EyeLink EEG / fNIRS / TMS Publications
All EyeLink EEG, fNIRS, and TMS research publications (with concurrent eye tracking) up until 2023 (with early 2024s) are listed below by year. You can search the publications using keywords such as P300, Gamma band, NIRS, etc. You can also search for individual author names. If we missed any EyeLink EEG, fNIRS, or TMS articles, please email us!
2019 |
Louisa Kulke Neural mechanisms of overt attention shifts to emotional faces Journal Article In: Neuroscience, vol. 418, pp. 59–68, 2019. @article{Kulke2019, Emotional faces draw attention and eye-movements towards them. However, the neural mechanisms of attention have mainly been investigated during fixation, which is uncommon in everyday life where people move their eyes to shift attention to faces. Therefore, the current study combined eye-tracking and Electroencephalography (EEG) to measure neural mechanisms of overt attention shifts to faces with happy, neutral and angry expressions, allowing participants to move their eyes freely towards the stimuli. Saccade latencies towards peripheral faces did not differ depending on expression and early neural response (P1) amplitudes and latencies were unaffected. However, the later occurring Early Posterior Negativity (EPN) was significantly larger for emotional than for neutral faces. This response appears after saccades towards the faces. Therefore, emotion modulations only occurred after an overt shift of gaze towards the stimulus had already been completed. Visual saliency rather than emotional content may therefore drive early saccades, while later top-down processes reflect emotion processing. |
Otto Loberg; Jarkko Hautala; Jarmo A. Hämäläinen; Paavo H. T. Leppänen Influence of reading skill and word length on fixation-related brain activity in school-aged children during natural reading Journal Article In: Vision Research, vol. 165, pp. 109–122, 2019. @article{Loberg2019, Word length is one of the main determinants of eye movements during reading and has been shown to influence slow readers more strongly than typical readers. The influence of word length on reading in individuals with different reading skill levels has been shown in separate eye-tracking and electroencephalography studies. However, the influence of reading difficulty on cortical correlates of word length effect during natural reading is unknown. To investigate how reading skill is related to brain activity during natural reading, we performed an exploratory analysis on our data set from a previous study, where slow reading (N = 27) and typically reading (N = 65) 12-to-13.5-year-old children read sentences while co-registered ET-EEG was recorded. We extracted fixation-related potentials (FRPs) from the sentences using the linear deconvolution approach. We examined standard eye-movement variables and deconvoluted FRP estimates: intercept of the response, categorical effect of first fixation versus additional fixation and continuous effect of word length. We replicated the pattern of stronger word length effect in eye movements for slow readers. We found a difference between typical readers and slow readers in the FRP intercept, which contains activity that is common to all fixations, within a fixation time-window of 50–300 ms. For both groups, the word length effect was present in brain activity during additional fixations; however, this effect was not different between groups. This suggests that stronger word length effect in the eye movements of slow readers might be mainly due re-fixations, which are more probable due to the lower efficiency of visual processing. |
Mary H. MacLean; Tom Bullock; Barry Giesbrecht Dual process coding of recalled locations in human oscillatory brain activity Journal Article In: Journal of Neuroscience, vol. 39, no. 34, pp. 6737–6750, 2019. @article{MacLean2019, A mental representation of the location of an object can be constructed using sensory information selected from the environment and information stored internally. Human electrophysiological evidence indicates that behaviorally relevant locations, regardless of the source of sensory information, are represented in alpha-band oscillations suggesting a shared process. Here, we present evidence from human subjects of either sex for two distinct alpha-band-based processes that separately support the representation of location, exploiting sensory evidence sampled either externally or internally. |
Sarah D. McCrackin; Roxane J. Itier Perceived gaze direction differentially affects discrimination of facial emotion, attention, and gender - An ERP study Journal Article In: Frontiers in Neuroscience, vol. 13, pp. 517, 2019. @article{McCrackin2019, The perception of eye-gaze is thought to be a key component of our everyday social interactions. While the neural correlates of direct and averted gaze processing have been investigated, there is little consensus about how these gaze directions may be processed differently as a function of the task being performed. In a within-subject design, we examined how perception of direct and averted gaze affected performance on tasks requiring participants to use directly available facial cues to infer the individuals' emotional state (emotion discrimination), direction of attention (attention discrimination) and gender (gender discrimination). Neural activity was recorded throughout the three tasks using EEG, and ERPs time-locked to face onset were analyzed. Participants were most accurate at discriminating emotions with direct gaze faces, but most accurate at discriminating attention with averted gaze faces, while gender discrimination was not affected by gaze direction. At the neural level, direct and averted gaze elicited different patterns of activation depending on the task over frontal sites, from approximately 220-290 ms. More positive amplitudes were seen for direct than averted gaze in the emotion discrimination task. In contrast, more positive amplitudes were seen for averted gaze than for direct gaze in the gender discrimination task. These findings are among the first direct evidence that perceived gaze direction modulates neural activity differently depending on task demands, and that at the behavioral level, specific gaze directions functionally overlap with emotion and attention discrimination, precursors to more elaborated theory of mind processes. |
Erik L. Meijs; Pim Mostert; Heleen A. Slagter; Floris P. Lange; Simon Gaal Exploring the role of expectations and stimulus relevance on stimulus-specific neural representations and conscious report Journal Article In: Neuroscience of Consciousness, vol. 5, no. 1, pp. 1–12, 2019. @article{Meijs2019, Subjective experience can be influenced by top-down factors, such as expectations and stimulus relevance. Recently, it has been shown that expectations can enhance the likelihood that a stimulus is consciously reported, but the neural mechanisms supporting this enhancement are still unclear. We manipulated stimulus expectations within the attentional blink (AB) paradigm using letters and combined visual psychophysics with magnetoencephalographic (MEG) recordings to investigate whether prior expectations may enhance conscious access by sharpening stimulus-specific neural representations. We further explored how stimulus-specific neural activity patterns are affected by the factors expectation, stimulus relevance and conscious report. First, we show that valid expectations about the identity of an upcoming stimulus increase the likelihood that it is consciously reported. Second, using a series of multivariate decoding analyses, we show that the identity of letters presented in and out of the AB can be reliably decoded from MEG data. Third, we show that early sensory stimulus-specific neural representations are similar for reported and missed target letters in the AB task (active report required) and an oddball task in which the letter was clearly presented but its identity was task-irrelevant. However, later sustained and stable stimulus-specific representations were uniquely observed when target letters were consciously reported (decision-dependent signal). Fourth, we show that global pre-stimulus neural activity biased perceptual decisions for a ‘seen' response. Fifth and last, no evidence was obtained for the sharpening of sensory representations by top-down expectations. We discuss these findings in light of emerging models of perception and conscious report highlighting the role of expectations and stimulus relevance. |
Davide Paoletti; Christoph Braun; Elisabeth Julie Vargo; Wieske Zoest Spontaneous pre-stimulus oscillatory activity shapes the way we look: A concurrent imaging and eye-movement study Journal Article In: European Journal of Neuroscience, vol. 49, pp. 137–149, 2019. @article{Paoletti2019, Previous behavioural studies have accrued evidence that response time plays a critical role in determining whether selection is influenced by stimulus saliency or target template. In the present work, we investigated to what extent the variations in timing and consequent oculomotor controls are influenced by spontaneous variations in pre-stimulus alpha oscillations. We recorded simultaneously brain activity using magnetoencephalography (MEG) and eye movements while participants performed a visual search task. Our results show that slower saccadic reaction times were predicted by an overall stronger alpha power in the 500 ms time window preceding the stimulus onset, while weaker alpha power was a signature of faster responses. When looking separately at performance for fast and slow responses, we found evidence for two specific sources of alpha activity predicting correct versus incorrect responses. When saccades were quickly elicited, errors were predicted by stronger alpha activity in posterior areas, comprising the angular gyrus in the temporal-parietal junction (TPJ) and possibly the lateral intraparietal area (LIP). Instead, when participants were slower in responding, an increase of alpha power in frontal eye fields (FEF), supplementary eye fields (SEF) and dorsolateral pre-frontal cortex (DLPFC) predicted erroneous saccades. In other words, oculomotor accuracy in fast responses was predicted by alpha power differences in more posterior areas, while the accuracy in slow responses was predicted by alpha power differences in frontal areas, in line with the idea that these areas may be differentially related to stimulus-driven and goal-driven control of selection. |
Nuno Alexandre De Sá Teixeira; Gianfranco Bosco; Sergio Delle Monache; Francesco Lacquaniti In: Experimental Brain Research, vol. 237, no. 12, pp. 3375–3390, 2019. @article{DeSaTeixeira2019, The perceived vanishing location of a moving target is systematically displaced forward, in the direction of motion—representational momentum—, and downward, in the direction of gravity—representational gravity. Despite a wealth of research on the factors that modulate these phenomena, little is known regarding their neurophysiological substrates. The present experiment aims to explore which role is played by cortical areas hMT/V5+, linked to the processing of visual motion, and TPJ, thought to support the functioning of an internal model of gravity, in modulating both effects. Participants were required to perform a standard spatial localization task while the activity of the right hMT/V5+ or TPJ sites was selectively disrupted with an offline continuous theta-burst stimulation (cTBS) protocol, interspersed with control blocks with no stimulation. Eye movements were recorded during all spatial localizations. Results revealed an increase in representational gravity contingent on the disruption of the activity of hMT/V5+ and, conversely, some evidence suggested a bigger representational momentum when TPJ was stimulated. Furthermore, stimulation of hMT/V5+ led to a decreased ocular overshoot and to a time-dependent downward drift of gaze location. These outcomes suggest that a reciprocal balance between perceived kinematics and anticipated dynamics might modulate these spatial localization responses, compatible with a push–pull mechanism. |
Ya Li; Yonghui Wang; Sheng Li Recurrent processing of contour integration in the human visual cortex as revealed by fMRI-guided TMS Journal Article In: Cerebral Cortex, vol. 29, no. 1, pp. 17–26, 2019. @article{Li2019i, Contour integration is a critical step in visual perception because it groups discretely local elements into perceptually global contours. Previous investigations have suggested that striate and extrastriate visual areas are involved in this mid-level processing of visual perception. However, the temporal dynamics of these areas in the human brain during contour integration is less understood. The present study used functional magnetic resonance imaging-guided transcranial magnetic stimulation (TMS) to briefly disrupt 1 of 2 visual areas (V1/V2 and V3B) and examined the causal contributions of these areas to contour detection. The results demonstrated that the earliest critical time window at which behavioral detection performance was impaired by TMS pluses differed between V1/V2 and V3B. The first critical window of V3B (90-110 ms after stimulus onset) was earlier than that of V1/V2 (120-140 ms after stimulus onset), thus indicating that feedback connection from higher to lower area was necessary for complete contour integration. These results suggested that the fine processing of contour-related information in V1/V2 follows the generation of a coarse template in the higher visual areas, such as V3B. Our findings provide direct causal evidence that a recurrent mechanism is necessary for the integration of contours from cluttered background in the human brain. |
Marine Vernet; Chloé Stengel; Romain Quentin; Julià L. Amengual; Antoni Valero-Cabré Entrainment of local synchrony reveals a causal role for high-beta right frontal oscillations in human visual consciousness Journal Article In: Scientific Reports, vol. 9, pp. 14510, 2019. @article{Vernet2019, Prior evidence supports a critical role of oscillatory activity in visual cognition, but are cerebral oscillations simply correlated or causally linked to our ability to consciously acknowledge the presence of a target in our visual field? Here, EEG signals were recorded on humans performing a visual detection task, while they received brief patterns of rhythmic or random transcranial magnetic stimulation (TMS) delivered to the right Frontal Eye Field (FEF) prior to the onset of a lateralized target. TMS entrained oscillations, i.e., increased high-beta power and phase alignment (the latter to a higher extent for rhythmic high-beta patterns than random patterns) while also boosting visual detection sensitivity. Considering post-hoc only those participants in which rhythmic stimulation enhanced visual detection, the magnitude of high-beta entrainment correlated with left visual performance increases. Our study provides evidence in favor of a causal link between high-beta oscillatory activity in the Frontal Eye Field and visual detection. Furthermore, it supports future applications of brain stimulation to manipulate local synchrony and improve or restore impaired visual behaviors. |
Sebastian Michelmann; Bernhard P. Staresina; Howard Bowman; Simon Hanslmayr Speed of time-compressed forward replay flexibly changes in human episodic memory Journal Article In: Nature Human Behaviour, vol. 3, no. 2, pp. 143–154, 2019. @article{Michelmann2019, Remembering information from continuous past episodes is a complex task 1 . On the one hand, we must be able to recall events in a highly accurate way, often including exact timings. On the other hand, we can ignore irrelevant details and skip to events of interest. Here, we track continuous episodes consisting of different subevents as they are recalled from memory. In behavioural and magnetoencephalography data, we show that memory replay is temporally compressed and proceeds in a forward direction. Neural replay is characterized by the reinstatement of temporal patterns from encoding 2,3 . These fragments of activity reappear on a compressed timescale. Herein, the replay of subevents takes longer than the transition from one subevent to another. This identifies episodic memory replay as a dynamic process in which participants replay fragments of fine-grained temporal patterns and are able to skip flexibly across subevents. |
Jana Annina Müller; Dorothea Wendt; Birger Kollmeier; Stefan Debener; Thomas Brand Effect of speech rate on neural tracking of speech Journal Article In: Frontiers in Psychology, vol. 10, pp. 449, 2019. @article{Mueller2019, Speech comprehension requires effort in demanding listening situations. Selective attention may be required for focusing on a specific talker in a multi-talker environment, may enhance effort by requiring additional cognitive resources, and is known to enhance the neural representation of the attended talker in the listener's neural response. The aim of the study was to investigate the relation of listening effort, as quantified by subjective effort ratings and pupil dilation, and neural speech tracking during sentence recognition. Task demands were varied using sentences with varying levels of linguistic complexity and using two different speech rates in a picture-matching paradigm with 20 normal-hearing listeners. The participants' task was to match the acoustically presented sentence with a picture presented before the acoustic stimulus. Afterwards they rated their perceived effort on a categorical effort scale. During each trial, pupil dilation (as an indicator of listening effort) and electroencephalogram (as an indicator of neural speech tracking) were recorded. Neither measure was significantly affected by linguistic complexity. However, speech rate showed a strong influence on subjectively rated effort, pupil dilation, and neural tracking. The neural tracking analysis revealed a shorter latency for faster sentences, which may reflect a neural adaptation to the rate of the input. No relation was found between neural tracking and listening effort, even though both measures were clearly influenced by speech rate. This is probably due to factors that influence both measures differently. Consequently, the amount of listening effort is not clearly represented in the neural tracking. |
2018 |
Eleanor J. Cole; Nick E. Barraclough; Peter G. Enticott Investigating mirror system (MS) activity in adults with ASD when inferring others' intentions using both TMS and EEG Journal Article In: Journal of Autism and Developmental Disorders, vol. 48, no. 7, pp. 2350–2367, 2018. @article{Cole2018, ASD is associated with mentalizing deficits that may correspond with atypical mirror system (MS) activation. We investigated MS activity in adults with and without ASD when inferring others' intentions using TMS-induced motor evoked potentials (MEPs) and mu suppression measured by EEG. Autistic traits were measured for all participants. Our EEG data show, high levels of autistic traits predicted reduced right mu (8–10 Hz) suppression when mentalizing. Higher left mu (8–10 Hz) suppression was associated with superior mentalizing performances. Eye-tracking and TMS data showed no differences associated with autistic traits. Our data suggest ASD is associated with reduced right MS activity when mentalizing, TMS-induced MEPs and mu suppression measure different aspects of MS functioning and the MS is directly involved in inferring intentions. |
Kivilcim Afacan-Seref; Natalie A. Steinemann; Annabelle Blangero; Simon P. Kelly Dynamic interplay of value and sensory information in high-speed decision making Journal Article In: Current Biology, vol. 28, no. 5, pp. 795–802, 2018. @article{AfacanSeref2018, In dynamic environments, split-second sensorimotor decisions must be prioritized according to potential payoffs to maximize overall rewards. The impact of relative value on deliberative perceptual judgments has been examined extensively [1–6], but relatively little is known about value-biasing mechanisms in the common situation where physical evidence is strong but the time to act is severely limited. In prominent decision models, a noisy but statistically stationary representation of sensory evidence is integrated over time to an action-triggering bound, and value-biases are affected by starting the integrator closer to the more valuable bound. Here, we show significant departures from this account for humans making rapid sensory-instructed action choices. Behavior was best explained by a simple model in which the evidence representation—and hence, rate of accumulation—is itself biased by value and is non-stationary, increasing over the short decision time frame. Because the value bias initially dominates, the model uniquely predicts a dynamic ‘‘turn-around'' effect on low-value cues, where the accumulator first launches toward the incorrect action but is then re-routed to the correct one. This was clearly exhibited in electrophysiological signals reflecting motor preparation and evidence accumulation. Finally, we construct an extended model that implements this dynamic effect through plausible sensory neural response modulations and demonstrate the correspondence between decision signal dynamics simulated from a behavioral fit of that model and the empirical decision signals. Our findings suggest that value and sensory information can exert simultaneous and dynamically countervailing influences on the trajectory of the accumulation-to-bound process, driving rapid, sensory-guided actions. |
Joshua D. Cosman; Kaleb A. Lowe; Wolf Zinke; Geoffrey F. Woodman; Jeffrey D. Schall Prefrontal control of visual distraction Journal Article In: Current Biology, vol. 28, no. 3, pp. 414–420, 2018. @article{Cosman2018, Avoiding distraction by conspicuous but irrelevant stimuli is critical to accomplishing daily tasks. Regions of prefrontal cortex control attention by enhancing the representation of task-relevant information in sensory cortex, which can be measured in modulation of both single neurons and event-related electrical potentials (ERPs) on the cranial surface [1, 2]. When irrelevant information is particularly conspicuous, it can distract attention and interfere with the selection of behaviorally relevant information. Such distraction can be minimized via top-down control [3–5], but the cognitive and neural mechanisms giving rise to this control over distraction remain uncertain and debated [6–9]. Bridging neurophysiology to electrophysiology, we simultaneously recorded neurons in prefrontal cortex and ERPs over extrastriate visual cortex to track the processing of salient distractors during a visual search task. Critically, when the salient distractor was successfully ignored, but not otherwise, we observed robust suppression of salient distractor representations. Like target selection, the distractor suppression was observed in prefrontal cortex before it appeared over extrastriate cortical areas. Furthermore, all prefrontal neurons that showed suppression of the task-irrelevant distractor also contributed to selecting the target. This suggests a common prefrontal mechanism is responsible for both selecting task-relevant and suppressing task-irrelevant information in sensory cortex. Taken together, our results resolve a long-standing debate over the mechanisms that prevent distraction, and provide the first evidence directly linking suppressed neural firing in prefrontal cortex with surface ERP measures of distractor suppression. |
Andrey R. Nikolaev; Radha Nila Meghanathan; Cees Leeuwen Refixation control in free viewing: A specialized mechanism divulged by eye-movement related brain activity. Journal Article In: Journal of neurophysiology, pp. 2311–2324, 2018. @article{Nikolaev2018, In free viewing, the eyes return to previously visited locations rather frequently, even though the attentional and memory-related processes controlling eye-movement show a strong anti-refixation bias. To overcome this bias, a special refixation triggering mechanism may have to be recruited. We probed the neural evidence for such a mechanism by combining eye tracking with EEG recording. A distinctive signal associated with refixation planning was observed in the EEG during the presaccadic interval: the presaccadic potential was reduced in amplitude prior to a refixation, compared to normal fixations. The result offers direct evidence for a special refixation mechanism that operates in the saccade planning stage of eye-movement control. Once the eyes have landed on the revisited location, acquisition of visual information proceeds indistinguishably from ordinary fixations. |
Elena V. Orekhova; Olga V. Sysoeva; Justin F. Schneiderman; Sebastian Lundström; Ilia A. Galuta; Dzerasa E. Goiaeva; Andrey O. Prokofyev; Bushra Riaz; Courtney Keeler; Nouchine Hadjikhani; Christopher Gillberg; Tatiana A. Stroganova Input-dependent modulation of MEG gamma oscillations reflects gain control in the visual cortex Journal Article In: Scientific Reports, vol. 8, pp. 8451, 2018. @article{Orekhova2018, Gamma-band oscillations arise from the interplay between neural excitation (E) and inhibition (I) and may provide a non-invasive window into the state of cortical circuitry. A bell-shaped modulation of gamma response power by increasing the intensity of sensory input was observed in animals and is thought to reflect neural gain control. Here we sought to find a similar input-output relationship in humans with MEG via modulating the intensity of a visual stimulation by changing the velocity/ temporal-frequency of visual motion. In the first experiment, adult participants observed static and moving gratings. The frequency of the MEG gamma response monotonically increased with motion velocity whereas power followed a bell-shape. In the second experiment, on a large group of children and adults, we found that despite drastic developmental changes in frequency and power of gamma oscillations, the relative suppression at high motion velocities was scaled to the same range of values across the life-span. In light of animal and modeling studies, the modulation of gamma power and frequency at high stimulation intensities characterizes the capacity of inhibitory neurons to counterbalance increasing excitation in visual networks. Gamma suppression may thus provide a non- invasive measure of inhibitory-based gain control in the healthy and diseased brain. |
Iske Bakker-Marshall; Atsuko Takashima; Jan-Mathijs Schoffelen; Janet G. Hell; Gabriele Janzen; James M. McQueen Theta-band oscillations in the middle temporal gyrus reflect novel word consolidation Journal Article In: Journal of Cognitive Neuroscience, vol. 30, no. 5, pp. 621–633, 2018. @article{BakkerMarshall2018, Like many other types of memory formation, novel word learning benefits from an offline consolidation period after the initial encoding phase. A previous EEG study has shown that retrieval of novel words elicited more word-like-induced electrophysiological brain activity in the theta band after consolidation [Bakker, I., Takashima, A., van Hell, J. G., Janzen, G., & McQueen, J. M. Changes in theta and beta oscillations as signatures of novel word consolidation. Journal of Cognitive Neuroscience, 27, 1286–1297, 2015]. This suggests that theta-band oscillations play a role in lexicalization, but it has not been demonstrated that this effect is directly caused by the formation of lexical representations. This study used magnetoencephalography to localize the theta consolidation effect to the left posterior middle temporal gyrus (pMTG), a region known to be involved in lexical storage. Both untrained novel words and words learned immediately before test elicited lower theta power during retrieval than existing words in this region. After a 24-hr consolidation period, the difference between novel and existing words decreased significantly, most strongly in the left pMTG. The magnitude of the decrease after consolidation correlated with an increase in behavioral competition effects between novel words and existing words with similar spelling, reflecting functional integration into the mental lexicon. These results thus provide new evidence that consolidation aids the development of lexical representations mediated by the left pMTG. Theta synchronizationmay enable lexical access by facilitating the simultaneous activation of distributed semantic, phonological, and orthographic representations that are bound together in the pMTG. |
Jeffrey S. Bedwell; Christopher C. Spencer; Chi C. Chan; Pamela D. Butler; Pejman Sehatpour; Joseph Schmidt The P1 visual-evoked potential, red light, and transdiagnostic psychiatric symptoms Journal Article In: Brain Research, vol. 1687, pp. 144–154, 2018. @article{Bedwell2018, A reduced P1 visual-evoked potential amplitude has been reported across several psychiatric disorders, including schizophrenia-spectrum, bipolar, and depressive disorders. In addition, a difference in P1 amplitude change to a red background compared to its opponent color, green, has been found in schizophrenia-spectrum samples. The current study examined whether specific psychiatric symptoms that related to these P1 abnormalities in earlier studies would be replicated when using a broad transdiagnostic sample. The final sample consisted of 135 participants: 26 with bipolar disorders, 25 with schizophrenia-spectrum disorders, 19 with unipolar depression, 62 with no current psychiatric disorder, and 3 with disorders in other categories. Low (8%) and high (64%) contrast check arrays were presented on gray, green, and red background conditions during electroencephalogram, while an eye tracker monitored visual fixation on the stimuli. Linear regressions across the entire sample (N = 135) found that greater severity of both clinician-rated and self-reported delusions/magical thinking correlated with a reduced P1 amplitude on the low contrast gray (neutral) background condition. In addition, across the entire sample, higher self-reported constricted affect was associated with a larger decrease in P1 amplitude (averaged across contrast conditions) to the red, compared to green, background. All relationships remained statistically significant after covarying for diagnostic class, suggesting that they are relatively transdiagnostic in nature. These findings indicate that early visual processing abnormalities may be more directly related to specific transdiagnostic symptoms such as delusions and constricted affect rather than specific psychiatric diagnoses or broad symptom factor scales. |
Adam Borowicz Using a multichannel Wiener filter to remove eye-blink artifacts from EEG data Journal Article In: Biomedical Signal Processing and Control, vol. 45, pp. 246–255, 2018. @article{Borowicz2018, This paper presents a novel method for removing ocular artifacts from EEG recordings. The proposed approach is based on time-domain linear filtering. Instead of directly estimating the artifact-free signal, we propose to obtain the eye-blink signal first, using a multichannel Wiener filter (MWF) and a small subset of the frontal electrodes, so that extra EOG sensors are unnecessary. Then, the estimate of the eye-blink signal is subtracted from the noisy EEG signal in accordance with principles of regression analysis. We have performed numerical simulations so as to compare our approach to the independent component analysis (ICA) that is commonly used in EEG enhancement. Our experiments show that the MWF-based approach can perform better than the ICA in terms of eye-blink cancellation and signal distortions. Besides that, the proposed approach is conceptually simpler and better suited to real-time applications. |
Hoseok Choi; Seho Lee; Jeyeon Lee; Kyeongran Min; Seokbeen Lim; Jinsick Park; Kyoung-ha Ahn; In Young Kim; Kyoung-Min Lee; Dong Pyo Jang Long-term evaluation and feasibility study of the insulated screw electrode for ECoG recording Journal Article In: Journal of Neuroscience Methods, vol. 308, pp. 261–268, 2018. @article{Choi2018, Background: A screw-shaped electrode can offer a compromise between signal quality and invasiveness. However, the standard screw electrode can be vulnerable to electrical noise while directly contact with the skull or skin, and the feasibility and stability for chronic implantation in primate have not been fully evaluated. New Method: We designed a novel screw electrocorticogram (ECoG) electrode composed of three parts: recording electrode, insulator, and nut. The recording electrode was made of titanium with high biocompatibility and high electrical conductivity. Zirconia is used for insulator and nut to prevent electrical noise. Result: In computer simulations, the screw ECoG with insulator showed a significantly higher performance in signal acquisition compared to the condition without insulator. In a non-human primate, using screw ECoG, clear visual-evoked potential (VEP) waveforms were obtained, VEP components were reliably maintained, and the electrode's impedance was stable during the whole evaluation period. Moreover, it showed higher SNR and wider frequency band compared to the electroencephalogram (EEG). We also observed the screw ECoG has a higher sensitivity that captures different responses on various stimuli than the EEG. Comparison: The screw ECoG showed reliable electrical characteristic and biocompatibility for three months, that shows great promise for chronic implants. These results contrasted with previous reports that general screw electrode was only applicable for acute applications. Conclusion: The suggested electrode can offer whole-brain monitoring with high signal quality and minimal invasiveness. The screw ECoG can be used to provide more in-depth understanding, not only relationship between functional networks and cognitive behavior, but also pathomechanisms in brain diseases. |
Gerard Derosiere; Pierre-Alexandre Klein; Sylvie Nozaradan; Alexandre Zénon; André Mouraux; Julie Duque Visuomotor correlates of conflict expectation in the context of motor decisions Journal Article In: Journal of Neuroscience, vol. 38, no. 44, pp. 9486–9504, 2018. @article{Derosiere2018, Many behaviors require choosing between conflicting options competing against each other in visuomotor areas. Such choices can benefit from top-down control processes engaging frontal areas in advance of conflict when it is anticipated. Yet, very little is known about how this proactive control system shapes the visuomotor competition. Here, we used electroencephalography in human subjects (male and female) to identify the visual and motor correlates of conflict expectation in a version ofthe Eriksen Flanker task that required left or right responses according to the direction of a central target arrow surrounded by congruent or incongruent (conflicting) flankers. Visual conflict was either highly expected (it occurred in 80% of trials; mostly incongruent blocks) or very unlikely (20% of trials; mostly congruent blocks). We evaluated selective attention in the visual cortex by recording target- and flanker-related steady-state visual- evoked potentials (SSVEPs) and probed action selection by measuring response-locked potentials (RLPs) in the motor cortex. Conflict expectation enhanced accuracy in incongruent trials, but this improvement occurred at the cost ofspeed in congruent trials. Intriguingly, this behavioral adjustment occurred while visuomotor activity was less finely tuned: target-related SSVEPs were smaller while flanker related SSVEPs were higher in mostly incongruent blocks than in mostly congruent blocks, and incongruent trials were associated with larger RLPs in the ipsilateral (nonselected) motor cortex. Hence, our data suggest that conflict expectation recruits control processes that augment the tolerance for inappropriate visuomotor activations (rather than processes that down regulate their amplitude), allowing for overflow activity to occur without having it turn into the selection of an incorrect response. |
Thérèse Collins; Pierre O. Jacquet TMS over posterior parietal cortex disrupts trans-saccadic visual stability Journal Article In: Brain Stimulation, vol. 11, no. 2, pp. 390–399, 2018. @article{Collins2018, Background: Saccadic eye movements change the retinal location of visual objects, but we do not experience the visual world as constantly moving, we perceive it as seamless and stable. This visual stability may be achieved by an internal or efference copy of each saccade that, combined with the retinal information, allows the visual system to cancel out or ignore the self-caused retinal motion. Objective: The current study investigated the underlying brain mechanisms responsible for visual stability in humans with online transcranial magnetic stimulation (TMS). Methods: We used two classic tasks that measure efference copy: the double-step task and the in-flight displacement task. The double-step task requires subjects to make two memory-guided saccades, the second of which depends on an accurate internal copy of the first. The in-flight displacement task requires subjects to report the relative location of a (possibly displaced) target across a saccade. In separate experimental sessions, subjects participated in each task while we delivered online 3-pulse TMS over frontal eye fields (FEF), posterior parietal cortex, or vertex. TMS was contingent on saccade execution. Results: Second saccades were not disrupted in the double-step task, but surprisingly, TMS over FEF modified the metrics of the ongoing saccade. Spatiotopic performance in the in-flight displacement task was altered following TMS over parietal cortex, but not FEF or vertex. Conclusion: These results suggest that TMS disrupted eye-centered position coding in the parietal cortex. Trans-saccadic correspondence, and visual stability, may therefore causally depend on parietal maps. |
Seref Can Gurel; Miguel Castelo-Branco; Alexander T. Sack; Felix Duecker Assessing the functional role of frontal eye fields in voluntary and reflexive saccades using continuous theta burst stimulation Journal Article In: Frontiers in Neuroscience, vol. 12, pp. 944, 2018. @article{Gurel2018, The frontal eye fields (FEFs) are core nodes of the oculomotor system contributing to saccade planning, control, and execution. Here, we aimed to reveal hemispheric asymmetries between left and right FEF in both voluntary and reflexive saccades toward horizontal and vertical targets. To this end, we applied fMRI-guided continuous theta burst stimulation (cTBS) over either left or right FEF and assessed the consequences of this disruption on saccade latencies. Using a fully counterbalanced within-subject design, we measured saccade latencies before and after the application of cTBS in eighteen healthy volunteers. In general, saccade latencies on both tasks were susceptible to our experimental manipulations, that is, voluntary saccades were slower than reflexive saccades, and downward saccades were slower than upward saccades. Contrary to our expectations, we failed to reveal any TMS-related effects on saccade latencies, and Bayesian analyses provided strong support in favor of a TMS null result for both tasks. Keeping in mind the interpretative challenges of null results, we discuss possible explanations for this absence of behavioral TMS effects, focusing on methodological differences compared to previous studies (task parameters and online vs. offline TMS interventions). We also speculate about what our results might reveal about the functional role of FEF. |
George L. Malcolm; Edward H. Silson; Jennifer R. Henry; Chris I. Baker Transcranial magnetic stimulation to the occipital place area biases gaze during scene viewing Journal Article In: Frontiers in Human Neuroscience, vol. 12, pp. 189, 2018. @article{Malcolm2018, We can understand viewed scenes and extract task-relevant information within a few hundred milliseconds. This process is generally supported by three cortical regions that show selectivity for scene images: parahippocampal place area (PPA), medial place area (MPA) and occipital place area (OPA). Prior studies have focused on the visual information each region is responsive to, usually within the context of recognition or navigation. Here, we move beyond these tasks to investigate gaze allocation during scene viewing. Eye movements rely on a scene's visual representation to direct saccades, and thus foveal vision. In particular, we focus on the contribution of OPA, which is: (i) located in occipito-parietal cortex, likely feeding information into parts of the dorsal pathway critical for eye movements; and (ii) contains strong retinotopic representations of the contralateral visual field. Participants viewed scene images for 1034 ms while their eye movements were recorded. On half of the trials, a 500 ms train of five transcranial magnetic stimulation (TMS) pulses was applied to the participant's cortex, starting at scene onset. TMS was applied to the right hemisphere over either OPA or the occipital face area (OFA), which also exhibits a contralateral visual field bias but shows selectivity for face stimuli. Participants generally made an overall left-toright, top-to-bottom pattern of eye movements across all conditions. When TMS was applied to OPA, there was an increased saccade latency for eye movements toward the contralateral relative to the ipsilateral visual field after the final TMS pulse (400 ms). Additionally, TMS to the OPA biased fixation positions away from the contralateral side of the scene compared to the control condition, while the OFA group showed no such effect. There was no effect on horizontal saccade amplitudes. These combined results suggest that OPA might serve to represent local scene information that can then be utilized by visuomotor control networks to guide gaze allocation in natural scenes. |
James Mathew; Frederic R. Danion Ups and downs in catch-up saccades following single-pulse TMS-methodological considerations Journal Article In: PLoS ONE, vol. 13, no. 10, pp. e0205208, 2018. @article{Mathew2018a, Transcranial magnetic stimulation (TMS) can interfere with smooth pursuit or with saccades initiated from a fixed position toward a fixed target, but little is known about the effect of TMS on catch-up saccade made to assist smooth pursuit. Here we explored the effect of TMS on catch-up saccades by means of a situation in which the moving target was driven by an external agent, or moved by the participants' hand, a condition known to decrease the occurrence of catch-up saccade. Two sites of stimulation were tested, the vertex and M1 hand area. Compared to conditions with no TMS, we found a consistent modulation of saccadic activity after TMS such that it decreased at 40-100ms, strongly resumed at 100-160ms, and then decreased at 200-300ms. Despite this modulatory effect, the accuracy of catch-up saccade was maintained, and the mean saccadic activity over the 0-300ms period remained unchanged. Those findings are discussed in the context of studies showing that single-pulse TMS can induce widespread effects on neural oscillations as well as perturbations in the latency of saccades during reaction time protocols. At a more general level, despite challenges and interpretational limitations making uncertain the origin of this modulatory effect, our study provides direct evidence that TMS over presumably non-oculomotor regions interferes with the initiation of catch-up saccades, and thus offers methodological considerations for future studies that wish to investigate the underlying neural circuitry of catch-up saccades using TMS. |
Denis Pélisson; Ouazna Habchi; Muriel T. N. Panouillères; Charles Hernoux; Alessandro Farnè A cortical substrate for the long-term memory of saccadic eye movements calibration Journal Article In: NeuroImage, vol. 179, pp. 348–356, 2018. @article{Pelisson2018, How movements are continuously adapted to physiological and environmental changes is a fundamental question in systems neuroscience. While many studies have elucidated the mechanisms which underlie short-term sensorimotor adaptation (∼10–30 min), how these motor memories are maintained over longer-term (>3–5 days) -and thanks to which neural systems-is virtually unknown. Here, we examine in healthy human participants whether the temporo-parietal junction (TPJ) is causally involved in the induction and/or the retention of saccadic eye movements' adaptation. Single-pulse transcranial magnetic stimulation (spTMS) was applied while subjects performed a ∼15min size-decrease adaptation task of leftward reactive saccades. A TMS pulse was delivered over the TPJ in the right hemisphere (rTPJ) in each trial either 30, 60, 90 or 120 msec (in 4 separate adaptation sessions) after the saccade onset. In two control groups of subjects, the same adaptation procedure was achieved either alone (No-TMS) or combined with spTMS applied over the vertex (SHAM-TMS). While the timing of spTMS over the rTPJ did not significantly affect the speed and immediate after-effect of adaptation, we found that the amount of adaptation retention measured 10 days later was markedly larger (42%) than in both the No-TMS (21%) and the SHAM-TMS (11%) control groups. These results demonstrate for the first time that the cerebral cortex is causally involved in maintaining long-term oculomotor memories. |
Pim Mostert; Anke Marit Albers; Loek Brinkman; Larisa Todorova; Peter Kok; Floris P. Lange Eye movement-related confounds in neural decoding of visual working memory representations Journal Article In: eNeuro, vol. 5, no. 4, pp. 1–14, 2018. @article{Mostert2018a, A relatively new analysis technique, known as neural decoding or multivariate pattern analysis (MVPA), has become increasingly popular for cognitive neuroimaging studies over recent years. These techniques promise to uncover the representational contents of neural signals, as well as the underlying code and the dynamic profile thereof. A field in which these techniques have led to novel insights in particular is that of visual working memory (VWM). In the present study, we subjected human volunteers to a combined VWM/imagery task while recording their neural signals using magnetoencephalography (MEG). We applied multivariate decoding analyses to uncover the temporal profile underlying the neural representations of the memorized item. Analysis of gaze position however revealed that our results were contaminated by systematic eye movements, suggesting that the MEG decoding results from our originally planned analyses were confounded. In addition to the eye movement analyses, we also present the original analyses to highlight how these might have readily led to invalid conclusions. Finally, we demonstrate a potential remedy, whereby we train the decoders on a functional localizer that was specifically designed to target bottom-up sensory signals and as such avoids eye movements. We conclude by arguing for more awareness of the potentially pervasive and ubiquitous effects of eye movement-related confounds. |
Pim Mostert; Sander Bosch; Nadine Dijkstra; Marcel A. J. Gerven; Floris P. Lange Differential temporal dynamics during visual imagery and perception Journal Article In: eLife, vol. 7, pp. 1–16, 2018. @article{Mostert2018, Visual perception and imagery rely on similar representations in the visual cortex. During perception, visual activity is characterized by distinct processing stages, but the temporal dynamics underlying imagery remain unclear. Here, we investigated the dynamics of visual imagery in human participants using magnetoencephalography. Firstly, we show that, compared to perception, imagery decoding becomes significant later and representations at the start of imagery already overlap with later time points. This suggests that during imagery, the entire visual representation is activated at once or that there are large differences in the timing of imagery between trials. Secondly, we found consistent overlap between imagery and perceptual processing around 160 ms and from 300 ms after stimulus onset. This indicates that the N170 gets reactivated during imagery and that imagery does not rely on early perceptual representations. Together, these results provide important insights for our understanding of the neural mechanisms of visual imagery. |
Karisa B. Parkington; Roxane J. Itier One versus two eyes makes a difference! Early face perception is modulated by featural fixation and feature context Journal Article In: Cortex, vol. 109, pp. 35–49, 2018. @article{Parkington2018, The N170 event-related potential component is an early marker of face perception that is particularly sensitive to isolated eye regions and to eye fixations within a face. Here, this eye sensitivity was tested further by measuring the N170 to isolated facial features and to the same features fixated within a face, using a gaze-contingent procedure. The neural response to single isolated eyes and eye regions (two eyes) was also compared. Pixel intensity and contrast were controlled at the global (image) and local (featural) levels. Consistent with previous findings, larger N170 amplitudes were elicited when the left or right eye was fixated within a face, compared to the mouth or nose, demonstrating that the N170 eye sensitivity reflects higher-order perceptual processes and not merely low-level perceptual effects. The N170 was also largest and most delayed for isolated features, compared to equivalent fixations within a face. Specifically, mouth fixation yielded the largest amplitude difference, and nose fixation yielded the largest latency difference between these two contexts, suggesting the N170 may reflect a complex interplay between holistic and featural processes. Critically, eye regions elicited consistently larger and shorter N170 responses compared to single eyes, with enhanced responses for contralat-eral eye content, irrespective of eye or nasion fixation. These results confirm the importance of the eyes in early face perception, and provide novel evidence of an increased sensitivity to the presence of two symmetric eyes compared to only one eye, consistent with a neural eye region detector rather than an eye detector per se. |
Thomas Pfeffer; Arthur Ervin Avramiea; Guido Nolte; Andreas K. Engel; Klaus Linkenkaer-Hansen; Tobias H. Donner Catecholamines alter the intrinsic variability of cortical population activity and perception Journal Article In: PLoS Biology, vol. 16, no. 2, pp. e2003453, 2018. @article{Pfeffer2018, The ascending modulatory systems of the brain stem are powerful regulators of global brain state. Disturbances of these systems are implicated in several major neuropsychiatric disorders. Yet, how these systems interact with specific neural computations in the cerebral cortex to shape perception, cognition, and behavior remains poorly understood. Here, we probed into the effect of two such systems, the catecholaminergic (dopaminergic and noradrenergic) and cholinergic systems, on an important aspect of cortical computation: its intrinsic variability. To this end, we combined placebo-controlled pharmacological intervention in humans, recordings of cortical population activity using magnetoencephalography (MEG), and psychophysical measurements of the perception of ambiguous visual input. A low-dose catecholaminergic, but not cholinergic, manipulation altered the rate of spontaneous perceptual fluctuations as well as the temporal structure of “scale-free” population activity of large swaths of the visual and parietal cortices. Computational analyses indicate that both effects were consistent with an increase in excitatory relative to inhibitory activity in the cortical areas underlying visual perceptual inference. We propose that catecholamines regulate the variability of perception and cognition through dynamically changing the cortical excitation–inhibition ratio. The combined readout of fluctuations in perception and cortical activity we established here may prove useful as an efficient and easily accessible marker of altered cortical computation in neuropsychiatric disorders. |
Anthony J. Ries; David Slayback; Jon Touryan The fixation-related lambda response: Effects of saccade magnitude, spatial frequency, and ocular artifact removal Journal Article In: International Journal of Psychophysiology, vol. 134, pp. 1–8, 2018. @article{Ries2018, Fixation-related potentials (FRPs) enable examination of electrophysiological signatures of visual perception under naturalistic conditions, providing a neural snapshot of the fixated scene. The most prominent FRP component, commonly referred to as the lambda response, is a large deflection over occipital electrodes (O1, Oz, O2) peaking 80–100 ms post fixation, reflecting afferent input to visual cortex. The lambda response is affected by bottom-up stimulus features and the size of the preceding saccade; however, prior research has not adequately controlled for these influences in free viewing paradigms. The current experiment (N = 16, 1 female) addresses these concerns by systematically manipulating spatial frequency in a free-viewing task requiring a range of saccade sizes. Given the close temporal proximity between saccade related activity and the onset of the lambda response, we evaluate how removing independent components (IC) associated with ocular motion artifacts affects lambda response amplitude. Our results indicate that removing ocular artifact ICs based on the covariance with gaze position did not significantly affect the amplitude of this occipital potential. Moreover, the results showed that spatial frequency and saccade magnitude each produce significant effects on lambda amplitude, where amplitude decreased with increasing spatial frequency and increased as a function of saccade size for small and medium-sized saccades. The amplitude differences between spatial frequencies were maintained across all saccade magnitudes suggesting these effects are produced from distinctly different and uncorrelated mechanisms. The current results will inform future analyses of the lambda potential in natural scenes where saccade magnitudes and spatial frequencies ultimately vary. |
Naoyuki Sato; Hiroaki Mizuhara Successful encoding during natural reading is associated with fixation-related potentials and large-scale network deactivation Journal Article In: eNeuro, vol. 5, no. 5, pp. 1–12, 2018. @article{Sato2018, Reading literature (e.g., an entire book) is an enriching experience that qualitatively differs from reading a single sentence; however, the brain dynamics of such context-dependent memory remains unclear. This study aimed to elucidate mnemonic neural dynamics during natural reading of literature by performing electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI). Brain activities of human participants recruited on campus were correlated with their subsequent memory, which was quantified by semantic correlation between the read text and reports subsequently written by them based on state of the art natural language processing procedures. The results of the EEG data analysis showed a significant positive relationship between subsequent memory and fixation-related EEG. Sentence-length and paragraph-length mnemonic processes were associated with N1-P2 and P3 fixation-related potential (FRP) components and fixation-related θ-band (4–8 Hz) EEG power, respectively. In contrast, the results of fMRI analysis showed a significant negative relationship between subsequent memory and blood oxygenation level-dependent (BOLD) activation. Sentence-length and paragraph-length mnemonic processes were associated with networks of regions forming part of the salience network and the default mode network (DMN), respectively. Taken together with the EEG results, these memory-related deactivations in the salience network and the DMN were thought to reflect the reading of sentences characterized by low mnemonic load and the suppression of task-irreverent thoughts, respectively. It was suggested that the context-dependent mnemonic process during literature reading requires large-scale network deactivation, which might reflect coordination of a range of voluntary processes during reading. |
Brian Scally; Melanie R. Burke; David Bunce; Jean Francois Delvenne Visual and visuomotor interhemispheric transfer time in older adults Journal Article In: Neurobiology of Aging, vol. 65, pp. 69–76, 2018. @article{Scally2018, Older adults typically experience reductions in the structural integrity of the anterior channels of the corpus callosum. Despite preserved structural integrity in central and posterior channels, many studies have reported that interhemispheric transfer, a function attributed to these regions, is detrimentally affected by aging. In this study, we use a constrained event-related potential analysis in the theta and alpha frequency bands to determine whether interhemispheric transfer is affected in older adults. The crossed-uncrossed difference and lateralized visual evoked potentials were used to assess interhemispheric transfer in young (18–27) and older adults (63–80). We observed no differences in the crossed-uncrossed difference measure between young and older groups. Older adults appeared to have elongated transfer in the theta band potentials, but this effect was driven by shortened contralateral peak latencies, rather than delayed ipsilateral latencies. In the alpha band, there was a trend toward quicker transfer in older adults. We conclude that older adults do not experience elongated interhemispheric transfer in the visuomotor or visual domains and that these functions are likely attributed to posterior sections of the corpus callosum, which are unaffected by aging. |
K. Seeliger; Matthias Fritsche; U. Güçlü; S. Schoenmakers; J. M. Schoffelen; S. E. Bosch; Marcel A. J. Gerven Convolutional neural network-based encoding and decoding of visual object recognition in space and time Journal Article In: NeuroImage, vol. 180, pp. 253–266, 2018. @article{Seeliger2018, Representations learned by deep convolutional neural networks (CNNs) for object recognition are a widely investigated model of the processing hierarchy in the human visual system. Using functional magnetic resonance imaging, CNN representations of visual stimuli have previously been shown to correspond to processing stages in the ventral and dorsal streams of the visual system. Whether this correspondence between models and brain signals also holds for activity acquired at high temporal resolution has been explored less exhaustively. Here, we addressed this question by combining CNN-based encoding models with magnetoencephalography (MEG). Human participants passively viewed 1,000 images of objects while MEG signals were acquired. We modelled their high temporal resolution source-reconstructed cortical activity with CNNs, and observed a feed-forward sweep across the visual hierarchy between 75 and 200 ms after stimulus onset. This spatiotemporal cascade was captured by the network layer representations, where the increasingly abstract stimulus representation in the hierarchical network model was reflected in different parts of the visual cortex, following the visual ventral stream. We further validated the accuracy of our encoding model by decoding stimulus identity in a left-out validation set of viewed objects, achieving state-of-the-art decoding accuracy. |
Adam C. Snyder; Deepa Issar; Matthew A. Smith What does scalp electroencephalogram coherence tell us about long-range cortical networks? Journal Article In: European Journal of Neuroscience, pp. 1–16, 2018. @article{Snyder2018, Long-range interactions between cortical areas are undoubtedly a key to the computational power of the brain. For healthy human subjects, the premier method for measuring brain activity on fast timescales is electroencephalography (EEG), and coherence between EEG signals is often used to assay functional connectivity between different brain regions. However, the nature of the underlying brain activity that is reflected in EEG coherence is currently the realm of speculation, because seldom have EEG signals been recorded simultaneously with intracranial recordings near cell bodies in multiple brain areas. Here, we take the early steps towards narrowing this gap in our understanding of EEG coherence by measuring local field potentials with microelectrode arrays in two brain areas (extrastriate visual area V4 and dorsolateral prefrontal cortex) simultaneously with EEG at the nearby scalp in rhesus macaque monkeys. Although we found inter-area coherence at both scales of measurement, we did not find that scalp-level coherence was reliably related to coherence between brain areas measured intracranially on a trial-to-trial basis, despite that scalp-level EEG was related to other important features of neural oscillations, such as trial-to-trial variability in overall amplitudes. This suggests that caution must be exercised when interpreting EEG coherence effects, and new theories devised about what aspects of neural activity long-range coherence in the EEG reflects. |
Rodolfo Solís-Vivanco; Ole Jensen; Mathilde Bonnefond Top–down control of alpha phase adjustment in anticipation of temporally predictable visual stimuli Journal Article In: Journal of Cognitive Neuroscience, vol. 30, no. 8, pp. 1157–1169, 2018. @article{SolisVivanco2018, Alpha oscillations (8–14 Hz) are proposed to represent an active mechanism of functional inhibition of neuronal processing. Specifically, alpha oscillations are associated with pulses of inhibition repeating every ∼100 msec. Whether alpha phase, similar to alpha power, is under top–down control remains unclear. Moreover, the sources of such putative top–down phase control are unknown. We designed a cross-modal (visual/auditory) attention study in which we used magnetoencephalography to record the brain activity from 34 healthy participants. In each trial, a somatosensory cue indicated whether to attend to either the visual or auditory domain. The timing of the stimulus onset was predictable across trials. We found that, when visual information was attended, anticipatory alpha power was reduced in visual areas, whereas the phase adjusted just before the stimulus onset. Performance in each modality was predicted by the phase of the alpha oscillations previous to stimulus onset. Alpha oscillations in the left pFC appeared to lead the adjustment of alpha phase in visual areas. Finally, alpha phase modulated stimulus-induced gamma activity. Our results confirm that alpha phase can be top–down adjusted in anticipation of predictable stimuli and improve performance. Phase adjustment of the alpha rhythm might serve as a neurophysiological resource for optimizing visual processing when temporal predictions are possible and there is considerable competition between target and distracting stimuli. |
Tobias Staudigl; Marcin Leszczynski; Joshua Jacobs; Sameer A. Sheth; Charles E. Schroeder; Ole Jensen; Christian F. Doeller Hexadirectional modulation of high-frequency electrophysiological activity in the human anterior medial temporal lobe maps visual space Journal Article In: Current Biology, vol. 28, pp. 1–5, 2018. @article{Staudigl2018, Grid cells are one of the core building blocks of spatial navigation [1]. Single-cell recordings of grid cells in the rodent entorhinal cortex revealed hexagonal coding of the local environment during spatial navigation [1]. Grid-like activity has also been identified in human single-cell recordings during virtual navigation [2]. Human fMRI studies further provide evidence that grid-like signals are also accessible on a macroscopic level [3–7]. Studies in both nonhuman primates [8] and humans [9, 10] suggest that grid-like coding in the entorhinal cortex generalizes beyond spatial navigation during locomotion, providing evidence for grid-like mapping of visual space during visual exploration—akin to the grid cell positional code in rodents during spatial navigation. However, electrophysiological correlates of the grid code in humans remain unknown. Here, we provide evidence for grid-like, hexadirectional coding of visual space by human high-frequency activity, based on two independent datasets: non-invasive magnetoencephalography (MEG) in healthy subjects and entorhinal intracranial electroencephalography (EEG) recordings in an epileptic patient. Both datasets consistently show a hexadirectional modulation of broadband high-frequency activity (60–120 Hz). Our findings provide first evidence for a grid-like MEG signal, indicating that the human entorhinal cortex codes visual space in a grid-like manner [8–10], and support the view that grid coding generalizes beyond environmental mapping during locomotion [4–6, 11]. Due to their millisecond accuracy, MEG recordings allow linking of grid-like activity to epochs during relevant behavior, thereby opening up the possibility for new MEG-based investigations of grid coding at high temporal resolution. |
Noam Tal; Shlomit Yuval-Greenberg Reducing saccadic artifacts and confounds in brain imaging studies through experimental design Journal Article In: Psychophysiology, vol. 55, no. 11, pp. e13215, 2018. @article{Tal2018, Saccades constitute a major source of artifacts and confounds in brain imaging studies. Whereas some artifacts can be removed by omitting segments of data, saccadic artifacts cannot be typically eliminated by this method because of their high occurrence rate even during fixation (1–3 per second). Some saccadic artifacts can be alleviated by offline-correction algorithms, but these methods leave nonnegligible residuals and cannot mitigate the saccade-related visual activity. Here, we propose a novel yet simple approach for diminishing saccadic artifacts and confounds through experimental design. We suggest that specific tasks can lead to substantially less saccade occurrences around the time of stimulus presentation, starting from slightly before its onset and lasting for a few hundred milliseconds. In three experiments, we compared the frequency and size of saccades in a variety of tasks. Results of Experiment 1 showed that a foveal change-detection task reduced the number and sizes of saccades, relative to a parafoveal orientation-discrimination task. Experiment 2 replicated this finding with a parafoveal object recognition task. Experiment 3 showed that both foveal and parafoveal continuous change detection tasks induced fewer and smaller saccades than a discrete orientation-discrimination task. We conclude that adding a foveal or a parafoveal continuous task reduces saccades' number and size. This would lead to better artifact correction and enable the omission of contaminated data segments. This study may be the first step toward developing saccade-free experimental designs. |
Nina N. Thigpen; L. Forest Gruss; Steven Garcia; David R. Herring; Andreas Keil What does the dot-probe task measure? A reverse correlation analysis of electrocortical activity Journal Article In: Psychophysiology, vol. 55, no. 6, pp. e13058, 2018. @article{Thigpen2018, The dot-probe task is considered a gold standard for assessing the intrinsic attentive selection of one of two lateralized visual cues, measured by the response time to a subsequent, lateralized response probe. However, this task has recently been associated with poor reliability and conflicting results. To resolve these discrepancies, we tested the underlying assumption of the dot-probe task-that fast probe responses index heightened cue selection-using an electrophysiological measure of selective attention. Specifically, we used a reverse correlation approach in combination with frequency-tagged steady-state visual potentials (ssVEPs). Twenty-one participants completed a modified dot-probe task in which each member of a pair of lateralized face cues, varying in emotional expression (angry-angry, neutral-angry, neutral-neutral), flickered at one of two frequencies (15 or 20 Hz), to evoke ssVEPs. One cue was then replaced by a response probe, and participants indicated the probe orientation (0° or 90°). We analyzed the ssVEP evoked by the cues as a function of response speed to the subsequent probe (i.e., a reverse correlation analysis). Electrophysiological measures of cue processing varied with probe hemifield location: Faster responses to left probes were associated with weak amplification of the preceding left cue, apparent only in a median split analysis. By contrast, faster responses to right probes were systematically and parametrically predicted by diminished visuocortical selection of the preceding right cue. Together, these findings highlight the poor validity of the dot-probe task, in terms of quantifying intrinsic, nondirected attentive selection irrespective of probe/cue location. |
Grace Edwards; Rufin VanRullen; Patrick Cavanagh Decoding trans-saccadic memory Journal Article In: Journal of Neuroscience, vol. 38, no. 5, pp. 1114–1123, 2018. @article{Edwards2018, We examine whether peripheral information at a planned saccade target affects immediate post-saccadic processing at the fovea on saccade landing. Current neuroimaging research suggests that pre-saccadic stimulation has a late effect on post-saccadic processing, in contrast to the early effect seen in behavioral studies. Human participants (both male and female) were instructed to saccade toward a face or a house that, on different trials, remained the same, changed, or disappeared during the saccade. We used a multivariate pattern analysis (MVPA) of electroencephalography (EEG) data to decode face versus house processing directly after the saccade. The classifier was trained on separate trials without a saccade, where a house or face was presented at the fovea. When the saccade target remained the same across the saccade, we could reliably decode the target 123 ms after saccade offset. In contrast, when the target was changed during the saccade, the new target was decoded at a later time-point, 151 ms after saccade offset. The "same" condition advantage suggests that congruent pre-saccadic information facilitates processing of the post-saccadic stimulus compared to incongruent information. Finally, the saccade target could be decoded above chance even when it had been removed during the saccade, albeit with a slower time-course (162 ms) and poorer signal strength. These findings indicate that information about the (peripheral) pre-saccadic stimulus is transferred across the saccade so that it becomes quickly available and influences processing at its expected, new retinal position (the fovea). |
Eran Eldar; Gyung Jin Bae; Zeb Kurth-Nelson; Peter Dayan; Raymond J. Dolan Magnetoencephalography decoding reveals structural differences within integrative decision processes Journal Article In: Nature Human Behaviour, vol. 2, no. 9, pp. 670–681, 2018. @article{Eldar2018, When confronted with complex inputs consisting of multiple elements, humans use various strategies to integrate the elements quickly and accurately. For instance, accuracy may or over be improved by processing elements one at a time1–4 extended periods5–8 ; speed can increase if the internal rep- resentation of elements is accelerated9,10 . However, little is known about how humans actually approach these challenges because behavioural findings can be accounted for by mul- tiple alternative process models11 and neuroimaging investi-gations typically rely on haemodynamic signals that change too slowly. Consequently, to uncover the fast neural dynamics that support information integration, we decoded magnetoencephalographic signals that were recorded as human subjects performed a complex decision task. Our findings reveal three sources of individual differences in the temporal structure of the integration process—sequential representation, partial reinstatement and early computation—each having a dissociable effect on how subjects handled problem complexity and temporal constraints. Our findings shed new light on the structure and influence of self-determined neural integration processes. |
Hagar Gelbard-Sagiv; Efrat Magidov; Haggai Sharon; Talma Hendler Noradrenaline modulates visual perception and late visually evoked activity Journal Article In: Current Biology, vol. 28, pp. 2239–2249, 2018. @article{GelbardSagiv2018, An identical sensory stimulus may or may not be incorporated into perceptual experience, depending on the behavioral and cognitive state of the organism. What determines whether a sensory stimulus will be perceived? While different behavioral and cognitive states may share a similar profile of electrophysiology, metabolism, and early sensory responses, neuromodulation is often different and therefore may constitute a key mechanism enabling perceptual awareness. Specifically, noradrenaline improves sensory responses, correlates with orienting toward behaviorally relevant stimuli, and is markedly reduced during sleep, while experience is largely ‘‘disconnected'' from external events. Despite correlative evidence hinting at a relationship between noradrenaline and perception, causal evidence remains absent. Here, we pharmacologically down- and upregulated noradrenaline signaling in healthy volunteers using clonidine and reboxetine in double-blind placebo-controlled experiments, testing the effects on perceptual abilities and visually evoked electroencephalography (EEG) and fMRI responses. We found that detection sensitivity, discrimination accuracy, and subjective visibility change in accordance with noradrenaline (NE) levels, whereas decision bias (criterion) is not affected. Similarly, noradrenaline increases the consistency of EEG visually evoked potentials, while lower noradrenaline levels delay response components around 200 ms. Furthermore, bloodoxygen-level-dependent (BOLD) fMRI activations in high-order visual cortex selectively vary along with noradrenaline signaling. Taken together, these results point to noradrenaline as a key factor causally linking visual awareness to external world events. |
Marcello Giannini; David M. Alexander; Andrey R. Nikolaev; Cees Leeuwen Large-scale traveling waves in EEG activity following eye movement Journal Article In: Brain Topography, vol. 31, no. 4, pp. 608–622, 2018. @article{Giannini2018, In spontaneous, stimulus-evoked, and eye-movement evoked EEG, the oscillatory signal shows large scale, dynamically organized patterns of phase. We investigated eye-movement evoked patterns in free-viewing conditions. Participants viewed photographs of natural scenes in anticipation of a memory test. From 200 ms intervals following saccades, we estimated the EEG phase gradient over the entire scalp, and the wave activity, i.e. the goodness of fit of a wave model involving a phase gradient assumed to be smooth over the scalp. In frequencies centered at 6.5 Hz, large-scale phase organization occurred, peaking around 70 ms after fixation onset and taking the form of a traveling wave. According to the wave gradient, most of the times the wave spreads from the posterior-inferior to anterior–superior direction. In these directions, the gradients depended on the size and direction of the saccade. Wave propagation velocity decreased in the course of the fixation, particularly in the interval from 50 to 150 ms after fixation onset. This interval corresponds to the fixation-related lambda activity, which reflects early perceptual processes following fixation onset. We conclude that lambda activity has a prominent traveling wave component. This component consists of a short-term whole-head phase pattern of specific direction and velocity, which may reflect feedforward propagation of visual information at fixation. |
Julia Habicht; Mareike Finke; Tobias Neher Auditory acclimatization to bilateral hearing aids: Effects on sentence-in-noise processing times and speech-evoked potentials Journal Article In: Ear & Hearing, vol. 39, no. 1, pp. 161–171, 2018. @article{Habicht2018, Objectives: Using a longitudinal design, the present study sought to substantiate indications from two previous cross-sectional studies that hearing aid (HA) experience leads to improved speech processing abilities as quantified using eye-gaze measurements. Another aim was to explore potential concomitant changes in event-related potentials (ERPs) to speech stimuli. Design: Groups of elderly novice (novHA) and experienced (expHA) HA users matched in terms of age and working memory capacity participated. The novHA users were acclimatized to bilateral HA fittings for up to 24 weeks. The expHA users continued to use their own HAs during the same period. The participants' speech processing abilities were assessed after 0 weeks (novHA: N = 16; expHA: N = 14), 12 weeks (novHA: N = 16; expHA: N = 14), and 24 weeks (N = 10 each). To that end, an eye-tracking paradigm was used for estimating how quickly the participants could grasp the meaning of sentences presented against background noise together with two similar pictures that either correctly or incorrectly depicted the meaning conveyed by the sentences (the “processing time”). Additionally, ERPs were measured with an active oddball paradigm requiring the participants to categorize word stimuli as living (targets) or nonliving (nontargets) entities. For all measurements, the stimuli were spectrally shaped according to individual real-ear insertion gains and presented via earphones. Results: Concerning the processing times, no changes across time were found for the expHA group. After 0 weeks of HA use, the novHA group had significantly longer (poorer) processing times than the expHA group, consistent with previous findings. After 24 weeks, a significant mean improvement of ~30% was observed for the novHA users, leading to a performance comparable with that of the expHA group. Concerning the ERPs, no changes across time were found. Conclusions: The results from this exploratory study are consistent with the view that auditory acclimatization to HAs positively impacts speech comprehension in noise. Further research is needed to substantiate them. |
Wei He; Blake W. Johnson Development of face recognition: Dynamic causal modelling of MEG data Journal Article In: Developmental Cognitive Neuroscience, vol. 30, pp. 13–22, 2018. @article{He2018, Electrophysiological studies of adults indicate that brain activity is enhanced during viewing of repeated faces, at a latency of about 250 ms after the onset of the face (M250/N250). The present study aimed to determine if this effect was also present in preschool-aged children, whose brain activity was measured in a custom-sized pediatric MEG system. The results showed that, unlike adults, face repetition did not show any significant modulation of M250 amplitude in children; however children's M250 latencies were significantly faster for repeated than non-repeated faces. Dynamic causal modelling (DCM) of the M250 in both age groups tested the effects of face repetition within the core face network including the occipital face area (OFA), the fusiform face area (FFA), and the superior temporal sulcus (STS). DCM revealed that repetition of identical faces altered both forward and backward connections in children and adults; however the modulations involved inputs to both FFA and OFA in adults but only to OFA in children. These findings suggest that the amplitude-insensitivity of the immature M250 may be due to a weaker connection between the FFA and lower visual areas. |
Simone G. Heideman; Gustavo Rohenkohl; Joshua J. Chauvin; Clare E. Palmer; Freek Ede; Anna C. Nobre Anticipatory neural dynamics of spatial-temporal orienting of attention in younger and older adults Journal Article In: NeuroImage, vol. 178, pp. 46–56, 2018. @article{Heideman2018a, Spatial and temporal expectations act synergistically to facilitate visual perception. In the current study, we sought to investigate the anticipatory oscillatory markers of combined spatial-temporal orienting and to test whether these decline with ageing. We examined anticipatory neural dynamics associated with joint spatial-temporal orienting of attention using magnetoencephalography (MEG) in both younger and older adults. Participants performed a cued covert spatial-temporal orienting task requiring the discrimination of a visual target. Cues indicated both where and when targets would appear. In both age groups, valid spatial-temporal cues significantly enhanced perceptual sensitivity and reduced reaction times. In the MEG data, the main effect of spatial orienting was the lateralised anticipatory modulation of posterior alpha and beta oscillations. In contrast to previous reports, this modulation was not attenuated in older adults; instead it was even more pronounced. The main effect of temporal orienting was a bilateral suppression of posterior alpha and beta oscillations. This effect was restricted to younger adults. Our results also revealed a striking interaction between anticipatory spatial and temporal orienting in the gamma-band (60–75 Hz). When considering both age groups separately, this effect was only clearly evident and only survived statistical evaluation in the older adults. Together, these observations provide several new insights into the neural dynamics supporting separate as well as combined effects of spatial and temporal orienting of attention, and suggest that different neural dynamics associated with attentional orienting appear differentially sensitive to ageing. |
Simone G. Heideman; Freek Ede; Anna C. Nobre Early behavioural facilitation by temporal expectations in complex visual-motor sequences Journal Article In: Neuroscience, vol. 389, pp. 74–84, 2018. @article{Heideman2018b, In daily life, temporal expectations may derive from incidental learning of recurring patterns of intervals. We investigated the incidental acquisition and utilisation of combined temporal-ordinal (spatial/effector) structure in complex visual-motor sequences using a modified version of a serial reaction time (SRT) task. In this task, not only the series of targets/responses, but also the series of intervals between subsequent targets was repeated across multiple presentations of the same sequence. Each participant completed three sessions. In the first session, only the repeating sequence was presented. During the second and third session, occasional probe blocks were presented, where a new (unlearned) spatial-temporal sequence was introduced. We first confirm that participants not only got faster over time, but that they were slower and less accurate during probe blocks, indicating that they incidentally learned the sequence structure. Having established a robust behavioural benefit induced by the repeating spatial-temporal sequence, we next addressed our central hypothesis that implicit temporal orienting (evoked by the learned temporal structure) would have the largest influence on performance for targets following short (as opposed to longer) intervals between temporally structured sequence elements, paralleling classical observations in tasks using explicit temporal cues. We found that indeed, reaction time differences between new and repeated sequences were largest for the short interval, compared to the medium and long intervals, and that this was the case, even when comparing late blocks (where the repeated sequence had been incidentally learned), to early blocks (where this sequence was still unfamiliar). We conclude that incidentally acquired temporal expectations that follow a sequential structure can have a robust facilitatory influence on visually-guided behavioural responses and that, like more explicit forms of temporal orienting, this effect is most pronounced for sequence elements that are expected at short inter-element intervals. |
Simone G. Heideman; Freek Ede; Anna C. Nobre Temporal alignment of anticipatory motor cortical beta lateralisation in hidden visual-motor sequences Journal Article In: European Journal of Neuroscience, vol. 48, no. 8, pp. 2684–2695, 2018. @article{Heideman2018, Performance improves when participants respond to events that are structured in repeating sequences, suggesting that learning can lead to proactive anticipatory preparation. Whereas most sequence-learning studies have emphasised spatial structure, most sequences also contain a prominent temporal structure. We used MEG to investigate spatial and temporal anticipatory neural dynamics in a modified serial reaction time (SRT) task. Performance and brain activity were compared between blocks with learned spatial-temporal sequences and blocks with new sequences. After confirming a strong behavioural benefit of spatial-temporal predictability, we show lateralisation of beta oscillations in anticipation of the response associated with the upcoming target location and show that this also aligns to the expected timing of these forthcoming events. This effect was found both when comparing between repeated (learned) and new (unlearned) sequences, as well as when comparing targets that were expected after short vs. long intervals within the repeated (learned) sequence. Our findings suggest that learning of spatial-temporal structure leads to proactive and dynamic modulation of motor cortical excitability in anticipation of both the location and timing of events that are relevant to guide action. |
Jenni Heikkilä; Kaisa Tiippana; Otto Loberg; Paavo H. T. Leppänen Neural processing of congruent and incongruent audiovisual speech in school-age children and adults Journal Article In: Language Learning, vol. 68, pp. 58–79, 2018. @article{Heikkilae2018, Seeing articulatory gestures enhances speech perception. Perception ofauditory speech can even be changed by incongruent visual gestures, which is known as the McGurk effect (e.g., dubbing a voice saying /mi/ onto a face articulating /ni/, observers often hear /ni/). In children, the McGurk effect is weaker than in adults, but no previous knowledge exists about the neural-level correlates of the McGurk effect in school-age children. Using brain event-related potentials, we investigated change detection responses to congruent and incongruent audiovisual speech in school-age children and adults. We used an oddball paradigm with a congruent audiovisual /mi/ as the standard stimulus and a congruent audiovisual /ni/ or McGurk A/mi/V/ni/ as the deviant stimulus. In adults, a similar change detection response was elicited by both deviant stimuli. In children, change detection responses differed between the congruent and the McGurk stimulus. This reflects a maturational difference in the influence of visual stimuli on auditory processing. |
Hannah Hiebel; Anja Ischebeck; Clemens Brunner; Andrey R. Nikolaev; Margit Höfler; Christof Körner Target probability modulates fixation-related potentials in visual search Journal Article In: Biological Psychology, vol. 138, pp. 199–210, 2018. @article{Hiebel2018, This study investigated the influence of target probability on the neural response to target detection in free viewing visual search. Participants were asked to indicate the number of targets (one or two) among distractors in a visual search task while EEG and eye movements were co-registered. Target probability was manipulated by varying the set size of the displays between 10, 22, and 30 items. Fixation-related potentials time-locked to first target fixations revealed a pronounced P300 at the centro-parietal cortex with larger amplitudes for set sizes 22 and 30 than for set size 10. With increasing set size, more distractor fixations preceded the detection of the target, resulting in a decreased target probability and, consequently, a larger P300. For distractors, no increase of P300 amplitude with set size was observed. The findings suggest that set size specifically affects target but not distractor processing in overt serial visual search. |
Rinat Hilo-Merkovich; Marisa Carrasco; Shlomit Yuval-Greenberg Task performance in covert, but not overt, attention correlates with early laterality of visual evoked potentials Journal Article In: Neuropsychologia, vol. 119, pp. 330–339, 2018. @article{HiloMerkovich2018, Attention affects visual perception at target locations via the amplification of stimuli signal strength, perceptual performance and perceived contrast. Behavioral and neural correlates of attention can be observed when attention is both covertly and overtly oriented (with or without accompanying eye movements). Previous studies have demonstrated that at the grand-average level, lateralization of Event Related Potentials (ERP) is associated with attentional facilitation at cued, relative to un-cued locations. Yet, the correspondence between ERP lateralization and behavior has not been established at the single-subject level. Specifically, it is an open question whether inter-individual differences in the neural manifestation of attentional orienting can predict differences in perception. Here, we addressed this question by examining the correlation between ERP lateralization and visual sensitivity at attended locations. Participants were presented with a cue indicating where a low-contrast grating patch target will appear, following a delay of varying durations. During this delay, while participants were waiting for the target to appear, a task-irrelevant checkerboard probe was presented briefly and bilaterally. ERP was measured relative to the onset of this probe. In separate blocks, participants were requested to report detection of a low-contrast target either by making a fast eye-movement toward the target (overt orienting), or by pressing a button (covert orienting). Results show that in the covert orienting condition, ERP lateralization of individual participants was positively correlated with their mean visual sensitivity for the target. But, no such correlation was found in the overt orienting condition. We conclude that ERP lateralization of individual participants can predict their performance on a covert, but not an overt, target detection task. |
Nora Hollenstein; Jonathan Rotsztejn; Marius Troendle; Andreas Pedroni; Ce Zhang; Nicolas Langer Data descriptor: ZuCo, a simultaneous EEG and eye-tracking resource for natural sentence reading Journal Article In: Scientific Data, vol. 5, pp. 180291, 2018. @article{Hollenstein2018, We present the Zurich Cognitive Language Processing Corpus (ZuCo), a dataset combining electroencephalography (EEG) and eye-tracking recordings from subjects reading natural sentences. ZuCo includes high-density EEG and eye-tracking data of 12 healthy adult native English speakers, each reading natural English text for 4–6 hours. The recordings span two normal reading tasks and one task-specific reading task, resulting in a dataset that encompasses EEG and eye-tracking data of 21,629 words in 1107 sentences and 154,173 fixations. We believe that this dataset represents a valuable resource for natural language processing (NLP). The EEG and eye-tracking signals lend themselves to train improved machine- learning models for various tasks, in particular for information extraction tasks such as entity and relation extraction and sentiment analysis. Moreover, this dataset is useful for advancing research into the human reading and language understanding process at the level of brain activity and eye-movement. |
Leyla Isik; Jedediah M. Singer; Joseph R. Madsen; Nancy Kanwisher; Gabriel Kreiman What is changing when: Decoding visual information in movies from human intracranial recordings Journal Article In: NeuroImage, vol. 180, pp. 147–159, 2018. @article{Isik2018, The majority of visual recognition studies have focused on the neural responses to repeated presentations of static stimuli with abrupt and well-defined onset and offset times. In contrast, natural vision involves unique renderings of visual inputs that are continuously changing without explicitly defined temporal transitions. Here we considered commercial movies as a coarse proxy to natural vision. We recorded intracranial field potential signals from 1,284 electrodes implanted in 15 patients with epilepsy while the subjects passively viewed commercial movies. We could rapidly detect large changes in the visual inputs within approximately 100 ms of their occurrence, using exclusively field potential signals from ventral visual cortical areas including the inferior temporal gyrus and inferior occipital gyrus. Furthermore, we could decode the content of those visual changes even in a single movie presentation, generalizing across the wide range of transformations present in a movie. These results present a methodological framework for studying cognition during dynamic and natural vision. |
Roxane J. Itier; Frank F. Preston Increased early sensitivity to eyes in mouthless faces: In support of the LIFTED model of early face processing Journal Article In: Brain Topography, vol. 31, no. 6, pp. 972–984, 2018. @article{Itier2018, The N170 ERP component is a central neural marker of early face perception usually thought to reflect holistic processing. However, it is also highly sensitive to eyes presented in isolation and to fixation on the eyes within a full face. The lateral inhibition face template and eye detector (LIFTED) model (Nemrodov et al. in NeuroImage 97:81–94, 2014) integrates these views by proposing a neural inhibition mechanism that perceptually glues features into a whole, in parallel to the activ- ity of an eye detector that accounts for the eye sensitivity. The LIFTED model was derived from a large number of results obtained with intact and eyeless faces presented upright and inverted. The present study provided a control condition to the original design by replacing eyeless with mouthless faces, hereby enabling testing of specific predictions derived from the model. Using the same gaze-contingent approach, we replicated the N170 eye sensitivity regardless of face orientation. Furthermore, when eyes were fixated in upright faces, the N170 was larger for mouthless compared to intact faces, while inverted mouthless faces elicited smaller amplitude than intact inverted faces when fixation was on the mouth and nose. The results are largely in line with the LIFTED model, in particular with the idea of an inhibition mechanism involved in holistic processing of upright faces and the lack of such inhibition in processing inverted faces. Some modifications to the original model are also proposed based on these results. |
Peiqing Jin; Jiajie Zou; Tao Zhou; Nai Ding Eye activity tracks task-relevant structures during speech and auditory sequence perception Journal Article In: Nature Communications, vol. 9, pp. 5374, 2018. @article{Jin2018a, The sensory and motor systems jointly contribute to complex behaviors, but whether motor systems are involved in high-order perceptual tasks such as speech and auditory comprehension remain debated. Here, we show that ocular muscle activity is synchronized to mentally constructed sentences during speech listening, in the absence of any sentence-related visual or prosodic cue. Ocular tracking of sentences is observed in the vertical electrooculogram (EOG), whether the eyes are open or closed, and in eye blinks measured by eyetracking. Critically, the phase of sentence-tracking ocular activity is strongly modulated by temporal attention, i.e., which word in a sentence is attended. Ocular activity also tracks high-level structures in non-linguistic auditory and visual sequences, and captures rapid fluctuations in temporal attention. Ocular tracking of non-visual rhythms possibly reflects global neural entrainment to task-relevant temporal structures across sensory and motor areas, which could serve to implement temporal attention and coordinate cortical networks. |
Juan E. Kamienkowski; Alexander Varatharajah; Mariano Sigman; Matias J. Ison Parsing a mental program: Fixation-related brain signatures of unitary operations and routines in natural visual search Journal Article In: NeuroImage, vol. 183, pp. 73–86, 2018. @article{Kamienkowski2018a, Visual search involves a sequence or routine of unitary operations (i.e. fixations) embedded in a larger mental global program. The process can indeed be seen as a program based on a while loop (while the target is not found), a conditional construct (whether the target is matched or not based on specific recognition algorithms) and a decision making step to determine the position of the next searched location based on existent evidence. Recent developments in our ability to co-register brain scalp potentials (EEG) during free eye movements has allowed investigating brain responses related to fixations (fixation-Related Potentials; fERPs), including the identification of sensory and cognitive local EEG components linked to individual fixations. However, the way in which the mental program guiding the search unfolds has not yet been investigated. We performed an EEG and eye tracking co-registration experiment in which participants searched for a target face in natural images of crowds. Here we show how unitary steps of the program are encoded by specific local target detection signatures and how the positioning of each unitary operation within the global search program can be pinpointed by changes in the EEG signal amplitude as well as the signal power in different frequency bands. By simultaneously studying brain signatures of unitary operations and those occurring during the sequence of fixations, our study sheds light into how local and global properties are combined in implementing visual routines in natural tasks. |
Carina Kelbsch; Archana Jalligampala; Torsten Strasser; Paul Richter; Katarina Stingl; Christoph Braun; Daniel L. Rathbun; Eberhart Zrenner; Helmut Wilhelm; Barbara Wilhelm; Tobias Peters; Krunoslav Stingl Phosphene perception and pupillary responses to sinusoidal electrostimulation - For an objective measurement of retinal function Journal Article In: Experimental Eye Research, vol. 176, pp. 210–218, 2018. @article{Kelbsch2018, The purpose was to evaluate retinal function by measuring pupillary responses to sinusoidal transcorneal electrostimulation in healthy young human subjects. This work also translates data from analogous in vitro experiments and connects it to the pupillary responses obtained in human experiments. 14 healthy human subjects participated (4 males, 10 females); for the in vitro experiments, two male healthy mouse retinas (adult wild-type C57B/6J) were used. Pupillary responses to sinusoidal transcorneal electrostimulation of varying stimulus carrier frequencies (10, 20 Hz; envelope frequency constantly kept at 1.2 Hz) and intensities (10, 20, 50 μA) were recorded and compared with those obtained with light stimulation (1.2 Hz sinusoidal blue, red light). A strong correlation between the sinusoidal stimulation (electrical as well as light) and the pupillary sinusoidal response was found. The difference between the lag of electrical and light stimulation allowed the estimation of an intensity threshold for pupillary responses to transcorneal electrostimulation (mean ± SD: 30 ± 10 μA (10 Hz); 38 ± 10 μA (20 Hz)). A comparison between the results of the two stimulation frequencies showed a not statistically significant smaller lag for 10 Hz (10 Hz: 633 ± 90 ms; 20 Hz: 725 ± 178 ms; 50 μA intensity). Analogous in vitro experiments on murine retinas indicated a selective stimulation of photoreceptors and bipolar cells (lower frequencies) and retinal ganglion cells (higher frequencies) and lower stimulation thresholds for the retinal network with sinusoidal compared to pulsatile stimulation – emphasizing that sinu- soidal waveforms are well-suited to our purposes. We demonstrate that pupillary responses to sinusoidal transcorneal electrostimulation are measurable as an objective marker in healthy young subjects, even at very low stimulus intensities. By using this unique approach, we unveil the potential for an estimation of the in- dividual intensity threshold and a selective activation of different retinal cell types in humans by varying the stimulation frequency. This technique may have broad clinical utility as well as specific relevance in the monitoring of patients with hereditary retinal disorders, especially as implemented in study protocols for novel therapies, e.g. retinal prostheses or gene therapies. |
Eline R. Kupers; Helena X. Wang; Kaoru Amano; Kendrick N. Kay; David J. Heeger; Jonathan Winawer A non-invasive, quantitative study of broadband spectral responses in human visual cortex Journal Article In: PLoS ONE, vol. 13, no. 3, pp. e0193107, 2018. @article{Kupers2018, Currently, non-invasive methods for studying the human brain do not routinely and reliably measure spike-rate-dependent signals, independent of responses such as hemodynamic coupling (fMRI) and subthreshold neuronal synchrony (oscillations and event-related potentials). In contrast, invasive methods-microelectrode recordings and electrocorticography (ECoG)-have recently measured broadband power elevation in field potentials (~50-200 Hz) as a proxy for locally averaged spike rates. Here, we sought to detect and quantify stimulus-related broadband responses using magnetoencephalography (MEG). Extracranial measurements like MEG and EEG have multiple global noise sources and relatively low signal-to-noise ratios; moreover high frequency artifacts from eye movements can be confounded with stimulus design and mistaken for signals originating from brain activity. For these reasons, we developed an automated denoising technique that helps reveal the broadband signal of interest. Subjects viewed 12-Hz contrast-reversing patterns in the left, right, or bilateral visual field. Sensor time series were separated into evoked (12-Hz amplitude) and broadband components (60-150 Hz). In all subjects, denoised broadband responses were reliably measured in sensors over occipital cortex, even in trials without microsaccades. The broadband pattern was stimulus-dependent, with greater power contralateral to the stimulus. Because we obtain reliable broadband estimates with short experiments (~20 minutes), and with sufficient signal-to-noise to distinguish responses to different stimuli, we conclude that MEG broadband signals, denoised with our method, offer a practical, non-invasive means for characterizing spike-rate-dependent neural activity for addressing scientific questions about human brain function. |
Hause Lin; Blair Saunders; Cendri A. Hutcherson; Michael Inzlicht Midfrontal theta and pupil dilation parametrically track subjective conflict (but also surprise) during intertemporal choice Journal Article In: NeuroImage, vol. 172, pp. 838–852, 2018. @article{Lin2018b, Many everyday choices are based on personal, subjective preferences. When choosing between two options, we often feel conflicted, especially when trading off costs and benefits occurring at different times (e.g., saving for later versus spending now). Although previous work has investigated the neurophysiological basis of conflict during inhibitory control tasks, less is known about subjective conflict resulting from competing subjective preferences. In this pre-registered study, we investigated subjective conflict during intertemporal choice, whereby participants chose between smaller immediate versus larger delayed rewards (e.g., $15 today vs. $22 in 30 days). We used economic modeling to parametrically vary eleven different levels of conflict, and recorded EEG data and pupil dilation. Midfrontal theta power, derived from EEG, correlated with pupil responses, and our results suggest that these signals track different gradations of subjective conflict. Unexpectedly, both signals were also maximally enhanced when decisions were surprisingly easy. Therefore, these signals may track events requiring increased attention and adaptive shifts in behavioral responses, with subjective conflict being only one type of such event. Our results suggest that the neural systems underlying midfrontal theta and pupil responses interact when weighing costs and benefits during intertemporal choice. Thus, understanding these interactions might elucidate how individuals resolve self-control conflicts. |
Mariya E. Manahova; Pim Mostert; Peter Kok; Jan-Mathijs Schoffelen; Floris P. Lange Stimulus familiarity and expectation jointly modulate neural activity in the visual ventral stream Journal Article In: Journal of Cognitive Neuroscience, vol. 30, no. 9, pp. 1366–1377, 2018. @article{Manahova2018, Prior knowledge about the visual world can change how a visual stimulus is processed. Two forms of prior knowledge are often distinguished: stimulus familiarity (i.e., whether a stimulus has been seen before) and stimulus expectation (i.e., whether a stimulus is expected to occur, based on the context). Neurophysiological studies in monkeys have shown suppression of spiking activity both for expected and for familiar items in object-selective inferotemporal cortex. It is an open question, however, if and how these types of knowledge interact in their modulatory effects on the sensory response. To address this issue and to examine whether previous findings generalize to noninvasively measured neural activity in humans, we separately manipulated stimulus familiarity and expectation while noninvasively recording human brain activity using magnetoencephalography. We observed independent suppression of neural activity by familiarity and expectation, specifically in the lateral occipital complex, the putative human homologue of monkey inferotemporal cortex. Familiarity also led to sharpened response dynamics, which was predominantly observed in early visual cortex. Together, these results show that distinct types of sensory knowledge jointly determine the amount of neural resources dedicated to object processing in the visual ventral stream. |
Anna Marzecová; Antonio Schettino; Andreas Widmann; Iria SanMiguel; Sonja A. Kotz; Erich Schröger Attentional gain is modulated by probabilistic feature expectations in a spatial cueing task: ERP evidence Journal Article In: Scientific Reports, vol. 8, pp. 54, 2018. @article{Marzecova2018, Several theoretical and empirical studies suggest that attention and perceptual expectations influence perception in an interactive manner, whereby attentional gain is enhanced for predicted stimuli. The current study assessed whether attention and perceptual expectations interface when they are fully orthogonal, i.e., each of them relates to different stimulus features. We used a spatial cueing task with block-wise spatial attention cues that directed attention to either left or right visual field, in which Gabor gratings of either predicted (more likely) or unpredicted (less likely) orientation were presented. The lateralised posterior N1pc component was additively influenced by attention and perceptual expectations. Bayesian analysis showed no reliable evidence for the interactive effect of attention and expectations on the N1pc amplitude. However, attention and perceptual expectations interactively influenced the frontally distributed anterior N1 component (N1a). The attention effect (i.e., enhanced N1a amplitude in the attended compared to the unattended condition) was observed only for the gratings of predicted orientation, but not in the unpredicted condition. These findings suggest that attention and perceptual expectations interactively influence visual processing within 200 ms after stimulus onset and such joint influence may lead to enhanced endogenous attentional control in the dorsal fronto-parietal attention network. |
Sarah D. McCrackin; Roxane J. Itier Is it about me? Time-course of self-relevance and valence effects on the perception of neutral faces with direct and averted gaze Journal Article In: Biological Psychology, vol. 135, pp. 47–64, 2018. @article{McCrackin2018, Most face processing research has investigated how we perceive faces presented by themselves, but we view faces everyday within a rich social context. Recent ERP research has demonstrated that context cues, including self-relevance and valence, impact electrocortical and emotional responses to neutral faces. However, the time-course of these effects is still unclear, and it is unknown whether these effects interact with the face gaze direction, a cue that inherently contains self-referential information and triggers emotional responses. We primed direct and averted gaze neutral faces (gaze manipulation) with contextual sentences that contained positive or negative opinions (valence manipulation) about the participants or someone else (self-relevance manipulation). In each trial, participants rated how positive or negative, and how affectively aroused, the face made them feel. Eye-tracking ensured sentence reading and face fixation while ERPs were recorded to face presentations. Faces put into self-relevant contexts were more arousing than those in other-relevant contexts, and elicited ERP differences from 150 to 750 ms post-face, encompassing EPN and LPP components. Self-relevance interacted with valence at both the behavioural and ERP level starting 150 ms post-face. Finally, faces put into positive, self-referential contexts elicited different N170 ERP amplitudes depending on gaze direction. Behaviourally, direct gaze elicited more positive valence ratings than averted gaze during positive, self-referential contexts. Thus, self-relevance and valence contextual cues impact visual perception of neutral faces and interact with gaze direction during the earliest stages of face processing. The results highlight the importance of studying face processing within contexts mimicking the complexities of real world interactions. |
Hyojin Park; Robin A. A. Ince; Philippe G. Schyns; Gregor Thut; Joachim Gross In: PLoS Biology, vol. 16, no. 8, pp. e2006558, 2018. @article{Park2018, Integration of multimodal sensory information is fundamental to many aspects of human behavior, but the neural mechanisms underlying these processes remain mysterious. For example, during face-to-face communication, we know that the brain integrates dynamic auditory and visual inputs, but we do not yet understand where and how such integration mechanisms support speech comprehension. Here, we quantify representational interactions between dynamic audio and visual speech signals and show that different brain regions exhibit different types of representational interaction. With a novel information theoretic measure, we found that theta (3-7 Hz) oscillations in the posterior superior temporal gyrus/sulcus (pSTG/S) represent auditory and visual inputs redundantly (i.e., represent common features of the two), whereas the same oscillations in left motor and inferior temporal cortex represent the inputs synergistically (i.e., the instantaneous relationship between audio and visual inputs is also represented). Importantly, redundant coding in the left pSTG/S and synergistic coding in the left motor cortex predict behavior-i.e., speech comprehension performance. Our findings therefore demonstrate that processes classically described as integration can have different statistical properties and may reflect distinct mechanisms that occur in different brain regions to support audiovisual speech comprehension. |
Andreas Widmann; Erich Schröger; Nicole Wetzel In: Biological Psychology, vol. 133, pp. 10–17, 2018. @article{Widmann2018, Novel sounds in the auditory oddball paradigm elicit a biphasic dilation of the pupil (PDR) and P3a as well as novelty P3 event-related potentials (ERPs). The biphasic PDR has been hypothesized to reflect the relaxation of the iris sphincter muscle due to parasympathetic inhibition and the constriction of the iris dilator muscle due to sympathetic activation. We measured the PDR and the P3 to neutral and to emotionally arousing negative novels in dark and moderate lighting conditions. By means of principal component analysis (PCA) of the PDR data we extracted two components: the early one was absent in darkness and, thus, presumably reflects parasympathetic inhibition, whereas the late component occurred in darkness and light and presumably reflects sympathetic activation. Importantly, only this sympathetic late component was enhanced for emotionally arousing (as compared to neutral) sounds supporting the hypothesis that emotional arousal specifically activates the sympathetic nervous system. In the ERPs we observed P3a and novelty P3 in response to novel sounds. Both components were enhanced for emotionally arousing (as compared to neutral) novels. Our results demonstrate that sympathetic and parasympathetic contributions to the PDR can be separated and link emotional arousal to sympathetic nervous system activation. |
Martin Völker; Lukas D. J. Fiederer; Sofie Berberich; Jiří Hammer; Joos Behncke; Pavel Kršek; Martin Tomášek; Petr Marusič; Peter C. Reinacher; Volker A. Coenen; Moritz Helias; Andreas Schulze-Bonhage; Wolfram Burgard; Tonio Ball The dynamics of error processing in the human brain as reflected by high-gamma activity in noninvasive and intracranial EEG Journal Article In: NeuroImage, vol. 173, no. 2018, pp. 564–579, 2018. @article{Voelker2018, Error detection in motor behavior is a fundamental cognitive function heavily relying on local cortical information processing. Neural activity in the high-gamma frequency band (HGB) closely reflects such local cortical processing, but little is known about its role in error processing, particularly in the healthy human brain. Here we characterize the error-related response of the human brain based on data obtained with noninvasive EEG optimized for HGB mapping in 31 healthy subjects (15 females, 16 males), and additional intracranial EEG data from 9 epilepsy patients (4 females, 5 males). Our findings reveal a multiscale picture of the global and local dynamics of error-related HGB activity in the human brain. On the global level as reflected in the noninvasive EEG, the error-related response started with an early component dominated by anterior brain regions, followed by a shift to parietal regions, and a subsequent phase characterized by sustained parietal HGB activity. This phase lasted for more than 1 s after the error onset. On the local level reflected in the intracranial EEG, a cascade of both transient and sustained error-related responses involved an even more extended network, spanning beyond frontal and parietal regions to the insula and the hippocampus. HGB mapping appeared especially well suited to investigate late, sustained components of the error response, possibly linked to downstream functional stages such as error-related learning and behavioral adaptation. Our findings establish the basic spatio-temporal properties of HGB activity as a neural correlate of error processing, complementing traditional error-related potential studies. |
Tommy J. Wilson; Michael J. Gray; Jan Willem Van Klinken; Melissa Kaczmarczyk; John J. Foxe Macronutrient composition of a morning meal and the maintenance of attention throughout the morning Journal Article In: Nutritional Neuroscience, vol. 21, no. 10, pp. 729–743, 2018. @article{Wilson2018, At present, the impact of macronutrient composition and nutrient intake on sustained attention in adults is unclear, although some prior work suggests that nutritive interventions that engender slow, steady glucose availability support sustained attention after consumption. A separate line of evidence suggests that nutrient consumption may alter electroencephalographic markers of neurophysiological activity, including neural oscillations in the alpha-band (8-14 Hz), which are known to be richly interconnected with the allocation of attention. It is here investigated whether morning ingestion of foodstuffs with differing macronutrient compositions might differentially impact the allocation of sustained attention throughout the day as indexed by both behavior and the deployment of attention-related alpha-band activity. METHODS: Twenty-four adult participants were recruited into a three-day study with a cross-over design that employed a previously validated sustained attention task (the Spatial CTET). On each experimental day, subjects consumed one of three breakfasts with differing carbohydrate availabilities (oatmeal, cornflakes, and water) and completed blocks of the Spatial CTET throughout the morning while behavioral performance, subjective metrics of hunger/fullness, and electroencephalographic (EEG) measurements of alpha oscillatory activity were recorded. RESULTS: Although behavior and electrophysiological metrics changed over the course of the day, no differences in their trajectories were observed as a function of breakfast condition. However, subjective metrics of hunger/fullness revealed that caloric interventions (oatmeal and cornflakes) reduced hunger across the experimental day with respect to the non-caloric, volume-matched control (water). Yet, no differences in hunger/fullness were observed between the oatmeal and cornflakes interventions. CONCLUSION: Observation of a relationship between macronutrient intervention and sustained attention (if one exists) will require further standardization of empirical investigations to aid in the synthesis and replicability of results. In addition, continued implementation of neurophysiological markers in this domain is encouraged, as they often produce nuanced insight into cognition even in the absence of overt behavioral changes. |
Nathalie Van Humbeeck; Radha Nila Meghanathan; Johan Wagemans; Cees Leeuwen; Andrey R. Nikolaev Presaccadic EEG activity predicts visual saliency in free-viewing contour integration Journal Article In: Psychophysiology, vol. 55, no. 12, pp. e13267, 2018. @article{VanHumbeeck2018, While viewing a scene, the eyes are attracted to salient stimuli. We set out to identify the brain signals controlling this process. In a contour integration task, in which participants searched for a collinear contour in a field of randomly oriented Gabor elements, a previously established model was applied to calculate a visual saliency value for each fixation location. We studied brain activity related to the modeled saliency values, using coregistered eye tracking and EEG. To disentangle EEG signals reflecting salience in free viewing from overlapping EEG responses to sequential eye movements, we adopted generalized additive mixed modeling (GAMM) to single epochs of saccade‐related EEG. We found that, when saliency at the next fixation location was high, amplitude of the presaccadic EEG activity was low. Since presaccadic activity reflects covert attention to the saccade target, our results indicate that larger attentional effort is needed for selecting less salient saccade targets than more salient ones. This effect was prominent in contour‐present conditions (half of the trials), but ambiguous in the contour‐absent condition. Presaccadic EEG activity may thus be indicative of bottom‐up factors in saccade guidance. The results underscore the utility of GAMM for EEG—eye movement coregistration research. |
2017 |
Matthew David Weaver; Wieske Zoest; Clayton Hickey A temporal dependency account of attentional inhibition in oculomotor control Journal Article In: NeuroImage, vol. 147, pp. 880–894, 2017. @article{Weaver2017a, We used concurrent electroencephalogram (EEG) and eye tracking to investigate the role of covert attentional mechanisms in the control of oculomotor behavior. Human participants made speeded saccades to targets that were presented alongside salient distractors. By subsequently sorting trials based on whether the distractor was strongly represented or suppressed by the visual system – as evident in the accuracy (Exp. 1) or quality of the saccade (Exp. 2) – we could characterize and contrast pre-saccadic neural activity as a function of whether oculomotor control was established. Results show that saccadic behavior is strongly linked to the operation of attentional mechanisms in visual cortex. In Experiment 1, accurate saccades were preceded by attentional selection of the target – indexed by a target-elicited N2pc component – and by attentional suppression of the distractor – indexed by early and late distractor-elicited distractor positivity (Pd) components. In Experiment 2, the strength of distractor suppression predicted the degree to which the path of slower saccades would deviate away from the distractor en route to the target. However, results also demonstrated clear dissociations of covert and overt selective control, with saccadic latency in particular showing no relationship to the latency of covert selective mechanisms. Eye movements could thus be initiated prior to the onset of attentional ERP components, resulting in stimulus-driven behaviour. Taken together, the results indicate that attentional mechanisms play a role in determining saccadic behavior, but that saccade timing is not contingent on the deployment of attention. This creates a temporal dependency, whereby attention fosters oculomotor control only when attentional mechanisms are given sufficient opportunity to impact stimuli representations before an eye movement is executed. |
Marjolein Waal; Jason Farquhar; Luciano Fasotti; Peter Desain Preserved and attenuated electrophysiological correlates of visual spatial attention in elderly subjects Journal Article In: Behavioural Brain Research, vol. 317, pp. 415–423, 2017. @article{Waal2017, Healthy aging is associated with changes in many neurocognitive functions. While on the behavioral level, visual spatial attention capacities are relatively stable with increasing age, the underlying neural processes change. In this study, we investigated attention-related modulations of the stimulus-locked event-related potential (ERP) and occipital oscillations in the alpha band (8–14 Hz) in young and elderly participants. Both groups performed a visual attention task equally well and the ERP showed comparable attention-related modulations in both age groups. However, in elderly subjects, oscillations in the alpha band were massively reduced both during the task and in the resting state and the typical task-related lateralized pattern of alpha activity was not observed. These differences between young and elderly participants were observed on the group level as well as on the single trial level. The results indicate that younger and older adults use different neural strategies to reach the same performance in a covert visual spatial attention task. |
Diana M. E. Torta; Emanuel N. Broeke; Lieve Filbrich; Benvenuto Jacob; Julien Lambert; André Mouraux Intense pain influences the cortical processing of visual stimuli projected onto the sensitized skin Journal Article In: Pain, vol. 158, no. 4, pp. 691–697, 2017. @article{Torta2017, Sensitization is a form of implicit learning produced by the exposure to a harmful stimulus. In humans and other mammals, sensitization after skin injury increases the responsiveness of peripheral nociceptors and enhances the synaptic transmission of nociceptive input in the central nervous system. Here, we show that sensitization-related changes in the central nervous system are not restricted to nociceptive pathways and, instead, also affect other sensory modalities, especially if that modality conveys information relevant for the sensitized body part. Specifically, we show that after sensitizing the forearm using high-frequency electrical stimulation (HFS) of the skin, visual stimuli projected onto the sensitized forearm elicit significantly enhanced brain responses. Whereas mechanical hyperalgesia was present both 20 and 45 minutes after HFS, the enhanced responsiveness to visual stimuli was present only 20 minutes after HFS. Taken together, our results indicate that sensitization involves both nociceptive-specific and multimodal mechanisms, having distinct time courses. |
Matthew David Weaver; Clayton Hickey; Wieske Zoest The impact of salience and visual working memory on the monitoring and control of saccadic behavior: An eye-tracking and EEG study Journal Article In: Psychophysiology, vol. 54, no. 4, pp. 544–554, 2017. @article{Weaver2017, In a concurrent eye-tracking and EEG study, we investigated the impact of salience on the monitoring and control of eye movement behavior and the role of visual working memory (VWM) capacity in mediating this effect. Participants made eye movements to a unique line-segment target embedded in a search display also containing a unique distractor. Target and distractor salience was manipulated by varying degree of orientation offset from a homogenous background. VWM capacity was measured using a change-detection task. Results showed greater likelihood of incorrect saccades when the distractor was relatively more salient than when the target was salient. Misdirected saccades to salient distractors were strongly represented in the error-monitoring system by rapid and robust errorrelated negativity (ERN), which predicted a significant adjustment of oculomotor behavior. Misdirected saccades to less-salient distractors, while arguably representing larger errors, were not as well detected or utilized by the error/ performance-monitoring system. This system was instead better engaged in tasks requiring greater cognitive control and by individuals with higher VWM capacity. Our findings show that relative salience of task-relevant and taskirrelevant stimuli can define situations where an increase in cognitive control is necessary, with individual differences in VWM capacity explaining significant variance in the degree of monitoring and control of goal-directed eye movement behavior. The present study supports a conflict-monitoring interpretation of the ERN, whereby the level of competition between different responses, and the stimuli that define these responses, was more important in the generation of an enhanced ERN than the error commission itself. |
Theresa Wildegger; Freek Ede; Mark W. Woolrich; Céline R. Gillebert; Anna C. Nobre Preparatory α-band oscillations reflect spatial gating independently of predictions regarding target identity Journal Article In: Journal of Neurophysiology, vol. 117, no. 3, pp. 1385–1394, 2017. @article{Wildegger2017, Preparatory modulations of cortical alpha-band oscillations are a reliable index of the voluntary allocation of covert spatial attention. It is currently unclear whether attentional cues containing information about a target's identity (such as its visual orientation), in addition to its location, might additionally shape preparatory alpha modulations. Here, we explore this question by directly comparing spatial and feature-based attention in the same visual detection task while recording brain activity using magneto-encephalography (MEG). At the behavioural level, preparatory feature-based and spatial attention cues both improved performance, and did so independently of each other. Using MEG, we replicated robust alpha lateralisation following spatial cues: in preparation for a visual target, alpha power decreased contralaterally, and increased ipsilaterally to the attended location. Critically, however, preparatory alpha lateralisation was not significantly modulated by predictions regarding target identity, as carried via the behaviourally effective feature-based attention cues. Furthermore, non-lateralised alpha power during the cue-target interval did not differentiate between uninformative cues and cues carrying feature-based predictions either. Based on these results we propose that preparatory alpha modulations play a role in the gating of information between spatially segregated cortical regions, and are therefore particularly well suited for spatial gating of information. |
Ulrich Pomper; Maria Chait The impact of visual gaze direction on auditory object tracking Journal Article In: Scientific Reports, vol. 7, pp. 4640, 2017. @article{Pomper2017, Subjective experience suggests that we are able to direct our auditory attention independent of our visual gaze, e.g when shadowing a nearby conversation at a cocktail party. But what are the consequences at the behavioural and neural level? While numerous studies have investigated both auditory attention and visual gaze independently, little is known about their interaction during selective listening. In the present EEG study, we manipulated visual gaze independently of auditory attention while participants detected targets presented from one of three loudspeakers. We observed increased response times when gaze was directed away from the locus of auditory attention. Further, we found an increase in occipital alpha-band power contralateral to the direction of gaze, indicative of a suppression of distracting input. Finally, this condition also led to stronger central theta-band power, which correlated with the observed effect in response times, indicative of differences in top-down processing. Our data suggest that a misalignment between gaze and auditory attention both reduce behavioural performance and modulate underlying neural processes. The involvement of central theta-band and occipital alpha-band effects are in line with compensatory neural mechanisms such as increased cognitive control and the suppression of task irrelevant inputs. |
Tzvetan Popov; Sabine Kastner; Ole Jensen FEF-controlled alpha delay activity precedes stimulus-induced gamma-band activity in visual cortex Journal Article In: Journal of Neuroscience, vol. 37, no. 15, pp. 4117–4127, 2017. @article{Popov2017, Recent findings in the visual system of nonhuman primates have demonstrated an important role of gamma-band activity (40–100 Hz) in the feedforward flow of sensory information, whereas feedback control appears to be established dynamically by oscillations in the alpha (8–13 Hz) and beta (13–18 Hz) bands (van Kerkoerle et al., 2014; Bastos et al., 2015). It is not clear, however, how alpha oscillations are controlled and how they interact with the flow of visual information mediated by gamma-band activity. Using noninvasive human MEG recordings in subjects performing a visuospatial attention task, we show that fluctuations in alpha power during a delay period in a spatial attention task preceded subsequent stimulus-driven gamma-band activity. Importantly, these interactions correlated with behavioral performance. Using Granger analysis, we further show that the right frontal-eye field (rFEF) exerted feedback control of the visual alpha oscillations. Our findings suggest that alpha oscillations controlled by the FEF route cortical information flow by modulating gamma-band activity. |
Malcolm Proudfoot; Gustavo Rohenkohl; Andrew Quinn; Giles L. Colclough; Joanne Wuu; Kevin Talbot; Mark W. Woolrich; Michael Benatar; Anna C. Nobre; Martin R. Turner Altered cortical beta-band oscillations reflect motor system degeneration in amyotrophic lateral sclerosis Journal Article In: Human Brain Mapping, vol. 38, pp. 237–254, 2017. @article{Proudfoot2017, Continuous rhythmic neuronal oscillations underpin local and regional cortical communication. The impact of the motor system neurodegenerative syndrome amyotrophic lateral sclerosis (ALS) on the neuronal oscillations subserving movement might therefore serve as a sensitive marker of disease activity. Movement preparation and execution are consistently associated with modulations to neuronal oscillation beta (15–30 Hz) power. Cortical beta-band oscillations were measured using magnetoencephalography (MEG) during preparation for, execution, and completion of a visually cued, lateralized motor task that included movement inhibition trials. Eleven “classical” ALS patients, 9 with the primary lateral sclerosis (PLS) phenotype, and 12 asymptomatic carriers of ALS-associated gene mutations were compared with age-similar healthy control groups. Augmented beta desynchronization was observed in both contra- and ipsilateral motor cortices of ALS patients during motor preparation. Movement execution coincided with excess beta desynchronization in asymptomatic mutation carriers. Movement completion was followed by a slowed rebound of beta power in all symptomatic patients, further reflected in delayed hemispheric lateralization for beta rebound in the PLS group. This may correspond to the particular involvement of interhemispheric fibers of the corpus callosum previously demonstrated in diffusion tensor imaging studies. We conclude that the ALS spectrum is characterized by intensified cortical beta desynchronization followed by delayed rebound, concordant with a broader concept of cortical hyperexcitability, possibly through loss of inhibitory interneuronal influences. MEG may potentially detect cortical dysfunction prior to the development of overt symptoms, and thus be able to contribute to the assessment of future neuroprotective strategies. |
Craig G. Richter; Mariana Babo-Rebelo; Denis Schwartz; Catherine Tallon-Baudry In: NeuroImage, vol. 146, pp. 951–958, 2017. @article{Richter2017, A fundamental feature of the temporal organization of neural activity is phase-amplitude coupling between brain rhythms at different frequencies, where the amplitude of a higher frequency varies according to the phase of a lower frequency. Here, we show that this rule extends to brain-organ interactions. We measured both the infra-slow (~0.05 Hz) rhythm intrinsically generated by the stomach – the gastric basal rhythm – using electrogastrography, and spontaneous brain dynamics with magnetoencephalography during resting-state with eyes open. We found significant phase-amplitude coupling between the infra-slow gastric phase and the amplitude of the cortical alpha rhythm (10–11 Hz), with gastric phase accounting for 8% of the variance of alpha rhythm amplitude fluctuations. Gastric-alpha coupling was localized to the right anterior insula, and bilaterally to occipito-parietal regions. Transfer entropy, a measure of directionality of information transfer, indicates that gastric-alpha coupling is due to an ascending influence from the stomach to both the right anterior insula and occipito-parietal regions. Our results show that phase-amplitude coupling so far only observed within the brain extends to brain-viscera interactions. They further reveal that the temporal structure of spontaneous brain activity depends not only on neuron and network properties endogenous to the brain, but also on the slow electrical rhythm generated by the stomach. |
Joseph Schmidt; Gregory J. Zelinsky Adding details to the attentional template offsets search difficulty: Evidence from contralateral delay activity Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 43, no. 3, pp. 429–437, 2017. @article{Schmidt2017a, We investigated how expected search difficultly affects the attentional template by having participants search for a teddy bear target among either other teddy bears (difficult search, high target-distractor similarity) or random nonbear objects (easy search, low target-distractor similarity). Target previews were identical in these 2 blocked conditions, and target-related visual working memory (VWM) load was measured using contralat- eral delay activity (CDA), an event-related potential indicating VWM load. CDA was assessed after target designation but before search display onset. Shortly after preview offset, the expectation of a difficult search produced a target-related CDA, suggesting the encoding and maintenance of target details inVWM.However, no differences in CDA were found immediately before search onset, suggesting a flexible and efficient weighting of the templates' features to reflect the expected demands of the search task. Moreover, CDA amplitude correlated with eye movement measures of search guidance in difficult search trials but not easy trials, suggesting that the utility of the attentional template is greater for more difficult searches. These findings are evidence that attentional templates depend on expected task difficulty, and that people may compensate for a more difficult search by adding details to their target representation in VWM, as measured by CDA. |
Hossein Seidkhani; Andrey R. Nikolaev; Radha Nila Meghanathan; Hamid Pezeshk; Ali Masoudi-Nejad; Cees Leeuwen Task modulates functional connectivity networks in free viewing behavior Journal Article In: NeuroImage, vol. 159, pp. 289–301, 2017. @article{Seidkhani2017, In free visual exploration, eye-movement is immediately followed by dynamic reconfiguration of brain functional connectivity. We studied the task-dependency of this process in a combined visual search-change detection experiment. Participants viewed two (nearly) same displays in succession. First time they had to find and remember multiple targets among distractors, so the ongoing task involved memory encoding. Second time they had to determine if a target had changed in orientation, so the ongoing task involved memory retrieval. From multichannel EEG recorded during 200 ms intervals time-locked to fixation onsets, we estimated the functional connectivity using a weighted phase lag index at the frequencies of theta, alpha, and beta bands, and derived global and local measures of the functional connectivity graphs. We found differences between both memory task conditions for several network measures, such as mean path length, radius, diameter, closeness and eccentricity, mainly in the alpha band. Both the local and the global measures indicated that encoding involved a more segregated mode of operation than retrieval. These differences arose immediately after fixation onset and persisted for the entire duration of the lambda complex, an evoked potential commonly associated with early visual perception. We concluded that encoding and retrieval differentially shape network configurations involved in early visual perception, affecting the way the visual input is processed at each fixation. These findings demonstrate that task requirements dynamically control the functional connectivity networks involved in early visual perception. |
Alon Shapira; Anna Sterkin; Moshe Fried; Oren Yehezkel; Zeev Zalevsky; Uri Polat Increased gamma band activity for lateral interactions in humans Journal Article In: PLoS ONE, vol. 12, no. 12, pp. e0187520, 2017. @article{Shapira2017, Collinear facilitation of contrast sensitivity supported by lateral interactions within primary visual cortex is implicated in contour and object perception, with neural correlates in several frequency bands. Although higher component of the ERP power spectrum, the gamma-band, is postulated to reflect object representation, attention and memory, its neuronal source has been questioned, suggesting it is an artifact reflecting saccadic eye movements. Here we explored the gamma-band activity during collinear facilitation with no saccade-related confounds. We used single-trial spectral analysis of ERP in occipital channels in a time-window of nearly complete saccadic suppression and discarded sporadic trials containing saccades, in order to avoid saccadic artifacts. Although converging evidence suggests that gamma-band oscillations emerge from local excitatory–inhibitory balance involving GABAergic inhibition, here we show activity amplification during facilitatory collinear interactions, presumably dominated by excitations, in the gamma-band 150–350 milliseconds following onset of low near-threshold contrast stimulus. This result highlights the potential role of gamma-band oscillations in neuronal encoding of basic processes in visual perception. Thus, our findings suggest that gamma-band ERP spectrum analysis may serve as a useful and reliable tool for exploring basic perception, both in normal adults and in special populations. |
Talia Shrem; Micah M. Murray; Leon Y. Deouell Auditory-visual integration modulates location-specific repetition suppression of auditory responses Journal Article In: Psychophysiology, vol. 54, no. 11, pp. 1663–1675, 2017. @article{Shrem2017a, Space is a dimension shared by different modalities, but at what stage spatial encoding is affected by multisensory processes is unclear. Early studies observed attenuation of N1/P2 auditory evoked responses following repetition of sounds from the same location. Here, we asked whether this effect is modulated by audiovisual interactions. In two experiments, using a repetition-suppression paradigm, we presented pairs of tones in free field, where the test stimulus was a tone presented at a fixed lateral location. Experiment 1 established a neural index of auditory spatial sensitivity, by comparing the degree of attenuation of the response to test stimuli when they were preceded by an adapter sound at the same location versus 30° or 60° away. We found that the degree of attenuation at the P2 latency was inversely related to the spatial distance between the test stimulus and the adapter stimulus. In Experiment 2, the adapter stimulus was a tone presented from the same location or a more medial location than the test stimulus. The adapter stimulus was accompanied by a simultaneous flash displayed orthogonally from one of the two locations. Sound-flash incongruence reduced accuracy in a same-different location discrimination task (i.e., the ventriloquism effect) and reduced the location-specific repetition-suppression at the P2 latency. Importantly, this multisensory effect included topographic modulations, indicative of changes in the relative contribution of underlying sources across conditions. Our findings suggest that the auditory response at the P2 latency is affected by spatially selective brain activity, which is affected crossmodally by visual information. |
P. Sotnikov; K. Finagin; S. Vidunova Selection of optimal frequency bands of the electroencephalogram signal in eye-brain-computer interface Journal Article In: Procedia Computer Science, vol. 103, pp. 168–175, 2017. @article{Sotnikov2017, An eye-brain-computer interface (EBCI) is a hybrid system that combines properties of eye tracking systems and brain-computer interfaces, based on the analysis of the electroencephalogram (EEG). In the hybrid interface the object of interest on a screen is determined by tracking the user's gaze direction. At the same time, the EEG signal is used to detect the user's intent to give a command. This article discusses the recognition of EEG patterns that correspond to spontaneous and control gaze fixations. We propose to extract the most informative features of the EEG signal by selecting optimal frequency bands of the signal. The method is based on solving one-criterion optimization task, in which variable parameters are the boundaries of frequency bands, and the quality of the class separation acts as an objective function. To find optimal values of variable parameters we suggest using the particle swarm optimization. We evaluate the efficiency of the proposed method on EEG recordings obtained at the Kurchatov Complex of NBICS Technologies for users working with a hybrid interface. It is shown that for all users our method improves classification accuracy in comparison with other methods of feature extraction. |
Bernhard Spitzer; Leonhard Waschke; Christopher Summerfield Selective overweighting of larger magnitudes during noisy numerical comparison Journal Article In: Nature Human Behaviour, vol. 1, no. 8, pp. 1–8, 2017. @article{Spitzer2017, Humans are often required to compare average magnitudes in numerical data; for example, when comparing product prices on two rival consumer websites. However, the neural and com- putational mechanisms by which numbers are weighted, inte- grated and compared during categorical decisions are largely unknown1–5 . Here, we show a systematic deviation from ‘opti- mality' in both visual and auditory tasks requiring averaging of symbolic numbers. Participants comparing numbers drawn from two categories selectively overweighted larger numbers when making a decision, and larger numbers evoked dispro- portionately stronger decision-related neural signals over the parietal cortex. A representational similarity analysis6 showed that neural (dis)similarity in patterns of electroencephalo- gram activity reflected numerical distance, but that encod- ing of number in neural data was systematically distorted in a way predicted by the behavioural weighting profiles, with greater neural distance between adjacent larger numbers. Finally, using a simple computational model, we show that although it is suboptimal for a lossless observer, this selective overweighting policy paradoxically maximizes expected accu- racy by making decisions more robust to noise arising during approximate numerical integration2 . In other words, although selective overweighting discards decision information, it can be beneficial for limited-capacity agents engaging in rapid numerical numerical averaging. |
Tobias Staudigl; Elisabeth Hartl; Soheyl Noachtar; Christian F. Doeller; Ole Jensen Saccades are phase-locked to alpha oscillations in the occipital and medial temporal lobe enhance memory encoding Journal Article In: PLoS Biology, vol. 15, no. 12, pp. e2003404, 2017. @article{Staudigl2017, Efficient sampling of visual information requires a coordination of eye movements and ongoing brain oscillations. Using intracranial and MEG recordings, we show that saccades are locked to the phase of visual alpha oscillations, and that this coordination supports mnemonic encoding of visual scenes. Furthermore, parahippocampal and retrosplenial cortex involvement in this coordination reflects effective vision-to-memory mapping, highlighting the importance of neural oscillations for the interaction between visual and memory domains. |
Jan-philipp Tauscher; Maryam Mustafa; Marcus Magnor; T. U. Braunschweig Comparative analysis of three different modalities for perception of artifacts in videos Journal Article In: ACM Transactions on Applied Perception, vol. 14, no. 4, pp. 1–12, 2017. @article{Tauscher2017, This study compares three popular modalities for analyzing perceived video quality; user ratings, eye tracking, and EEG. We contrast these three modalities for a given video sequence to determine if there is a gap between what humans consciously see and what we implicitly perceive. Participants are shown a video sequence with different artifacts appearing at specific distances in their field of vision; near foveal, middle peripheral, and far peripheral. Our results show distinct differences between what we saccade to (eye tracking), howwe consciously rate video quality, and our neural responses (EEG data). Our findings indicate that the measurement of perceived quality depends on the specific modality used. |
Tahereh Toosi; Ehsan K. Tousi; Hossein Esteky Learning temporal context shapes prestimulus alpha oscillations and improves visual discrimination performance Journal Article In: Journal of Neurophysiology, vol. 118, no. 2, pp. 771–777, 2017. @article{Toosi2017, Time is an inseparable component of every physical event that we perceive, yet it is not clear how the brain processes time or how the neuronal representation of time affects our perception of events. Here, we asked subjects to perform a visual discrimination task, while we changed the temporal context in which the stimuli were presented. We collected electroencephalography (EEG) signals in two temporal contexts. Predictable blocks: stimuli were presented after a constant delay relative to a visual cue, and unpredictable blocks: stimuli were presented after variable delays relative to the visual cue. Four sub-second delays of 83, 150, 400 and 800 ms were used in the predictable and unpredictable blocks. We observed that predictability modulated the power of prestimulus alpha oscillations in the parieto-occipital sites and this modulation only occurred in the longest delay period, 800 ms, in which the predictability also improved the behavioral performance of the subjects. Moreover, learning the temporal context shaped the prestimulus alpha power: modulation of prestimulus alpha power grew during the predictable block and correlated with performance enhancement. These results suggest that the brain is able to learn the sub-second temporal context of stimuli and use this to enhance the sensory processing. Furthermore, the neural correlate of this temporal prediction is reflected in the alpha oscillations. |
Daniel P. Newman; Gerard M. Loughnane; Simon P. Kelly; Redmond G. O'Connell; Mark A. Bellgrove Visuospatial asymmetries arise from differences in the onset time of perceptual evidence accumulation Journal Article In: Journal of Neuroscience, vol. 37, no. 12, pp. 3378–3385, 2017. @article{Newman2017, Healthy subjects tend to exhibit a bias of visual attention whereby left hemifield stimuli are processed more quickly and accurately than stimuli appearing in the right hemifield. It has long been held that this phenomenon arises from the dominant role of the right cerebral hemisphere in regulating attention. However, methods that would enable more precise understanding of the mechanisms underpinning visuospatial bias have remained elusive. We sought to finely trace the temporal evolution of spatial biases by leveraging a novel bilateral dot motion detection paradigm. In combination with electroencephalography, this paradigm enables researchers to isolate discrete neural signals reflecting the key neural processes needed for making these detection decisions. These include signals for spatial attention, early target selection, evidence accumulation, and motor preparation. Using this method, we established that three key neural markers accounted for unique between-subject variation in visuospatial bias: hemispheric asymmetry in posterior α power measured before target onset, which is related to the distribution of preparatory attention across the visual field; asymmetry in the peak latency of the early N2c target-selection signal; and, finally, asymmetry in the onset time of the subsequent neural evidence-accumulation process with earlier onsets for left hemifield targets. Our development of a single paradigm to dissociate distinct processing components that track the temporal evolution of spatial biases not only advances our understanding of the neural mechanisms underpinning normal visuospatial attention bias, but may also in the future aid differential diagnoses in disorders of spatial attention. |
C. J. Aine; H. J. Bockholt; J. R. Bustillo; J. M. Cañive; A. Caprihan; C. Gasparovic; F. M. Hanlon; J. M. Houck; R. E. Jung; J. Lauriello; J. Liu; A. R. Mayer; N. I. Perrone-Bizzozero; S. Posse; Julia M. Stephen; J. A. Turner; V. P. Clark; Vince D. Calhoun Multimodal neuroimaging in schizophrenia: Description and dissemination Journal Article In: Neuroinformatics, vol. 15, no. 4, pp. 343–364, 2017. @article{Aine2017, In this paper we describe an open-access collection ofmultimodal neuroimaging data in schizophrenia for release to the community. Data were acquired from approximately 100 patients with schizophrenia and 100 age-matched controls during rest as well as several task activation paradigms targeting a hierarchy of cognitive constructs. Neuroimaging data include structural MRI, functional MRI, diffusion MRI, MR spectroscopic imaging, and magnetoencephalography. For three of the hypothesis-driven projects, task activation paradigms were acquired on subsets of~200 volunteers which examined a range of sensory and cognitive processes (e.g., auditory sensory gating, auditory/visual multisensory integration, visual transverse patterning). Neuropsychological data were also acquired and genetic material via saliva samples were collected from most of the participants and have been typed for both genome-wide polymorphism data as well as genome-wide methylation data. Some results are also present- ed from the individual studies as well as from our data-driven multimodal analyses (e.g., multimodal examinations of network structure and network dynamics and multitask fMRI data analysis across projects). All data will be released through the Mind Research Network's collaborative informatics and neuroimaging suite (COINS). |
Lucía Amoruso; Agustín Ibáñez; Bruno Fonseca; Sebastián Gadea; Lucas Sedeño; Mariano Sigman; Adolfo M. García; Ricardo Fraiman; Daniel Fraiman Variability in functional brain networks predicts expertise during action observation Journal Article In: NeuroImage, vol. 146, pp. 690–700, 2017. @article{Amoruso2017, Observing an action performed by another individual activates, in the observer, similar circuits as those involved in the actual execution of that action. This activation is modulated by prior experience; indeed, sustained training in a particular motor domain leads to structural and functional changes in critical brain areas. Here, we capitalized on a novel graph-theory approach to electroencephalographic data (Fraiman et al., 2016) to test whether variability in functional brain networks implicated in Tango observation can discriminate between groups differing in their level of expertise. We found that experts and beginners significantly differed in the functional organization of task-relevant networks. Specifically, networks in expert Tango dancers exhibited less variability and a more robust functional architecture. Notably, these expertise-dependent effects were captured within networks derived from electrophysiological brain activity recorded in a very short time window (2 s). In brief, variability in the organization of task-related networks seems to be a highly sensitive indicator of long-lasting training effects. This finding opens new methodological and theoretical windows to explore the impact of domain-specific expertise on brain plasticity, while highlighting variability as a fruitful measure in neuroimaging research. |
Ayelet Arazi; Gil Gonen-Yaacovi; Ilan Dinstein The magnitude of trial-by-trial neural variability Is reproducible over time and across tasks in humans Journal Article In: eNeuro, vol. 4, no. 6, pp. 1–12, 2017. @article{Arazi2017, Numerous studies have shown that neural activity in sensory cortices is remarkably variable over time and across trials even when subjects are presented with an identical repeating stimulus or task. This trial-by-trial neural variability is relatively large in the prestimulus period and considerably smaller (quenched) following stimulus presentation. Previous studies have suggested that the magnitude of neural variability affects behavior such that perceptual performance is better on trials and in individuals where variability quenching is larger. To what degree are neural variability magnitudes of individual subjects flexible or static? Here, we used EEG recordings from adult humans to demonstrate that neural variability magnitudes in visual cortex are remarkably consistent across different tasks and recording sessions. While magnitudes of neural variability differed dramatically across individual subjects, they were surprisingly stable across four tasks with different stimuli, temporal structures, and attentional/cognitive demands as well as across experimental sessions separated by one year. These experiments reveal that, in adults, neural variability magnitudes are mostly solidified individual characteristics that change little with task or time, and are likely to predispose individual subjects to exhibit distinct behavioral capabilities. |
Cathleen Bache; Anne Springer; Hannes Noack; Waltraud Stadler; Franziska Kopp; Ulman Lindenberger; Markus Werkle-Bergner 10-month-old infants are sensitive to the time course of perceived actions: Eye-tracking and EEG evidence Journal Article In: Frontiers in Psychology, vol. 8, pp. 1170, 2017. @article{Bache2017, Research has shown that infants are able to track a moving target efficiently – even if it is transiently occluded from sight. This basic ability allows prediction of when and where events happen in everyday life. Yet, it is unclear whether, and how, infants internally represent the time course of ongoing movements to derive predictions. In this study, 10-month-old crawlers observed the video of a same-aged crawling baby that was transiently occluded and reappeared in either a temporally continuous or non-continuous manner (i.e., delayed by 500 ms vs. forwarded by 500 ms relative to the real-time movement). Eye movement and rhythmic neural brain activity (EEG) were measured simultaneously. Eye movement analyses showed that infants were sensitive to slight temporal shifts in movement continuation after occlusion. Furthermore, brain activity associated with sensorimotor processing differed between observation of continuous and non-continuous movements. Early sensitivity to an action's timing may hence be explained within the internal real-time simulation account of action observation. Overall, the results support the hypothesis that 10-month-old infants are well prepared for internal representation of the time course of observed movements that are within the infants' current motor repertoire. |
Mareike Bayer; Valentina Rossi; Naomi Vanlessen; Annika Grass; Annekathrin Schacht; Gilles Pourtois Independent effects of motivation and spatial attention in the human visual cortex Journal Article In: Social Cognitive and Affective Neuroscience, vol. 12, no. 1, pp. 146–156, 2017. @article{Bayer2017a, Motivation and attention constitute major determinants of human perception and action. Nonetheless, it remains a matter of debate whether motivation effects on the visual cortex depend on the spatial attention system, or rely on independent pathways. This study investigated the impact of motivation and spatial attention on the activity of the human primary and extrastriate visual cortex by employing a factorial manipulation of the two factors in a cued pattern discrimination task. During stimulus presentation, we recorded event-related potentials and pupillary responses. Motivational relevance increased the amplitudes of the C1 component at ∼70 ms after stimulus onset. This modulation occurred independently of spatial attention effects, which were evident at the P1 level. Furthermore, motivation and spatial attention had independent effects on preparatory activation as measured by the contingent negative variation; and pupil data showed increased activation in response to incentive targets. Taken together, these findings suggest independent pathways for the influence of motivation and spatial attention on the activity of the human visual cortex. |
Mareike Bayer; Katja Ruthmann; Annekathrin Schacht The impact of personal relevance on emotion processing: Evidence from event-related potentials and pupillary responses Journal Article In: Social Cognitive and Affective Neuroscience, vol. 12, no. 9, pp. 1470–1479, 2017. @article{Bayer2017, Emotional stimuli attract attention and lead to increased activity in the visual cortex. The present study investigated the impact of personal relevance on emotion processing by presenting emotional words within sentences that referred to participants' significant others or to unknown agents. In event-related potentials, personal relevance increased visual cortex activity within 100 ms after stimulus onset and the amplitudes of the Late Positive Complex (LPC). Moreover, personally relevant contexts gave rise to augmented pupillary responses and higher arousal ratings, suggesting a general boost of attention and arousal. Finally, personal relevance increased emotion-related ERP effects starting around 200 ms after word onset; effects for negative words compared to neutral words were prolonged in duration. Source localizations of these interactions revealed activations in prefrontal regions, in the visual cortex and in the fusiform gyrus. Taken together, these results demonstrate the high impact of personal relevance on reading in general and on emotion processing in particular. |
Annabelle Blangero; Simon P. Kelly Neural signature of value-based sensorimotor prioritization in humans Journal Article In: Journal of Neuroscience, vol. 37, no. 44, pp. 10725–10737, 2017. @article{Blangero2017, In situations in which impending sensory events demand fast action choices, we must be ready to prioritize higher-value courses of action to avoid missed opportunities. When such a situation first presents itself, stimulus-action contingencies and their relative value must be encoded to establish a value-biased state of preparation for an impending sensorimotor decision. Here, we sought to identify neurophysiological signatures of such processes in the human brain (both female and male). We devised a task requiring fast action choices based on the discrimination of a simple visual cue in which the differently valued sensory alternatives were presented 750-800 ms before as peripheral "targets" that specified the stimulus-action mapping for the upcoming decision. In response to the targets, we identified a discrete, transient, spatially selective signal in the event-related potential (ERP), which scaled with relative value and strongly predicted the degree of behavioral bias in the upcoming decision both across and within subjects. This signal is not compatible with any hitherto known ERP signature of spatial selection and also bears novel distinctions with respect to characterizations of value-sensitive, spatially selective activity found in sensorimotor areas of nonhuman primates. Specifically, a series of follow-up experiments revealed that the signal was reliably invoked regardless of response laterality, response modality, sensory feature, and reward valence. It was absent, however, when the response deadline was relaxed and the strategic need for biasing removed. Therefore, more than passively representing value or salience, the signal appears to play a versatile and active role in adaptive sensorimotor prioritization. |
Nathan Caruana; Peter Lissa; Genevieve McArthur Beliefs about human agency influence the neural processing of gaze during joint attention Journal Article In: Social Neuroscience, vol. 12, no. 2, pp. 194–206, 2017. @article{Caruana2017b, The current study measured adults' P350 and N170 ERPs while they interacted with a character in a virtual reality paradigm. Some participants believed the character was controlled by a human ("avatar" condition |
Jing Chen; Matteo Valsecchi; Karl R. Gegenfurtner Enhanced brain responses to color during smooth-pursuit eye movements Journal Article In: Journal of Neurophysiology, vol. 118, pp. 749–754, 2017. @article{Chen2017a, Eye movements alter visual perceptions in a number of ways. During smooth pursuit eye movements, previous studies reported decreased detection threshold for colored stimuli and for high-spatial-frequency luminance stimuli, suggesting a boost in the parvocellular system. The present study investigated the underlying neural mechanism using EEG in human participants. Participants followed a moving target with smooth pursuit eye movements while steady-state visually Evoked potentials (SSVEPs) were elicited by equiluminant red-green flickering gratings in the background. SSVEP responses to color gratings were 18.9% higher during smooth pursuit than during fixation. There was no enhancement of SSVEPs by smooth pursuit when the flickering grating was defined by luminance instead of color. This result provides physiological evidence that the chromatic response in the visual system is boosted by the execution of smooth pursuit eye movements in humans. Since the response improvement is thought to be due to an improved response in the parvocellular system, SSVEPs to equiluminant stimuli could provide a direct test of parvocellular signaling, especially in populations where an explicit behavioral response from the participant is not feasible. |
Daniel J. Acheson; Peter Hagoort Stimulating the brainʼs language network: Syntactic ambiguity resolution after TMS to the inferior frontal gyrus and middle temporal gyrus Journal Article In: Journal of Cognitive Neuroscience, vol. 25, no. 10, pp. 1664–1677, 2017. @article{Acheson2017, The posterior middle temporal gyrus (MTG) and inferior frontal gyrus (IFG) are two critical nodes of the brainʼs language network. Previous neuroimaging evidence has supported a dis- sociation in language comprehension in which parts of the MTG are involved in the retrieval of lexical syntactic informa- tion and the IFG in unification operations that maintain, select, and integrate multiple sources of information over time. In the present investigation, we tested for causal evidence of this dis- sociation by modulating activity in IFG and MTG using an off- line TMS procedure: continuous theta-burst stimulation. Lexical–syntactic retrieval was manipulated by using sentences with and without a temporarily word-class (noun/verb) ambiguity (e.g., run). In one group of participants, TMS was applied to the IFG and MTG, and in a control group, no TMS was applied. Eye movements were recorded and quantified at two critical sentence regions: a temporarily ambiguous region and a disambig- uating region. Results show that stimulation of the IFG led to a modulation of the ambiguity effect (ambiguous–unambiguous) at the disambiguating sentence region in three measures: first fixation durations, total reading times, and regressive eye movements into the region. Both IFG and MTG stimulation modulated the ambiguity effect for total reading times in the temporarily ambiguous sentence region relative to the control group. The current results demonstrate that an offline repetitive TMS protocol can have influences at a different point in time during online processing and provide causal evidence for IFG involvement in unification operations during sentence comprehension. |
Hui-Yan Chiau; Neil G. Muggleton; Chi-Hung Juan Exploring the contributions of the supplementary eye field to subliminal inhibition using double-pulse transcranial magnetic stimulation Journal Article In: Human Brain Mapping, vol. 38, pp. 339–351, 2017. @article{Chiau2017, It is widely accepted that the supplementary eye fields (SEF) are involved in the control of voluntary eye movements. However, recent evidence suggests that SEF may also be important for unconscious and involuntary motor processes. Indeed, Sumner et al. ([2007]: Neuron 54:697-711) showed that patients with micro-lesions of the SEF demonstrated an absence of subliminal inhibition as evoked by masked-prime stimuli. Here, we used double-pulse transcranial magnetic stimulation (TMS) in healthy volunteers to investigate the role of SEF in subliminal priming. We applied double-pulse TMS at two time windows in a masked-prime task: the first during an early phase, 20-70 ms after the onset of the mask but before target presentation, during which subliminal inhibition is present; and the second during a late phase, 20-70 ms after target onset, during which the saccade is being prepared. We found no effect of TMS with the early time window of stimulation, whereas a reduction in the benefit of an incompatible subliminal prime stimulus was found when SEF TMS was applied at the late time window. These findings suggest that there is a role for SEF related to the effects of subliminal primes on eye movements, but the results do not support a role in inhibiting the primed tendency. |
Sergio Delle Monache; Francesco Lacquaniti; Gianfranco Bosco In: Journal of Neurophysiology, vol. 118, no. 3, pp. 1809–1823, 2017. @article{DelleMonache2017, The ability to catch objects when tran- siently occluded from view suggests their motion can be extrapolated. Intraparietal cortex (IPS) plays a major role in this process along with other brain structures, depending on the task. For example, intercep- tion of objects under Earth's gravity effects may depend on time-to-contact predictions derived from integration of visual signals processed by hMT/V5⫹ with a priori knowledge of gravity residing in the temporoparietal junction (TPJ). To investigate this issue further, we disrupted TPJ, hMT/V5⫹, and IPS activities with transcranial magnetic stimulation (TMS) while subjects intercepted computer- simulated projectile trajectories perturbed randomly with either hypo- or hypergravity effects. In experiment 1, trajectories were occluded either 750 or 1,250 ms before landing. Three subject groups underwent triple-pulse TMS (tpTMS, 3 pulses at 10 Hz) on one target area (TPJ | hMT/V5⫹ | IPS) and on the vertex (control site), timed at either trajectory perturbation or occlusion. In experiment 2, trajectories were entirely visible and participants received tpTMS on TPJ and hMT/ V5+ with same timing as experiment 1. tpTMS of TPJ, hMT/V5⫹, and IPS affected differently the interceptive timing. TPJ stimulation affected preferentially responses to 1-g motion, hMT/V5+ all response types, and IPS stimulation induced opposite effects on 0-g and 2-g responses, being ineffective on 1-g responses. Only IPS stimulation was effective when applied after target disappearance, implying this area might elaborate memory representations of occluded target motion. Results are compatible with the idea that IPS, TPJ, and hMT/V5+ contribute to distinct aspects of visual motion extrapolation, perhaps through parallel processing. |
Grace Edwards; Céline Paeye; Philippe Marque; Rufin VanRullen; Patrick Cavanagh Predictive position computations mediated by parietal areas: TMS evidence Journal Article In: NeuroImage, vol. 153, pp. 49–57, 2017. @article{Edwards2017, When objects move or the eyes move, the visual system can predict the consequence and generate a percept of the target at its new position. This predictive localization may depend on eye movement control in the frontal eye fields (FEF) and the intraparietal sulcus (IPS) and on motion analysis in the medial temporal area (MT). Across two experiments we examined whether repetitive transcranial magnetic stimulation (rTMS) over right FEF, right IPS, right MT, and a control site, peripheral V1/V2, diminished participants' perception of two cases of predictive position perception: trans-saccadic fusion, and the flash grab illusion, both presented in the contralateral visual field. In trans-saccadic fusion trials, participants saccade toward a stimulus that is replaced with another stimulus during the saccade. Frequently, predictive position mechanisms lead to a fused percept of pre- and post-saccade stimuli (Paeye et al., 2017). We found that rTMS to IPS significantly decreased the frequency of perceiving trans-saccadic fusion within the first 10 min after stimulation. In the flash grab illusion, a target is flashed on a moving background leading to the percept that the target has shifted in the direction of the motion after the flash (Cavanagh and Anstis, 2013). In the first experiment, the reduction in the flash grab illusion after rTMS to IPS and FEF did not reach significance. In the second experiment, using a stronger version of the flash grab, the illusory shift did decrease significantly after rTMS to IPS although not after rTMS to FEF or to MT. These findings suggest that right IPS contributes to predictive position perception during saccades and motion processing in the contralateral visual field. |
Wayne E. MacKey; Clayton E. Curtis Distinct contributions by frontal and parietal cortices support working memory Journal Article In: Scientific Reports, vol. 7, pp. 6188, 2017. @article{MacKey2017, Although subregions of frontal and parietal cortex both contribute and coordinate to support working memory (WM) functions, their distinct contributions remain elusive. Here, we demonstrate that perturbations to topographically organized human frontal and parietal cortex during WM maintenance cause distinct but systematic distortions in WM. The nature of these distortions supports theories positing that parietal cortex mainly codes for retrospective sensory information, while frontal cortex codes for prospective action. |