represent sensory, cognitive, and movement-related information. Such multiplexing poses a conundrum—how does a decoder know precisely when to initiate a movement if its inputs are active at times when a movement is not desired (e.g., in response to sensory stimulation)? Here, we propose a novel hypothesis: movement is triggered not only by an increase in firing rate but, critically, also by a reliable temporal pattern in the population response. Laminar recordings in the macaque superior colliculus (SC), a midbrain hub of orienting control, and pseudo-population analyses in SC and cortical frontal eye fields (FEFs) corroborated this hypothesis. Specifically, using a measure that captures the fidelity of the population code—here called temporal stability—we show that the temporal structure fluctuates during the visual response but becomes increasingly stable during the movement command. Importantly, we used spatiotemporally patterned microstimulation to causally test the contribution of population temporal stability in gating movement initiation and found that stable stimulation patterns were more likely to evoke a movement. Finally, a spiking neuron model was able to discriminate between stable and unstable input patterns, providing a putative biophysical mechanism for decoding temporal structure. These findings offer new insights into the long-standing debate on motor preparation and generation by situating the movement gating signal in temporal features of activity in shared neural substrates, and they highlight the importance of short-term population history in neuronal communication and behavior. |
Divya Jain; Kristy B. Arbogast; Catherine C. McDonald; Olivia E. Podolak; Susan S. Margulies; Kristina B. Metzger; David R. Howell; Mitchell M. Scheiman; Christina L. Master Eye tracking metrics differences among uninjured adolescents and those with acute or persistent post-concussion symptoms Journal Article In: Optometry and Vision Science, vol. 99, no. 8, pp. 616–625, 2022. @article{Jain2022, SIGNIFICANCE Eye tracking assessments that include pupil metrics can supplement current clinical assessments of vision and autonomic dysfunction in concussed adolescents. PURPOSE This study aimed to explore the utility of a 220-second eye tracking assessment in distinguishing eye position, saccadic movement, and pupillary dynamics among uninjured adolescents, those with acute post-concussion symptoms (≤28 days since concussion), or those with persistent post-concussion symptoms (>28 days since concussion). METHODS Two hundred fifty-six eye tracking metrics across a prospective observational cohort of 180 uninjured adolescents recruited from a private suburban high school and 224 concussed adolescents, with acute or persistent symptoms, recruited from a tertiary care subspecialty concussion care program, 13 to 17 years old, from August 2017 to June 2021 were compared. Kruskal-Wallis tests were used, and Bonferroni corrections were applied to account for multiple comparisons and constructed receiver operating characteristic curves. Principal components analysis and regression models were applied to determine whether eye tracking metrics can augment clinical and demographic information in differentiating uninjured controls from concussed adolescents. RESULTS Two metrics of eye position were worse in those with concussion than uninjured adolescents, and only one metric was significantly different between acute cases and persistent cases. Concussed adolescents had larger left and right mean, median, minimum, and maximum pupil size than uninjured controls. Concussed adolescents had greater differences in mean, median, and variance of left and right pupil size. Twelve metrics distinguished female concussed participants from uninjured; only four were associated with concussion status in males. A logistic regression model including clinical and demographics data and transformed eye tracking metrics performed better in predicting concussion status than clinical and demographics data alone. CONCLUSIONS Objective eye tracking technology is capable of quickly identifying vision and pupillary disturbances after concussion, augmenting traditional clinical concussion assessments. These metrics may add to existing clinical practice for monitoring recovery in a heterogeneous adolescent concussion population. |
Anupama Janardhanan; Vijaylakshmi Perumalswamy; Shashikant Shetty; Chitaranjan Mishra; Matt J. Dunn Acquired vertical pendular nystagmus in diffuse unilateral subacute neuroretinitis: A diagnostic dilemma Journal Article In: Indian Journal of Ophthalmology, vol. 2, pp. 503–505, 2022. @article{Janardhanan2022, A retinal infectious pathology, an acquired vertical nystagmus, and a suspicious neuroimaging result! Independently, these three entities are not uncommon. However, when they are consecutively observed in a young patient, it ramifies into an intriguing clinical scenario. A 17-year-old diagnosed case of diffuse unilateral subacute neuroretinitis presented to us with acute-onset vertical oscillations. On neuroimaging, she was found to have cerebellar dysgenesis. This case prompted us to revisit the pathogenesis of acquired vertical nystagmus and evaluate whether it resulted from disturbance of afferent (severe visual impairment) or efferent (cerebellar dysfunction) components of the neural integrator mechanism. |
Ómar I. Jóhannesson; Árni Kristjánsson; Jérôme Tagu Contrasting attentional biases in a saccadic choice task Journal Article In: Experimental Brain Research, vol. 240, no. 1, pp. 173–187, 2022. @article{Johannesson2022, To gain insight into how human observers select items in the visual field we pitted two attentional biases against one another in a single free choice design. The first bias is the nasal-temporal asymmetry during free choice tasks, where observers tend to choose targets that appear in their temporal hemifield over targets appearing in their nasal hemifield. The second is the choice bias found in studies of attentional priming. When observers have to select between a stimulus that shares features with a preceding target and a stimulus sharing features with previous distractors, they have a strong tendency to choose the preceding search target and this bias increases the more often the same search is repeated. Our results show that both biases affect saccadic choice, but they also show that the nasal-temporal bias can modulate the strength of the priming effects, but not vice versa. The priming effect was stronger for stimuli appearing in the temporal than in the nasal hemifield, but the nasal-temporal bias was similar for primed and unprimed targets. Additionally, our findings are the first to show how search repetition leads to faster saccades. The observed difference between the effects of the NTA and priming biases may reflect the difference in neural mechanisms thought to be behind these biases and that biases at lower levels may outrank higher-level biases, at least in their effect on visual attention. |
Richard Johnston; Adam C. Snyder; Sanjeev B. Khanna; Deepa Issar; Matthew A. Smith The eyes reflect an internal cognitive state hidden in the activity of the neurons Journal Article In: Cerebral Cortex, vol. 32, pp. 3331–3346, 2022. @article{Johnston2022, Decades of research have shown that global brain states such as arousal can be indexed by measuring the properties of the eyes. The spiking responses of neurons throughout the brain have been associated with the pupil, small fixational saccades, and vigor in eye movements, but it has been difficult to isolate how internal states affect the eyes, and vice versa. While recording from populations of neurons in the visual and prefrontal cortex (PFC), we recently identified a latent dimension of neural activity called “slow drift,” which appears to reflect a shift in a global brain state. Here, we asked if slow drift is correlated with the action of the eyes in distinct behavioral tasks. We recorded from visual cortex (V4) while monkeys performed a change detection task, and PFC, while they performed a memory-guided saccade task. In both tasks, slow drift was associated with the size of the pupil and the microsaccade rate, two external indicators of the internal state of the animal. These results show that metrics related to the action of the eyes are associated with a dominant and task-independent mode of neural activity that can be accessed in the population activity of neurons across the cortex. |
Oren Kadosh; Yoram Bonneh Face familiarity revealed by fixational eye movements and fixation-related potentials in free viewing Journal Article In: Scientific Reports, vol. 12, no. 1, pp. 1–13, 2022. @article{Kadosh2022a, Event-related potentials (ERPs) and the oculomotor inhibition (OMI) in response to visual transients are known to be sensitive to stimulus properties, attention, and expectation. We have recently found that the OMI is also sensitive to face familiarity. In natural vision, stimulation of the visual cortex is generated primarily by saccades, and it has been recently suggested that fixation-related potentials (FRPs) share similar components with the ERPs. Here, we investigated whether FRPs and microsaccade inhibition (OMI) in free viewing are sensitive to face familiarity. Observers freely watched a slideshow of seven unfamiliar and one familiar facial images presented randomly for 4-s periods, with multiple images per identity. We measured the occipital fixation-related N1 relative to the P1 magnitude as well as the associated fixation-triggered OMI. We found that the average N1-P1 was significantly smaller and the OMI was shorter for the familiar face, compared with any of the seven unfamiliar faces. Moreover, the P1 was suppressed across saccades for the familiar but not for the unfamiliar faces. Our results highlight the sensitivity of the occipital FRPs to stimulus properties such as face familiarity and advance our understanding of the integration process across successive saccades in natural vision. |
Oren Kadosh; Yoram S. Bonneh Fixation-related saccadic inhibition in free viewing in response to stimulus saliency Journal Article In: Scientific Reports, vol. 12, pp. 1–12, 2022. @article{Kadosh2022b, Microsaccades that occur during fixation were studied extensively in response to transient stimuli, showing a typical inhibition (Oculomotor Inhibition, OMI), and a later release with a latency that depends on stimulus saliency, attention, and expectations. Here, we investigated the hypothesis that in free viewing every saccade provides a new transient stimulation that should result in a stimulus-dependent OMI like a flashed presentation during fixation. Participants (N = 16) freely inspected static displays of randomly oriented Gabor texture images, with varied contrast and spatial frequency (SF) for periods of 10 s each. Eye tracking recordings were divided into epochs triggered by saccade landing (> 1 dva), and microsaccade latency relative to fixation onset was computed (msRT). We found that the msRT in free viewing was shorter for more salient stimuli (higher contrast or lower SF), as previously found for flashed stimuli. It increased with saccade size and decreased across successive saccades, but only for higher contrast, suggesting contrast-dependent repetition enhancement in free viewing. Our results indicate that visual stimulus-dependent inhibition of microsaccades also applies to free viewing. These findings are in agreement with the similarity found between event-related and fixation-related potentials and open the way for studies combining both approaches to study natural vision. |
Oren Kadosh; Yoram S. Bonneh Involuntary oculomotor inhibition markers of saliency and deviance in response to auditory sequences Journal Article In: Journal of Vision, vol. 22, no. 5, pp. 1–19, 2022. @article{Kadosh2022, Our eyes move constantly but are often inhibited momentarily in response to external stimuli (oculomotor inhibition [OMI]), depending on the stimulus saliency, anticipation, and attention. Previous studies have shown prolonged OMI for auditory oddballs; however, they required counting the oddballs, possibly reflecting voluntary attention. Here, we investigated whether the “passive” OMI response to auditory deviants can provide a quantitative measure of deviance strength (pitch difference) and studied its dependence on the inter-trial interval (ITI). Participants fixated centrally and passively listened to repeated short sequences of pure tones that contained a deviant tone either regularly or with 20% probability (oddballs). In an “active” control experiment, participants counted the deviant or the standard. As in previous studies, the results showed prolonged microsaccade inhibition and increased pupil dilation following the rare deviant tone. Earlier inhibition onset was found in proportion to the pitch deviance (the saliency effect), and a later release was found for oddballs, but only for ITI <2.5 seconds. The active control experiment showed similar results when counting the deviant but longer OMI for the standard when counting it. Taken together, these results suggest that OMI provides involuntary markers of saliency and deviance, which can be obtained without the participant's response. |
Tatiana Karpouzian-Rogers; Rob Hurley; Mustafa Seckin; Stacey Moeller; Nathan Gill; Hui Zhang; Christina Coventry; Matthew Nelson; Sandra Weintraub; Emily Rogalski; M. Marsel Mesulam Eye movements as a measure of word comprehension deficits in primary progressive aphasia Journal Article In: Brain and Language, vol. 232, pp. 1–5, 2022. @article{KarpouzianRogers2022, Introduction: Eye movement studies can uncover subtle aspects of language processing impairment in individuals with primary progressive aphasia (PPA), who may have difficulty understanding words. This study examined eye movement patterns on a word-object matching task in response to varying levels of word-knowledge in PPA. Methods: Participants with semantic and non-semantic PPA completed an object-matching task, where a word was presented and participants then selected the corresponding pictured object from an array. Afterwards, participants defined words for trials to which they incorrectly pointed. Linear mixed-effects analyses examined fixation differences on targets and related and unrelated foils. Results: On incorrectly-pointed trials, participants demonstrated greater fixation duration on related foils, demonstrating intra-category blurring. For words that could not be defined, there was similar fixation duration on related and unrelated foils, demonstrating inter-category semantic blurring. Discussion: This study demonstrated that fixation patterns reflect varying levels of word knowledge in PPA. |
Chaim N. Katz; Andrea G. P. Schjetnan; Kramay Patel; Victoria Barkley; Kari L. Hoffman; Suneil K. Kalia; Katherine D. Duncan; Taufik A. Valiante A corollary discharge mediates saccade-related inhibition of single units in mnemonic structures of the human brain Journal Article In: Current Biology, vol. 32, no. 14, pp. 3082–3094, 2022. @article{Katz2022, Despite the critical link between visual exploration and memory, little is known about how neuronal activity in the human mesial temporal lobe (MTL) is modulated by saccades. Here, we characterize saccade-associated neuronal modulations, unit-by-unit, and contrast them to image onset and to occipital lobe neurons. We reveal evidence for a corollary discharge (CD)-like modulatory signal that accompanies saccades, inhibiting/exciting a unique population of broad-/narrow-spiking units, respectively, before and during saccades and with directional selectivity. These findings comport well with the timing, directional nature, and inhibitory circuit implementation of a CD. Additionally, by linking neuronal activity to event-related potentials (ERPs), which are directionally modulated following saccades, we recontextualize the ERP associated with saccades as a proxy for both the strength of inhibition and saccade direction, providing a mechanistic underpinning for the more commonly recorded saccade-related ERP in the human brain. |
Johannes Kirchner; Tamara Watson; Niko A. Busch; Markus Lappe Timing and kinematics of horizontal within-blink saccades measured by EOG Journal Article In: Journal of Neurophysiology, vol. 127, no. 6, pp. 1655–1668, 2022. @article{Kirchner2022, Eyeblinks are the brief closures of the lid. They are accompanied by a cocontraction of the eye muscles that temporarily pulls the whole eyeball back into its socket. When blinks occur together with execution of saccadic gaze shifts, they interfere with the saccadic premotor circuit, causing these within-blink saccades to be slower than normal and also time-locked to blinks. To analyze the trajectory of within-blink saccades, subtraction of the entangled blink-related eye movement is required. Here we propose a combination of principal component analysis (PCA) and a regression model to subtract the blink-related component of the eye movement based on the respective blink metrics. We used electrooculography (EOG) to measure eye and lid movements of 12 participants who performed saccades with and without blinks. We found that within-blink saccades are slower than without-blink saccades and are tightly coupled in time to blink onset. Surprisingly, in some participants we observed large dynamic overshoots of up to 15° for saccades of only 5° amplitude. The finding of dynamic overshoots was independently confirmed by dynamic MRI for two of the participants and challenges the current view that within-blink saccades are programmed as slow, but straight, saccades. We hypothesize that the dynamic overshoots could be attributed to inhibition of omnipause neurons during blinks, the simultaneous cocontraction of extraocular muscles, or a combination of both. |
Colin C. Korbisch; Daniel R. Apuan; Reza Shadmehr; Alaa A. Ahmed Saccade vigor reflects the rise of decision variables during deliberation Journal Article In: Current Biology, vol. 32, pp. 5374–5381, 2022. @article{Korbisch2022, During deliberation, as we quietly consider our options, the neural activities representing the decision variables that reflect the goodness of each option rise in various regions of the cerebral cortex.1,2,3,4,5,6,7 If the options are depicted visually, we make saccades, focusing gaze on each option. Do the kinematics of these saccades reflect the state of the decision variables? To test this idea, we engaged human participants in a decision-making task in which they considered two effortful options that required walking across various distances and inclines. As they deliberated, they made saccades between the symbolic representations of their options. These deliberation period saccades had no bearing on the effort they would later expend, yet saccade velocities increased gradually and differentially: the rate of rise was faster for saccades toward the option that they later indicated as their choice. Indeed, the rate of rise encoded the difference in the subjective value of the two options. Importantly, the participants did not reveal their choice at the conclusion of deliberation, but rather waited during a delay period, and finally expressed their choice by making another saccade. Remarkably, vigor for this saccade dropped to baseline and no longer encoded subjective value. Thus, saccade vigor appeared to provide a real-time window to the otherwise hidden process of option evaluation during deliberation. |
Lisa M. Kroell; Martin Rolfs Foveal vision anticipates defining features of eye movement targets Journal Article In: eLife, vol. 11, pp. 1–38, 2022. @article{Kroell2022, High-acuity foveal processing is vital for human vision. Nonetheless, little is known about how the preparation of large-scale rapid eye movements (saccades) affects visual sensitivity in the center of gaze. Based on findings from passive fixation tasks, we hypothesized that during saccade preparation, foveal processing anticipates soon-to-be fixated visual features. Using a dynamic large-field noise paradigm, we indeed demonstrate that defining features of an eye movement target are enhanced in the pre-saccadic center of gaze. Enhancement manifested as higher Hit Rates for foveal probes with target-congruent orientation and a sensitization to incidental, target-like orientation information in foveally presented noise. Enhancement was spatially confined to the center of gaze and its immediate vicinity, even after parafoveal task performance had been raised to a foveal level. Moreover, foveal enhancement during saccade preparation was more pronounced and developed faster than enhancement during passive fixation. Based on these findings, we suggest a crucial contribution of foveal processing to trans-saccadic visual continuity: Foveal processing of saccade targets commences before the movement is executed and thereby enables a seamless transition once the center of gaze reaches the target. |
Jens Kürten; Tim Raettig; Julian Gutzeit; Lynn Huestegge In: Psychological Research, pp. 1–15, 2022. @article{Kuerten2022, Previous research has shown that the simultaneous execution of two actions (instead of only one) is not necessarily more difficult but can actually be easier (less error-prone), in particular when executing one action requires the simultaneous inhibition of another action. Corresponding inhibitory demands are particularly challenging when the to-be-inhibited action is highly prepotent (i.e., characterized by a strong urge to be executed). Here, we study a range of important potential sources of such prepotency. Building on a previously established paradigm to elicit dual-action benefits, participants responded to stimuli with single actions (either manual button press or saccade) or dual actions (button press and saccade). Crucially, we compared blocks in which these response demands were randomly intermixed (mixed blocks) with pure blocks involving only one type of response demand. The results highlight the impact of global (action-inherent) sources of action prepotency, as reflected in more pronounced inhibitory failures in saccade vs. manual control, but also more local (transient) sources of influence, as reflected in a greater probability of inhibition failures following trials that required the to-be-inhibited type of action. In addition, sequential analyses revealed that inhibitory control (including its failure) is exerted at the level of response modality representations, not at the level of fully specified response representations. In sum, the study highlights important preconditions and mechanisms underlying the observation of dual-action benefits. |
Sunwoo Kwon; Berkeley K. Fahrenthold; Matthew R. Cavanaugh; Krystel R. Huxlin; Jude F. Mitchell Perceptual restoration fails to recover unconscious processing for smooth eye movements after occipital stroke Journal Article In: eLife, vol. 11, pp. 1–23, 2022. @article{Kwon2022, The visual pathways that guide actions do not necessarily mediate conscious perception. Patients with primary visual cortex (V1) damage lose conscious perception but often retain unconscious abilities (e.g. blindsight). Here, we asked if saccade accuracy and post-saccadic following responses (PFRs) that automatically track target motion upon saccade landing are retained when conscious perception is lost. We contrasted these behaviors in the blind and intact fields of 11 chronic V1-stroke patients, and in 8 visually intact controls. Saccade accuracy was relatively normal in all cases. Stroke patients also had normal PFR in their intact fields, but no PFR in their blind fields. Thus, V1 damage did not spare the unconscious visual processing necessary for automatic, postsaccadic smooth eye movements. Importantly, visual training that recovered motion perception in the blind field did not restore the PFR, suggesting a clear dissociation between pathways mediating perceptual restoration and automatic actions in the V1-damaged visual system. |
Natalia Ladyka-Wojcik; Zhong-Xu Liu; Jennifer D. Ryan Unrestricted eye movements strengthen effective connectivity from hippocampal to oculomotor regions during scene construction Journal Article In: NeuroImage, vol. 260, pp. 1–15, 2022. @article{LadykaWojcik2022, Scene construction is a key component of memory recall, navigation, and future imagining, and relies on the medial temporal lobes (MTL). A parallel body of work suggests that eye movements may enable the imagination and construction of scenes, even in the absence of external visual input. There are vast structural and functional connections between regions of the MTL and those of the oculomotor system. However, the directionality of connections between the MTL and oculomotor control regions, and how it relates to scene construction, has not been studied directly in human neuroimaging. In the current study, we used dynamic causal modeling (DCM) to interrogate effective connectivity between the MTL and oculomotor regions using a scene construction task in which participants' eye movements were either restricted (fixed-viewing) or unrestricted (free-viewing). By omitting external visual input, and by contrasting free- versus fixed- viewing, the directionality of neural connectivity during scene construction could be determined. As opposed to when eye movements were restricted, allowing free-viewing during construction of scenes strengthened top-down connections from the MTL to the frontal eye fields, and to lower-level cortical visual processing regions, suppressed bottom-up connections along the visual stream, and enhanced vividness of the constructed scenes. Taken together, these findings provide novel, non-invasive evidence for the underlying, directional, connectivity between the MTL memory system and oculomotor system associated with constructing vivid mental representations of scenes. |
Marcel Linka; Maximilian Davide Broda; Tamara Alsheimer; Benjamin Haas; Meike Ramon Characteristic fixation biases in Super-Recognizers Journal Article In: Journal of Vision, vol. 22, no. 8, pp. 1–15, 2022. @article{Linka2022, Neurotypical observers show large and reliable individual differences in gaze behavior along several semantic object dimensions. Individual gaze behavior toward faces has been linked to face identity processing, including that of neurotypical observers. Here, we investigated potential gaze biases in Super-Recognizers (SRs), individuals with exceptional face identity processing skills. Ten SRs, identified with a novel conservative diagnostic framework, and 43 controls freely viewed 700 complex scenes depicting more than 5000 objects. First, we tested whether SRs and controls differ in fixation biases along four semantic dimensions: faces, text, objects being touched, and bodies. Second, we tested potential group differences in fixation biases toward eyes and mouths. Finally, we tested whether SRs fixate closer to the theoretical optimal fixation point for face identification. SRs showed a stronger gaze bias toward faces and away from text and touched objects, starting from the first fixation onward. Further, SRs spent a significantly smaller proportion of first fixations and dwell time toward faces on mouths but did not differ in dwell time or first fixations devoted to eyes. Face fixation of SRs also fell significantly closer to the theoretical optimal fixation point for identification, just below the eyes. Our findings suggest that reliable superiority for face identity processing is accompanied by early fixation biases toward faces and preferred saccadic landing positions close to the theoretical optimum for face identification.We discuss future directions to investigate the functional basis of individual fixation behavior and face identity processing ability. |
Matteo Lisi; Michael J. Morgan; Joshua A. Solomon Perceptual decisions and oculomotor responses rely on temporally distinct streams of evidence Journal Article In: Communications Biology, vol. 5, pp. 1–8, 2022. @article{Lisi2022, Perceptual decisions often require the integration of noisy sensory evidence over time. This process is formalized with sequential sampling models, where evidence is accumulated up to a decision threshold before a choice is made. Although intuition suggests that decision formation must precede the preparation of a motor response (i.e., the action used to communicate the choice), neurophysiological findings have suggested that these two processes might be one and the same. To test this idea, we developed a reverse-correlation protocol in which the visual stimuli that influence decisions can be distinguished from those guiding motor responses. In three experiments, we found that the temporal weighting function of oculomotor responses did not overlap with the relatively early weighting function of stimulus properties having an impact on decision formation. These results support a timeline in which perceptual decisions are formed, at least in part, prior to the preparation of a motor response. |
Baiwei Liu; Anna C. Nobre; Freek Ede Functional but not obligatory link between microsaccades and neural modulation by covert spatial attention Journal Article In: Nature Communications, vol. 13, pp. 1–10, 2022. @article{Liu2022, Covert spatial attention is associated with spatial modulation of neural activity as well as with directional biases in fixational eye movements known as microsaccades. We studied how these two ‘fingerprints' of attention are interrelated in humans. We investigated spatial modulation of 8-12 Hz EEG alpha activity and microsaccades when attention is directed internally within the spatial layout of visual working memory. Consistent with a common origin, spatial modulations of alpha activity and microsaccades co-vary: alpha lateralisation is stronger in trials with microsaccades toward versus away from the memorised location of the to-be-attended item and occurs earlier in trials with earlier microsaccades toward this item. Critically, however, trials without attention-driven microsaccades nevertheless show clear spatial modulation of alpha activity – comparable to trials with attention-driven microsaccades. Thus, directional biases in microsaccades correlate with neural signatures of spatial attention, but they are not necessary for neural modulation by spatial attention to be manifest. |
Jia Liu; Jinsheng Hu; Qi Li; Xiaoning Zhao; Ying Liu; Shuqing Liu Atypical processing pattern of gaze cues in dynamic situations in autism spectrum disorders Journal Article In: Scientific Reports, vol. 12, pp. 1–11, 2022. @article{Liu2022c, Psychological studies have generally shown that individuals with Autism Spectrum Disorder (ASD) have particularity in the processing of social information by using static or abstract images. Yet, a recent study showed that there was no difference in their use of social or non-social cues in dynamic interactive situations. To establish the cause of the inconsistent results, we added gaze cues in different directions to the chase detection paradigm to explore whether they would affect the performance of participants with ASD. Meanwhile, eye-tracking methodology was used to investigate whether the processing patterns of gaze cues were different between individuals with ASD and TD. In this study, unlike typical controls, participants with ASD showed no detection advantage when the direction of gaze was consistent with the direction of movement (oriented condition). The results suggested that individuals with ASD may utilize an atypical processing pattern, which makes it difficult for them to use social information contained in oriented gaze cues in dynamic interactive situations. |
Vanessa M. Loaiza; Alessandra S. Souza The eyes don't have it: Eye movements are unlikely to reflect refreshing in working memory Journal Article In: PLoS ONE, vol. 17, no. 7, pp. 1–18, 2022. @article{Loaiza2022, There is a growing interest in specifying the mechanisms underlying refreshing, i.e., the use of attention to keep working memory (WM) contents accessible. Here, we examined whether participants' visual fixations during the retention interval of a WM task indicate the current focus of internal attention, thereby serving as an online measure of refreshing. Eye movements were recorded while participants studied and maintained an array of colored dots followed by probed recall of one (Experiments 1A and 1B) or all (Experiment 2) of the memoranda via a continuous color wheel. Experiments 1A and 2 entailed an unfilled retention interval in which refreshing is assumed to occur spontaneously, and Experiment 1B entailed a retention interval embedded with cues prompting the sequential refreshment of a subset of the memoranda. During the retention interval, fixations revisited the locations occupied by the memoranda, consistent with a looking-at-nothing phenomenon in WM, but the pattern was only evident when placeholders were onscreen in Experiment 2, indicating that most of these fixations may largely reflect random gaze. Furthermore, spontaneous fixations did not predict recall precision (Experiments 1A and 2), even when ensuring that they did not reflect random gaze (Experiment 2). In Experiment 1B, refreshing cues increased fixations to the eventually tested target and predicted better recall precision, which interacted with an overall benefit of target fixations, such that the benefit of fixations decreased as the number of refreshing cues increased. Thus, fixations under spontaneous conditions had no credible effect on recall precision, whereas the beneficial effect of fixations under instructed refreshing conditions may indicate situations in which cues were disregarded. Consequently, we conclude that eye movements do not seem suitable as an online measure of refreshing. |
Zoe Loh; Elizabeth H. Hall; Deborah Cronin; John M. Henderson Working memory control predicts fixation duration in scene-viewing Journal Article In: Psychological Research, pp. 1–12, 2022. @article{Loh2022, When viewing scenes, observers differ in how long they linger at each fixation location and how far they move their eyes between fixations. What factors drive these differences in eye-movement behaviors? Previous work suggests individual differences in working memory capacity may influence fixation durations and saccade amplitudes. In the present study, participants (N = 98) performed two scene-viewing tasks, aesthetic judgment and memorization, while viewing 100 photographs of real-world scenes. Working memory capacity, working memory processing ability, and fluid intelligence were assessed with an operation span task, a memory updating task, and Raven's Advanced Progressive Matrices, respectively. Across participants, we found significant effects of task on both fixation durations and saccade amplitudes. At the level of each individual participant, we also found a significant relationship between memory updating task performance and participants' fixation duration distributions. However, we found no effect of fluid intelligence and no effect of working memory capacity on fixation duration or saccade amplitude distributions, inconsistent with previous findings. These results suggest that the ability to flexibly maintain and update working memory is strongly related to fixation duration behavior. |
Dillon Lohr; Henry Griffith; Oleg V. Komogortsev Eye know you: Metric learning for end-to-end biometric authentication using eye movements from a longitudinal dataset Journal Article In: IEEE Transactions on Biometrics, Behavior, and Identity Science, vol. 4, no. 2, pp. 276–288, 2022. @article{Lohr2022, The permanence of eye movements as a biometric modality remains largely unexplored in the literature. The present study addresses this limitation by evaluating a novel exponentially-dilated convolutional neural network for eye movement authentication using a recently proposed longitudinal dataset known as GazeBase. The network is trained using multi-similarity loss, which directly enables the enrollment and authentication of out-of-sample users. In addition, this study includes an exhaustive analysis of the effects of evaluating on various tasks and downsampling from 1000 Hz to several lower sampling rates. Our results reveal that reasonable authentication accuracy may be achieved even during both a low-cognitive-load task and at low sampling rates. Moreover, we find that eye movements are quite resilient against template aging after as long as 3 years. |
Floor C. Loonstra; Lodewijk R. J. De Ruiter; Djoeke Doesburg; Ka-Hoo Lam; Zoe Y. G. J. Van Lierop; Bastiaan Moraal; Eva M. M. Strijbis; Joep Killestein; Bernard M. J. Uitdehaag Project Y: The search for clues explaining phenotype variability in MS Journal Article In: Multiple Sclerosis and Related Disorders, vol. 57, pp. 1–8, 2022. @article{Loonstra2022, Background: To study phenotypic variability in MS patients, well-defined unbiased cohort studies are necessary. The most common and probably most important confounding factor when studying disease phenotype in MS is age. Objective: To describe study design and subject characteristics of a unique birth cohort (Project Y). The overall aim of Project Y is to identify determinants associated with phenotypic variability in MS, eliminating the possibility of confounding by age. Methods: Project Y is a population-based cross-sectional study of all people with MS born in the Netherlands in 1966. Patients and healthy controls were subjected to comprehensive examinations: functional and static imaging, physical and cognitive measurements, and lifestyle factors early and later in life. In addition body fluids were collected and stored for future biomarker research. Results: 452 eligible MS patients were identified. Between December 2017 and January 2021, 367 MS patients and 125 healthy controls participated. The total number of identified cases results in a current prevalence of at least 189/100.000 for people born in the year 1966 in The Netherlands. Conclusion: Project Y is a unique cohort designed to identify factors associated with phenotypic variability in MS patients without the confounding effects of age. This first description of the Project Y cohort indicates that the prevalence of MS in the Netherlands might be higher than previously presumed. Various studies using Project Y data are ongoing and results will be published in upcoming years. |
Kaleb A. Lowe; Wolf Zinke; Joshua D. Cosman; Jeffrey D. Schall Frontal eye fields in macaque monkeys: Prefrontal and premotor contributions to visually guided saccades Journal Article In: Cerebral Cortex, vol. 32, pp. 5083–5107, 2022. @article{Lowe2022, Neuronal spiking was sampled from the frontal eye field (FEF) and from the rostral part of area 6 that reaches to the superior limb of the arcuate sulcus, dorsal to the arcuate spur when present (F2vr) in macaque monkeys performing memory-guided saccades and visually guided saccades for visual search. Neuronal spiking modulation in F2vr resembled that in FEF in many but not all respects. A new consensus clustering algorithm of neuronal modulation patterns revealed that F2vr and FEF contain a greater variety of modulation patterns than previously reported. The areas differ in the proportions of visuomotor neuron types, the proportions of neurons discriminating a target from distractors during visual search, and the consistency of modulation patterns across tasks. However, between F2vr and FEF we found no difference in the magnitude of delay period activity, the timing of the peak discharge rate relative to saccades, or the time of search target selection. The observed similarities and differences between the 2 cortical regions contribute to other work establishing the organization of eye fields in the frontal lobe and may help explain why FEF in monkeys is identified within granular prefrontal area 8 but in humans is identified within agranular premotor area 6. |
Yun-Jhen Lu; I. -Chun Kuo; Ming-Chou Ho The effects of emotional films and subtitle types on eye movement patterns Journal Article In: Acta Psychologica, vol. 230, no. 110, pp. 1–7, 2022. @article{Lu2022, Background: In Taiwan, the use of subtitle is common in TV programs and movies. However, studies on subtitles mostly focus on foreign language learning and film subtitle translation. Few studies address how subtitle types and emotion-laden films affect the viewers' eye movement patterns. Purpose: We aim to examine how the emotion type of film (happy, sad, angry, fear, or neutral) and subtitle type (meaningful subtitle, no subtitle, or meaningless subtitle) affect the dwell times and fixation counts in the subtitle area. Methods: This study is a 5 (emotion type of film) × 3 (subtitle type) between-participants design. There were 15 participants per condition, resulting in a total of 225 participants. After watching a film, participants filled out a self-reported questionnaire regarding this film. Results: The subtitled films have more fixation counts and dwell time for the meaningful subtitle compared to meaningless subtitle and no subtitle. The dwell time was longer on the subtitle area for the sad film than the neutral and happy films. Also, the dwell time was longer on the subtitle area for the fear film than the happy film. There were more fixation counts on the subtitle area for the sad film than the angry and happy films. Conclusions: The subtitle meaning is critical in directing overt attention. Also, overt attention directed to the subtitle area is affected by the different emotion types of films. |
Malte Lüken; Šimon Kucharský; Ingmar Visser Characterising eye movement events with an unsupervised hidden markov model Journal Article In: Journal of Eye Movement Research, vol. 15, no. 1, pp. 1–29, 2022. @article{Lueken2022, Eye-tracking allows researchers to infer cognitive processes from eye movements that are classified into distinct events. Parsing the events is typically done by algorithms. Here we aim at developing an unsupervised, generative model that can be fitted to eye-movement data using maximum likelihood estimation. This approach allows hypothesis testing about fitted models, next to being a method for classification. We developed gazeHMM, an algorithm that uses a hidden Markov model as a generative model, has few critical parameters to be set by users, and does not require human coded data as input. The algorithm classifies gaze data into fixations, saccades, and optionally postsaccadic oscillations and smooth pursuits. We evaluated gazeHMM's performance in a simulation study, showing that it successfully recovered hidden Markov model parameters and hidden states. Parameters were less well recovered when we included a smooth pursuit state and/or added even small noise to simulated data. We applied generative models with different numbers of events to benchmark data. Comparing them indicated that hidden Markov models with more events than expected had most likely generated the data. We also applied the full algorithm to benchmark data and assessed its similarity to human coding and other algorithms. For static stimuli, gazeHMM showed high similarity and outperformed other algorithms in this regard. For dynamic stimuli, gazeHMM tended to rapidly switch between fixations and smooth pursuits but still displayed higher similarity than most other algorithms. Concluding that gazeHMM can be used in practice, we recommend parsing smooth pursuits only for exploratory purposes. Future hidden Markov model algorithms could use covariates to better capture eye movement processes and explicitly model event durations to classify smooth pursuits more accurately. |
Xiaoxiao Luo; Jiayan Gu; Yueyuan Zheng; Xiaolin Zhou Making a saccade enhances Stroop and Simon conflict control Journal Article In: Attention, Perception, and Psychophysics, vol. 84, no. 3, pp. 795–814, 2022. @article{Luo2022, Cognitive control is an important ability instantiated in many situations such as conflict control (e.g., Stroop/Simon task) and the control of eye movements (e.g., saccades). However, it is unclear whether eye movement control shares a common cognitive control system with the conflict control. In Experiment 1, we asked participants to make a prosaccade or antisaccade and then to identify the color of a lateralized color word (i.e., a Stroop–Simon stimulus). The stimulus onset asynchrony (SOA) between the saccadic cue and the Stroop–Simon stimulus was manipulated to be either short (200 ms) or long (600 ms). Results showed that the Stroop effect at the response level and the (negative) Simon effect were smaller when the SOA was short than long, demonstrating a decline of response control over time after making a saccade. Moreover, this temporal change of the Simon effect was more pronounced in the antisaccade session than in the prosaccade session. Furthermore, individuals who had better performance in the antisaccade task performed better in the response control of Stroop interference. When the saccade task was removed in Experiment 2, the temporal declines of the response control observed in Experiment 1 were absent. Experiment 3 replicated the key results of Experiment 1 by replacing the Stroop–Simon task with a typical Simon task and separately testing the typical Stroop and Simon tasks. Overall, our findings suggest that a common system is shared between the control of eye movements and the conflict control at the response level. |
Yingyi Luo; Dixiao Tan; Ming Yan Morphological structure influences saccade generation in Chinese reading Journal Article In: Reading and Writing, pp. 1–17, 2022. @article{Luo2022a, Recent studies have demonstrated that saccadic programming in reading is not only determined by low-level visual factors. High-level morphological effects on saccade have been shown in two morphologically rich languages. In the present study, we examined the underlying mechanism of such morphological influences by comparing the processes of reading three-character Chinese compound words that differ in their structures in terms of morphological decomposition. Consistent with earlier reports, our results showed an effect of morphological structure on saccade. The readers' first-fixation location shifted further away from the beginning of the word, when the last two characters were more morphologically bounded and thus formed a [1 + 2] structure, than when the first two characters were more bounded (i.e., a [2 + 1] structure). The results are not accountable by a processing difficulty hypothesis, which proposes that saccade amplitude is determined by morphological complexity; rather, they suggest that Chinese readers parafoveally decompose a word and spontaneously target its longer stem, thus reflecting parafoveal access to words' stems. |
Xinyu Lv; Suping Cheng; Zhiguo Wang; Jianrong Jia The dynamics of microsaccade amplitude reflect shifting of covert attention Journal Article In: Consciousness and Cognition, vol. 101, pp. 1–10, 2022. @article{Lv2022, Attention flexibly shifts between spatial locations to accommodate task demands. The present study examined if the dynamics of attentional shifting are seen in microsaccades whose direction has been shown to accompany the shifts of covert attention. In a spatial cueing task, the cue predicted the target location on 100%, 75%, or 50% of the trials. The results revealed that microsaccade rate and amplitude were both reduced following cue onset and then rebounded. Both microsaccade rate and amplitude were biased towards the opposite direction of the cue and then returned to the cued direction. Importantly, the cue validity modulated the temporal profile of microsaccade amplitude but had little impact on the temporal profile of microsaccade rate. In line with this, the cueing effect measured with target response accuracy was correlated with the microsaccade amplitude only. These results indicate that the temporal dynamics of microsaccade amplitude reflect shifting of covert attention. |
Wenbo Ma; Min Li; Junru Wu; Zhihao Zhang; Fangfang Jia; Mingsha Zhang; Hagai Bergman; Xuemei Li; Zhipei Ling; Xin Xu Multiple step saccades in simply reactive saccades could serve as a complementary biomarker for the early diagnosis of Parkinson's disease Journal Article In: Frontiers in Aging Neuroscience, vol. 14, pp. 1–14, 2022. @article{Ma2022a, Objective: It has been argued that the incidence of multiple step saccades (MSS) in voluntary saccades could serve as a complementary biomarker for diagnosing Parkinson's disease (PD). However, voluntary saccadic tasks are usually difficult for elderly subjects to complete. Therefore, task difficulties restrict the application of MSS measurements for the diagnosis of PD. The primary objective of the present study is to assess whether the incidence of MSS in simply reactive saccades could serve as a complementary biomarker for the early diagnosis of PD. Materials and methods: There were four groups of human subjects: PD patients, mild cognitive impairment (MCI) patients, elderly healthy controls (EHCs), and young healthy controls (YHCs). There were four monkeys with subclinical hemi-PD induced by injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) through the unilateral internal carotid artery and three healthy control monkeys. The behavioral task was a visually guided reactive saccade. Results: In a human study, the incidence of MSS was significantly higher in PD than in YHC, EHC, and MCI groups. In addition, receiver operating characteristic (ROC) analysis could discriminate PD from the EHC and MCI groups, with areas under the ROC curve (AUCs) of 0.76 and 0.69, respectively. In a monkey study, while typical PD symptoms were absent, subclinical hemi-PD monkeys showed a significantly higher incidence of MSS than control monkeys when the dose of MPTP was greater than 0.4 mg/kg. Conclusion: The incidence of MSS in simply reactive saccades could be a complementary biomarker for the early diagnosis of PD. |
Wenbo Ma; Mingsha Zhang The effects of age and sex on the incidence of multiple step saccades and corrective saccades Journal Article In: Frontiers in Aging Neuroscience, vol. 14, pp. 1–11, 2022. @article{Ma2022b, Objective: Although multiple step saccades (MSS) is occasionally observed in healthy subjects, it is more pronounced in patients with aging-related neurodegenerative diseases, particularly Parkinson's disease (PD). Thus, MSS has been treated as a complementary biomarker for diagnosing PD. Despite the aforementioned knowledge, several questions remain unexplored: (1) How does aging affect MSS? (2) Is there a sex difference in MSS? (3) Are there differences in MSS between vertical and horizontal saccades? (4) Are MSS and corrective saccade (CS) the same behavior? (5) How do age and sex affect CS? The objectives of the present study are to address these questions. Method: Four hundred eighty healthy participants were recruited to perform a visually guided reactive saccade task. Participants were divided into six groups according to their ages. Each group consisted of 40 male and 40 female participants. Eye movements were recorded with infrared eye trackers. Results: The incidence of MSS increased as a function of age, whereas the incidence of CS first increased with age 20–49 and then decreased with age 50–79. The incidences of both MSS and CS did not show sex differences. The incidence of MSS in vertical saccades was significantly higher than that in horizontal saccades, and their difference increased with increasing age, whereas the incidence of CS showed a reversed pattern. Conclusion: Age and saccadic direction affect the occurrences of MSS and CS differently, indicating that MSS and CS are different saccadic behaviors. In addition, measuring saccades could reliably reflect the function of human's brain which is affected by aging. |
Elham Azizi; Joanne Fielding; Larry A. Abel Video game training in traumatic brain injury patients: an exploratory case report study using eye tracking Journal Article In: Journal of Eye Movement Research, vol. 15, no. 1, pp. 1–14, 2022. @article{Azizi2022, Remediation of attentional impairments is an essential component of cognitive rehabilitation after traumatic brain injury (TBI). Evidence from healthy participants has demonstrated attentional improvement following playing an action video game. This exploratory study investigated its application in TBI participants in a multiple baselines single case experimental design (SCED). Saccadic eye movements, recognized as the visible indicators of visual attention, were assessed to evaluate the effectiveness of the game training. Three severe TBI participants were trained in an action game for 10 hours. Saccadic eye movements during a self-paced saccade and an abstract visual search task were investigated during baseline, mid training and post-training. Using Percentage of Non-overlapping Data (PND), analysis showed consistent increase in the rate of the self-paced saccades in participants 1 (PND=80%) and 2 (PND=70%). In abstract search, fixation duration showed a minimally effective decrease for participant 2 (PND= 60%) and a moderately effective reduction in participant 3 (PND= 80%). Search time showed a highly effective reduction in participant 2 (PND = 100%) and moderately effective decrease in participant 3 (PND=70%). Overall, video game training might modify allocation of attention in eye movements. More evidence is required to validate the usefulness of this novel method of the cognitive training |
Daniela Balslev; Alexandra G. Mitchell; Patrick J. M. Faria; Lukasz Priba; Jennifer A. Macfarlane Proprioceptive contribution to oculomotor control in humans Journal Article In: Human Brain Mapping, vol. 43, no. 16, pp. 5081–5090, 2022. @article{Balslev2022, Stretch receptors in the extraocular muscles (EOMs) inform the central nervous system about the rotation of one's own eyes in the orbits. Whereas fine control of the skeletal muscles hinges critically on proprioceptive feedback, the role of proprioception in oculomotor control remains unclear. Human behavioural studies provide evidence for EOM proprioception in oculomotor control, however, behavioural and electrophysiological studies in the macaque do not. Unlike macaques, humans possess numerous muscle spindles in their EOMs. To find out whether the human oculomotor nuclei respond to proprioceptive feedback we used functional magnetic resonance imaging (fMRI). With their eyes closed, participants placed their right index finger on the eyelid at the outer corner of the right eye. When prompted by a sound, they pushed the eyeball gently and briefly towards the nose. Control conditions separated out motor and tactile task components. The stretch of the right lateral rectus muscle was associated with activation of the left oculomotor nucleus and subthreshold activation of the left abducens nucleus. Because these nuclei control the horizontal movements of the left eye, we hypothesized that proprioceptive stimulation of the right EOM triggered left eye movement. To test this, we followed up with an eye-tracking experiment in complete darkness using the same behavioural task as in the fMRI study. The left eye moved actively in the direction of the passive displacement of the right eye, albeit with a smaller amplitude. Eye tracking corroborated neuroimaging findings to suggest a proprioceptive contribution to ocular alignment. |
Sinem B. Beylergil; Camilla Kilbane; Aasef G. Shaikh; Fatema F. Ghasia Eye movements in Parkinson's disease during visual search Journal Article In: Journal of the Neurological Sciences, vol. 440, pp. 1–16, 2022. @article{Beylergil2022, Visual spatial dysfunction is not uncommon in Parkinson's disease. We hypothesized that visual search behavior is impaired in Parkinson's disease and the deficits correlate with changes in the amplitudes and frequency of fixational and non-fixational rapid eye movements. We measured eye movements, the horizontal and vertical angular position vectors of the right and left eye using high-resolution video oculography, in the Parkinsonian cohort who viewed a blank scene and pictures with real-life scene. Latter was associated with a task of searching an object hidden in a clutter, either at an expected or an unexpected location. Parkinsonian cohort took longer initial time to reach the region of interest. The ultimate response time was comparable in both Parkinson's disease and their healthy peers. The fixation duration was comparable in two cohorts but there was a trend wise decline for the ones located at unexpected locations. Parkinson's disease participants made more fixational saccades with significantly larger amplitude and less non-fixational saccades with significantly smaller amplitude during blank scene viewing. However, overall scanned area of the blank scene was not affected in Parkinson's disease. The Parkinson's disease participants made less non-fixational saccades with amplitudes comparable to healthy control during the visual search of a target object. Fixational saccades during visual search were larger in Parkinson's disease particularly when target was placed at an unexpected location, but the frequency was unchanged. |
Sinem Balta Beylergil; Jordan Murray; Angela M. Noecker; Palak Gupta; Camilla Kilbane; Cameron C. McIntyre; Fatema F. Ghasia; Aasef G. Shaikh Temporal patterns of spontaneous fixational eye movements: The influence of basal ganglia Journal Article In: Journal of Neuro-Ophthalmology, vol. 42, no. 1, pp. 45–55, 2022. @article{Beylergil2022a, Background:Spontaneity is a unique feature of the nervous system. One of the fundamentally critical and recognized forms of spontaneous motor activity is witnessed in the visuomotor system. Microsaccades, the miniature spontaneous eye movements, are critical for the visual perception. We hypothesized that microsaccades follow specific temporal patterns that are modulated by the basal ganglia output.Methods:We used high-resolution video-oculography to capture microsaccades in 48 subjects (31 healthy and 17 with Parkinson's disease) when subjects were asked to hold their gaze on a straight-ahead target projected on white background. We analyzed spontaneous discharge patterns of microsaccades.Results:The first analysis considering coefficient of variation in intersaccadic interval distribution demonstrated that microsaccades in Parkinson's disease are more dispersed than the control group. The second analysis scrutinized microsaccades' temporal variability and revealed 3 distinct occurrence patterns: regular rhythmic, clustered, and randomly occurring following a Poisson-like process. The regular pattern was relatively more common in Parkinson's disease. Subthalamic DBS modulated this temporal pattern. The amount of change in the temporal variability depended on the DBS-induced volume of tissue activation and its overlap with the subthalamic nucleus. The third analysis determined the autocorrelations of microsaccades within 2-second time windows. We found that Parkinson's disease altered local temporal organization in microsaccade generation, and DBS had a modulatory effect.Conclusion:The microsaccades occur in 3 temporal patterns. The basal ganglia are one of the modulators of the microsaccade spontaneity. |
Daniel Ernst; Jeremy M. Wolfe How fixation durations are affected by search difficulty manipulations Journal Article In: Visual Cognition, vol. 30, pp. 339–353, 2022. @article{Ernst2022, Many eye tracking studies of visual search have focused on the role of the number of fixations and the nature of scan paths. Less attention has been paid to fixation durations and to how those durations are affected by stimulus features. Previous studies have shown that fixation durations can be as important as the number of fixations in explaining search times with complex stimuli (e.g., in search for specific faces). In the present study, simple stimuli were used in a search experiment where participants searched for a closed ring among rings with a gap. We manipulated distractor heterogeneity (DH), target-distractor similarity (TDS), and stimulus density (SDY, set size within a constant search window), and estimated the contributions of these factors to gaze behaviour and trial search time. The results show that fixation durations contribute less to variation in overall search time with simple search stimuli as compared to previous studies with more complex stimuli. However, fixation durations still increased with DH, TDS, and SDY. These effects were mainly additive, and we did not find an interaction between DH and closer element spacing at high levels of SDY that might have been expected since both DH and SDY influence distractor grouping. |
Peter Essig; Jonas Müller; Siegfried Wahl Parameters of optokinetic nystagmus are influenced by the nature of a visual stimulus Journal Article In: Applied Sciences, vol. 12, pp. 1–13, 2022. @article{Essig2022, Studies on contrast sensitivity (CS) testing using optokinetic nystagmus (OKN) proposed adjusting the stimulus presentation duration based on its contrast, to increase the time efficiency of such measurement. Furthermore, stimulus-specific limits of the least OKN gain might reduce false negatives in OKN detection procedures. Therefore, we aimed to test the effects of various stimulus characteristics on OKN and to propose the stimulus-specific limits for the OKN gain and stimulus presentation duration. We tested the effect of contrast (C), spatial frequency ((Formula presented.)), and color on selected parameters of robust OKN response, namely its onset and offset time, amplitude, and gain. The right eyes of fifteen emmetropes were tracked with an infrared eye tracker during monocular observations of sinusoidal gratings moving over the horizontal plane with a velocity of ((Formula presented.)). The available contrast levels were C: 0.5%, 2.0%, 8.2%, 16.5%, 33.0%, and 55.5% presented in a random order for ten times in all measurements of (Formula presented.) : 0.12, 0.25, 0.5, and 1.00 cycles per degree and grating type: luminance, red-green, and blue-yellow. This study showed a significant effect of the stimulus characteristics on the OKN onset, offset and gain. The effect of (Formula presented.) was insignificant in OKN amplitude; however, it indicated significance for the C and grating type. Furthermore, the OKN gain and offset limits were proposed as functions of contrast for the luminance and chromatic gratings. This study concludes the characteristics of a visual stimulus have an effect on the OKN gain and onset and offset time, yet do not affect the eye-movement amplitude considerably. Moreover, the proposed limits are expected to improve the time efficiency and eye-movement detection in OKN-based contrast sensitivity measurements. |
Peter Essig; Yannick Sauer; Siegfried Wahl Reflexive saccades used for objective and automated measurements of contrast sensitivity in selected areas of visual field Journal Article In: Translational Vision Science & Technology, vol. 11, no. 5, pp. 1–12, 2022. @article{Essig2022a, Purpose: This study proposes a novel approach for objective and automated peripheral contrast sensitivity (CS) testing using reflexive saccades. Here the CS was examined in various areas the of visual field (VF) using a live analysis of gaze data. For validation of the new test, we examined CS with an established procedure of identifying the orientation of a contrast stimulus. Methods: To perform and validate the saccade-based testing, two separate measurement events were performed. In the first, participants were asked to execute a saccade toward a newly-appeared stimulus in their VF. After the saccade execution or stimulus expiry, reporting the target orientation was required in a four-alternatives forced choice (4AFC). Therefore the first measurement yields two outcomes (objective and subjec-tive). In the second measurement, only the identification of the stimulus orientation was requested, while fixating a central mark. Stimulus contrast was controlled by an adaptive psychometric procedure in both measurements. Results: The study found strong correlations (all r ≥ 0.79) of CS values for all three possible testing methods (saccade-based responding in saccadic measurements, keyboard-based responding in saccadic measurements, keyboard-based responding in non-saccadic measurements), showing the feasibility of employment of reflexive saccades in such testing. Second, this study shows a significant influence of eccentricity and direction of the stimulus on the CS function. Conclusions: CS measured with reflexive saccades is comparable to other testing methods over several areas of the participant's VF. Hence, we propose it as a novel and objective testing procedure for CS measurements. |
Marzieh Salehi Fadardi; Javad Salehi Fadardi; Monireh Mahjoob; Hassan Doosti Post-saccadic eye movement indices under cognitive load: A path analysis to determine visual performance Journal Article In: Journal of Ophthalmic and Vision Research, vol. 17, no. 3, pp. 397–404, 2022. @article{Fadardi2022, Purpose: The evidence on the linear relationship between cognitive load, saccade, fixation, and task performance was uncertain. We tested pathway models for degraded task performance resulting from changes in saccadic and post-saccadic fixation under cognitive load. Methods: Participants' (n = 38) eye movements were recorded using a post-saccadic discrimination task with and without arithmetic operations to impose cognitive load, validated through recording heart rate variability and subjective measurement. Results: Results showed that cognitive load led to longer latencies of saccade and fixation; more inaccurate responses and fewer secondary saccades (P < 0.001). Longer saccade latencies influenced task performance indirectly via increases in fixation latency, therefore, longer reaction times and higher response errors were observed due to limited fixation duration on desired target. Conclusion: We suggest that latency and duration of fixation indicate efficiency of information processing and can predict the speed and accuracy of task performance under cognitive load. |
Cecilia E. García Cena; David Gómez-Andrés; Irene Pulido-Valdeolivas; Victoria Galán Sánchez-Seco; Angela Domingo-Santos; Sara Moreno-García; Julián Benito-León Toward an automatic assessment of cognitive dysfunction in relapsing–remitting multiple sclerosis patients using eye movement analysis Journal Article In: Sensors, vol. 22, pp. 1–18, 2022. @article{GarciaCena2022, Despite the importance of cognitive function in multiple sclerosis, it is poorly represented in the Expanded Disability Status Scale (EDSS), the commonly used clinical measure to assess disability, suggesting that an analysis of eye movement, which is generated by an extensive and well-coordinated functional network that is engaged in cognitive function, could have the potential to extend and complement this more conventional measure. We aimed to measure the eye movement of a case series of MS patients with relapsing–remitting MS to assess their cognitive status using a conventional gaze tracker. A total of 41 relapsing–remitting MS patients and 43 age-matched healthy controls were recruited for this study. Overall, we could not find a clear common pattern in the eye motor abnormalities. Vertical eye movement was more impaired in MS patients than horizontal movement. Increased latencies were found in the prosaccades and reflexive saccades of antisaccade tests. The smooth pursuit was impaired with more corrections (backup and catchup movements, p<0.01). No correlation was found between eye movement variables and EDSS or disease duration. Despite significant alterations in the behavior of the eye movements in MS patients, which are compatible with altered cognitive status, there is no common pattern of these alterations. We interpret this as a consequence of the patchy, heterogeneous distribution of white matter involvement in MS that provokes multiple combinations of impairment at different points in the different networks involved in eye motor control. Further studies are therefore required. |
Nora Geiser; Brigitte Charlotte Kaufmann; Henrik Rühe; Noortje Maaijwee; Tobias Nef; Dario Cazzoli; Thomas Nyffeler Visual neglect after PICA stroke—A case study Journal Article In: Brain Sciences, vol. 12, pp. 1–10, 2022. @article{Geiser2022, After cerebellar stroke, cognition can be impaired, as described within the framework of the so-called Cerebellar Cognitive Affective Syndrome (CCAS). However, it remains unclear whether visual neglect can also be part of CCAS. We describe the case of a patient with a subacute cerebellar stroke after thrombosis of the left posterior inferior cerebellar artery (PICA), who showed a left-sided visual neglect, indicating that the cerebellum also has a modulatory function on visual attention. The neglect, however, was mild and only detectable when using the sensitive neuro-psychological Five-Point Test as well as video-oculography assessment, yet remained unnoticed when evaluated with common neglect-specific paper-pencil tests. Three weeks later, follow-up assessments revealed an amelioration of neglect symptoms. Therefore, these findings suggest that visual neglect may be a part of CCAS, but that the choice of neglect assessments and the time delay since stroke onset may be crucial. Although the exact underlying pathophysiological mechanisms remain unclear, we propose cerebellar–cerebral diaschisis as a possible explanation of why neglect can occur on the ipsilateral side. Further research applying sensitive assessment tools at different post-stroke stages is needed to investigate the incidence, lesion correlates, and pathophysiology of neglect after cerebellar lesions. |
Amirhossein Ghaderi; Matthias Niemeier; John Douglas Crawford Linear vector models of time perception account for saccade and stimulus novelty interactions Journal Article In: Heliyon, vol. 8, pp. 1–13, 2022. @article{Ghaderi2022, Various models (e.g., scalar, state-dependent network, and vector models) have been proposed to explain the global aspects of time perception, but they have not been tested against specific visual phenomena like perisaccadic time compression and novel stimulus time dilation. Here, in two separate experiments (N = 31), we tested how the perceived duration of a novel stimulus is influenced by 1) a simultaneous saccade, in combination with 2) a prior series of repeated stimuli in human participants. This yielded a novel behavioral interaction: pre-saccadic stimulus repetition neutralizes perisaccadic time compression. We then tested these results against simulations of the above models. Our data yielded low correlations against scalar model simulations, high but non-specific correlations for our feedforward neural network, and correlations that were both high and specific for a vector model based on identity of objective and subjective time. These results demonstrate the power of global time perception models in explaining disparate empirical phenomena and suggest that subjective time has a similar essence to time's physical vector. |
Alma Gharib; Barbara L. Thompson Analysis and novel methods for capture of normative eye-tracking data in 2.5-month old infants Journal Article In: PloS ONE, vol. 17, pp. 1–22, 2022. @article{Gharib2022, Development of attention systems is essential for both cognitive and social behavior maturation. Visual behavior has been used to assess development of these attention systems. Yet, given its importance, there is a notable lack of literature detailing successful methods and procedures for using eye-tracking in early infancy to assess oculomotor and attention dynamics. Here we show that eye-tracking technology can be used to automatically record and assess visual behavior in infants as young as 2.5 months, and present normative data describing fixation and saccade behavior at this age. Features of oculomotor dynamics were analyzed from 2.5-month old infants who viewed videos depicting live action, cartoons, geometric shapes, social and non-social scenes. Of the 54 infants enrolled, 50 infants successfully completed the eye-tracking task and high-quality data was collected for 32 of those infants. We demonstrate that modifications specifically tailored for the infant population allowed for consistent tracking of pupil and corneal reflection and minimal data loss. Additionally, we found consistent fixation and saccade behaviors across the entire six-minute duration of the videos, indicating that this is a feasible task for 2.5-month old infants. Moreover, normative oculomotor metrics for a free-viewing task in 2.5-month old infants are documented for the first time as a result of this high-quality data collection. |
Hanbin Go; James Danckert; Britt Anderson Saccadic eye movement metrics reflect surprise and mental model updating Journal Article In: Attention, Perception, and Psychophysics, vol. 84, no. 5, pp. 1553–1565, 2022. @article{Go2022, Two experiments investigated what eye movements can reveal about how we process surprising information and how we update mental models in dynamic and unstructured environments. Participants made saccades to visual targets presented one at a time, radially, around an invisible perimeter. Target locations were normally distributed and shifted at an unannounced point during the task. Trials following the shift were considered surprising and unexpected. These unexpected and surprising events prompted the need to update. Slower saccadic latencies were observed for surprising/unexpected events, perhaps indicative of the need to reorient attention to the unexpected target location. Longer dwell times were observed for events that signaled a change in the distribution. These data show that eye movement metrics provide a reliable indicator of mental model updating when contingencies change even in the absence of explicit change signals. |
Alexander Goettker; Emma E. M. Stewart Serial dependence for oculomotor control depends on early sensory signals Journal Article In: Current Biology, vol. 32, pp. 2956–2961, 2022. @article{Goettker2022, To create an accurate percept of the world, the visual system relies on past experience and prior assumptions.1 For example, although the retinal projection of an object moving in depth changes drastically, we still perceive the object at a constant size and velocity.2,3 Consequently, if we see the same object with a constant retinal size at two different depth levels, the perceived size differs (illustrated by the Ponzo illusion). Past experience also directly influences perceptual judgments, an effect known as serial dependence.4,5 Such sequential effects have also been reported for oculomotor behavior, even on the trial-by-trial level.6–10 An integration of past experiences seems like a smart and sophisticated mechanism to reduce uncertainty and improve behavior in a world full of statistical regularities. By leveraging the Ponzo illusion to dissociate perceived size and speed from retinal signals, we show that serial-dependence effects for oculomotor control are mediated by retinal error signals. These sequential effects likely take place in early sensory processing because they transfer to different visual stimuli. In contrast to recently reported history effects for perceptual decisions,11 sequential effects for oculomotor control deviate from perceptual mechanisms by not integrating spatial context and by ignoring size and velocity constancy. Although this dissociation might appear suboptimal, we argue that this effect reveals the different goals of the oculomotor and perceptual systems. The oculomotor system tries to reduce retinal error signals to bring and keep the target close to the fovea, whereas the visual system interprets retinal input to achieve an accurate representation of the world.12 |
A. Grillini; L. H. Koens; G. Lizaitiene; F. Lange; F. W. Cornelissen; M. A. J. Tijssen In: Clinical Parkinsonism and Related Disorders, vol. 7, pp. 1–6, 2022. @article{Grillini2022, Introduction: Vertical supranuclear gaze palsy is a key feature of Niemann-Pick type C (NP-C) and is commonly quantified using video-oculography (VOG). VOG requires sitting still for long times and performing specific tasks, thus it can be challenging or impossible for patients severely affected by movement disorders or cognitive impairment. To overcome this limitation, we measure saccades of NP-C patients using a fast eye tracking test based on continuous psychophysics and compare it to VOG. Methods: Saccades of six NP-C patients and six age-matched controls were assessed using VOG and Standardized Oculomotor and Neuro-ophthalmic Disorders Assessment (SONDA). In SONDA, participants continuously track a semi-randomly moving dot on a computer screen while their gaze is being tracked. For both assessments, sac- cades were quantified using four conventional measures: amplitude, gain, latency, and peak velocity. Further- more, SONDA's continuous measures were quantified with several novel spatio-temporal properties. Results: In the NP-C patients, both methods revealed reduced amplitude, gain, peak velocity, and increased la- tency of vertical saccades compared to horizontal saccades and compared to healthy controls. Effect sizes ob- tained with SONDA were overall larger than those for VOG. SONDA's spatio-temporal properties showed similar trends. Conclusion: SONDA reveals a deterioration of vertical saccades in NP-C patients that is consistent with VOG. SONDA's measures based on continuous psychophysics are consistent with traditional saccadic parameters and can potentially provide complementary information. SONDA shows larger effect sizes than VOG, suggesting that it provides robust and clinically relevant outcomes with a more intuitive task and shorter testing time. |
Scott N. Grossman; Rachel Calix; Todd Hudson; John Ross Rizzo; Ivan Selesnick; Steven Frucht; Steven L. Galetta; Laura J. Balcer; Janet C. Rucker Accuracy of clinical versus oculographic detection of pathological saccadic slowing Journal Article In: Journal of the Neurological Sciences, vol. 442, pp. 1–8, 2022. @article{Grossman2022, Saccadic slowing as a component of supranuclear saccadic gaze palsy is an important diagnostic sign in multiple neurologic conditions, including degenerative, inflammatory, genetic, or ischemic lesions affecting brainstem structures responsible for saccadic generation. Little attention has been given to the accuracy with which clinicians correctly identify saccadic slowing. We compared clinician (n = 19) judgements of horizontal and vertical saccade speed on video recordings of saccades (from 9 patients with slow saccades, 3 healthy controls) to objective saccade peak velocity measurements from infrared oculographic recordings. Clinician groups included neurology residents, general neurologists, and fellowship-trained neuro-ophthalmologists. Saccades with normal peak velocities on infrared recordings were correctly identified as normal in 57% (91/171; 171 = 9 videos × 19 clinicians) of clinician decisions; saccades determined to be slow on infrared recordings were correctly identified as slow in 84% (224/266; 266 = 14 videos × 19 clinicians) of clinician decisions. Vertical saccades were correctly identified as slow more often than horizontal saccades (94% versus 74% of decisions). No significant differences were identified between clinician training levels. Reliable differentiation between normal and slow saccades is clinically challenging; clinical performance is most accurate for detection of vertical saccade slowing. Quantitative analysis of saccade peak velocities enhances accurate detection and is likely to be especially useful for detection of mild saccadic slowing. |
Leslie Guadron; A. John Opstal; Jeroen Goossens Speed-accuracy tradeoffs influence the main sequence of saccadic eye movements Journal Article In: Scientific Reports, vol. 12, pp. 1–14, 2022. @article{Guadron2022, Several studies have proposed that an optimal speed-accuracy tradeoff underlies the stereotyped relationship between amplitude, duration and peak velocity of saccades (main sequence). To test this theory, we asked 8 participants to make saccades to Gaussian-blurred spots and manipulated the task's accuracy constraints by varying target size (1, 3, and 5°). The largest targets indeed yielded more endpoint scatter (and lower gains) than the smallest targets, although this effect subsided with target eccentricity. The main sequence depended on several interacting factors: saccade latency, saccade gain and target size. Early saccades, which were faster than amplitude-matched late saccades, followed the target-size dependency one would expect from a speed-accuracy tradeoff process. They had higher peak velocities and shorter durations for larger targets than for smaller targets. For late saccades, however, the opposite was found. Deviations from the main sequence also covaried with saccade gain, in line with the idea that motor noise underlies part of the endpoint variability. Thus, our data provide partial evidence that the saccadic system weighs the detrimental effects of motor noise on saccade accuracy against movement duration and speed, but other factors also modulate the kinematics. We discuss the possible involvement of parallel saccade pathways to account for our findings. |
Walker S. McKinney; Shannon E. Kelly; Kathryn E. Unruh; Robin L. Shafer; John A. Sweeney; Martin Styner; Matthew W. Mosconi Cerebellar volumes and sensorimotor behavior in autism spectrum disorder Journal Article In: Frontiers in Integrative Neuroscience, vol. 16, pp. 1–16, 2022. @article{McKinney2022, Background: Sensorimotor issues are common in autism spectrum disorder (ASD), though their neural bases are not well understood. The cerebellum is vital to sensorimotor control and reduced cerebellar volumes in ASD have been documented. Our study examined the extent to which cerebellar volumes are associated with multiple sensorimotor behaviors in ASD. Materials and Methods: Fifty-eight participants with ASD and 34 typically developing (TD) controls (8–30 years) completed a structural MRI scan and precision grip testing, oculomotor testing, or both. Force variability during precision gripping as well as absolute error and trial-to-trial error variability of visually guided saccades were examined. Volumes of cerebellar lobules, vermis, and white matter were quantified. The relationships between each cerebellar region of interest (ROI) and force variability, saccade error, and saccade error variability were examined. Results: Relative to TD controls, individuals with ASD showed increased force variability. Individuals with ASD showed a reduced volume of cerebellar vermis VI-VII relative to TD controls. Relative to TD females, females with ASD showed a reduced volume of bilateral cerebellar Crus II/lobule VIIB. Increased volume of Crus I was associated with increased force variability. Increased volume of vermal lobules VI-VII was associated with reduced saccade error for TD controls but not individuals with ASD. Increased right lobule VIII and cerebellar white matter volumes as well as reduced right lobule VI and right lobule X volumes were associated with greater ASD symptom severity. Reduced volumes of right Crus II/lobule VIIB were associated with greater ASD symptom severity in only males, while reduced volumes of right Crus I were associated with more severe restricted and repetitive behaviors only in females. Conclusion: Our finding that increased force variability in ASD is associated with greater cerebellar Crus I volumes indicates that disruption of sensory feedback processing supported by Crus I may contribute to skeletomotor differences in ASD. Results showing that volumes of vermal lobules VI-VII are associated with saccade precision in TD but not ASD implicates atypical organization of the brain systems supporting oculomotor control in ASD. Associations between volumes of cerebellar subregions and ASD symptom severity suggest cerebellar pathological processes may contribute to multiple developmental challenges in ASD. |
Miranda J. Munoz; James L. Reilly; Gian D. Pal; Leo Verhagen Metman; Yessenia M. Rivera; Quentin H. Drane; Daniel M. Corcos; Fabian J. David; Lisa C. Goelz Medication adversely impacts visually-guided eye movements in Parkinson's disease Journal Article In: Clinical Neurophysiology, vol. 143, pp. 145–153, 2022. @article{Munoz2022, Objective: We examined whether previous inconsistent findings about the effect of anti-Parkinsonian medication on visually-guided saccades (VGS) were due to the use of different paradigms, which change the timing of fixation offset and target onset, or different target eccentricities. Methods: Thirty-three participants with Parkinson's disease (PD) completed the VGS tasks OFF and ON medication, along with 13 healthy controls. Performance on 3 paradigms (gap, step, and overlap) and 2 target eccentricities was recorded. We used mixed models to determine the effect of medication, paradigm, and target eccentricity on saccade latency, gain, and peak velocity. Results: First, we confirmed known paradigm effects on latency, and target eccentricity effects on gain and peak velocity in participants with PD. Second, latency was positively associated with OFF medication Movement Disorders Society – Unified Parkinson's Disease Rating Scale (MDS-UPDRS) motor score in PD. Third, medication prolonged latency for the larger target eccentricity across the 3 paradigms, while decreasing gain and peak velocity in the step paradigm across target eccentricities. Conclusions: Medication adversely affected and was not therapeutically beneficial for VGS. Previous inconsistencies may have resulted from chosen target eccentricity. Significance: The negative medication effect on VGS may be clinically significant, as many activities in daily life require oculomotor control, inhibitory control, and visually-guided shifts of attention. |
Ryohei Nakayama; Jean Baptiste Bardin; Ai Koizumi; Isamu Motoyoshi; Kaoru Amano Building a decoder of perceptual decisions from microsaccades and pupil size Journal Article In: Frontiers in Psychology, vol. 13, pp. 1–14, 2022. @article{Nakayama2022, Many studies have reported neural correlates of visual awareness across several brain regions, including the sensory, parietal, and frontal areas. In most of these studies, participants were instructed to explicitly report their perceptual experience through a button press or verbal report. It is conceivable, however, that explicit reporting itself may trigger specific neural responses that can confound the direct examination of the neural correlates of visual awareness. This suggests the need to assess visual awareness without explicit reporting. One way to achieve this is to develop a technique to predict the visual awareness of participants based on their peripheral responses. Here, we used eye movements and pupil sizes to decode trial-by-trial changes in the awareness of a stimulus whose visibility was deteriorated due to adaptation-induced blindness (AIB). In the experiment, participants judged whether they perceived a target stimulus and rated the confidence they had in their perceptual judgment, while their eye movements and pupil sizes were recorded. We found that not only perceptual decision but also perceptual confidence can be separately decoded from the eye movement and pupil size. We discuss the potential of this technique with regard to assessing visual awareness in future neuroimaging experiments. |
Kien Trong Nguyen; Wei-Kuang Liang; Chi-Hung Juan; Chin-An Wang Time-frequency analysis of pupil size modulated by global luminance, arousal, and saccade preparation signals using Hilbert-Huang transform Journal Article In: International Journal of Psychophysiology, vol. 176, pp. 89–99, 2022. @article{Nguyen2022, Pupil size changes constantly and is mainly determined by global luminance signals. In addition, the pupil responds to various cognitive and arousal processes, with larger pupil dilation observed in higher levels of cognitive or arousal processing. Although these task-evoked pupillary responses are extensively used in the pupil research, pupil analysis focusing on the frequency domain, particularly in the context of arousal and cognitive modulations, is less established. Fourier Transform method (FFT) has been used to understand the modulation of task difficulty on pupil oscillations. However, physiological signals are often characterized as non-linear and non-stationary waves, and the conventional spectral analytical method with linearity presumption is less appropriate to reveal modulation dynamics between time and frequency. Here, we used Hilbert-Huang Transform (HHT) to examine the time-frequency modulations on pupil size regulated by arousal, cognitive, and global luminance signals. Consistent with previous research, using FFT, higher spectral densities were obtained with lower luminance background. Moreover, higher spectral densities were found in the high emotional arousal condition. With HHT, we further demonstrated temporal changes on amplitude spectrum and inter-trial phase coherence (ITPC) in each intrinsic mode function (IMF), with stronger amplitudes in higher IMFs (i.e., low frequencies). Moreover, although global luminance, arousal and saccade preparation modulated pupil oscillatory responses, the modulation pattern in different IMFs was different. Together, our results demonstrated dynamics between the time and frequency domain on pupil oscillatory responses, highlighting the importance of examining the time-frequency interactions in the context of various pupil modulations. |
James E. Niemeyer; Seth Akers-Campbell; Aaron Gregoire; Michael A. Paradiso Perceptual enhancement and suppression correlate with V1 neural activity during active sensing Journal Article In: Current Biology, vol. 32, pp. 2654–2667, 2022. @article{Niemeyer2022, Perception in multiple sensory modalities is an active process that involves exploratory behaviors. In humans and other primates, vision results from sensory sampling guided by saccadic eye movements. Saccades are known to modulate visual perception, and a corollary discharge signal associated with saccades appears to establish a sense of visual stability. Neural recordings have shown that saccades also modulate activity widely across the brain. To investigate the neural basis of saccadic effects on perception, simultaneous recordings from multiple neurons in area V1 were made as animals performed a contrast detection task. Perceptual and neural measures were compared when the animal made real saccades that brought a stimulus into V1 receptive fields and when simulated saccades were made (identical retinal stimulation but no eye movement). When real saccades were made and low spatial frequency stimuli were presented, we observed a reduction in both perceptual sensitivity and neural activity compared with simulated saccades; conversely, with higher spatial frequency stimuli, saccades increased visual sensitivity and neural activity. The performance of neural decoders, which used the activity of the population of simultaneously recorded neurons, showed saccade effects on sensitivity that mirrored the frequency-dependent perceptual changes, suggesting that the V1 population activity could support the perceptual effects. A minority of V1 neurons had significant choice probabilities, and the saccades decreased both average choice probability and pairwise noise correlations. Taken together, the findings suggest that a signal related to saccadic eye movements alters V1 spiking to increase the independence of spiking neurons and bias the system toward processing higher spatial frequencies, presumably to enhance object recognition. The effects of saccades on visual perception and noise correlations appear to parallel effects observed in other sensory modalities, suggesting a general principle of active sensory processing. |
Olivia G. Calancie; Donald C. Brien; Jeff Huang; Brian C. Coe; Linda Booij; Sarosh Khalid-Khan; Douglas P. Munoz Maturation of temporal saccade prediction from childhood to adulthood: Predictive saccades, reduced pupil size, and blink synchronization Journal Article In: Journal of Neuroscience, vol. 42, no. 1, pp. 69–80, 2022. @article{Calancie2022, When presented with a periodic stimulus, humans spontaneously adjust their movements from reacting to predicting the timing of its arrival, but little is known about how this sensorimotor adaptation changes across development. To investigate this, we analyzed saccade behavior in 114 healthy humans (ages 6–24 years) performing the visual metronome task, who were instructed to move their eyes in time with a visual target that alternated between two known locations at a fixed rate, and we compared their behavior to per- formance in a random task, where target onsets were randomized across five interstimulus intervals (ISIs) and thus the timing of appearance was unknown. Saccades initiated before registration of the visual target, thus in anticipation of its appearance, were la- beled predictive [saccade reaction time (SRT),90ms] and saccades that were made in reaction to its appearance were labeled reac- tive (SRT.90ms). Eye-tracking behavior including saccadic metrics (e.g., peak velocity, amplitude), pupil size following saccade to target, and blink behavior all varied as a function of predicting or reacting to periodic targets. Compared with reactive saccades, pre- dictive saccades had a lower peak velocity, a hypometric amplitude, smaller pupil size, and a reduced probability of blink occurrence before target appearance. The percentage of predictive and reactive saccades changed inversely from ages 8–16, at which they reached adult-levels of behavior. Differences in predictive saccades for fast and slow target rates are interpreted by differential maturation of cerebellar-thalamic-striatal pathways. |
Amy Chow; Rajkumar Nallour Raveendran; Ian Erkelens; Raiju Babu; Benjamin Thompson Increased saccadic latency in Amblyopia: Oculomotor and attentional factors Journal Article In: Vision Research, vol. 197, pp. 1–11, 2022. @article{Chow2022, Amblyopia is a neurodevelopmental disorder of vision that arises from disrupted binocular vision during early childhood. Delayed initiation of saccadic eye movements is an established feature of amblyopia. The present study investigated whether oculomotor and/or attentional factors contribute to increased amblyopic eye saccadic latencies. Participants with normal vision (n = 10) and amblyopia (n = 10; 4 anisometropia, 6 strabismic/mixed) performed visually-guided saccades to targets presented via a mirror haploscope. Eye movements were recorded for both eyes even under monocular viewing conditions. In Experiment 1, we measured the latency, amplitude gain and peak velocity of saccades as targets were presented binocularly, or monocularly. Saccadic latencies were significantly longer for both eyes when targets were presented to only the amblyopic eye compared to all other conditions. Saccade gain and main sequence rate constants were similar across groups for all viewing conditions. In Experiment 2, we tested the hypothesis that shifts of overt attention may be deficient when viewing with the amblyopic eye. We presented the fixation target to one eye and the subsequent peripheral target (saccadic error signal) to the other eye. Shifting saccadic targets between the eyes expedited saccadic latencies irrespective of which eye viewed the target in the amblyopia group. These findings indicate that oculomotor factors related to saccade generation are unlikely to be responsible for amblyopic eye saccadic latency delays. We propose that an impairment in the ability to disengage attention from a fixation target and orient to a peripheral target when both targets are seen by the amblyopic eye may contribute to increased saccadic latency. |
Alessio D'Aquino; Cornelia Frank; John Elvis Hagan; Thomas Schack Imagining interceptions: Eye movements as an online indicator of covert motor processes during motor imagery Journal Article In: Frontiers in Neuroscience, vol. 16, pp. 1–15, 2022. @article{DAquino2022, The analysis of eye movements during motor imagery has been used to understand the influence of covert motor processes on visual-perceptual activity. There is evidence showing that gaze metrics seem to be affected by motor planning often dependent on the spatial and temporal characteristics of a task. However, previous research has focused on simulated actions toward static targets with limited empirical evidence of how eye movements change in more dynamic environments. The study examined the characteristics of eye movements during motor imagery for an interception task. Twenty-four participants were asked to track a moving target over a computer display and either mentally simulate an interception or rest. The results showed that smooth pursuit variables, such as duration and gain, were lower during motor imagery when compared to passive observation. These findings indicate that motor plans integrate visual-perceptual information based on task demands and that eye movements during imagery reflect such constraint. |
Bertrand Degos; Pierre Pouget; Marcus Missal From anticipation to impulsivity in Parkinson's disease Journal Article In: npj Parkinson's Disease, vol. 8, pp. 1–12, 2022. @article{Degos2022, Anticipatory actions require to keep track of elapsed time and inhibitory control. These cognitive functions could be impacted in Parkinson's disease (iPD). To test this hypothesis, a saccadic reaction time task was used where a visual warning stimulus (WS) predicted the occurrence of an imperative one (IS) appearing after a short delay. In the implicit condition, subjects were not informed about the duration of the delay, disfavoring anticipatory behavior but leaving inhibitory control unaltered. In the explicit condition, delay duration was cued. This should favor anticipatory behavior and perhaps alter inhibitory control. This hypothesis was tested in controls (N = 18) and age-matched iPD patients (N = 20; ON and OFF L-DOPA). We found that the latency distribution of saccades before the IS was bimodal. The 1st mode weakly depended on temporal information and was more prominent in iPD. Saccades in this mode were premature and could result of a lack of inhibition. The 2nd mode covaried with cued duration suggesting that these movements were genuine anticipatory saccades. The explicit condition increased the probability of anticipatory saccades before the IS in controls and iPDON but not iPDOFF patients. Furthermore, in iPD patients the probability of sequences of 1st mode premature responses increased. In conclusion, the triggering of a premature saccade or the initiation of a controlled anticipatory one could be conceptualized as the output of two independent stochastic processes. Altered time perception and increased motor impulsivity could alter the balance between these two processes in favor of the latter in iPD, particularly OFF L-Dopa. |
Dominika Drcażyk; Marcus Missal The oculomotor signature of expected surprise Journal Article In: Scientific Reports, vol. 12, no. 1, pp. 1–14, 2022. @article{Dra̧zyk2022, Expected surprise, defined as the anticipation of uncertainty associated with the occurrence of a future event, plays a major role in gaze shifting and spatial attention. In the present study, we analyzed its impact on oculomotor behavior. We hypothesized that the occurrence of anticipatory saccades could decrease with increasing expected surprise and that its influence on visually-guided responses could be different given the presence of sensory information and perhaps competitive attentional effects. This hypothesis was tested in humans using a saccadic reaction time task in which a cue indicated the future stimulus position. In the ‘no expected surprise' condition, the visual target could appear only at one previously cued location. In other conditions, more likely future positions were cued with increasing expected surprise. Anticipation was more frequent and pupil size was larger in the ‘no expected surprise' condition compared with all other conditions, probably due to increased arousal. The latency of visually-guided saccades increased linearly with the logarithm of surprise (following Hick's law) but their maximum velocity repeated the arousal-related pattern. Therefore, expected surprise affects anticipatory and visually-guided responses differently. Moreover, these observations suggest a causal chain linking surprise, attention and saccades that could be disrupted in attentional or impulse control disorders. |
Matt J. Dunn; J. Margaret Woodhouse Voluntary flutter presenting during ophthalmoscopy: A case report Journal Article In: Case Reports in Ophthalmology, pp. 286–291, 2022. @article{Dunn2022a, Voluntary flutter (sometimes known as “voluntary nystagmus”) is a conjugate saccadic oscillation of the eyes that occurs in some healthy individuals. It has no relation to pathological nystagmus, which can manifest in infancy or become acquired later in life. This report presents an unusual case of voluntary flutter that presented in a 20-year-old male with autism spectrum disorder during ocular examination via direct ophthalmoscopy. Refraction and ocular motor balance were normal, and visual acuity was good in each eye (−0.10 logMAR). During direct ophthalmoscopy, a fine intermittent tremor was initiated. The patient was referred for further assessment, and eye movements were recorded at 1,000 Hz with an EyeLink 1000 eye tracker. Upon request, the patient could manifest voluntary flutter again and sustain the eye movements with effort during convergence. The voluntary flutter consisted of back-to-back saccadic oscillations in a predominantly horizontal direction, with an average frequency of 13 Hz and an amplitude of ∼8°, both reducing over time. We speculate that the discomfort induced by the proximity of the clinician during direct ophthalmoscopy examination may have triggered the eye oscillations. Although the oscillations typically manifest during convergence, atypical forms of voluntary flutter can also occur during divergence. Voluntary flutter can be a useful differential diagnosis in patients with a recently onset apparent “nystagmus,” and no other neurological signs and symptoms. |
Soon Young Park; Kenneth Holmqvist; Diederick C. Niehorster; Ludwig Huber; Zsófia Virányi How to improve data quality in dog eye tracking Journal Article In: Behavior Research Methods, pp. 1–24, 2022. @article{Park2022a, Pupil–corneal reflection (P–CR) eye tracking has gained a prominent role in studying dog visual cognition, despite methodological challenges that often lead to lower-quality data than when recording from humans. In the current study, we investigated if and how the morphology of dogs might interfere with tracking of P–CR systems, and to what extent such interference, possibly in combination with dog-unique eye-movement characteristics, may undermine data quality and affect eye-movement classification when processed through algorithms. For this aim, we have conducted an eye-tracking experiment with dogs and humans, and investigated incidences of tracking interference, compared how they blinked, and examined how differential quality of dog and human data affected the detection and classification of eye-movement events. Our results show that the morphology of dogs' face and eye can interfere with tracking methods of the systems, and dogs blink less often but their blinks are longer. Importantly, the lower quality of dog data lead to larger differences in how two different event detection algorithms classified fixations, indicating that the results of key dependent variables are more susceptible to choice of algorithm in dog than human data. Further, two measures of the Nyström & Holmqvist (Behavior Research Methods, 42(4), 188–204, 2010) algorithm showed that dog fixations are less stable and dog data have more trials with extreme levels of noise. Our findings call for analyses better adjusted to the characteristics of dog eye-tracking data, and our recommendations help future dog eye-tracking studies acquire quality data to enable robust comparisons of visual cognition between dogs and humans. |
Suhyun Park; Louis Wiliams; Rebecca Chamberlain Global saccadic eye movements characterise artists' visual ttention while drawing Journal Article In: Empirical Studies of the Arts, vol. 40, no. 2, pp. 228–244, 2022. @article{Park2022b, Previous research has shown that artists employ flexible attentional strategies during offline perceptual tasks. The current study explored visual processing online, by tracking the eye movements of artists and non-artists (n=65) while they produced representational drawings of photographic stimuli. The findings revealed that it is possible to differentiate artists from non-artists on the basis of the relative amount of global-to-local saccadic eye movements they make when looking at the target stimulus while drawing, but not in a preparatory free viewing phase. Results indicated that these differences in eye movements are not specifically related to representational drawing ability, and may be a feature of artistic ability more broadly. This eye movement analysis technique may be used in future research to characterise the dynamics of attentional shifts in eye movements while artists are carrying out a range of artistic tasks. |
Christina U. Pfeuffer; Andrea Kiesel; Lynn Huestegge Similar proactive effect monitoring in free and forced choice action modes Journal Article In: Psychological Research, pp. 1–16, 2022. @article{Pfeuffer2022, When our actions yield predictable consequences in the environment, our eyes often already saccade towards the locations we expect these consequences to appear at. Such spontaneous anticipatory saccades occur based on bi-directional associations between action and effect formed by prior experience. That is, our eye movements are guided by expectations derived from prior learning history. Anticipatory saccades presumably reflect a proactive effect monitoring process that prepares a later comparison of expected and actual effect. Here, we examined whether anticipatory saccades emerged under forced choice conditions when only actions but not target stimuli were predictive of future effects and whether action mode (forced choice vs. free choice, i.e., stimulus-based vs. stimulus-independent choice) affected proactive effect monitoring. Participants produced predictable visual effects on the left/right side via forced choice and free choice left/right key presses. Action and visual effect were spatially compatible in one half of the experiment and spatially incompatible in the other half. Irrespective of whether effects were predicted by target stimuli in addition to participants' actions, in both action modes, we observed anticipatory saccades towards the location of future effects. Importantly, neither the frequency, nor latency or amplitude of these anticipatory saccades significantly differed between forced choice and free choice action modes. Overall, our findings suggest that proactive effect monitoring of future action consequences, as reflected in anticipatory saccades, is comparable between forced choice and free choice action modes. |
Mattia Pietrelli; Jason Samaha; Bradley R. Postle Spectral distribution dynamics across different attentional priority states Journal Article In: Journal of Neuroscience, vol. 42, no. 19, pp. 4026–4041, 2022. @article{Pietrelli2022, Anticipatory covert spatial attention improves performance on tests of visual detection and discrimination, and shifts are accompanied by decreases and increases of a band power at electroencephalography (EEG) electrodes corresponding to the attended and unattended location, respectively. Although the increase at the unattended location is often interpreted as an active mechanism (e.g., inhibiting processing at the unattended location), most experiments cannot rule out the alternative possibility that it is a secondary consequence of selection elsewhere. To adjudicate between these accounts, we designed a Posner- style visual cueing task in which male and female human participants made orientation judgments of targets appearing at one of four locations: up, down, right, or left. Critically, trials were blocked such that within a block the locations along one meridian alternated in status between attended and unattended, and targets never appeared at the other two, making them irrelevant. Analyses of the concurrently measured EEG signal were conducted on “traditional” narrowband a (8–14 Hz), as well as on two components resulting from the decomposition of this signal: “periodic” a;and the slope of the aperiodic 1/f-like component. Although data from right-left blocks replicated the familiar pattern of lateralized asymmetry in narrowband a power, with neither a signal couldwe findevidence for any difference inthe time course at unattended versus irrelevant locations, an outcome consistent with the secondary-consequence interpretation of attention- related dynamics in the a band. Additionally, 1/f slope was shallower at attended and unattended locations, relative to irrelevant, suggesting a tonic adjustment of physiological state. |
Alessandro Piras; Aurelio Trofè; Andrea Meoni; Milena Raffi Influence of radial optic flow stimulation on static postural balance in Parkinson's disease: A preliminary study Journal Article In: Human Movement Science, vol. 81, pp. 1–11, 2022. @article{Piras2022, The role of optic flow in the control of balance in persons with Parkinson's disease (PD) has yet to be studied. Since basal ganglia are understood to have a role in controlling ocular fixation, we have hypothesized that persons with PD would exhibit impaired performance in fixation tasks, i.e., altered postural balance due to the possible relationships between postural disorders and visual perception. The aim of this preliminary study was to investigate how people affected by PD respond to optic flow stimuli presented with radial expanding motion, with the intention to see how the stimulation of different retinal portions may alter the static postural sway. We measured the body sway using center of pressure parameters recorded from two force platforms during the presentation of the foveal, peripheral and full field radial optic flow stimuli. Persons with PD had different visual responses in terms of fixational eye movement characteristics, with greater postural alteration in the sway area and in the medio-lateral direction than the age-matched control group. Balance impairment in the medio-lateral oscillation is often observed in persons with atypical Parkinsonism, but not in Parkinson's disease. Persons with PD are more dependent on visual feedback with respect to age-matched control subjects, and this could be due to their impaired peripheral kinesthetic feedback. Visual stimulation of standing posture would provide reliable signs in the differential diagnosis of Parkinsonism. |
Milena Raffi; Aurelio Trofè; Andrea Meoni; Luca Gallelli; Alessandro Piras Optic flow speed and retinal stimulation influence microsaccades Journal Article In: International Journal of Environmental Research and Public Health, vol. 19, pp. 1–10, 2022. @article{Raffi2022, Microsaccades are linked with extraretinal mechanisms that significantly alter spatial perception before the onset of eye movements. We sought to investigate whether microsaccadic activity is modulated by the speed of radial optic flow stimuli. Experiments were performed in the dark on 19 subjects who stood in front of a screen covering 135 × 107◦ of the visual field. Subjects were instructed to fixate on a central fixation point while optic flow stimuli were presented in full field, in the foveal, and in the peripheral visual field at different dot speeds (8, 11, 14, 17, and 20◦/s). Fixation in the dark was used as a control stimulus. For almost all tested speeds, the stimulation of the peripheral retina evoked the highest microsaccade rate. We also found combined effects of optic flow speed and the stimulated retinal region (foveal, peripheral, and full field) for microsaccade latency. These results show that optic flow speed modulates microsaccadic activity when presented in specific retinal portions, suggesting that eye movement generation is strictly dependent on the stimulated retinal regions. |
Hamidreza Ramezanpour; Shawn Blizzard; Devin Heinze Kehoe; Mazyar Fallah Oculomotor system can differentially process red and green colors during saccade programming in the presence of a competing distractor Journal Article In: Experimental Brain Research, vol. 240, no. 11, pp. 2847–2860, 2022. @article{Ramezanpour2022, Selective attention filters irrelevant information entering our brain to allow for fine-tuning of the relevant information processing. In the visual domain, shifts of attention are most often followed by a saccadic eye movement to objects and places of high relevance. Recent studies have shown that the stimulus color can affect saccade target selection and saccade trajectories. While those saccade modulations are based on perceptual color space, the level in the visual processing hierarchy at which color selection biases saccade programming remains unclear. As color has also been shown to influence manual response inhibition which is a key function of the prefrontal cortex, we hypothesized that the effects of color on executive functions would also inherently affect saccade programming. To test this hypothesis, we measured behavioral performance and saccade metrics during a modified saccadic Stroop task which reflects competition between color words (“RED” and “GREEN”) and their color at the level of the prefrontal cortex. Our results revealed that the oculomotor system can differentially process red and green colors when planning a saccade in the presence of a competing distractor. |
Lukas Recker; Rebecca M. Foerster; Werner X. Schneider; Christian H. Poth In: PLoS ONE, vol. 17, pp. 1–19, 2022. @article{Recker2022, The Trail-Making-Test (TMT) is one of the most widely used neuropsychological tests for assessing executive functions, the brain functions underlying cognitively controlled thought and action. Obtaining a number of test scores at once, the TMT allows to characterize an assortment of executive functions efficiently. Critically, however, as most test scores are derived from test completion times, the scores only provide a summary measure of various cognitive control processes. To address this problem, we extended the TMT in two ways. First, using a computerized eye-tracking version of the TMT, we added specific eye movement measures that deliver a richer set of data with a higher degree of cognitive process specificity. Second, we included an experimental manipulation of a fundamental executive function, namely participants' ability to emphasize speed or accuracy in task performance. Our study of healthy participants showed that eye movement measures differed between TMT conditions that are usually compared to assess the cognitive control process of alternating between task sets for action control. This demonstrates that eye movement measures are indeed sensitive to executive functions implicated in the TMT. Crucially, comparing performance under cognitive control sets of speed vs. accuracy emphasis revealed which test scores primarily varied due to this manipulation (e.g., trial duration, number of fixations), and which were still more sensitive to other differences between individuals (e.g., fixation duration, saccade amplitude). This provided an experimental construct validation of the test scores by distinguishing scores primarily reflecting the executive function of emphasizing speed vs. accuracy and those independent from it. In sum, both the inclusion of eye movement measures and of the experimental manipulation of executive functions in the TMT enabled a more specific interpretation of the TMT in terms of cognitive functions and mechanisms, which offers more precise diagnoses in clinical applications and basic research. |
Oded Rock; Andrea Albonico; Farnaz Javadian; Mohammad Ashkanani; Alisdair J. G. Taylor; Michael Dreyer; Jason J. S. Barton Oblique saccades in internuclear ophthalmoplegia Journal Article In: Experimental Brain Research, vol. 240, no. 3, pp. 861–869, 2022. @article{Rock2022, Purpose: Oblique saccades often display component stretching, in which the shorter vector in one cardinal direction is slowed so that its duration matches that of the longer vector in the orthogonal direction, resulting in a straighter trajectory. In internuclear ophthalmoplegia, adducting saccades are typically slowed while vertical saccades are unaffected. It is not known whether these slowed adducting movements are accompanied by adaptive component stretching of the vertical vector during oblique saccades. This was a cross-sectional study. We recorded the saccadic eye movement in 5 patients with right or bilateral internuclear ophthalmoplegia from multiple sclerosis and 17 healthy controls, using an EyeLink 1000 machine. The target stimulus was located at varying angles (0–360) and amplitudes (4, 8, 12 degrees). For each saccade we have calculated the curvature index as the main outcome measure, which is the area between the actual and ideal straight trajectory for oblique saccadic eye movements, divided by the square of the length of the straight trajectory, to give a unit-less metric for curvature. In the 17 control subjects, curvature showed a strong positive correlation between adducting saccades and the yoked abducting saccades of the other eye. In internuclear ophthalmoplegia, adducting saccades showed a strong curvature concave to the horizontal meridian, indicating inadequate component stretching, while abducting saccades did not differ from controls. This new sign of oblique saccadic curvature in internuclear ophthalmoplegia indicates a limitation of the range of central adaptive changes in response to distal lesions affecting transmission of the saccadic command. |
Shannon Ross-Sheehy; Bret Eschman; Esther E. Reynolds Seeing and looking: Evidence for developmental and stimulus-dependent changes in infant scanning efficiency Journal Article In: PLoS ONE, vol. 17, no. 9, pp. 1–24, 2022. @article{RossSheehy2022, Though previous work has examined infant attention across a variety of tasks, less is known about the individual saccades and fixations that make up each bout of attention, and how individual differences in saccade and fixation patterns (i.e., scanning efficiency) change with development, scene content and perceptual load. To address this, infants between the ages of 5 and 11 months were assessed longitudinally (Experiment 1) and cross-sectionally (Experiment 2). Scanning efficiency (fixation duration, saccade rate, saccade amplitude, and saccade velocity) was assessed while infants viewed six quasi-naturalistic scenes that varied in content (social or non-social) and scene complexity (3, 6 or 9 people/objects). Results from Experiment 1 revealed moderate to strong stability of individual differences in saccade rate, mean fixation duration, and saccade amplitude, and both experiments revealed 5-month-old infants to make larger, faster, and more frequent saccades than older infants. Scanning efficiency was assessed as the relation between fixation duration and saccade amplitude, and results revealed 11-month-olds to have high scanning efficiency across all scenes. However, scanning efficiency also varied with scene content, such that all infants showing higher scanning efficiency when viewing social scenes, and more complex scenes. These results suggest both developmental and stimulus-dependent changes in scanning efficiency, and further highlight the use of saccade and fixation metrics as a sensitive indicator of cognitive processing. |
Jingqi Jiang; Yiqin Zhu; Marcus A. Rodriguez; Xu Wen; Mingyi Qian Social anxiety does not impair attention inhibition: An emotion anti-saccade task Journal Article In: Journal of Behavior Therapy and Experimental Psychiatry, vol. 77, pp. 1–7, 2022. @article{Jiang2022, Background and objectives: Attention avoidance and attention vigilance are two typical attentional biases in individuals with social anxiety disorder (SAD). Attention inhibition is a type of attention control, which may be the key factor affecting attention vigilance and attention avoidance. However, previous studies have not examined the difference between the attention inhibition in individuals with SAD and healthy controls. Methods: To further explore this question, the current study used the single anti-saccade task with emotional facial stimuli to assess attention inhibition in 27 individuals with SAD and 22 healthy controls. Results: Regardless of the emotional valence of the facial stimuli, error rates in the social anxiety group were lower than that of the healthy control group, but there was no significant group difference in the saccade latency. Limitations: This research only examined the attentional inhibition process highly related to attention avoidance and attention vigilance. Future research may benefit from adopting different research paradigms for more robust and generalizable conclusions. Conclusions: Results suggest that individuals with SAD have better attention inhibition abilities than healthy control. Such enhanced attention inhibition may underlie their avoidance of threatening social cues. |
Martin E. Johansson; Ian G. M. Cameron; Nicolien M. Van der Kolk; Nienke M. Vries; Eva Klimars; Ivan Toni; Bastiaan R. Bloem; Rick C. Helmich Aerobic exercise alters brain function and structure in Parkinson's disease: A randomized controlled trial Journal Article In: Annals of Neurology, vol. 91, pp. 203–216, 2022. @article{Johansson2022, Objective: Randomized clinical trials have shown that aerobic exercise attenuates motor symptom progression in Parkinson's disease, but the underlying neural mechanisms are unclear. Here, we investigated how aerobic exercise influences disease-related functional and structural changes in the corticostriatal sensorimotor network, which is involved in the emergence of motor deficits in Parkinson's disease. Additionally, we explored effects of aerobic exercise on tissue integrity of the substantia nigra, and on behavioral and cerebral indices of cognitive control. Methods: The Park-in-Shape trial is a single-center, double-blind randomized controlled trial in 130 Parkinson's disease patients who were randomly assigned (1:1 ratio) to aerobic exercise (stationary home trainer) or stretching (active control) interventions (duration = 6 months). An unselected subset from this trial (exercise |
Holly Joseph; Daisy Powell Does a specialist typeface affect how fluently children with and without dyslexia process letters, words, and passages? Journal Article In: Dyslexia, vol. 28, no. 4, pp. 448–470, 2022. @article{Joseph2022, Children with dyslexia are at risk of poor academic attainment and lower life chances if they do not receive the support they need. Alongside phonics-based interventions which already have a strong evidence base, specialist dyslexia typefaces have been offered as an additional or alternative form of support. The current study examined whether one such typeface, Dyslexie, had a benefit over a standard typeface in identifying letters, reading words, and reading passages. 71 children, aged 8–12 years, 37 of whom had a diagnosis of dyslexia, completed a rapid letter naming task, a word reading efficiency task, and a passage reading task in two typefaces, Dyslexie and Calibri. Spacing between letters and words was kept constant. Results showed no differences in word or passage reading between the two typesfaces, but letter naming did appear to be more fluent when letters were presented in Dyslexie rather than Calibri text for all children. The results suggest that a typeface in which letters are designed to be distinctive from one another may be beneficial for letter identification and that an intervention in which children are taught letters in a specialist typeface is worthy of consideration. |