Biology subjects

Brittenham, C.

Publications and source records attributed to Brittenham, C..

6 recordsLinked to original sources

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

neuroscience↗

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.

neuroscience↗

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.

neuroscience↗

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↗