Biology subjects

Vanneau, T.

Publications and source records attributed to Vanneau, T..

11 recordsLinked to original sources

bioRxiv2026

Revisiting post-stimulus theta activity: evidence for an aperiodic rather than oscillatory origin

The aperiodic, 1/f-like component of electrophysiological activity is increasingly recognized as a meaningful feature of neural function, rather than background noise. In parallel, many EEG studies report transient changes in oscillatory power following stimulus onset and interpret these effects as signatures of attention, salience, or cognitive control. However, such conclusions usually rely on baseline normalization procedures that assume aperiodic activity remains stable from pre-to post-stimulus periods. Using high-density EEG recordings from typically developing children, we tested this assumption in two paradigms: an audiovisual simple reaction-time task (n = 36) and a visual oddball task (n = 38). For each task, conventional spectral analyses were compared with analyses that explicitly modeled and removed the aperiodic component in both pre- and post-stimulus windows. Across tasks, stimulus onset was associated with robust increases in aperiodic exponent and offset, indicating systematic changes in the 1/f component of the spectrum. In the audiovisual task, these changes were modality-specific, with central, parieto-occipital, or combined topographies depending on stimulus type. These effects were reduced but remained significant after ERP removal, indicating that they were not fully explained by phase-locked activity. Critically, once aperiodic activity was accounted for, the apparent post-stimulus increase in theta power was largely abolished in both tasks, including the canonical fronto-central theta enhancement to infrequent targets in the oddball paradigm. The conventional method also overestimated the magnitude of beta desynchronization, particularly in the induced (ERP-removed) signal. The apparent gamma desynchronization detected by conventional analyses was reversed after aperiodic correction, revealing either synchronization or no change, indicating that it reflects a spurious consequence of spectral slope steepening rather than a true suppression of gamma oscillatory activity. In contrast, alpha desynchronization remained robust after aperiodic correction and was in fact enhanced, suggesting it reflects genuine oscillatory suppression. Together, these findings indicate that a substantial portion of conventional time-frequency effects, particularly apparent theta synchronization, may reflect changes in aperiodic activity in response to stimulation rather than genuine periodic oscillations, challenging core assumptions of conventional time-frequency analyses. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=123 SRC="FIGDIR/small/732609v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@1d25f43org.highwire.dtl.DTLVardef@6c476aorg.highwire.dtl.DTLVardef@c4a02aorg.highwire.dtl.DTLVardef@ef417d_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO C_FIG

neuroscience↗

bioRxiv2026

Asymmetric neural dynamics of visuospatial attention in autism spectrum disorder

BackgroundSelective attention enables the prioritization of behaviorally relevant information in complex sensory environments. Despite substantial evidence for altered attention in autism spectrum disorder (ASD), the neurophysiological mechanisms underlying these differences remain poorly understood. MethodsHere, we integrate high-density electroencephalography (EEG), pupillometry, and behavioral measures collected during a cued covert visuospatial selective attention task to characterize mechanisms of spatial attention in children and adolescents with ASD (n = 18; 13.4 {+/-} 3.0 YO), and how they differ from age- and IQ- matched individuals with typical-development (TD) (n = 21; 14.7 {+/-} 3.8 YO). ResultsBoth groups demonstrated high target detection accuracy and comparable response times, with no significant between-group differences in behavioral performance. Furthermore, neurophysiological measures demonstrated that during leftward attention, both TD and ASD participants exhibited canonical attentional processes, including lateralized anticipatory parieto-occipital alpha modulation and enhanced P1 sensory responses to attended stimuli. Additionally, across both groups, trial-level analyses revealed that decreased anticipatory alpha power and increased P1 amplitude contralateral to the attended hemifield were associated with faster reaction times. In contrast, there were notable group differences in the neural dynamics supporting rightward spatial attention. TD participants showed early sensory gain (P1 modulation) without alpha-band modulation, whereas ASD participants exhibited modulation of posterior alpha power without effective sensory gain. Interestingly, for rightward attention, only P1 amplitude predicted reaction time, and this was the case for both groups. Resting-state alpha dynamics did not differ between groups, indicating that the attended hemifield differences reflect task-dependent differences in attentional control rather than baseline oscillatory differences. LimitationsLimitations include modest sample size and restriction to autistic individuals with relatively low support needs, which may limit the generalizability of these findings to the broader autism spectrum. ConclusionsThe similarity of leftward attention mechanisms across groups, which includes intact recruitment of anticipatory alpha modulation, argues against a global disruption of basic visuo-spatial attentional function in autistic individuals with low support needs. However, group differences emerged specifically during rightward attention, where ASD participants showed a more uniform pattern of oscillatory modulation, warranting further investigation. Collectively, these findings provide novel insight into the neural architecture of visuospatial attention in ASD, revealing how preparatory oscillatory activity shapes early sensory responses and behavior during selective attention.

neuroscience↗

bioRxiv2026

Reduced flexibility in predictive tuning and contextual adaptation in autism: an EEG and behavioral study.

The brain generates predictions to prepare for upcoming events. Because the environment is not perfectly predictable, the brain also estimates the certainty of these predictions and adjusts preparatory processes accordingly. Given that autistic individuals often resist even small changes to everyday routines, we hypothesized altered tuning of prediction certainty in autism. To test this, EEG was recorded from adolescents and young autistic adults (n = 20) and from age- and IQ-matched non-autistic adults (n = 19) during a probabilistic cued target identification task during which cue validity was systematically varied across four levels: 100%, 84%, 67%, and 33%. Participants were not informed of the cue-target validity nor when it changed. We focused on two neural signatures of anticipatory readiness, contingent negative variation (CNV) and alpha-band event-related desynchronization (-ERD), and one of cognitive updating: the P3 to targets and to invalid (e.g., a non-target in place of the target) stimuli. Across groups, preparatory activity increased as contextual certainty decreased, with larger CNV amplitudes and stronger -ERD preceding targets in lower-probability contexts, suggesting enhanced preparatory engagement under greater uncertainty. Furthermore, larger CNV amplitudes predicted faster reaction times, indicating functionally significant anticipatory dynamics. However, modulation of both neural preparation and response times as a function of cue-target probability was significantly reduced in the autistic group. In addition, autistic participants showed diminished probability-dependent modulation of the P3b to both targets and invalid stimuli, and coupling between anticipatory activity (CNV) and subsequent updating (P3b) was observed in non-autistic participants whereas it was absent in autism. Together, these findings suggest that while predictive mechanisms are present in autism, anticipatory processes are less flexibly tuned to contextual uncertainty and less effectively linked to subsequent cognitive updating. This reduced adaptability may reflect difficulty adjusting internal predictive models to changing environmental contingencies, potentially contributing to core features of autism such as resistance to change and insistence on sameness. HighlightsO_LIAnticipatory brain mechanisms (CNV and alpha desynchronization) are present in autism and are behaviorally relevant, predicting faster responses. C_LIO_LIAutistic individuals exhibit reduced modulation of anticipatory CNV and alpha activity as a function of cue-target validity. C_LIO_LIP3b responses to both targets and invalid stimuli show diminished sensitivity to contextual probability in autism, consistent with altered prior updating. C_LIO_LIThe link between anticipatory activity and cognitive updating (i.e., CNV to P3b) is disrupted in autism. C_LIO_LIP3a amplitude to invalid stimuli is reduced in autism, suggesting diminished engagement of violation-sensitive processes. C_LIO_LITogether, findings point to less flexible tuning of predictive mechanisms and reduced adaptation to contextual uncertainty in autism. C_LI

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bioRxiv2026

Instability of Alpha Oscillatory States in Autism and Familial Liability: Evidence from Burst-Resolved High-Density Electroencephalography (EEG)

Atypical sensory experiences are highly prevalent in autistic children and include both hyper- and hypo-responsivity, often accompanied by sensory overload. Alpha oscillations (7-13 Hz), which dynamically regulate cortical excitability, represent a plausible neural mechanism underlying these phenomena: reduced alpha activity is associated with enhanced sensory responsiveness, whereas increased alpha supports suppression of external input. Although decreased alpha power has been repeatedly reported in autism, it remains unclear whether this reduction reflects lower oscillatory amplitude or reduced temporal stability of alpha rhythms, two mechanisms with distinct neurophysiological implications. To better characterize alpha activity in autism, we examined resting-state alpha dynamics in non-autistic children (NA; n = 39), autistic children (AU; n = 52), and siblings of autistic children (SIB; n = 26), aged 8-14 years. We combined traditional broadband measures of relative alpha power, parametric separation of periodic and aperiodic activity, and single-event analyses that quantify the temporal structure of alpha oscillations. Both broadband relative alpha power and periodic alpha power were reduced in autism over parietal regions, replicating prior findings. Importantly, ordinal analyses revealed an intermediate profile in siblings, supporting a liability-related gradient of alpha alterations. However, single-event analyses demonstrated that the average amplitude of individual alpha bursts did not differ between groups. Instead, autistic children showed significantly shorter alpha burst duration and reduced alpha abundance (i.e., proportion of time occupied by rhythmic alpha episodes), with siblings again exhibiting intermediate values. Linear regression analyses confirmed that reductions in relative and periodic alpha power were primarily driven by decreased alpha abundance rather than diminished burst amplitude. These findings indicate that altered alpha activity in autism reflects reduced temporal stability and density of alpha events rather than weaker oscillatory amplitude per se. Reduced persistence of alpha rhythms may therefore represent a neural marker of altered cortical excitability and sensory regulation in autism. Lay summaryAutistic children often experience the world differently at the sensory level, including being more easily overwhelmed by sounds, lights, or other stimuli. In this study, we looked at a type of brain activity called alpha rhythms, which help regulate how strongly the brain responds to incoming information. We found that, in autistic children, these alpha rhythms were not weaker when they occurred, but they lasted for a shorter time and happened less often. Siblings of autistic children showed an intermediate pattern. These results suggest that sensory differences in autism may be linked to less stable brain rhythms that normally help control sensory input. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=158 SRC="FIGDIR/small/716324v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@1be733dorg.highwire.dtl.DTLVardef@7fea49org.highwire.dtl.DTLVardef@1ee9124org.highwire.dtl.DTLVardef@17af139_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2026

Frontal theta phase modulates asymmetric posterior neural mechanisms of spatial attention

Selective attention enables prioritization of behaviorally relevant information through coordinated control of neural excitability. Although theta-band (3-7 Hz) rhythms are implicated in top-down attentional sampling in non-human primates, how intrinsic theta phase organizes sensory gain and behavior in humans, and whether this control operates symmetrically across hemispheres, remains unknown. We recorded electroencephalography (EEG) and pupillometry in typically developing human participants (n = 21; 14.7 {+/-} 3.8 YO) performing a covert spatial attention task. Behaviorally, participants responded faster during leftward relative to rightward attention. This behavioral asymmetry was paralleled in the neural data: anticipatory modulation of parieto-occipital alpha and beta power emerged selectively during leftward attention, whereas rightward attention did not recruit comparable posterior oscillatory processes. Mechanistically, ipsilateral fronto-central theta phase emerged as a potential driver of this asymmetry. Intrinsic theta phase predicted trial-by-trial reaction time (RT) in a cue-direction-specific manner. During leftward attention, 3-Hz theta-phase over left fronto-central cortex modulated behavior and was significantly coupled to coordinated posterior alpha-band activity. In contrast, 6-7-Hz theta-phase over right fronto-central cortex modulated behavior during rightward attention but showed no relationship with alpha or beta modulation; instead, it modulated early sensory gain, indexed by P1 amplitude. Consistent with these distinct architectures, RT was jointly predicted by lower pre-stimulus alpha power and higher P1 amplitude over the attended hemisphere during leftward attention, whereas only P1 amplitude predicted performance during rightward attention. Resting-state alpha power did not differ across hemispheres, indicating that these effects were task-evoked rather than baseline spectral differences. Critically, older participants, who demonstrated enhanced behavioral performance, also exhibited a larger hemispheric asymmetry. Together, these findings reveal developmentally emerging, direction-specific neural control dynamics underlying human spatial attention. Significance StatementSpatial attention is often assumed to rely on symmetric neural mechanisms across left and right space. Using EEG in typically developing children and adolescents, we show that intrinsic theta rhythms organize attention through direction-specific control architectures. Leftward attention engages slower frontal theta (3-Hz) that coordinates posterior alpha and beta activity, consistent with oscillatory sensory gating. Rightward attention instead relies on faster theta (6-7-Hz) that modulates early sensory responses without coordinated alpha dynamics. These asymmetric mechanisms occur despite lack of hemispheric differences in resting alpha activity, indicating that they emerge during active control rather than reflecting baseline biases. These findings reveal that human attentional sampling is rhythmically organized but fundamentally asymmetric across space.

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bioRxiv2025

Disrupted Top-Down Modulation as a Mechanism of Impaired Multisensory Processing in Children with an Autism Spectrum Diagnosis.

Atypical sensory processing is a core feature of autism, particularly when integration across sensory modalities is required. The neural mechanisms underlying these multisensory differences remain unclear. We recorded high-density EEG while autistic children aged 8-13 (AU; n=40), unaffected siblings of autistic children (SIB; n=26), and non-autistic controls (NA; n=36) performed a simple reaction-time task to auditory (A), visual (V), and audiovisual (AV) stimuli. Analyses targeted event-related potentials (ERPs; P1/N1/P2), alpha-band event-related desynchronization (-ERD), and long-range theta-band functional connectivity (weighted phase-lag index, wPLI). Across all unisensory measures (ERPs, -ERD, and connectivity), groups did not differ, indicating broadly comparable unisensory processing. By contrast, multisensory integration (MSI; operationalized for ERPs and -ERD as AV - (A+V)) differed across groups: NA children showed significant ERP MSI over parieto-central sites that was absent in AU and SIB; and -ERD MSI was present in all groups but significantly reduced in AU, with SIB showing an intermediate profile. Connectivity analyses revealed that AV theta-band fronto-parieto-occipital coupling was reduced in autistic relative to non-autistic children, consistent with weaker large-scale coordination during multisensory processing. Together, these results point to a multisensory-specific deficit in autism spanning early sensory encoding, posterior -ERD, and fronto-posterior coupling. The convergence of results supports a mechanistic account of disrupted multisensory influences on sensory processing due to reduced multisensory attentional orientation. Intermediate SIB profiles suggest inherited liability for these neural phenotypes. These results help explain well-documented behavioral MSI differences in autism by linking impaired early enhancement with attenuated top-down control of sensory cortex.

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bioRxiv2025

Neural oscillatory dynamics reveal altered top-down and integrative mechanisms during face processing in autistic children and unaffected siblings of autistic children

Face processing is fundamental to social communication and has been a major focus of autism research. While event-related potential (ERPs) studies of face processing have produced mixed results, little work has examined neuro-oscillatory dynamics, which may better capture the integrity of underlying networks. To address this gap, EEG was recorded from children aged 8-13 across three groups: autistic (n = 50), non-autistic (n = 38) and siblings of autistic children (n = 26), during a visual oddball task. In a blocked design, participants viewed faces and objects, presented upright and inverted (non-targets), to assess the face inversion effect (the FIE; a larger or earlier N170 to inverted than upright faces), and responded to infrequent shadow versions (targets). Analyses using permutation statistics and linear mixed models focused on non-target stimuli, quantifying face-related ERPs (P1, N170) and oscillatory activity associated with sensory and attentional processing (theta, alpha, gamma). Across groups, faces elicited earlier P1 and larger N170 amplitudes than objects, and showed a FIE. Furthermore, the rightward lateralization of the FIE was reduced for autistic participants. Analyses in the frequency domain revealed greater induced theta for inverted versus upright stimuli and for faces versus objects, revealing face specific effects, and stronger theta for inverted faces for the autistic and sibling groups, suggesting greater cognitive effort in processing these social stimuli. Gamma-band inter-trial phase coherence exhibited face selectivity only in the non-autistic group, pointing to differences in early network synchronization in autistic children relative to their non-autistic peers, whereas alpha event-related desynchronization did not vary by group or category. Altogether, these findings support altered neural synchronization/efficiency for autistic participants and siblings of autistic children, that is specific to face stimuli and seen despite largely typical sensory driven encoding. These data suggest that neural oscillatory assays are more sensitive to face processing differences in autism than broadband ERPs and that these oscillatory assays may be endophenotypic.

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bioRxiv2025

Multisensory attenuation of the pupil light response in autistic and non-autistic children

Autonomic responses to sensory stimuli are altered in autism, yet little is known about how multisensory input modulates these responses. This study examined whether auditory stimuli affect the pupil light reflex (PLR), a parasympathetically driven response to light, in autistic and non-autistic children. Pupillometry was used to measure responses to visual-only (V), auditory-only (A), and audiovisual (AV) stimuli in 72 children aged 6-14 years (34 non-autistic, 38 autistic). We hypothesized that auditory input would attenuate pupil constriction in non-autistic children and that this cross-modal modulation might differ in autism, reflecting altered sensory-autonomic functioning. Across groups, results revealed a consistent pattern: auditory stimuli elicited pupil dilation, visual stimuli evoked constriction, and simultaneous audiovisual stimuli led to attenuated constriction relative to visual-only trials. This attenuation lends support to prior findings of multisensory attenuation of the PLR. Time-binned analysis revealed a group effect during the 500-1000 ms post-stimulus window: autistic children showed significantly more positive baseline-corrected pupil responses across conditions (i.e., less constriction in V/AV and greater dilation in A), suggesting group differences in the dynamic trajectory of the pupil response. Contrary to expectations, autistic and non-autistic children did not differ significantly on peak constriction or constriction latency within visual conditions. Findings support the presence of cross-modal modulation of the PLR in both autistic and non-autistic children and suggest that auditory signals influence early-stage visual-autonomic processing similarly across groups. Pupillometry may provide a promising, noninvasive tool for probing sensory-autonomic interactions in autism. Future studies with paradigms optimized for pupil measurement may reveal more nuanced group differences and clarify links to real-world sensory challenges.

neuroscience↗

bioRxiv2025

Testing the auditory steady-state response (ASSR) to 40-Hz and 27-Hz click trains in children with autism spectrum disorder and their first-degree biological relatives: A high-density electroencephalographic (EEG) study

MotivationAltered auditory processing likely contributes to core social and attentional impairments in autism spectrum disorder (ASD). The auditory steady-state response (ASSR)-- a neural measure of auditory processing and cortical excitatory-inhibitory balance--has yielded mixed results in ASD. This study uses high density electroencephalography (EEG) to evaluate ASSR in ASD and unaffected siblings to clarify neural mechanisms underlying auditory deficits in autism. MethodsHigh-density 70-channel EEG was recorded in children (8-12 years, IQ >80) with ASD (n=53), typically developing (TD) peers (n=35), and unaffected biological siblings (n=26) during 500-ms binaural click trains (27- and 40-Hz) in an active oddball task. ResultsNo group differences were observed in frequency-following responses (FFR) to 27- or 40-Hz stimuli, although higher 40-Hz power was associated with older age and better behavioral performance in ASD. The broad-band response from 180-250 ms was reduced in ASD for both stimulation frequencies--particularly in the low-frequency (<8 Hz) range--and significantly correlated with IQ and age. Siblings showed intermediate broad-band responses. DiscussionWhile FFRs appeared intact in ASD, we observed reduced broad-band response in the transition period to the steady state FFR, which was specific to low (<8-Hz) frequencies--potentially reflecting reduced synchronization at timescales that correspond with slower, syllabic rhythms ([~]4-8 Hz) occurring in natural speech. Intermediate responses in first-degree relatives suggest that this is related to genetic vulnerability for ASD and highlights its clinical relevance. These findings suggest intact sensory processing in ASD alongside possible top-down auditory feedback deficits, which may serve as heritable neurophysiological markers. Lay AbstractChildren with autism may process sounds differently, which could contribute to challenges with attention and communication. Here, electroencephalography (EEG) measured how the brain responds to rapidly repeating sounds and found that, while basic sound processing was intact, children with autism showed significantly reduced low-frequency responses that may reflect difficulty tracking speech rhythm. Interestingly, unaffected siblings showed an intermediate response, suggesting this may be a heritable marker of neural differences in autism.

neuroscience↗

bioRxiv2025

Not Just Noise: Impaired Oscillatory Entrainment Reflects Reduced Temporal Flexibility in Autism

Rhythmic patterns in the environment enhance neural activity, perception, and action. However, natural rhythms are often imprecise, requiring flexible adaptation. In autism Spectrum Disorder (ASD), characterized by cognitive rigidity and atypical use of prior information - favoring immediate sensory input over predictive cues - entrainment to temporally variable input may be reduced at both neural and behavioral levels, though the neural mechanisms remain unclear. Here, we recorded high-density EEG and behavior in adults with ASD (n=20) and neurotypical (NT) controls (n=21) during a visual detection task with four rhythmic structures, parametrically varied from an isochronous fully regular rhythm, to a highly irregular one. Spectral analysis and temporal response function (TRF) models revealed significantly reduced modulation by temporal regularity in ASD, particularly in mildly jittered stimulation streams. Additionally, the coupling between phases of neural oscillations and behavior was diminished in ASD under the jittered conditions, suggesting reduced functional relevance of neural synchronization. Residual spectral power post-stimulation showed lower oscillatory entrainment in ASD, ruling out simple evoked-response explanations. Notably, the degree of neural modulation by temporal regularity was correlated with IQ within the ASD group, suggesting a link between temporal flexibility and individual cognitive profiles. These findings highlight impaired neural entrainment and reduced behavioral modulation by temporal structure in ASD, offering insight into inflexible responses to uncertain, volatile sensory environments. InnovationEntrainment to rhythmic events is reduced in autism, but it remains unclear whether this reflects a general, non-selective deficit in neuro-oscillatory alignment or a selective vulnerability to volatile temporal structures, such as those with embedded jitter. To address this, we recorded cortical activity and behavioral performance as participants with ASD engaged with visual sequences of varying rhythmic regularity, and examined how temporal predictability modulated oscillatory entrainment. By correlating neural entrainment with target detection and clinical profiles, we sought to uncover a key feature of the autistic phenotype: reduced temporal flexibility in adapting to unpredictable sensory environments.

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bioRxiv2024

Neural Mechanisms of Intersensory Switching: Evidence for Delayed Sensory Processing and Increased Cognitive Effort

Intersensory switching (IS), the ability to shift attention between different sensory systems, is essential for cognitive flexibility, yet leads to slower responses compared to repeating the same sensory modality. The underlying neural mechanisms of IS remain largely unknown. In this study, high-density EEG was used to investigate these mechanisms in healthy adults (n=53) performing a speeded reaction time (RT) task involving visual and auditory stimuli. Trials were categorized as Repeat (same preceding modality) or Switch (different preceding modality). Switch trials showed slower RTs and delayed sensory responses (N1 and P2 components). Furthermore, across both Repeat and Switch trials, RT correlated with the latency of these neural responses. Additionally, lower alpha-band inter-trial phase coherence (ITPC) in primary sensory regions was noted for Switch compared to Repeat trials, suggesting reduced efficiency of sensory processing. Greater induced theta activity over fronto-central scalp regions in Switch trials suggested increased cognitive control demands, potentially involving the anterior cingulate cortex (ACC). These findings reveal that IS is characterized by delayed sensory processing and heightened cognitive load, supporting a model where prior stimulus primes the sensory cortex for faster processing in Repeat trials, while Switch trials demand more cognitive resources for adjustment. The similarity of effects across both auditory and visual sensory modalities suggests that IS effects represent core features of sensory processing, potentially reflecting a fundamental, modality-independent mechanism of attentional switching across sensory domains.

neuroscience↗