EyeLink Usability / Applied Publications
All EyeLink usability and applied research publications up until 2023 (with some early 2024s) are listed below by year. You can search the publications using keywords such as Driving, Sport, Workload, etc. You can also search for individual author names. If we missed any EyeLink usability or applied article, please email us!
2020 |
Rick A. Adams; Daniel Bush; Fanfan Zheng; Sofie S. Meyer; Raphael Kaplan; Stelios Orfanos; Tiago Reis Marques; Oliver D. Howes; Neil Burgess Impaired theta phase coupling underlies frontotemporal dysconnectivity in schizophrenia Journal Article In: Brain, vol. 143, no. 3, pp. 1261–1277, 2020. @article{Adams2020a, Frontotemporal dysconnectivity is a key pathology in schizophrenia. The specific nature of this dysconnectivity is unknown, but animal models imply dysfunctional theta phase coupling between hippocampus and medial prefrontal cortex (mPFC). We tested this hypothesis by examining neural dynamics in 18 participants with a schizophrenia diagnosis, both medicated and unmedicated; and 26 age, sex and IQ matched control subjects. All participants completed two tasks known to elicit hippocampal-prefrontal theta coupling: a spatial memory task (during magnetoencephalography) and a memory integration task. In addition, an overlapping group of 33 schizophrenia and 29 control subjects underwent PET to measure the availability of GABAARs expressing the a5 subunit (concentrated on hippocampal somatostatin interneurons). We demonstrate-in the spatial memory task, during memory recall-that theta power increases in left medial temporal lobe (mTL) are impaired in schizophrenia, as is theta phase coupling between mPFC and mTL. Importantly, the latter cannot be explained by theta power changes, head movement, antipsychotics, cannabis use, or IQ, and is not found in other frequency bands. Moreover, mPFC-mTL theta coupling correlated strongly with performance in controls, but not in subjects with schizophrenia, who were mildly impaired at the spatial memory task and no better than chance on the memory integration task. Finally, mTL regions showing reduced phase coupling in schizophrenia magnetoencephalography participants overlapped substantially with areas of diminished a5-GABAAR availability in the wider schizophrenia PET sample. These results indicate that mPFC-mTL dysconnectivity in schizophrenia is due to a loss of theta phase coupling, and imply a5-GABAARs (and the cells that express them) have a role in this process. |
Carmel R. Auerbach-Asch; Oded Bein; Leon Y. Deouell Face selective neural activity: Comparisons between fixed and free viewing Journal Article In: Brain Topography, vol. 33, no. 3, pp. 336–354, 2020. @article{AuerbachAsch2020, Event Related Potentials (ERPs) are widely used to study category-selective EEG responses to visual stimuli, such as the face-selective N170 component. Typically, this is done by flashing stimuli at the point of static gaze fixation. While allowing for good experimental control, these paradigms ignore the dynamic role of eye-movements in natural vision. Fixation-related potentials (FRPs), obtained using simultaneous EEG and eye-tracking, overcome this limitation. Various studies have used FRPs to study processes such as lexical processing, target detection and attention allocation. The goal of this study was to carefully compare face-sensitive activity time-locked to an abrupt stimulus onset at fixation, with that time-locked to a self-generated fixation on a stimulus. Twelve participants participated in three experimental conditions: Free-viewing (FRPs), Cued-viewing (FRPs) and Control (ERPs). We used a multiple regression approach to disentangle overlapping activity components. Our results show that the N170 face-effect is evident for the first fixation on a stimulus, whether it follows a self-generated saccade or stimulus appearance at fixation point. The N170 face-effect has similar topography across viewing conditions, but there were major differences within each stimulus category. We ascribe these differences to an overlap of the fixation-related lambda response and the N170. We tested the plausibility of this account using dipole simulations. Finally, the N170 exhibits category-specific adaptation in free viewing. This study establishes the comparability of the free-viewing N170 face-effect with the classic event-related effect, while highlighting the importance of accounting for eye-movement related effects. |
Yasaman Bagherzadeh; Daniel Baldauf; Dimitrios Pantazis; Robert Desimone Alpha synchrony and the neurofeedback control of spatial attention Journal Article In: Neuron, vol. 105, no. 3, pp. 577–587.e5, 2020. @article{Bagherzadeh2020, During MEG neurofeedback training, subjects learned to manipulate the degree of alpha synchrony over the left versus right parietal cortex. The change in alpha synchrony was associated with a corresponding bias in visual processing and attention in the corresponding visual field. |
Sonya Bells; Silvia L. Isabella; Donald C. Brien; Brian C. Coe; Douglas P. Munoz; Donald J. Mabbott; Douglas O. Cheyne Mapping neural dynamics underlying saccade preparation and execution and their relation to reaction time and direction errors Journal Article In: Human Brain Mapping, vol. 41, no. 7, pp. 1934–1949, 2020. @article{Bells2020, Our ability to control and inhibit automatic behaviors is crucial for negotiating complex environments, all of which require rapid communication between sensory, motor, and cognitive networks. Here, we measured neuromagnetic brain activity to investigate the neural timing of cortical areas needed for inhibitory control, while 14 healthy young adults performed an interleaved prosaccade (look at a peripheral visual stimulus) and antisaccade (look away from stimulus) task. Analysis of how neural activity relates to saccade reaction time (SRT) and occurrence of direction errors (look at stimulus on antisaccade trials) provides insight into inhibitory control. Neuromagnetic source activity was used to extract stimulus-aligned and saccade-aligned activity to examine temporal differences between prosaccade and antisaccade trials in brain regions associated with saccade control. For stimulus-aligned antisaccade trials, a longer SRT was associated with delayed onset of neural activity within the ipsilateral parietal eye field (PEF) and bilateral frontal eye field (FEF). Saccade-aligned activity demonstrated peak activation 10ms before saccade-onset within the contralateral PEF for prosaccade trials and within the bilateral FEF for antisaccade trials. In addition, failure to inhibit prosaccades on anti-saccade trials was associated with increased activity prior to saccade onset within the FEF contralateral to the peripheral stimulus. This work on dynamic activity adds to our knowledge that direction errors were due, at least in part, to a failure to inhibit automatic prosaccades. These findings provide novel evidence in humans regarding the temporal dynamics within oculomotor areas needed for saccade programming and the role frontal brain regions have on top-down inhibitory control. |
Nicholas S. Bland; Jason B. Mattingley; Martin V. Sale Gamma coherence mediates interhemispheric integration during multiple object tracking Journal Article In: Journal of Neurophysiology, vol. 123, no. 5, pp. 1630–1644, 2020. @article{Bland2020, Our ability to track the paths of multiple visual objects moving between the hemifields requires effective integration of information between the two cerebral hemispheres. Coherent neural oscillations in the gamma band (35-70 Hz) are hypothesized to drive this information transfer. Here we manipulated the need for interhemispheric integration using a novel multiple object tracking (MOT) task in which stimuli either moved between the two visual hemifields, requiring interhemispheric integration, or moved within separate visual hemifields. We used electroencephalography (EEG) to measure interhemispheric coherence during the task. Human observers (21 women; 20 men) were poorer at tracking objects between versus within hemifields, reflecting a cost of interhemispheric integration. Critically, gamma coherence was greater in trials requiring interhemispheric integration, particularly between sensors over parieto-occipital areas. In approximately half of the participants, the observed cost of integration was associated with a failure of the cerebral hemispheres to become coherent in the gamma band. Moreover, individual differences in this integration cost correlated with endogenous gamma coherence at these same sensors, although with generally opposing relationships for the real and imaginary part of coherence. The real part (capturing synchronization with a near-zero phase lag) benefited between-hemifield tracking; imaginary coherence was detrimental. Finally, instantaneous phase coherence over the tracking period uniquely predicted between-hemifield tracking performance, suggesting that effective integration benefits from sustained interhemispheric synchronization. Our results show that gamma coherence mediates interhemispheric integration during MOT and add to a growing body of work demonstrating that coherence drives communication across cortically distributed neural networks. NEW & NOTEWORTHY Using a multiple object tracking paradigm, we were able to manipulate the need for interhemispheric integration on a per-trial basis, while also having an objective measure of integration efficacy (i.e., tracking performance). We show that tracking performance reflects a cost of integration, which correlates with individual differences in interhemispheric EEG coherence. Gamma coherence appears to uniquely benefit between-hemifield tracking, predicting performance both across participants and across trials. |
Louisa Bogaerts; Craig G. Richter; Ayelet N. Landau; Ram Frost Beta-band activity is a signature of statistical learning Journal Article In: Journal of Neuroscience, vol. 40, no. 39, pp. 7523–7530, 2020. @article{Bogaerts2020, Through statistical learning (SL), cognitive systems may discover the underlying regularities in the environment. Testing human adults (n = 35, 21 females), we document, in the context of a classical visual SL task, divergent rhythmic EEG activity in the interstimulus delay periods within patterns versus between patterns (i.e., pattern transitions). Our findings reveal increased oscillatory activity in the beta band (∼20 Hz) at triplet transitions that indexes learning: It emerges with increased pattern repetitions; and importantly, it is highly correlated with behavioral learning outcomes. These findings hold the promise of converging on an online measure of learning regularities and provide important theoretical insights regarding the mechanisms of SL and prediction. |
Mathieu Bourguignon; Martijn Baart; Efthymia C. Kapnoula; Nicola Molinaro Lip-reading enables the brain to synthesize auditory features of unknown silent speech Journal Article In: Journal of Neuroscience, vol. 40, no. 5, pp. 1053–1065, 2020. @article{Bourguignon2020, Lip-reading is crucial for understanding speech in challenging conditions. But how the brain extracts meaning from, silent, visual speech is still under debate. Lip-reading in silence activates the auditory cortices, but it is not known whether such activation reflects immediate synthesis of the corresponding auditory stimulus or imagery of unrelated sounds. To disentangle these possibilities, we used magnetoencephalography to evaluate how cortical activity in 28 healthy adult humans (17 females) entrained to the auditory speech envelope and lip movements (mouth opening) when listening to a spoken story without visual input (audio-only), and when seeing a silent video of a speaker articulating another story (video-only). In video-only, auditory cortical activity entrained to the absent auditory signal at frequencies <1 Hz more than to the seen lip movements. This entrainment process was characterized by an auditory-speech-to-brain delay of ~70 ms in the left hemisphere, compared with ~20 ms in audio-only. Entrainment to mouth opening was found in the right angular gyrus at <1 Hz, and in early visual cortices at 1– 8 Hz. These findings demonstrate that the brain can use a silent lip-read signal to synthesize a coarse-grained auditory speech representation in early auditory cortices. Our data indicate the following underlying oscillatory mechanism: seeing lip movements first modulates neuronal activity in early visual cortices at frequencies that match articulatory lip movements; the right angular gyrus then extracts slower features of lip movements, mapping them onto the corresponding speech sound features; this information is fed to auditory cortices, most likely facilitating speech parsing. |
Méadhbh B. Brosnan; Kristina Sabaroedin; Tim Silk; Sila Genc; Daniel P. Newman; Gerard M. Loughnane; Alex Fornito; Redmond G. O'Connell; Mark A. Bellgrove Evidence accumulation during perceptual decisions in humans varies as a function of dorsal frontoparietal organization Journal Article In: Nature Human Behaviour, vol. 4, no. 8, pp. 844–855, 2020. @article{Brosnan2020, Animal neurophysiological studies have identified neural signals within dorsal frontoparietal areas that trace a perceptual decision by accumulating sensory evidence over time and trigger action upon reaching a threshold. Although analogous accumulation-to-bound signals are identifiable on extracranial human electroencephalography, their cortical origins remain unknown. Here neural metrics of human evidence accumulation, predictive of the speed of perceptual reports, were isolated using electroencephalography and related to dorsal frontoparietal network (dFPN) connectivity using diffusion and resting-state functional magnetic resonance imaging. The build-up rate of evidence accumulation mediated the relationship between the white matter macrostructure of dFPN pathways and the efficiency of perceptual reports. This association between steeper build-up rates of evidence accumulation and the dFPN was recapitulated in the resting-state networks. Stronger connectivity between dFPN regions is thus associated with faster evidence accumulation and speeded perceptual decisions. Our findings identify an integrated network for perceptual decisions that may be targeted for neurorehabilitation in cognitive disorders. |
Maximilian Bruchmann; Sebastian Schindler; Thomas Straube The spatial frequency spectrum of fearful faces modulates early and mid-latency ERPs but not the N170 Journal Article In: Psychophysiology, vol. 57, no. 9, pp. e13597, 2020. @article{Bruchmann2020, Prioritized processing of fearful compared to neutral faces is reflected in behavioral advantages such as lower detection thresholds, but also in enhanced early and late event-related potentials (ERPs). Behavioral advantages have recently been associated with the spatial frequency spectrum of fearful faces, better fitting the human contrast sensitivity function than the spectrum of neutral faces. However, it is unclear whether and to which extent early and late ERP differences are due to low-level spatial frequency spectrum information or high-level representations of the facial expression. In this pre-registered EEG study (N = 38), the effects of fearful-specific spatial frequencies on event-related ERPs were investigated by presenting faces with fearful and neutral expressions whose spatial frequency spectra were manipulated so as to contain either the average power spectra of neutral, fearful, or both expressions combined. We found an enlarged N170 to fearful versus neutral faces, not interacting with spatial frequency. Interactions of emotional expression and spatial frequencies were observed for the P1 and Early Posterior Negativity (EPN). For both components, larger emotion differences were observed when the spectrum contained neutral as opposed to fearful frequencies. Importantly, for the EPN, fearful and neutral expressions did not differ anymore when inserting fearful frequencies into neutral expressions, whereas typical emotion differences were found when faces contained average or neutral frequencies. Our findings show that N170 emotional modulations are unaffected by expression-specific spatial frequencies. However, expression-specific spatial frequencies alter early and mid-latency ERPs. Most notably, the EPN to neutral expressions is boosted by adding fearful spectra—but not vice versa. |
Antimo Buonocore; Olaf Dimigen; David Melcher Post-saccadic face processing is modulated by pre-saccadic preview: Evidence from fixation-related potentials Journal Article In: Journal of Neuroscience, vol. 40, no. 11, pp. 2305–2313, 2020. @article{Buonocore2020, Humans actively sample their environment with saccadic eye movements to bring relevant information into high-acuity foveal vision. Despite being lower in resolution, peripheral information is also available before each saccade. How the pre-saccadic extrafoveal preview of a visual object influences its post-saccadic processing is still an unanswered question. The current study investigated this question by simultaneously recording behavior and fixation-related brain potentials while human subjects made saccades to face stimuli. We manipulated the relationship between pre-saccadic "previews" and post-saccadic images to explicitly isolate the influences of the former. Subjects performed a gender discrimination task on a newly foveated face under three preview conditions: scrambled face, incongruent face (different identity from the foveated face), and congruent face (same identity). As expected, reaction times were faster after a congruent-face preview compared with a scrambled-face preview. Importantly, intact face previews (either incongruent or congruent) resulted in a massive reduction of post-saccadic neural responses. Specifically, we analyzed the classic face-selective N170 component at occipitotemporal electroencephalogram electrodes, which was still present in our experiments with active looking. However, the post-saccadic N170 was strongly attenuated following intact-face previews compared with the scrambled condition. This large and long-lasting decrease in evoked activity is consistent with a trans-saccadic mechanism of prediction that influences category-specific neural processing at the start of a new fixation. These findings constrain theories of visual stability and show that the extrafoveal preview methodology can be a useful tool to investigate its underlying mechanisms. |
2019 |
Ying Joey Zhou; Alexis Pérez-Bellido; Saskia Haegens; Floris P. Lange Perceptual expectations modulate low-frequency activity: A statistical learning magnetoencephalographystudy Journal Article In: Journal of Cognitive Neuroscience, pp. 1–12, 2019. @article{Zhou2019c, Perceptual expectations can change how a visual stimulus is perceived. Recent studies have shown mixed results in terms of whether expectations modulate sensory representations. Here, we used a statistical learning paradigm to study the temporal characteristics of perceptual expectations. We presented participants with pairs of object images organized in a predictive manner and then recorded their brain activity with magnetoencephalography while they viewed expected and unexpected image pairs on the subsequent day. We observed stronger alpha-band (7–14 Hz) activity in response to unexpected compared with expected object images. Specifically, the alpha-band modulation occurred as early as the onset of the stimuli and was most pronounced in left occipito-temporal cortex. Given that the differential response to expected versus unexpected stimuli occurred in sensory regions early in time, our results suggest that expectations modulate perceptual decision-making by changing the sensory response elicited by the stimuli. |
Praghajieeth Raajhen Santhana Gopalan; Otto Loberg; Jarmo A. Hämäläinen; Paavo H. T. Leppänen In: Scientific Reports, vol. 9, pp. 2940, 2019. @article{Gopalan2019, Attention-related processes include three functional sub-components: alerting, orienting, and inhibition. We investigated these components using EEG-based, brain event-related potentials and their neuronal source activations during the Attention Network Test in typically developing school-aged children. Participants were asked to detect the swimming direction of the centre fish in a group of five fish. The target stimulus was either preceded by a cue (centre, double, or spatial) or no cue. An EEG using 128 electrodes was recorded for 83 children aged 12–13 years. RTs showed significant effects across all three sub-components of attention. Alerting and orienting (responses to double vs non-cued target stimulus and spatially vs centre-cued target stimulus, respectively) resulted in larger N1 amplitude, whereas inhibition (responses to incongruent vs congruent target stimulus) resulted in larger P3 amplitude. Neuronal source activation for the alerting effect was localized in the right anterior temporal and bilateral occipital lobes, for the orienting effect bilaterally in the occipital lobe, and for the inhibition effect in the medial prefrontal cortex and left anterior temporal lobe. Neuronal sources of ERPs revealed that sub-processes related to the attention network are different in children as compared to earlier adult fMRI studies, which was not evident from scalp ERPs. |
M. Isabel Vanegas; Annabelle Blangero; James E. Galvin; Alessandro Di Rocco; Angelo Quartarone; M. Felice Ghilardi; Simon P. Kelly Altered dynamics of visual contextual interactions in Parkinson's disease Journal Article In: npj Parkinson's Disease, vol. 5, no. 13, 2019. @article{Vanegas2019, Over the last decades, psychophysical and electrophysiological studies in patients and animal models of Parkinson's disease (PD), have consistently revealed a number of visual abnormalities. In particular, specific alterations of contrast sensitivity curves, electroretinogram (ERG), and visual-evoked potentials (VEP), have been attributed to dopaminergic retinal depletion. However, fundamental mechanisms of cortical visual processing, such as normalization or “gain control” computations, have not yet been examined in PD patients. Here, we measured electrophysiological indices of gain control in both space (surround suppression) and time (sensory adaptation) in PD patients based on steady-state VEP (ssVEP). Compared with controls, patients exhibited a significantly higher initial ssVEP amplitude that quickly decayed over time, and greater relative suppression of ssVEP amplitude as a function of surrounding stimulus contrast. Meanwhile, EEG frequency spectra were broadly elevated in patients relative to controls. Thus, contrary to what might be expected given the reduced contrast sensitivity often reported in PD, visual neural responses are not weaker; rather, they are initially larger but undergo an exaggerated degree of spatial and temporal gain control and are embedded within a greater background noise level. These differences may reflect cortical mechanisms that compensate for dysfunctional center-surround interactions at the retinal level. |
Mariya E. Manahova; Eelke Spaak; Floris P. Lange Familiarity increases processing speed in the visual system Journal Article In: Journal of Cognitive Neuroscience, pp. 1–12, 2019. @article{Manahova2019, Familiarity with a stimulus leads to an attenuated neural response to the stimulus. Alongside this attenuation, recent studies have also observed a truncation of stimulus-evoked activity for familiar visual input. One proposed function of this truncation is to rapidly put neurons in a state of readiness to respond to new input. Here, we examined this hypothesis by presenting human participants with target stimuli that were embedded in rapid streams of familiar or novel distractor stimuli at different speeds of presentation, while recording brain activity using magnetoencephalography and measuring behavioral performance. We investigated the temporal and spatial dynamics of signal truncation and whether this phenomenon bears relationship to participants' ability to categorize target items within a visual stream. Behaviorally, target categorization performance was markedly better when the target was embedded within familiar distractors, and this benefit became more pronounced with increasing speed of presentation. Familiar distractors showed a truncation of neural activity in the visual system. This truncation was strongest for the fastest presentation speeds and peaked in progressively more anterior cortical regions as presentation speeds became slower. Moreover, the neural response evoked by the target was stronger when this target was preceded by familiar distractors. Taken together, these findings demonstrate that item familiarity results in a truncated neural response, is associated with stronger processing of relevant target information, and leads to superior perceptual performance. |
Moreno I. Coco; Antje Nuthmann; Olaf Dimigen Fixation-related brain potentials during semantic integration of object–scene information Journal Article In: Journal of Cognitive Neuroscience, vol. 32, no. 4, pp. 571–589, 2019. @article{Coco2019, In vision science, a particularly controversial topic is whether and how quickly the semantic information about objects is available outside foveal vision. Here, we aimed at contributing to this debate by coregistering eye movements and EEG while participants viewed photographs of indoor scenes that contained a semantically consistent or inconsistent target object. Linear deconvolution modeling was used to analyze the ERPs evoked by scene onset as well as the fixation-related potentials (FRPs) elicited by the fixation on the target object (t) and by the preceding fixation (t − 1). Object–scene consistency did not influence the probability of immediate target fixation or the ERP evoked by scene onset, which suggests that object–scene semantics was not accessed immediately. However, during the subsequent scene exploration, inconsistent objects were prioritized over consistent objects in extrafoveal vision (i.e., looked at earlier) and were more effortful to process in foveal vision (i.e., looked at longer). In FRPs, we demonstrate a fixation-related N300/N400 effect, whereby inconsistent objects elicit a larger frontocentral negativity than consistent objects. In line with the behavioral findings, this effect was already seen in FRPs aligned to the pretarget fixation t − 1 and persisted throughout fixation t, indicating that the extraction of object semantics can already begin in extrafoveal vision. Taken together, the results emphasize the usefulness of combined EEG/eye movement recordings for understanding the mechanisms of object–scene integration during natural viewing. |
Christoph Huber-Huber; Antimo Buonocore; Olaf Dimigen; Clayton Hickey; David Melcher In: NeuroImage, vol. 200, pp. 344–362, 2019. @article{HuberHuber2019, The world appears stable despite saccadic eye-movements. One possible explanation for this phenomenon is that the visual system predicts upcoming input across saccadic eye-movements based on peripheral preview of the saccadic target. We tested this idea using concurrent electroencephalography (EEG) and eye-tracking. Participants made cued saccades to peripheral upright or inverted face stimuli that changed orientation (invalid preview) or maintained orientation (valid preview) while the saccade was completed. Experiment 1 demonstrated better discrimination performance and a reduced fixation-locked N170 component (fN170) with valid than with invalid preview, demonstrating integration of pre- and post-saccadic information. Moreover, the early fixation-related potentials (FRP) showed a preview face inversion effect suggesting that some pre-saccadic input was represented in the brain until around 170 ms post fixation-onset. Experiment 2 replicated Experiment 1 and manipulated the proportion of valid and invalid trials to test whether the preview effect reflects context-based prediction across trials. A whole-scalp Bayes factor analysis showed that this manipulation did not alter the fN170 preview effect but did influence the face inversion effect before the saccade. The pre-saccadic inversion effect declined earlier in the mostly invalid block than in the mostly valid block, which is consistent with the notion of pre-saccadic expectations. In addition, in both studies, we found strong evidence for an interaction between the pre-saccadic preview stimulus and the post-saccadic target as early as 50 ms (Experiment 2) or 90 ms (Experiment 1) into the new fixation. These findings suggest that visual stability may involve three temporal stages: prediction about the saccadic target, integration of pre-saccadic and post-saccadic information at around 50-90 ms post fixation onset, and post-saccadic facilitation of rapid categorization. |
Florian Sandhaeger; Constantin Nicolai; Earl K. Miller; Markus Siegel Monkey EEG links neuronal color and motion information across species and scales Journal Article In: eLife, vol. 8, pp. 1–21, 2019. @article{Sandhaeger2019, It remains challenging to relate EEG and MEG to underlying circuit processes and comparable experiments on both spatial scales are rare. To close this gap between invasive and non-invasive electrophysiology we developed and recorded human-comparable EEG in macaque monkeys during visual stimulation with colored dynamic random dot patterns. Furthermore, we performed simultaneous microelectrode recordings from 6 areas of macaque cortex and human MEG. Motion direction and color information were accessible in all signals. Tuning of the non- invasive signals was similar to V4 and IT, but not to dorsal and frontal areas. Thus, MEG and EEG were dominated by early visual and ventral stream sources. Source level analysis revealed corresponding information and latency gradients across cortex. We show how information-based methods and monkey EEG can identify analogous properties of visual processing in signals spanning spatial scales from single units to MEG – a valuable framework for relating human and animal studies. |
Amirsaman Sajad; David C. Godlove; Jeffrey D. Schall Cortical microcircuitry of performance monitoring Journal Article In: Nature Neuroscience, vol. 22, pp. 265–274, 2019. @article{Sajad2019, The medial frontal cortex enables performance monitoring, indexed by the error-related negativity (ERN) and manifested by performance adaptations. We recorded electroencephalogram over and neural spiking across all layers of the supplementary eye field, an agranular cortical area, in monkeys performing a saccade-countermanding (stop signal) task. Neurons signaling error production, feedback predicting reward gain or loss, and delivery of fluid reward had different spike widths and were concentrated differently across layers. Neurons signaling error or loss of reward were more common in layers 2 and 3 (L2/3), whereas neurons signaling gain of reward were more common in layers 5 and 6 (L5/6). Variation of error– and reinforcement-related spike rates in L2/3 but not L5/6 predicted response time adaptation. Variation in error-related spike rate in L2/3 but not L5/6 predicted ERN magnitude. These findings reveal novel features of cortical microcircuitry supporting performance monitoring and confirm one cortical source of the ERN. |
Sebastian Schindler; Maximilian Bruchmann; Florian Bublatzky; Thomas Straube Modulation of face- and emotion-selective ERPs by the three most common types of face image manipulations Journal Article In: Social Cognitive and Affective Neuroscience, vol. 14, no. 5, pp. 493–503, 2019. @article{Schindler2019, In neuroscientific studies, the naturalness of face presentation differs; a third of published studies makes use of close-up full coloured faces, a third uses close-up grey-scaled faces and another third employs cutout grey-scaled faces. Whether and how these methodological choices affect emotion-sensitive components of the event-related brain potentials (ERPs) is yet unclear. Therefore, this pre-registered study examined ERP modulations to close-up full-coloured and grey-scaled faces as well as cutout fearful and neutral facial expressions, while attention was directed to no-face oddballs. Results revealed no interaction of face naturalness and emotion for any ERP component, but showed, however, large main effects for both factors. Specifically, fearful faces and decreasing face naturalness elicited substantially enlarged N170 and early posterior negativity amplitudes and lower face naturalness also resulted in a larger P1.This pattern reversed for the LPP, showing linear increases in LPP amplitudes with increasing naturalness.We observed no interaction of emotion with face naturalness, which suggests that face naturalness and emotion are decoded in parallel at these early stages. Researchers interested in strong modulations of early components should make use of cutout grey-scaled faces, while those interested in a pronounced late positivity should use close-up coloured faces. |
Shirin Vafaei Shooshtari; Jamal Esmaily Sadrabadi; Zahra Azizi; Reza Ebrahimpour Confidence representation of perceptual decision by EEG and eye data in a random dot motion task Journal Article In: Neuroscience, vol. 406, pp. 510–527, 2019. @article{Shooshtari2019, The Confidence of a decision could be considered as the internal estimate of decision accuracy. This variable has been studied extensively by different types of recording data such as behavioral, electroencephalography (EEG), eye and electrophysiology data. Although the value of the reported confidence is considered as one of the most important parameters in decision making, the confidence reporting phase might be considered as a restrictive element in investigating the decision process. Thus, decision confidence should be extracted by means of other provided types of information. Here, we proposed eight confidence related properties in EEG and eye data which are significantly descriptive of the defined confidence levels in a random dot motion (RDM) task. As a matter of fact, our proposed EEG and eye data properties are capable of recognizing more than nine distinct levels of confidence. Among our proposed features, the latency of the pupil maximum diameter through the stimulus presentation was established to be the most associated one to the confidence levels. Through the time-dependent analysis of these features, we recognized the time interval of 500–600 ms after the stimulus onset as an important time in correlating features to the confidence levels. |
Lisa Stacchi; Meike Ramon; Junpeng Lao; Roberto Caldara Neural representations of faces are tuned to eye movements Journal Article In: Journal of Neuroscience, vol. 39, no. 21, pp. 4113–4123, 2019. @article{Stacchi2019, Eye movements provide a functional signature of how human vision is achieved. Many recent studies have consistently reported robust idiosyncratic visual sampling strategies during face recognition. Whether these interindividual differences are mirrored by idiosyncratic neural responses remains unknown. To this aim, we first tracked eye movements of male and female observers during face recognition. Additionally, for every observer we obtained an objective index of neural face discrimination through EEG that was recorded while they fixated different facial information. We found that foveation of facial features fixated longer during face recognition elicited stronger neural face discrimination responses across all observers. This relationship occurred independently of interindividual differences in preferential facial information sampling (e.g., eye vs mouth lookers), and started as early as the first fixation. Our data show that eye movements play a functional role during face processing by providing the neural system with the information that is diagnostic to a specific observer. The effective processing of identity involves idiosyncratic, rather than universal face representations. |
David W. Sutterer; Joshua J. Foster; Kirsten C. S. Adam; Edward K. Vogel; Edward Awh Item-specific delay activity demonstrates concurrent storage of multiple active neural representations in working memory Journal Article In: PLoS Biology, vol. 17, no. 4, pp. e3000239, 2019. @article{Sutterer2019, Persistent neural activity that encodes online mental representations plays a central role in working memory (WM). However, there has been debate regarding the number of items that can be concurrently represented in this active neural state, which is often called the “focus of attention.” Some models propose a strict single-item limit, such that just 1 item can be neurally active at once while other items are relegated to an activity-silent state. Although past studies have decoded multiple items stored in WM, these studies cannot rule out a switching account in which only a single item is actively represented at a time. Here, we directly tested whether multiple representations can be held concurrently in an active state. We tracked spatial representations in WM using alpha-band (8–12 Hz) activity, which encodes spatial positions held in WM. Human observers remembered 1 or 2 positions over a short delay while we recorded electroencephalography (EEG) data. Using a spatial encoding model, we reconstructed active stimulus-specific representations (channel-tuning functions [CTFs]) from the scalp distribution of alpha-band power. Consistent with past work, we found that the selectivity of spatial CTFs was lower when 2 items were stored than when 1 item was stored. Critically, data-driven simulations revealed that the selectivity of spatial representations in the two-item condition could not be explained by models that propose that only a single item can exist in an active state at once. Thus, our findings demonstrate that multiple items can be concurrently represented in an active neural state. |
David W. Sutterer; Joshua J. Foster; John T. Serences; Edward K. Vogel; Edward Awh Alpha-band oscillations track the retrieval of precise spatial representations from long-term memory Journal Article In: Journal of Neurophysiology, vol. 122, no. 2, pp. 539–551, 2019. @article{Sutterer2019a, A hallmark of episodic memory is the phenomenon of mentally reexperiencing the details of past events, and a well-established concept is that the neuronal activity that mediates encoding is reinstated at retrieval. Evidence for reinstatement has come from multiple modalities, including functional magnetic resonance imaging and electroencephalography (EEG). These EEG studies have shed light on the time course of reinstatement but have been limited to distinguishing between a few categories. The goal of this work was to use recently developed experimental and technical approaches, namely continuous report tasks and inverted encoding models, to determine which frequencies of oscillatory brain activity support the retrieval of precise spatial memories. In experiment 1, we establish that an inverted encoding model applied to multivariate alpha topography tracks the retrieval of precise spatial memories. In experiment 2, we demonstrate that the frequencies and patterns of multivariate activity at study are similar to the frequencies and patterns observed during retrieval. These findings highlight the broad potential for using encoding models to characterize long-term memory retrieval. NEW & NOTEWORTHY Previous EEG work has shown that category-level information observed during encoding is recapitulated during memory retrieval, but studies with this time-resolved method have not demonstrated the reinstatement of feature-specific patterns of neural activity during retrieval. Here we show that EEG alpha-band activity tracks the retrieval of spatial representations from long-term memory. Moreover, we find considerable overlap between the frequencies and patterns of activity that track spatial memories during initial study and at retrieval. |
Yuta Suzuki; Tetsuto Minami; Shigeki Nakauchi Pupil constriction in the glare illusion modulates the steady-state visual evoked potentials Journal Article In: Neuroscience, vol. 416, pp. 221–228, 2019. @article{Suzuki2019, The glare illusion enhances the perceived brightness of a central white area surrounded by a luminance gradient, without any actual change in light intensity. In this study, we measured the varied brightness and neurophysiological responses of electroencephalography (EEG) and pupil size with the several luminance contrast patterns of the glare illusion to address the question of whether the illusory brightness changes to the glare illusion process in the early visual cortex. We hypothesized that if the illusory brightness enhancement was created in the early stages of visual processing, the neural response would be similar to how it processes an actual change in light intensity. To test this, we observed the sustained visual cortical response of steady-state visual evoked potentials (SSVEPs), while participants watched flickering dots displayed in the central white area of both the varied luminance contrast of glare illusion and a control stimulus (no glare condition). We found the SSVEP amplitude was lower in the glare illusion than in the control condition, especially under high luminance contrast conditions. Furthermore, we found the probable mechanisms of the inhibited SSVEP amplitude to the high luminance contrast of glare illusion based on the greater pupil constriction, thereby decreasing the amount of light entering the pupil. Thus, the brightness enhancement in the glare illusion is already represented at the primary stage of visual processing linked to the larger pupil constriction. |
Pei -Yi Tsai; Hsiao-Ching She; Sheng-Chang Chen; Li-Yu Huang; Wen-Chi Chou; Jeng-Ren Duann; Tzyy-Ping Jung Eye fixation-related fronto-parietal neural network correlates of memory retrieval Journal Article In: International Journal of Psychophysiology, vol. 138, pp. 57–70, 2019. @article{Tsai2019, Eye movements are considered to be informative with regard to the underlying cognitive processes of human beings. Previous studies have reported that eye movements are associated with which scientific concepts are retrieved correctly. Moreover, other studies have also suggested that eye movements involve the cooperative activity of the human brain's fronto-parietal circuits. Less research has been conducted to investigate whether fronto-parietal EEG oscillations are associated with the retrieval processing of scientific concepts. Our findings in this study demonstrated that the fronto-parietal network is indeed crucial for successful memory retrieval. In short, significantly lower theta augmentation in the frontal midline and lower alpha suppression in the right parietal region were observed at the 5th eye fixation for physics concepts that were correctly retrieved than for those that were incorrectly retrieved. Moreover, the visual cortex in the occipital lobe exhibits a significantly greater theta augmentation followed by an alpha suppression following each eye fixation, while a right fronto-parietal asymmetry was also found for the successful retrieval of presentations of physics concepts. In particular, the study results showed that eye fixation-related frontal midline theta power and right parietal alpha power at the 5th eye fixation have the greatest predictive power regarding the correctness of the retrieval of physics concepts. |
Raphael Vallat; David Meunier; Alain Nicolas; Perrine Ruby Hard to wake up? The cerebral correlates of sleep inertia assessed using combined behavioral, EEG and fMRI measures Journal Article In: NeuroImage, vol. 184, pp. 266–278, 2019. @article{Vallat2019, The first minutes following awakening from sleep are typically marked by reduced vigilance, increased sleepiness and impaired performance, a state referred to as sleep inertia. Although the behavioral aspects of sleep inertia are well documented, its cerebral correlates remain poorly understood. The present study aimed at filling this gap by measuring in 34 participants the changes in behavioral performance (descending subtraction task, DST), EEG spectral power, and resting-state fMRI functional connectivity across three time points: before an early-afternoon 45-min nap, 5 min after awakening from the nap and 25 min after awakening. Our results showed impaired performance at the DST at awakening and an intrusion of sleep-specific features (spectral power and functional connectivity) into wakefulness brain activity, the intensity of which was dependent on the prior sleep duration and depth for the functional connectivity (14 participants awakened from N2 sleep, 20 from N3 sleep). Awakening in N3 (deep) sleep induced the most robust changes and was characterized by a global loss of brain functional segregation between task-positive (dorsal attention, salience, sensorimotor) and task-negative (default mode) networks. Significant correlations were observed notably between the EEG delta power and the functional connectivity between the default and dorsal attention networks, as well as between the percentage of mistake at the DST and the default network functional connectivity. These results highlight (1) significant correlations between EEG and fMRI functional connectivity measures, (2) significant correlations between the behavioral aspect of sleep inertia and measures of the cerebral functioning at awakening (both EEG and fMRI), and (3) the important difference in the cerebral underpinnings of sleep inertia at awakening from N2 and N3 sleep. |
Joram Driel; Eduard Ort; Johannes J. Fahrenfort; Christian N. L. Olivers Beta and theta oscillations differentially support free versus forced control over multiple-target search Journal Article In: Journal of Neuroscience, vol. 39, no. 9, pp. 1733–1743, 2019. @article{Driel2019, Many important situations require human observers to simultaneously search for more than one object. Despite a long history of research into visual search, the behavioral and neural mechanisms associated with multiple-target search are poorly understood. Here we test the novel theory that the efficiency of looking for multiple targets critically depends on the mode of cognitive control the environment affords to the observer. We used an innovative combination of electroencephalogram (EEG) and eye tracking while participants searched for two targets, within two different contexts: either both targets were present in the search display and observers were free to prioritize either one of them, thus enabling proactive control over selection; or only one of the two targets would be present in each search display, which requires reactive control to reconfigure selection when the wrong target has been prioritized. During proactive control, both univariate and multivariate signals of beta-band (15–35 Hz) power suppression before display onset predicted switches between target selections. This signal originated over midfrontal and sensorimotor regions and has previously been associated with endogenous state changes. In contrast, imposed target selections requiring reactive control elicited prefrontal power enhancements in the delta/theta band (2– 8 Hz), but only after display onset. This signal predicted individual differences in associated oculomotor switch costs, reflecting reactive reconfiguration of target selection. The results provide compelling evidence that multiple target representations are differentially prioritized during visual search, and for the first time reveal distinct neural mechanisms underlying proactive and reactive control over multiple-target search. |
Mats W. J. Es; Jan-Mathijs Schoffelen Stimulus-induced gamma power predicts the amplitude of the subsequent visual evoked response Journal Article In: NeuroImage, vol. 186, pp. 703–712, 2019. @article{Es2019a, The efficiency of neuronal information transfer in activated brain networks may affect behavioral performance. Gamma-band synchronization has been proposed to be a mechanism that facilitates neuronal processing of behaviorally relevant stimuli. In line with this, it has been shown that strong gamma-band activity in visual cortical areas leads to faster responses to a visual go cue. We investigated whether there are directly observable consequences of trial-by-trial fluctuations in non-invasively observed gamma-band activity on the neuronal response. Specifically, we hypothesized that the amplitude of the visual evoked response to a go cue can be predicted by gamma power in the visual system, in the window preceding the evoked response. Thirty-three human subjects (22 female) performed a visual speeded response task while their magnetoencephalogram (MEG) was recorded. The participants had to respond to a pattern reversal of a concentric moving grating. We estimated single trial stimulus-induced visual cortical gamma power, and correlated this with the estimated single trial amplitude of the most prominent event-related field (ERF) peak within the first 100 ms after the pattern reversal. In parieto-occipital cortical areas, the amplitude of the ERF correlated positively with gamma power, and correlated negatively with reaction times. No effects were observed for the alpha and beta frequency bands, despite clear stimulus onset induced modulation at those frequencies. These results support a mechanistic model, in which gamma-band synchronization enhances the neuronal gain to relevant visual input, thus leading to more efficient downstream processing and to faster responses. |
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. |
Leonhard Waschke; Sarah Tune; Jonas Obleser Local cortical desynchronization and pupil-linked arousal differentially shape brain states for optimal sensory performance Journal Article In: eLife, vol. 8, pp. 1–27, 2019. @article{Waschke2019, Instantaneous brain states have consequences for our sensation, perception, and behaviour. Fluctuations in arousal and neural desynchronization likely pose perceptually relevant states. However, their relationship and their relative impact on perception is unclear. We here show that, at the single-trial level in humans, local desynchronization in sensory cortex (expressed as time-series entropy) versus pupil- linked arousal differentially impact perceptual processing. While we recorded electroencephalography (EEG) and pupillometry data, stimuli of a demanding auditory discrimination task were presented into states of high or low desynchronization of auditory cortex via a real-time closed-loop setup. Desynchronization and arousal distinctly influenced stimulus-evoked activity and shaped behaviour displaying an inverted u-shaped relationship: States of intermediate desynchronization elicited minimal response bias and fastest responses, while states of intermediate arousal gave rise to highest response sensitivity. Our results speak to a model in which independent states of local desynchronization and global arousal jointly optimise sensory processing and performance. |
Rasa Gulbinaite; Diane H. M. Roozendaal; Rufin VanRullen Attention differentially modulates the amplitude of resonance frequencies in the visual cortex Journal Article In: NeuroImage, vol. 203, pp. 116146, 2019. @article{Gulbinaite2019, Rhythmic visual stimuli (flicker) elicit rhythmic brain responses at the frequency of the stimulus, and attention generally enhances these oscillatory brain responses (steady state visual evoked potentials, SSVEPs). Although SSVEP responses have been tested for flicker frequencies up to 100 Hz [Herrmann, 2001], effects of attention on SSVEP amplitude have only been reported for lower frequencies (up to ~30 Hz), with no systematic comparison across a wide, finely sampled frequency range. Does attention modulate SSVEP amplitude at higher flicker frequencies (gamma band, 30–80 Hz), and is attentional modulation constant across frequencies? By isolating SSVEP responses from the broadband EEG signal using a multivariate spatiotemporal source separation method, we demonstrate that flicker in the alpha and gamma bands elicit strongest and maximally phase stable brain responses (resonance), on which the effect of attention is opposite: positive for gamma and negative for alpha. Finding subject-specific gamma resonance frequency and a positive attentional modulation of gamma-band SSVEPs points to the untapped potential of flicker as a non-invasive tool for studying the causal effects of interactions between visual gamma-band rhythmic stimuli and endogenous gamma oscillations on perception and attention. |
Nicole Hakim; Kirsten C. S. Adam; Eren Gunseli; Edward Awh; Edward K. Vogel Dissecting the neural focus of attention reveals distinct processes for spatial attention and object-based storage in visual working memory Journal Article In: Psychological Science, vol. 30, no. 4, pp. 526–540, 2019. @article{Hakim2019, Complex cognition relies on both on-line representations in working memory (WM), said to reside in the focus of attention, and passive off-line representations of related information. Here, we dissected the focus of attention by showing that distinct neural signals index the on-line storage of objects and sustained spatial attention. We recorded electroencephalogram (EEG) activity during two tasks that employed identical stimulus displays but varied the relative demands for object storage and spatial attention. We found distinct delay-period signatures for an attention task (which required only spatial attention) and a WM task (which invoked both spatial attention and object storage). Although both tasks required active maintenance of spatial information, only the WM task elicited robust contralateral delay activity that was sensitive to mnemonic load. Thus, we argue that the focus of attention is maintained via a collaboration between distinct processes for covert spatial orienting and object-based storage. |
Nicole Hakim; Tobias Feldmann-Wüstefeld; Edward Awh; Edward K. Vogel Perturbing neural representations of working memory with task-irrelevant interruption Journal Article In: Journal of Cognitive Neuroscience, vol. 32, no. 3, pp. 558–569, 2019. @article{Hakim2019a, Working memory maintains information so that it can be used in complex cognitive tasks. A key challenge for this system is to maintain relevant information in the face of task-irrelevant perturbations. Across two experiments, we investigated the impact of task-irrelevant interruptions on neural representations of working memory. We recorded EEG activity in humans while they performed a working memory task. On a subset of trials, we interrupted participants with salient but task-irrelevant objects. To track the impact of these task-irrelevant interruptions on neural representations of working memory, we measured two well-characterized, temporally sensitive EEG markers that reflect active, prioritized working memory representations: the contralateral delay activity and lateralized alpha power (8–12 Hz). After interruption, we found that contralateral delay activity amplitude momentarily sustained but was gone by the end of the trial. Lateralized alpha power was immediately influenced by the interrupters but recovered by the end of the trial. This suggests that dissociable neural processes contribute to the maintenance of working memory information and that brief irrelevant onsets disrupt two distinct online aspects of working memory. In addition, we found that task expectancy modulated the timing and magnitude of how these two neural signals responded to task-irrelevant interruptions, suggesting that the brain's response to task-irrelevant interruption is shaped by task context. |
Qiming Han; Huan Luo Visual crowding involves delayed frontoparietal response and enhanced top-down modulation Journal Article In: European Journal of Neuroscience, vol. 50, no. 6, pp. 2931–2941, 2019. @article{Han2019a, Crowding, the disrupted recognition of a peripheral target in the presence of nearby flankers, sets a fundamental limit on peripheral vision perception. Debates persist on whether the limit occurs at early visual cortices or is induced by top-down modulation, leaving the neural mechanism for visual crowding largely unclear. To resolve the debate, it is crucial to extract the neural signals elicited by the target from that by the target-flanker clutter, with high temporal resolution. To achieve this purpose, here we employed a temporal response function (TRF) approach to dissociate target-specific response from the overall electroencephalograph (EEG) recordings when the target was presented with (crowded) or without flankers (uncrowded) while subjects were performing a discrimination task on the peripherally presented target. Our results demonstrated two components in the target-specific contrast-tracking TRF response—an early component (100–170 ms) in occipital channels and a late component (210–450 ms) in frontoparietal channels. The late frontoparietal component, which was delayed in time under the crowded condition, was correlated with target discrimination performance, suggesting its involvement in visual crowding. Granger causality analysis further revealed stronger top-down modulation on the target stimulus under the crowded condition. Taken together, our findings support that crowding is associated with a top-down process which modulates the low-level sensory processing and delays the behavioral-relevant response in the high-level region. |
Linda Henriksson; Marieke Mur; Nikolaus Kriegeskorte Rapid invariant encoding of scene layout in human OPA Journal Article In: Neuron, vol. 103, no. 1, pp. 161–171.e3, 2019. @article{Henriksson2019, Successful visual navigation requires a sense of the geometry of the local environment. How do our brains extract this information from retinal images? Here we visually presented scenes with all possible combinations of five scene-bounding elements (left, right, and back walls; ceiling; floor) to human subjects during functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG). The fMRI response patterns in the scene-responsive occipital place area (OPA) reflected scene layout with invariance to changes in surface texture. This result contrasted sharply with the primary visual cortex (V1), which reflected low-level image features of the stimuli, and the parahippocampal place area (PPA), which showed better texture than layout decoding. MEG indicated that the texture-invariant scene layout representation is computed from visual input within ∼100 ms, suggesting a rapid computational mechanism. Taken together, these results suggest that the cortical representation underlying our instant sense of the environmental geometry is located in the OPA. |
Piril Hepsomali; Julie A. Hadwin; Simon P. Liversedge; Federica Degno; Matthew Garner In: Experimental Brain Research, vol. 237, no. 4, pp. 897–909, 2019. @article{Hepsomali2019, Anxiety has been associated with poor attentional control, as reflected in lowered performance on experimental measures of executive attention and inhibitory control. Recent conceptualisations of anxiety propose that individuals who report elevated anxiety symptoms worry about performance and will exert greater cognitive effort to complete tasks well, particularly when cognitive demands are high. Across two experiments, we examined the effect of anxiety on task performance and across two load conditions using (1) measures of inhibitory control (behavioural reaction times and eye-movement responses) and (2) task effort with pupillary and electrocortical markers of effort (CNV) and inhibitory control (N2). Experiment 1 used an oculomotor-delayed-response task that manipulated load by increasing delay duration to create a high load, relative to a low load, condition. Experiment 2 used a Go/No-Go task and load was manipulated by decreasing the No-Go probabilities (i.e., 20% No-Go in the high load condition and 50% No-Go in the low load condition). Experiment 1 showed individuals with high (vs. low) anxiety made more antisaccade errors across load conditions, and made more effort during the high load condition, as evidenced by greater frontal CNV and increased pupillary responses. In Experiment 2, individuals with high anxiety showed increased effort (irrespective of cognitive load), as characterised by larger pupillary responses. In addition, N2 amplitudes were sensitive to load only in individuals with low anxiety. Evidence of reduced performance effectiveness and efficiency across electrophysiological, pupillary, and oculomotor systems in anxiety provides some support for neurocognitive models of frontocortical attentional dysfunction in anxiety. |
Jan Herding; Simon Ludwig; Alexander Lautz; Bernhard Spitzer; Felix Blankenburg Centro-parietal EEG potentials index subjective evidence and confidence during perceptual decision making Journal Article In: NeuroImage, vol. 201, pp. 116011, 2019. @article{Herding2019, Recent studies suggest that a centro-parietal positivity (CPP) in the EEG signal tracks the absolute (unsigned) strength of accumulated evidence for choices that require the integration of noisy sensory input. Here, we investigated whether the CPP might also reflect the evidence for decisions based on a quantitative comparison between two sequentially presented stimuli (a signed quantity). We recorded EEG while participants decided whether the latter of two vibrotactile frequencies was higher or lower than the former in six variants of this task (n ¼ 116). To account for biases in sequential comparisons, we applied a behavioral model based on Bayesian inference that estimated subjectively perceived frequency differences. Immediately after the second stimulus, parietal ERPs reflected the signed value of subjectively perceived differences and afterwards their absolute value. Strikingly, the modulation by signed difference was evident in trials without any objective evidence for either choice and correlated with choice-selective premotor beta band amplitudes. Modulations by the absolute strength of subjectively perceived evidence-a direct indicator of task difficulty-exhibited all features of statistical decision confidence. Together, our data suggest that parietal EEG signals first index subjective evidence, and later include a measure of confidence in the context of perceptual decision making. |
Jim D. Herring; Sophie Esterer; Tom R. Marshall; Ole Jensen; Til O. Bergmann Low-frequency alternating current stimulation rhythmically suppresses gamma-band oscillations and impairs perceptual performance Journal Article In: NeuroImage, vol. 184, pp. 440–449, 2019. @article{Herring2019, Low frequency oscillations such as alpha (8–12 Hz) are hypothesized to rhythmically gate sensory processing, reflected by 40–100 Hz gamma band activity, via the mechanism of pulsed inhibition. We applied transcranial alternating current stimulation (TACS) at individual alpha frequency (IAF) and flanking frequencies (IAF-4 Hz, IAF+4 Hz) to the occipital cortex of healthy human volunteers during concurrent magnetoencephalography (MEG), while participants performed a visual detection task inducing strong gamma-band responses. Occipital (but not retinal) TACS phasically suppressed stimulus-induced gamma oscillations in the visual cortex and impaired target detection, with stronger phase-to-amplitude coupling predicting behavioral impairments. Retinal control TACS ruled out retino-thalamo-cortical entrainment resulting from (subthreshold) retinal stimulation. All TACS frequencies tested were effective, suggesting that visual gamma-band responses can be modulated by a range of low frequency oscillations. We propose that TACS-induced membrane potential modulations mimic the rhythmic change in cortical excitability by which spontaneous low frequency oscillations may eventually exert their impact when gating sensory processing via pulsed inhibition. |
Taylor Hornung; Wen Hsuan Chan; Ralph Axel Müller; Jeanne Townsend; Brandon Keehn Dopaminergic hypo-activity and reduced theta-band power in autism spectrum disorder: A resting-state EEG study Journal Article In: International Journal of Psychophysiology, vol. 146, pp. 101–106, 2019. @article{Hornung2019, Background: Prior studies using a variety of methodologies have reported inconsistent dopamine (DA) findings in individuals with autism spectrum disorder (ASD), ranging from dopaminergic hypo- to hyper-activity. Theta-band power derived from scalp-recorded electroencephalography (EEG), which may be associated with dopamine levels in frontal cortex, has also been shown to be atypical in ASD. The present study examined spontaneous eye-blink rate (EBR), an indirect, non-invasive measure of central dopaminergic activity, and theta power in children with ASD to determine: 1) whether ASD may be associated with atypical DA levels, and 2) whether dopaminergic dysfunction may be associated with aberrant theta-band activation. Method: Participants included thirty-two children with ASD and thirty-two age-, IQ-, and sex-matched typically developing (TD) children. Electroencephalography and eye-tracking data were acquired while participants completed an eyes-open resting-state session. Blinks were counted and EBR was determined by dividing blink frequency by session duration and theta power (4–7.5 Hz) was extracted from midline leads. Results: Eye-blink rate and theta-band activity were significantly reduced in children with ASD as compared to their TD peers. For all participants, greater midline theta power was associated with increased EBR (related to higher DA levels). Conclusions: These results suggest that ASD may be associated with dopaminergic hypo-activity, and that this may contribute to atypical theta-band power. Lastly, EBR may be a useful tool to non-invasively index dopamine levels in ASD and could potentially have many clinical applications, including selecting treatment options and monitoring treatment response. |
Robert Jagiello; Ulrich Pomper; Makoto Yoneya; Sijia Zhao; Maria Chait Rapid brain sesponses to familiar vs. unfamiliar music-an EEG and pupillometry study Journal Article In: Scientific Reports, vol. 9, pp. 15570, 2019. @article{Jagiello2019, Human listeners exhibit marked sensitivity to familiar music, perhaps most readily revealed by popular "name that tune" games, in which listeners often succeed in recognizing a familiar song based on extremely brief presentation. In this work, we used electroencephalography (EEG) and pupillometry to reveal the temporal signatures of the brain processes that allow differentiation between a familiar, well liked, and unfamiliar piece of music. In contrast to previous work, which has quantified gradual changes in pupil diameter (the so-called "pupil dilation response"), here we focus on the occurrence of pupil dilation events. This approach is substantially more sensitive in the temporal domain and allowed us to tap early activity with the putative salience network. Participants (N = 10) passively listened to snippets (750 ms) of a familiar, personally relevant and, an acoustically matched, unfamiliar song, presented in random order. A group of control participants (N = 12), who were unfamiliar with all of the songs, was also tested. We reveal a rapid differentiation between snippets from familiar and unfamiliar songs: Pupil responses showed greater dilation rate to familiar music from 100-300 ms post-stimulus-onset, consistent with a faster activation of the autonomic salience network. Brain responses measured with EEG showed a later differentiation between familiar and unfamiliar music from 350 ms post onset. Remarkably, the cluster pattern identified in the EEG response is very similar to that commonly found in the classic old/new memory retrieval paradigms, suggesting that the recognition of brief, randomly presented, music snippets, draws on similar processes. |
Woojae Jeong; Seolmin Kim; Yee-Joon Kim; Joonyeol Lee Motion direction representation in multivariate electroencephalography activity for smooth pursuit eye movements Journal Article In: NeuroImage, vol. 202, pp. 116160, 2019. @article{Jeong2019, Visually-guided smooth pursuit eye movements are composed of initial open-loop and later steady-state periods. Feedforward sensory information dominates the motor behavior during the open-loop pursuit, and a more complex feedback loop regulates the steady-state pursuit. To understand the neural representations of motion direction during open-loop and steady-state smooth pursuits, we recorded electroencephalography (EEG) responses from human observers while they tracked random-dot kinematograms as pursuit targets. We estimated population direction tuning curves from multivariate EEG activity using an inverted encoding model. We found significant direction tuning curves as early as about 60 ms from stimulus onset. Direction tuning responses were generalized to later times during the open-loop smooth pursuit, but they became more dynamic during the later steady-state pursuit. The encoding quality of retinal motion direction information estimated from the early direction tuning curves was predictive of trial-by-trial variation in initial pursuit directions. These results suggest that the movement directions of open-loop smooth pursuit are guided by the representation of the retinal motion present in the multivariate EEG activity. |
Jianrong Jia; Fang Fang; Huan Luo Selective spatial attention involves two alpha-band components associated with distinct spatiotemporal and functional characteristics Journal Article In: NeuroImage, vol. 199, pp. 228–236, 2019. @article{Jia2019, Attention is crucial for efficiently coordinating resources over multiple objects in a visual scene. Recently, a growing number of studies suggest that attention is implemented through a temporal organization process during which resources are dynamically allocated over a multitude of objects, yet the associated neural evidence, particularly in low-level sensory areas, is still limited. Here we used EEG recordings in combination with a temporal response function (TRF) approach to examine the spatiotemporal characteristics of neuronal impulse response in covert selective attention. We demonstrate two distinct alpha-band components – one in post-central parietal area and one in contralateral occipital area – that are involved in coordinating neural representations of attended and unattended stimuli. Specifically, consistent with previous findings, the central alpha-band component showed enhanced activities for unattended versus attended stimuli within the first 200 ms temporal lag of TRF response, suggesting its inhibitory function in attention. In contrast, the contralateral occipital component displayed relatively earlier activation for the attended than unattended one in the TRF response. Furthermore, the central component but not the occipital component was correlated with attentional behavioral performance. Finally, the parietal area exerted directional influences on the occipital activity through alpha-band rhythm. Taken together, spatial attention involves two hierarchically organized alpha-band components that are associated with distinct spatiotemporal characteristics and presumably play different functions. |
Han-Gue Gue Jo; Thilo Kellermann; Conrad Baumann; Junji Ito; Barbara Schulte Holthausen; Frank Schneider; Sonja Grün; Ute Habel Distinct modes of top-down cognitive processing in the ventral visual cortex Journal Article In: NeuroImage, vol. 193, pp. 201–213, 2019. @article{Jo2019, Top-down cognitive control leads to changes in the sensory processing of the brain. In visual perception such changes can take place in the ventral visual cortex altering the functional asymmetry in forward and backward connections. Here we used fixation-related evoked responses of EEG measurement and dynamic causal modeling to examine hierarchical forward-backward asymmetry, while twenty-six healthy adults performed cognitive tasks that require different types of top-down cognitive control (memorizing or searching visual objects embedded in a natural scene image). The generative model revealed an enhanced asymmetry toward forward connections during memorizing, whereas enhanced backward connections were found during searching. This task-dependent modulation of forward and backward connections suggests two distinct modes of top-down cognitive processing in cortical networks. The alteration in forward-backward asymmetry might underlie the functional role in the cognitive control of visual information processing. |
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. |
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. |
Judith Nicolas; Aline Bompas; Romain Bouet; Olivier Sillan; Eric Koun; Christian Urquizar; Aurélie Bidet-Caulet; Denis Pélisson Saccadic adaptation boosts ongoing gamma activity in a subsequent visuoattentional task Journal Article In: Cerebral Cortex, vol. 29, no. 9, pp. 3606–3617, 2019. @article{Nicolas2019a, Attention and saccadic adaptation (SA) are critical components of visual perception, the former enhancing sensory processing of selected objects, the latter maintaining the eye movements accuracy toward them. Recent studies propelled the hypothesis of a tight functional coupling between these mechanisms, possibly due to shared neural substrates. Here, we used magnetoencephalography to investigate for the first time the neurophysiological bases of this coupling and of SA per se. We compared visual discrimination performance of 12 healthy subjects before and after SA. Eye movements and magnetic signals were recorded continuously. Analyses focused on gamma band activity (GBA) during the pretarget period of the discrimination and the saccadic tasks. We found that GBA increases after SA. This increase was found in the right hemisphere for both postadaptation saccadic and discrimination tasks. For the latter, GBA also increased in the left hemisphere. We conclude that oculomotor plasticity involves GBA modulation within an extended neural network which persists after SA, suggesting a possible role of gamma oscillations in the coupling between SA and attention. |
Elena V. Orekhova; Tatiana A. Stroganova; Justin F. Schneiderman; Sebastian Lundström; Bushra Riaz; Darko Sarovic; Olga V. Sysoeva; Georg Brant; Christopher Gillberg; Nouchine Hadjikhani Neural gain control measured through cortical gamma oscillations is associated with sensory sensitivity Journal Article In: Human Brain Mapping, vol. 40, no. 5, pp. 1583–1593, 2019. @article{Orekhova2019, Gamma oscillations facilitate information processing by shaping the excitatory input/output of neuronal populations. Recent studies in humans and nonhuman primates have shown that strong excitatory drive to the visual cortex leads to suppression of induced gamma oscillations, which may reflect inhibitory-based gain control of network excitation. The efficiency of the gain control measured through gamma oscillations may in turn affect sensory sensitivity in everyday life. To test this prediction, we assessed the link between self-reported sensitivity and changes in magneto-encephalographic gamma oscillations as a function of motion velocity of high-contrast visual gratings. The induced gamma oscillations increased in frequency and decreased in power with increasing stimulation intensity. As expected, weaker suppression of the gamma response correlated with sensory hypersensitivity. Robustness of this result was confirmed by its replication in the two samples: neurotypical subjects and people with autism, who had generally elevated sensory sensitivity. We conclude that intensity-related suppression of gamma response is a promising biomarker of homeostatic control of the excitation–inhibition balance in the visual cortex. |
Aisling E. O'Sullivan; Chantelle Y. Lim; Edmund C. Lalor In: European Journal of Neuroscience, vol. 50, no. 8, pp. 3282–3295, 2019. @article{OSullivan2019, Recent work using electroencephalography has applied stimulus reconstruction techniques to identify the attended speaker in a cocktail party environment. The success of these approaches has been primarily based on the ability to detect cortical tracking of the acoustic envelope at the scalp level. However, most studies have ignored the effects of visual input, which is almost always present in naturalistic scenarios. In this study, we investigated the effects of visual input on envelope-based cocktail party decoding in two multisensory cocktail party situations: (a) Congruent AV—facing the attended speaker while ignoring another speaker represented by the audio-only stream and (b) Incongruent AV (eavesdropping)—attending the audio-only speaker while looking at the unattended speaker. We trained and tested decoders for each condition separately and found that we can successfully decode attention to congruent audiovisual speech and can also decode attention when listeners were eavesdropping, i.e., looking at the face of the unattended talker. In addition to this, we found alpha power to be a reliable measure of attention to the visual speech. Using parieto-occipital alpha power, we found that we can distinguish whether subjects are attending or ignoring the speaker's face. Considering the practical applications of these methods, we demonstrate that with only six near-ear electrodes we can successfully determine the attended speech. This work extends the current framework for decoding attention to speech to more naturalistic scenarios, and in doing so provides additional neural measures which may be incorporated to improve decoding accuracy. |
Luis Aguado; Karisa B. Parkington; Teresa Dieguez-Risco; José A. Hinojosa; Roxane J. Itier Joint modulation of facial expression processing by contextual congruency and task demands Journal Article In: Brain Sciences, vol. 9, pp. 1–20, 2019. @article{Aguado2019, Faces showing expressions of happiness or anger were presented together with sentences that described happiness-inducing or anger-inducing situations. Two main variables were manipulated: (i) congruency between contexts and expressions (congruent/incongruent) and (ii) the task assigned to the participant, discriminating the emotion shown by the target face (emotion task) or judging whether the expression shown by the face was congruent or not with the context (congruency task). Behavioral and electrophysiological results (event-related potentials (ERP)) showed that processing facial expressions was jointly influenced by congruency and task demands. ERP results revealed task effects at frontal sites, with larger positive amplitudes between 250–450 ms in the congruency task, reflecting the higher cognitive effort required by this task. Effects of congruency appeared at latencies and locations corresponding to the early posterior negativity (EPN) and late positive potential (LPP) components that have previously been found to be sensitive to emotion and affective congruency. The magnitude and spatial distribution of the congruency effects varied depending on the task and the target expression. These results are discussed in terms of the modulatory role of context on facial expression processing and the different mechanisms underlying the processing of expressions of positive and negative emotions. |
Máté Aller; Uta Noppeney To integrate or not to integrate: Temporal dynamics of hierarchical Bayesian causal inference Journal Article In: PLoS Biology, vol. 17, no. 4, pp. e3000210, 2019. @article{Aller2019, To form a percept of the environment, the brain needs to solve the binding problem—inferring whether signals come from a common cause and are integrated or come from independent causes and are segregated. Behaviourally, humans solve this problem near-optimally as predicted by Bayesian causal inference; but the neural mechanisms remain unclear. Combining Bayesian modelling, electroencephalography (EEG), and multivariate decoding in an audiovisual spatial localisation task, we show that the brain accomplishes Bayesian causal inference by dynamically encoding multiple spatial estimates. Initially, auditory and visual signal locations are estimated independently; next, an estimate is formed that combines information from vision and audition. Yet, it is only from 200 ms onwards that the brain integrates audiovisual signals weighted by their bottom-up sensory reliabilities and top-down task relevance into spatial priority maps that guide behavioural responses. As predicted by Bayesian causal inference, these spatial priority maps take into account the brain's uncertainty about the world's causal structure and flexibly arbitrate between sensory integration and segregation. The dynamic evolution of perceptual estimates thus reflects the hierarchical nature of Bayesian causal inference, a statistical computation, which is crucial for effective interactions with the environment. |
Roy Amit; Dekel Abeles; Marisa Carrasco; Shlomit Yuval-Greenberg Oculomotor inhibition reflects temporal expectations Journal Article In: NeuroImage, vol. 184, pp. 279–292, 2019. @article{Amit2019a, The accurate extraction of signals out of noisy environments is a major challenge of the perceptual system. Forming temporal expectations and continuously matching them with perceptual input can facilitate this process. In humans, temporal expectations are typically assessed using behavioral measures, which provide only retrospective but no real-time estimates during target anticipation, or by using electrophysiological measures, which require extensive preprocessing and are difficult to interpret. Here we show a new correlate of temporal expectations based on oculomotor behavior. Observers performed an orientation-discrimination task on a central grating target, while their gaze position and EEG were monitored. In each trial, a cue preceded the target by a varying interval (“foreperiod”). In separate blocks, the cue was either predictive or non-predictive regarding the timing of the target. Results showed that saccades and blinks were inhibited more prior to an anticipated regular target than a less-anticipated irregular one. This consistent oculomotor inhibition effect enabled a trial-by-trial classification according to interval-regularity. Additionally, in the regular condition the slope of saccade-rate and drift were shallower for longer than shorter foreperiods, indicating their adjustment according to temporal expectations. Comparing the sensitivity of this oculomotor marker with those of other common predictability markers (e.g. alpha-suppression) showed that it is a sensitive marker for cue-related anticipation. In contrast, temporal changes in conditional probabilities (hazard-rate) modulated alpha-suppression more than cue-related anticipation. We conclude that pre-target oculomotor inhibition is a correlate of temporal predictions induced by cue-target associations, whereas alpha-suppression is more sensitive to conditional probabilities across time. |
Ayelet Arazi; Yaffa Yeshurun; Ilan Dinstein Neural variability is quenched by attention Journal Article In: Journal of Neuroscience, vol. 39, no. 30, pp. 5975–5985, 2019. @article{Arazi2019, Attention can be subdivided into several components, including alertness and spatial attention. It is believed that the behavioral benefits of attention, such as increased accuracy and faster reaction times, are generated by an increase in neural activity and a decrease in neural variability, which enhance the signal-to-noise ratio of task-relevant neural populations. However, empirical evidence regarding attention-related changes in neural variability in humans is extremely rare. Here we used EEG to demonstrate that trial-by-trial neural variability was reduced by visual cues that modulated alertness and spatial attention. Reductions in neural variability were specific to the visual system and larger in the contralateral hemisphere of the attended visual field. Subjects with higher initial levels of neural variability and larger decreases in variability exhibited greater behavioral benefits from attentional cues. These findings demonstrate that both alertness and spatial attention modulate neural variability and highlight the importance of reducing/quenching neural variability for attaining the behavioral benefits of attention. |
Ryszard Auksztulewicz; Nicholas E. Myers; Jan W. Schnupp; Anna C. Nobre Rhythmic temporal expectation boosts neural activity by increasing neural gain Journal Article In: Journal of Neuroscience, vol. 39, no. 49, pp. 9806–9817, 2019. @article{Auksztulewicz2019, Temporal orienting improves sensory processing, akin to other top–down biases. However, it is unknown whether these improvements reflect increased neural gain to any stimuli presented at expected time points, or specific tuning to task-relevant stimulus aspects. Furthermore, while other top–down biases are selective, the extent of trade-offs across time is less well characterized. Here, we tested whether gain and/or tuning ofauditory frequency processing in humans is modulated by rhythmic temporal expectations, and whether these modulations are specific to time points relevant for task performance. Healthy participants (N⫽ 23) of either sex performed an auditory discrimination task while their brain activity was measured using magnetoencephalography/electroencephalography (M/EEG). Acoustic stimulation consisted ofsequences ofbriefdistractors interspersed with targets, presented in a rhythmic or jittered way. Target rhythmicity not only improved behavioral discrimination accuracy and M/EEG-based decoding oftargets, but also ofirrelevant distrac- tors preceding these targets. To explain this finding in terms ofincreased sensitivity and/or sharpened tuning to auditory frequency, we estimated tuning curves based on M/EEG decoding results, with separate parameters describing gain and sharpness. The effect of rhythmic expectation on distractor decoding was linked to gain increase only, suggesting increased neural sensitivity to any stimuli presented at relevant time points. |
Sonya Bells; Jérémie Lefebvre; Giulia Longoni; Sridar Narayanan; Douglas L. Arnold; Eleun Ann Yeh; Donald J. Mabbott White matter plasticity and maturation in human cognition Journal Article In: Glia, vol. 67, no. 11, pp. 2020–2037, 2019. @article{Bells2019, White matter plasticity likely plays a critical role in supporting cognitive development. However, few studies have used the imaging methods specific to white matter tissue structure or experimental designs sensitive to change in white matter necessary to elucidate these relations. Here we briefly review novel imaging approaches that provide more specific information regarding white matter microstructure. Furthermore, we highlight recent studies that provide greater clarity regarding the relations between changes in white matter and cognition maturation in both healthy children and adolescents and those with white matter insult. Finally, we examine the hypothesis that white matter is linked to cognitive function via its impact on neural synchro- nization. We test this hypothesis in a population of children and adolescents with recurrent demyelinating syndromes. Specifically, we evaluate group differences in white matter microstructure within the optic radiation; and neural phase synchrony in visual cortex during a visual task between 25 patients and 28 typically developing age-matched controls. Children and adolescents with demyelinating syndromes show evidence of myelin and axonal compromise and this compromise predicts reduced phase synchrony during a visual task compared to typically developing controls. We investigate one plausible mechanism at play in this relationship using a computational model of gamma generation in early visual cortical areas. Overall, our findings show a fundamental connection between white matter microstructure and neural synchronization that may be critical for cognitive processing. In the future, longitudinal or interventional studies can build upon our knowledge of these exciting relations between white matter, neural communication, and cognition. |
Chad C. Williams; Mitchel Kappen; Cameron D. Hassall; Bruce Wright; Olave E. Krigolson Thinking theta and alpha: Mechanisms of intuitive and analytical reasoning Journal Article In: NeuroImage, vol. 189, pp. 574–580, 2019. @article{Williams2019, Humans have a unique ability to engage in different modes of thinking. Intuitive thinking (coined System 1, see Kahneman, 2011) is fast, automatic, and effortless whereas analytical thinking (coined System 2) is slow, contemplative, and effortful. We extend seminal pupillometry research examining these modes of thinking by using electroencephalography (EEG) to decipher their respective underlying neural mechanisms. We demonstrate that System 1 thinking is characterized by an increase in parietal alpha EEG power reflecting autonomic access to long-term memory and a release of attentional resources whereas System 2 thinking is characterized by an increase in frontal theta EEG power indicative of the engagement of cognitive control and working memory processes. Consider our results in terms of an example - a child may need cognitive control and working memory when contemplating a mathematics problem yet an adullt can drive a car with little to no attention by drawing on easily accessed memories. Importantly, the unravelling of intuitive and analytical thinking mechanisms and their neural signatures will provide insight as to how different modes of thinking drive our everyday lives. |
Jing Zhu; Ying Wang; Rong La; Jiawei Zhan; Junhong Niu; Shuai Zeng; Xiping Hu Multimodal mild depression recognition based on EEG-EM synchronization acquisition network Journal Article In: IEEE Access, vol. 7, pp. 28196–28210, 2019. @article{Zhu2019, In this paper, we used electroencephalography (EEG)-eye movement (EM) synchronization acquisition network to simultaneously record both EEG and EM physiological signals of the mild depression and normal controls during free viewing. Then, we consider a multimodal feature fusion method that can best discriminate between mild depression and normal control subjects as a step toward achieving our long-term aim of developing an objective and effective multimodal system that assists doctors during diagnosis and monitoring of mild depression. Based on the multimodal denoising autoencoder, we use two feature fusion strategies (feature fusion and hidden layer fusion) for fusion of the EEG and EM signals to improve the recognition performance of classifiers for mild depression. Our experimental results indicate that the EEG-EM synchronization acquisition network ensures that the recorded EM and EEG data require that both the data streams are synchronized with millisecond precision, and both fusion methods can improve the mild depression recognition accuracy, thus demonstrating the complementary nature of the modalities. Compared with the unimodal classification approach that uses only EEG or EM, the feature fusion method slightly improved the recognition accuracy by 1.88%, while the hidden layer fusion method significantly improved the classification rate by up to 7.36%. In particular, the highest classification accuracy achieved in this paper was 83.42%. These results indicate that the multimodal deep learning approaches with input data using a combination of EEG and EM signals are promising in achieving real-time monitoring and identification of mild depression. |
Nathan Caruana; Genevieve McArthur The mind minds minds: The effect of intentional stance on the neural encoding of joint attention Journal Article In: Cognitive, Affective and Behavioral Neuroscience, vol. 19, no. 6, pp. 1479–1491, 2019. @article{Caruana2019a, Recent neuroimaging studies have observed that the neural processing of social cues from a virtual reality character appears to be affected by "intentional stance" (i.e., attributing mental states, agency, and "humanness"). However, this effect could also be explained by individual differences or perceptual effects resulting from the design of these studies. The current study used a new design that measured centro-parietal P250, P350, and N170 event-related potentials (ERPs) in 20 healthy adults while they initiated gaze-related joint attention with a virtual character (“Alan”) in two conditions. In one condition, they were told that Alan was controlled by a human; in the other, they were told that he was controlled by a computer. When participants believed Alan was human, his congruent gaze shifts, which resulted in joint attention, generated significantly larger P250 ERPs than his incongruent gaze shifts. In contrast, his incongruent gaze shifts triggered significantly larger increases in P350 ERPs than his congruent gaze shifts. These findings support previous studies suggesting that intentional stance affects the neural processing of social cues from a virtual character. The outcomes also suggest the use of the P250 and P350 ERPs as objective indices of social engagement during the design of socially approachable robots and virtual agents. |
Jing Chen; Matteo Valsecchi; Karl R. Gegenfurtner Saccadic suppression measured by steady-state visual evoked potentials Journal Article In: Journal of Neurophysiology, vol. 122, no. 1, pp. 251–258, 2019. @article{Chen2019e, Visual sensitivity is severely impaired during the execution of saccadic eye movements. This phenomenon has been extensively characterized in human psychophysics and nonhuman primate single-neuron studies, but a physiological characterization in humans is less established. Here, we used a method based on steadystate visually evoked potential (SSVEP), an oscillatory brain response to periodic visual stimulation, to examine how saccades affect visual sensitivity. Observers made horizontal saccades back and forth, while horizontal black-and-white gratings flickered at 5-30 Hz in the background. We analyzed EEG epochs with a length of 0.3 s either centered at saccade onset (saccade epochs) or centered at fixations half a second before the saccade (fixation epochs). Compared with fixation epochs, saccade epochs showed a broadband power increase, which most likely resulted from saccade-related EEG activity. The execution of saccades, however, led to an average reduction of 57% in the SSVEP amplitude at the stimulation frequency. This result provides additional evidence for an active saccadic suppression in the early visual cortex in humans. Compared with previous functional MRI and EEG studies, an advantage of this approach lies in its capability to trace the temporal dynamics of neural activity throughout the time course of a saccade. In contrast to previous electrophysiological studies in nonhuman primates, we did not find any evidence for postsaccadic enhancement, even though simulation results show that our method would have been able to detect it. We conclude that SSVEP is a useful technique to investigate the neural correlates of visual perception during saccadic eye movements in humans. |
Rajib Chowdhury; A. F. M. Saifuddin Saif Efficient method to improve human brain sensor activities using proposed neuroheadset device embedded with sensors: A comprehensive study Journal Article In: International Journal of Software Engineering and Computer Systems, vol. 53, no. 1, pp. 52–56, 2019. @article{Chowdhury2019, The main purpose of this research is to investigate the human brain sensor activities related prior researches towards the needs of an efficient method to improve the human brain sensor activities. Human brain activities mainly measured by brain signal acquired from the brain sensor electrodes positioned on several parts of the brain cortex. Although previous researches investigated human brain activities in various aspects, the improvement of the human brain sensor activities is still unsolved. In today's world, it is very crucial need for improving the sensor activities of the human brain using that human brain improved signal externally. This research demonstrated a comprehensive critical analysis of human brain activities related prior researches to claim for an efficient method integrated with proposed neuroheadset device. This research presented a comprehensive review in various aspects like previous methods, existing frameworks analysis and existing results analysis with the discussion to establish an efficient method for acquiring human brain signal, improving the acquired signal and developing the sensor activities of the human brain using that human brain improved signal. Demonstrated critical review has expected for constituting an efficient method to improve the performance of maneuverability, visualization, subliminal activities and so forth on human brain activities. |
Tim H. W. Cornelissen; Jona Sassenhagen; Melissa L. -H. Võ Improving free-viewing fixation-related EEG potentials with continuous-time regression Journal Article In: Journal of Neuroscience Methods, vol. 313, pp. 77–94, 2019. @article{Cornelissen2019, Background: In the analysis of combined ET-EEG data, there are several issues with estimating FRPs by averaging. Neural responses associated with fixations will likely overlap with one another in the EEG recording and neural responses change as a function of eye movement characteristics. Especially in tasks that do not constrain eye movements in any way, these issues can become confounds. New method: Here, we propose the use of regression based estimates as an alternative to averaging. Multiple regression can disentangle different influences on the EEG and correct for overlap. It thereby accounts for potential confounds in a way that averaging cannot. Specifically, we test the applicability of the rERP framework, as proposed by Smith and Kutas (2015b), (2017), or Sassenhagen (2018) to combined eye tracking and EEG data from a visual search and a scene memorization task. Results: Results show that the method successfully estimates eye movement related confounds in real experimental data, so that these potential confounds can be accounted for when estimating experimental effects. Comparison with existing methods: The rERP method successfully corrects for overlapping neural responses in instances where averaging does not. As a consequence, baselining can be applied without risking distortions. By estimating a known experimental effect, we show that rERPs provide an estimate with less variance and more accuracy than averaged FRPs. The method therefore provides a practically feasible and favorable alternative to averaging. Conclusions: We conclude that regression based ERPs provide novel opportunities for estimating fixation related EEG in free-viewing experiments. |
Antea D'Andrea; Federico Chella; Tom R. Marshall; Vittorio Pizzella; Gian Luca Romani; Ole Jensen; Laura Marzetti In: NeuroImage, vol. 188, pp. 722–732, 2019. @article{DAndrea2019, It is well known that attentional selection of relevant information relies on local synchronization of alpha band neuronal oscillations in visual cortices for inhibition of distracting inputs. Additionally, evidence for long-range coupling of neuronal oscillations between visual cortices and regions engaged in the anticipation of upcoming stimuli has been more recently provided. Nevertheless, on the one hand the relation between long-range functional coupling and anatomical connections is still to be assessed, and, on the other hand, the specific role of the alpha and beta frequency bands in the different processes underlying visuo-spatial attention still needs further clarification. We address these questions using measures of linear (frequency-specific) and nonlinear (cross-frequency) phase-synchronization in a cohort of 28 healthy subjects using magnetoencephalography. We show that alpha band phase-synchronization is modulated by the orienting of attention according to a parieto-occipital top-down mechanism reflecting behavior, and its hemispheric asymmetry is predicted by volume's asymmetry of specific tracts of the Superior-Longitudinal-Fasciculus. We also show that a network comprising parietal regions and the right putative Frontal-Eye-Field, but not the left, is recruited in the deployment of spatial attention through an alpha-beta cross-frequency coupling. Overall, we demonstrate that the visuospatial attention network features subsystems indexed by characteristic spectral fingerprints, playing different functional roles in the anticipation of upcoming stimuli and with diverse relation to fiber tracts. |
Peter Lissa; Genevieve McArthur; Stefan Hawelka; Romina Palermo; Yatin Mahajan; Federica Degno; Florian Hutzler Peripheral preview abolishes N170 face-sensitivity at fixation: Using fixation-related potentials to investigate dynamic face processing Journal Article In: Visual Cognition, vol. 27, no. 9-10, pp. 740–759, 2019. @article{Lissa2019, The N170 ERP peak has been found to be consistently larger in response to the presentation of faces than to other objects, yet it is not clear whether this face-sensitive N170 is also elicited during fixations made subsequent to the initial presentation. To investigate this question, the current study utilised Event and Fixation-Related Potentials in two experiments, time-locking brain potentials to the presentation of faces and objects (watches) images in participants' peripheral vision, and to their first fixations on the images. Experiment 1 found that a face-sensitive N170 was elicited by the onset of images but not by a subsequent fixation on the images, and that face inversion did not modulate N170 beyond presentation. Experiment 2 found that disrupting the structure of the peripheral preview (phase-scrambling) led to a face-sensitive N170 at fixation onsets on the intact-images. Interestingly, N170 amplitudes for both faces and objects were significantly enhanced after the peripheral preview was phase-scrambled, suggesting that the N170 in part reflects a category-detection process that is elicited once when an image structure is viewed. These results indicate that neural processing during fixations will be significantly modulated when they are immediately preceded by peripheral previews, and is not specific to faces. |
Federica Degno; Otto Loberg; Chuanli Zang; Manman Zhang; Nick Donnelly; Simon P. Liversedge A co-registration investigation of inter-word spacing and parafoveal preview: Eye movements and fixation-related potentials Journal Article In: PLoS ONE, vol. 14, no. 12, pp. e0225819, 2019. @article{Degno2019, Participants' eye movements (EMs) and EEG signal were simultaneously recorded to examine foveal and parafoveal processing during sentence reading. All the words in the sentence were manipulated for inter-word spacing (intact spaces vs. spaces replaced by a random letter) and parafoveal preview (identical preview vs. random letter string preview). We observed disruption for unspaced text and invalid preview conditions in both EMs and fixation- related potentials (FRPs). Unspaced and invalid preview conditions received longer reading times than spaced and valid preview conditions. In addition, the FRP data showed that unspaced previews disrupted reading in earlier time windows of analysis, compared to string preview conditions. Moreover, the effect of parafoveal preview was greater for spaced relative to unspaced conditions, in both EMs and FRPs. These findings replicate well-established preview effects, provide novel insight into the neural correlates of reading with and without inter-word spacing and suggest that spatial selection precedes lexical processing. |
Federica Degno; Otto Loberg; Chuanli Zang; Manman Zhang; Nick Donnelly; Simon P. Liversedge Parafoveal previews and lexical frequency in natural reading: Evidence from eye movements and fixation-related potentials. Journal Article In: Journal of Experimental Psychology: General, vol. 148, no. 3, pp. 453–474, 2019. @article{Degno2019a, Participants' eye movements and electroencephalogram (EEG) signal were recorded as they read sentences displayed according to the gaze-contingent boundary paradigm. Two target words in each sentence were manipulated for lexical frequency (high vs. low frequency) and parafoveal preview of each target word (identical vs. string of random letters vs. string of Xs). Eye movement data revealed visual parafoveal-on-foveal (PoF) effects, as well as foveal visual and orthographic preview effects and word frequency effects. Fixation-related potentials (FRPs) showed visual and orthographic PoF effects as well as foveal visual and orthographic preview effects. Our results replicated the early preview positivity effect (Dimigen, Kliegl, & Sommer, 2012) in the X-string preview condition, and revealed different neural correlates associated with a preview comprised of a string of random letters relative to a string of Xs. The former effects seem likely to reflect difficulty associated with the integration of parafoveal and foveal information, as well as feature overlap, while the latter reflect inhibition, and potentially disruption, to processing underlying reading. Interestingly, and consistent with Kretzschmar, Schlesewsky, and Staub (2015), no frequency effect was reflected in the FRP measures. The findings provide insight into the neural correlates of parafoveal processing and written word recognition in reading and demonstrate the value of utilizing ecologically valid paradigms to study well established phenomena that occur as text is read naturally. |
Christ Devia; Rocio Mayol-Troncoso; Javiera Parrini; Gricel Orellana; Aida Ruiz; Pedro E. Maldonado; Jose Ignacio Egaña EEG classification during scene free-viewing for schizophrenia detection Journal Article In: IEEE Transactions on Neural Systems and Rehabilitation Engineering, vol. 27, no. 6, pp. 1193–1199, 2019. @article{Devia2019, Currently, the diagnosis of schizophrenia is made solely based on interviews and behavioral observations by a trained psychiatrist. Technologies such as electroencephalography (EEG) are used for differential diagnosis and not to support the psychiatrist's positive diagnosis. Here, we show the potential of EEG recordings as biomarkers of the schizophrenia syndrome. We recorded EEG while schizophrenia patients freely viewed natural scenes, and we analyzed the average EEG activity locked to the image onset. We found significant differences between patients and healthy controls in occipital areas approximately 500 ms after image onset. These differences were used to train a classifier to discriminate the schizophrenia patients from the controls. The best classifier had 81% sensitivity for the detection of patients and specificity of 59% for the detection of controls, with an overall accuracy of 71%. These results indicate that EEG signals from a free-viewing paradigm discriminate patients from healthy controls and have the potential to become a tool for the psychiatrist to support the positive diagnosis of schizophrenia. |
Linda Drijvers; Mircea Plas; Asli Özyürek; Ole Jensen Native and non-native listeners show similar yet distinct oscillatory dynamics when using gestures to access speech in noise Journal Article In: NeuroImage, vol. 194, pp. 55–67, 2019. @article{Drijvers2019a, Listeners are often challenged by adverse listening conditions during language comprehension induced by external factors, such as noise, but also internal factors, such as being a non-native listener. Visible cues, such as semantic information conveyed by iconic gestures, can enhance language comprehension in such situations. Using magnetoencephalography (MEG) we investigated whether spatiotemporal oscillatory dynamics can predict a listener's benefit of iconic gestures during language comprehension in both internally (non-native versus native listeners) and externally (clear/degraded speech) induced adverse listening conditions. Proficient non-native speakers of Dutch were presented with videos in which an actress uttered a degraded or clear verb, accompanied by a gesture or not, and completed a cued-recall task after every video. The behavioral and oscillatory results obtained from non-native listeners were compared to an MEG study where we presented the same stimuli to native listeners (Drijvers et al., 2018a). Non-native listeners demonstrated a similar gestural enhancement effect as native listeners, but overall scored significantly slower on the cued-recall task. In both native and non-native listeners, an alpha/beta power suppression revealed engagement of the extended language network, motor and visual regions during gestural enhancement of degraded speech comprehension, suggesting similar core processes that support unification and lexical access processes. An individual's alpha/beta power modulation predicted the gestural benefit a listener experienced during degraded speech comprehension. Importantly, however, non-native listeners showed less engagement of the mouth area of the primary somatosensory cortex, left insula (beta), LIFG and ATL (alpha) than native listeners, which suggests that non-native listeners might be hindered in processing the degraded phonological cues and coupling them to the semantic information conveyed by the gesture. Native and non-native listeners thus demonstrated similar yet distinct spatiotemporal oscillatory dynamics when recruiting visual cues to disambiguate degraded speech. |
Susanne Eisenhauer; Christian J. Fiebach; Benjamin Gagl Context-based facilitation in visual word recognition: Evidence for visual and lexical but not pre-lexical contributions Journal Article In: eNeuro, vol. 6, no. 2, pp. 1–25, 2019. @article{Eisenhauer2019, Word familiarity and predictive context facilitate visual word processing, leading to faster recognition times and reduced neuronal responses. Previously, models with and without top-down connections, including lexical-semantic, pre-lexical (e.g., orthographic/phonological), and visual processing levels were successful in accounting for these facilitation effects. Here we systematically assessed context-based facilitation with a repetition priming task and explicitly dissociated pre-lexical and lexical processing levels using a pseudoword (PW) familiarization procedure. Experiment 1 investigated the temporal dynamics of neuronal facilitation effects with magnetoencephalography (MEG; N = 38 human participants), while experiment 2 assessed behavioral facilitation effects (N = 24 human participants). Across all stimulus conditions, MEG demonstrated context-based facilitation across multiple time windows starting at 100 ms, in occipital brain areas. This finding indicates context-based facilitation at an early visual processing level. In both experiments, we furthermore found an interaction of context and lexical familiarity, such that stimuli with associated meaning showed the strongest context-dependent facilitation in brain activation and behavior. Using MEG, this facilitation effect could be localized to the left anterior temporal lobe at around 400 ms, indicating within-level (i.e., exclusively lexical-semantic) facilitation but no top-down effects on earlier processing stages. Increased pre-lexical familiarity (in PWs familiarized utilizing training) did not enhance or reduce context effects significantly. We conclude that context-based facilitation is achieved within visual and lexical processing levels. Finally, by testing alternative hypotheses derived from mechanistic accounts of repetition suppression, we suggest that the facilitatory context effects found here are implemented using a predictive coding mechanism. |
Matthew W. Flounders; Carlos González-García; Richard Hardstone; Biyu J. He Neural dynamics of visual ambiguity resolution by perceptual prior Journal Article In: eLife, vol. 8, pp. 1–25, 2019. @article{Flounders2019, Past experiences have enormous power in shaping our daily perception. Currently, dynamical neural mechanisms underlying this process remain mysterious. Exploiting a dramatic visual phenomenon, where a single experience of viewing a clear image allows instant recognition of a related degraded image, we investigated this question using MEG and 7 Tesla fMRI in humans. We observed that following the acquisition of perceptual priors, different degraded images are represented much more distinctly in neural dynamics starting from ~500 ms after stimulus onset. Content-specific neural activity related to stimulus-feature processing dominated within 300 ms after stimulus onset, while content-specific neural activity related to recognition processing dominated from 500 ms onward. Model-driven MEG-fMRI data fusion revealed the spatiotemporal evolution of neural activities involved in stimulus, attentional, and recognition processing. Together, these findings shed light on how experience shapes perceptual processing across space and time in the brain. |
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. |
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. |
Karisa B. Parkington; Roxane J. Itier From eye to face: The impact of face outline, feature number, and feature saliency on the early neural response to faces Journal Article In: Brain Research, vol. 1722, pp. 1–14, 2019. @article{Parkington2019, The LIFTED model of early face perception postulates that the face-sensitive N170 event-related potential may reflect underlying neural inhibition mechanisms which serve to regulate holistic and featural processing. It remains unclear, however, what specific factors impact these neural inhibition processes. Here, N170 peak responses were recorded whilst adults maintained fixation on a single eye using a gaze-contingent paradigm, and the presence/absence of a face outline, as well as the number and type of parafoveal features within the outline, were manipulated. N170 amplitudes and latencies were reduced when a single eye was fixated within a face outline compared to fixation on the same eye in isolation, demonstrating that the simple presence of a face outline is sufficient to elicit a shift towards a more face-like neural response. A monotonic decrease in the N170 amplitude and latency was observed with increasing numbers of parafoveal features, and the type of feature(s) present in parafovea further modulated this early face response. These results support the idea of neural inhibition exerted by parafoveal features onto the foveated feature as a function of the number, and possibly the nature, of parafoveal features. Specifically, the results suggest the use of a feature saliency framework (eyes > mouth > nose) at the neural level, such that the parafoveal eye may play a role in down-regulating the response to the other eye (in fovea) more so than the nose or the mouth. These results confirm the importance of parafoveal features and the face outline in the neural inhibition mechanism, and provide further support for a feature saliency mechanism guiding early face perception. |
Thomas Parr; M. Berk Mirza; Hayriye Cagnan; Karl J. Friston Dynamic causal modelling of active vision Journal Article In: Journal of Neuroscience, vol. 39, no. 32, pp. 6265–6275, 2019. @article{Parr2019, In this paper, we draw from recent theoretical work on active perception, which suggests that the brain makes use of an internal (i.e., generative) model to make inferences about the causes of sensations. This view treats visual sensations as consequent on action (i.e., saccades) and implies that visual percepts must be actively constructed via a sequence ofeye movements. Oculomotor control calls on a distributed set ofbrain sources that includes the dorsal and ventral frontoparietal (attention) networks.Weargue that connections from the frontal eye fields to ventral parietal sources represent the mapping from “where”, fixation location to information derived from “what” representations in the ventral visual stream. During scene construction, this mapping must be learned, putatively through changes in the effective connectivityofthese synapses. Here,wetest the hypothesis that the couplingbetweenthe dorsal frontal cortexand the right temporoparietal cortex is modulated during saccadic interrogation ofa simple visual scene. Using dynamic causal modeling for magnetoencephalography with (male and female) human participants, we assess the evidence for changes in effective connectivity by comparing models that allow for this modulation with models that do not. We find strong evidence for modulation of connections between the two attention networks; namely, a disinhibition ofthe ventral network by its dorsal counterpart. |
Nathan M. Petro; Nina N. Thigpen; Steven Garcia; Maeve R. Boylan; Andreas Keil Pre-target alpha power predicts the speed of cued target discrimination Journal Article In: NeuroImage, vol. 189, pp. 878–885, 2019. @article{Petro2019, The human visual system selects information from dense and complex streams of spatiotemporal input. This selection process is aided by prior knowledge of the features, location, and temporal proximity of an upcoming stimulus. In the laboratory, this knowledge is often conveyed by cues, preceding a task-relevant target stimulus. Response speed in cued selection tasks varies within and across participants and is often thought to index efficient selection of a cued feature, location, or moment in time. The present study used a reverse correlation approach to identify neural predictors of efficient target discrimination: Participants identified the orientation of a sinusoidal grating, which was presented in one hemifield following the presentation of bilateral visual cues that carried temporal but not spatial information about the target. Across different analytic approaches, faster target responses were predicted by larger alpha power preceding the target. These results suggest that heightened pre-target alpha power during a cue period may index a state that is beneficial for subsequent target processing. Our findings are broadly consistent with models that emphasize capacity sharing across time, as well as models that link alpha oscillations to temporal predictions regarding upcoming events. |
Ella Podvalny; Matthew W. Flounders; Leana E. King; Tom Holroyd; Biyu J. He A dual role of prestimulus spontaneous neural activity in visual object recognition Journal Article In: Nature Communications, vol. 10, pp. 3910, 2019. @article{Podvalny2019, Vision relies on both specific knowledge of visual attributes, such as object categories, and general brain states, such as those reflecting arousal. We hypothesized that these phenomena independently influence recognition of forthcoming stimuli through distinct processes reflected in spontaneous neural activity. Here, we recorded magnetoencephalographic (MEG) activity in participants (N = 24) who viewed images of objects presented at recognition threshold. Using multivariate analysis applied to sensor-level activity patterns recorded before stimulus presentation, we identified two neural processes influencing subsequent subjective recognition: a general process, which disregards stimulus category and correlates with pupil size, and a specific process, which facilitates category-specific recognition. The two processes are doubly-dissociable: the general process correlates with changes in criterion but not in sensitivity, whereas the specific process correlates with changes in sensitivity but not in criterion. Our findings reveal distinct mechanisms of how spontaneous neural activity influences perception and provide a framework to integrate previous findings. |
Ulrich Pomper; Thomas Ditye; Ulrich Ansorge Contralateral delay activity during temporal order memory Journal Article In: Neuropsychologia, vol. 129, pp. 104–116, 2019. @article{Pomper2019, In everyday life, we constantly need to remember the temporal sequence of visual events over short periods of time, for example, when making sense of others' actions or watching a movie. While there is increasing knowledge available on neural mechanisms underlying visual working memory (VWM) regarding the identity and spatial location of objects, less is known about how the brain encodes and retains information on temporal sequences. Here, we investigate whether the contralateral-delay activity (CDA), a well-studied electroencephalographic (EEG) component associated with VWM of object identity, also reflects the encoding and retention of temporal order. In two independent experiments, we presented participants with a sequence of four or six images, followed by a 1 s retention period. Participants judged temporal order by indicating whether a subsequently presented probe image was originally displayed during the first or the second half of the sequence. As a main novel result, we report the emergence of a contralateral negativity already following the presentation of the first item of the sequence, which increases over the course of a trial with every presented item, up to a limit of four items. We further observed no differences in the CDA during the temporal-order task compared to one obtained during a task concerning the spatial location of the presented items. Since the characteristics of the CDA appear to be highly similar between different encoded feature dimensions and increases as additional items are being encoded, we suggest this component might be a general characteristic of various types of VWM. |
Tzvetan Popov; Bart Gips; Sabine Kastner; Ole Jensen Spatial specificity of alpha oscillations in the human visual system Journal Article In: Human Brain Mapping, vol. 40, no. 15, pp. 4432–4440, 2019. @article{Popov2019, Alpha oscillations are strongly modulated by spatial attention. To what extent, the generators of cortical alpha oscillations are spatially distributed and have selectivity that can be related to retinotopic organization is a matter of continuous scientific debate. In the present report, neuromagnetic activity was quantified by means of spatial location tuning functions from 30 participants engaged in a visuospatial attention task. A cue presented briefly in one of 16 locations directing covert spatial attention resulted in a robust modulation of posterior alpha oscillations. The distribution of the alpha sources approximated the retinotopic organization of the human visual system known from hemodynamic studies. Better performance in terms of target identification was associated with a more spatially constrained alpha modulation. The present findings demonstrate that the generators of posterior alpha oscillations are retinotopically organized when modulated by spatial attention. |
Silvan C. Quax; Nadine Dijkstra; Mariel J. Staveren; Sander E. Bosch; Marcel A. J. Gerven Eye movements explain decodability during perception and cued attention in MEG Journal Article In: NeuroImage, vol. 195, pp. 444–453, 2019. @article{Quax2019, Eye movements are an integral part of human perception, but can induce artifacts in many magneto-encephalography (MEG) and electroencephalography (EEG) studies. For this reason, investigators try to minimize eye movements and remove these artifacts from their data using different techniques. When these artifacts are not purely random, but consistent regarding certain stimuli or conditions, the possibility arises that eye movements are actually inducing effects in the MEG signal. It remains unclear how much of an influence eye movements can have on observed effects in MEG, since most MEG studies lack a control analysis to verify whether an effect found in the MEG signal is induced by eye movements. Here, we find that we can decode stimulus location from eye movements in two different stages of a working memory match-to-sample task that encompass different areas of research typically done with MEG. This means that the observed MEG effect might be (partly) due to eye movements instead of any true neural correlate. We suggest how to check for eye movement effects in the data and make suggestions on how to minimize eye movement artifacts from occurring in the first place. |
Romain Quentin; Jean Rémi King; Etienne Sallard; Nathan Fishman; Ryan Thompson; Ethan R. Buch; Leonardo G. Cohen Differential brain mechanisms of selection and maintenance of information during working memory Journal Article In: Journal of Neuroscience, vol. 39, no. 19, pp. 3728–3740, 2019. @article{Quentin2019, Working memory is our ability to select and temporarily hold information as needed for complex cognitive operations. The temporal dynamics of sustained and transient neural activity supporting the selection and holding of memory content is not known. To address this problem, we recorded magnetoencephalography in healthy participants performing a retro-cue working memory task in which the selection rule and the memory content varied independently. Multivariate decoding and source analyses showed that selecting the memory content relies on prefrontal and parieto-occipital persistent oscillatory neural activity. By contrast, the memory content was reactivated in a distributed occipitotemporal posterior network, preceding the working memory decision and in a different format than during the visual encoding. These results identify a neural signature of content selection and characterize differentiated spatiotemporal constraints for subprocesses of working memory. |
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. |
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. |
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. |
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. |
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. |
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. |
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. |