The development of multisensory integration in high-functioning autism: high-density electrical mapping and psychophysical measures reveal impairments in the processing of audiovisual inputs

Altered functional connectivity of unimodal sensory and multisensory integration networks is related to symptom severity in autism spectrum disorders

BACKGROUND

Atypical sensory processing is a prevalent feature in autism spectrum disorders (ASD) and constitutes a core diagnostic criterion in the Diagnostic and Statistical Manual of Mental of Disorders, 5th edition (DSM-5). However, neurocognitive underpinnings of atypical unimodal and multimodal sensory processing and their relationships with autism symptoms remain unclear.

METHODS

This study examined intrinsic functional connectivity (FC) patterns among five unimodal sensory and multisensory integration (MSI) networks in ASD with a large multi-site dataset (n = 646), and investigated the relationships among altered FC, atypical sensory processing, social communicative deficits, and overall autism symptoms with correlation and mediation analyses.

RESULTS

Relative to typically developing (TD) controls, the ASD group demonstrated increased FC of the olfactory network, decreased FC within the MSI network, and decreased FC of the MSI-unimodal-sensory networks. Furthermore, altered FC was positively associated with autism symptom severity, and such associations were completely mediated by atypical sensory processing and social communicative deficits.

CONCLUSIONS

ASD-specific olfactory overconnectivity and MSI-unimodal-sensory underconnectivity lend support to the Intense World Theory and Weak Central Coherence Theory, suggesting olfactory hypersensitivity at the expense of multisensory integration as potential neural mechanisms underlying atypical sensory processing in ASD. These atypical FC patterns further suggest potential targets for psychological and neuromodulatory interventions.

Unveiling neurodevelopmental changes in multisensory integration while controlling attention

It is well-accepted that multisensory integration (MSI) undergoes protracted maturation from childhood to adulthood. However, existing evidence may have been confounded by potential age-related differences in attention. To unveil neurodevelopmental changes in MSI while matching top-down attention between children and adults, we recorded event-related potentials of healthy children aged 7 to 9 years and young adults in the visual-to-auditory attentional spreading paradigm wherein attention and MSI could be measured concurrently. The absence of children versus adults differences in the visual selection negativity component and behavioral measures of auditory interference first demonstrates that the child group could maintain top-down visual attention and ignore task-irrelevant auditory information to a similar extent as adults. Then, the stimulus-driven attentional spreading quantified by the auditory negative difference (Nd) component was found to be overall absent in the child group, revealing the children's largely immature audiovisual binding process. These findings furnish strong evidence for the protracted maturation of MSI per se from childhood to adulthood, hence providing a new benchmark for characterizing the developmental course of MSI. In addition, we also found that the representation-driven attentional spreading measured by another Nd was present but less robust in children, suggesting their substantially but not fully developed audiovisual representation coactivation process.

Assessing the Effectiveness of Audio-Visual vs. Visual Neurofeedback for Attention Enhancement: A Pilot Study with Neurological, Behavioural, and Neuropsychological Measures

Electroencephalogram (EEG) based Neurofeedback training has gained traction as a practical method for enhancing executive functions, particularly attention, among healthy individuals. The neurofeedback protocols based on EEG channel locations, frequency bands, or EEG features has been tested. However, the improvement in attention was not measured by comparing different feedback stimulus types. We believe that multisensory nature feedback even with few training sessions may induce strong effect. Therefore, this study compares the effect of audio-visual and visual feedback stimuli for attention enhancement utilizing neurophysiological, behavioural and neuropsychological measures. Total 21 subjects were recruited, undergoing six alternate days of neurofeedback training sessions to upregulate EEG beta power of frontocentral (FC5). Dwell time, fractional occupancy and transition probability were also estimated from the EEG beta power. Audiovisual group (G1) as compared to visual group (G2) demonstrate a significant increase of global EEG beta activity alongside improved dwell time (t = 2.76, p = 0.003), fractional occupancy (t = 1.73, p = 0.042) and transition probability (t = 2.46, p = 0.008) over the course of six neurofeedback training sessions. Similarly, the group (G1) shows higher scores (t = 2.13, p = 0.032) and faster reaction times (t = 2.22, p = 0.028) in Stroop task, along with increased score in Mindfulness Attention Awareness Scale (MAAS-15) questionnaire (t = 2.306, p = 0.012). Audiovisual neurofeedback may enhance training effectiveness, potentially achieving the same outcomes in fewer sessions compared to visual-only feedback. However, sufficient training days are essential for effect consolidation. This highlights the feasibility of completing neurofeedback training, a significant challenge in practice.

The dissociating effects of fear and disgust on multisensory integration in autism: evidence from evoked potentials

Background

Deficits in Multisensory Integration (MSI) in ASD have been reported repeatedly and have been suggested to be caused by altered long-range connectivity. Here we investigate behavioral and ERP correlates of MSI in ASD using ecologically valid videos of emotional expressions.

Methods

In the present study, we set out to investigate the electrophysiological correlates of audiovisual MSI in young autistic and neurotypical adolescents. We employed dynamic stimuli of high ecological validity (500 ms clips produced by actors) that depicted fear or disgust in unimodal (visual and auditory), and bimodal (audiovisual) conditions.

Results

We report robust MSI effects at both the behavioral and electrophysiological levels and pronounced differences between autistic and neurotypical participants. Specifically, neurotypical controls showed robust behavioral MSI for both emotions as seen through a significant speed-up of bimodal response time (RT), confirmed by Miller's Race Model Inequality (RMI), with greater MSI effects for fear than disgust. Adolescents with ASD, by contrast, showed behavioral MSI only for fear. At the electrophysiological level, the bimodal condition as compared to the unimodal conditions reduced the amplitudes of the visual P100 and auditory P200 and increased the amplitude of the visual N170 regardless of group. Furthermore, a cluster-based analysis across all electrodes revealed that adolescents with ASD showed an overall delayed and spatially constrained MSI effect compared to controls.

Conclusion

Given that the variables we measured reflect attention, our findings suggest that MSI can be modulated by the differential effects on attention that fear and disgust produce. We also argue that the MSI deficits seen in autistic individuals can be compensated for at later processing stages by (a) the attention-orienting effects of fear, at the behavioral level, and (b) at the electrophysiological level via increased attentional effort.

Probing a neural unreliability account of auditory sensory processing atypicalities in Rett Syndrome

BACKGROUND

In the search for objective tools to quantify neural function in Rett Syndrome (RTT), which are crucial in the evaluation of therapeutic efficacy in clinical trials, recordings of sensory-perceptual functioning using event-related potential (ERP) approaches have emerged as potentially powerful tools. Considerable work points to highly anomalous auditory evoked potentials (AEPs) in RTT. However, an assumption of the typical signal-averaging method used to derive these measures is "stationarity" of the underlying responses - i.e. neural responses to each input are highly stereotyped. An alternate possibility is that responses to repeated stimuli are highly variable in RTT. If so, this will significantly impact the validity of assumptions about underlying neural dysfunction, and likely lead to overestimation of underlying neuropathology. To assess this possibility, analyses at the single-trial level assessing signal-to-noise ratios (SNR), inter-trial variability (ITV) and inter-trial phase coherence (ITPC) are necessary.

METHODS

AEPs were recorded to simple 100 Hz tones from 18 RTT and 27 age-matched controls (Ages: 6-22 years). We applied standard AEP averaging, as well as measures of neuronal reliability at the single-trial level (i.e. SNR, ITV, ITPC). To separate signal-carrying components from non-neural noise sources, we also applied a denoising source separation (DSS) algorithm and then repeated the reliability measures.

RESULTS

Substantially increased ITV, lower SNRs, and reduced ITPC were observed in auditory responses of RTT participants, supporting a "neural unreliability" account. Application of the DSS technique made it clear that non-neural noise sources contribute to overestimation of the extent of processing deficits in RTT. Post-DSS, ITV measures were substantially reduced, so much so that pre-DSS ITV differences between RTT and TD populations were no longer detected. In the case of SNR and ITPC, DSS substantially improved these estimates in the RTT population, but robust differences between RTT and TD were still fully evident.

CONCLUSIONS

To accurately represent the degree of neural dysfunction in RTT using the ERP technique, a consideration of response reliability at the single-trial level is highly advised. Non-neural sources of noise lead to overestimation of the degree of pathological processing in RTT, and denoising source separation techniques during signal processing substantially ameliorate this issue.

Age, not autism, influences multisensory integration of speech stimuli among adults in a McGurk/MacDonald paradigm

Differences between autistic and non-autistic individuals in perception of the temporal relationships between sights and sounds are theorized to underlie difficulties in integrating relevant sensory information. These, in turn, are thought to contribute to problems with speech perception and higher level social behaviour. However, the literature establishing this connection often involves limited sample sizes and focuses almost entirely on children. To determine whether these differences persist into adulthood, we compared 496 autistic and 373 non-autistic adults (aged 17 to 75 years). Participants completed an online version of the McGurk/MacDonald paradigm, a multisensory illusion indicative of the ability to integrate audiovisual speech stimuli. Audiovisual asynchrony was manipulated, and participants responded both to the syllable they perceived (revealing their susceptibility to the illusion) and to whether or not the audio and video were synchronized (allowing insight into temporal processing). In contrast with prior research with smaller, younger samples, we detected no evidence of impaired temporal or multisensory processing in autistic adults. Instead, we found that in both groups, multisensory integration correlated strongly with age. This contradicts prior presumptions that differences in multisensory perception persist and even increase in magnitude over the lifespan of autistic individuals. It also suggests that the compensatory role multisensory integration may play as the individual senses decline with age is intact. These findings challenge existing theories and provide an optimistic perspective on autistic development. They also underline the importance of expanding autism research to better reflect the age range of the autistic population.

Differences in audiovisual temporal processing in autistic adults are specific to simultaneity judgments

Research has shown that children on the autism spectrum and adults with high levels of autistic traits are less sensitive to audiovisual asynchrony compared to their neurotypical peers. However, this evidence has been limited to simultaneity judgments (SJ) which require participants to consider the timing of two cues together. Given evidence of partly divergent perceptual and neural mechanisms involved in making temporal order judgments (TOJ) and SJ, and given that SJ require a more global type of processing which may be impaired in autistic individuals, here we ask whether the observed differences in audiovisual temporal processing are task and stimulus specific. We examined the ability to detect audiovisual asynchrony in a group of 26 autistic adult males and a group of age and IQ-matched neurotypical males. Participants were presented with beep-flash, point-light drumming, and face-voice displays with varying degrees of asynchrony and asked to make SJ and TOJ. The results indicated that autistic participants were less able to detect audiovisual asynchrony compared to the control group, but this effect was specific to SJ and more complex social stimuli (e.g., face-voice) with stronger semantic correspondence between the cues, requiring a more global type of processing. This indicates that audiovisual temporal processing is not generally different in autistic individuals and that a similar level of performance could be achieved by using a more local type of processing, thus informing multisensory integration theory as well as multisensory training aimed to aid perceptual abilities in this population.

Tactile cues are more intrinsically linked to motor timing than visual cues in visual-tactile sensorimotor synchronization

Many tasks require precise synchronization with external sensory stimuli, such as driving a car. This study investigates whether combined visual-tactile information provides additional benefits to movement synchrony over separate visual and tactile stimuli and explores the relationship with the temporal binding window for multisensory integration. In Experiment 1, participants completed a sensorimotor synchronization task to examine movement variability and a simultaneity judgment task to measure the temporal binding window. Results showed similar synchronization variability between visual-tactile and tactile-only stimuli, but significantly lower than visual only. In Experiment 2, participants completed a visual-tactile sensorimotor synchronization task with cross-modal stimuli presented inside (stimulus onset asynchrony 80 ms) and outside (stimulus-onset asynchrony 400 ms) the temporal binding window to examine temporal accuracy of movement execution. Participants synchronized their movement with the first stimulus in the cross-modal pair, either the visual or tactile stimulus. Results showed significantly greater temporal accuracy when only one stimulus was presented inside the window and the second stimulus was outside the window than when both stimuli were presented inside the window, with movement execution being more accurate when attending to the tactile stimulus. Overall, these findings indicate there may be a modality-specific benefit to sensorimotor synchronization performance, such that tactile cues are weighted more strongly than visual information as tactile information is more intrinsically linked to motor timing than visual information. Further, our findings indicate that the visual-tactile temporal binding window is related to the temporal accuracy of movement execution.

Neural correlates of audiovisual narrative speech perception in children and adults on the autism spectrum: A functional magnetic resonance imaging study

Autistic individuals show substantially reduced benefit from observing visual articulations during audiovisual speech perception, a multisensory integration deficit that is particularly relevant to social communication. This has mostly been studied using simple syllabic or word-level stimuli and it remains unclear how altered lower-level multisensory integration translates to the processing of more complex natural multisensory stimulus environments in autism. Here, functional neuroimaging was used to examine neural correlates of audiovisual gain (AV-gain) in 41 autistic individuals to those of 41 age-matched non-autistic controls when presented with a complex audiovisual narrative. Participants were presented with continuous narration of a story in auditory-alone, visual-alone, and both synchronous and asynchronous audiovisual speech conditions. We hypothesized that previously identified differences in audiovisual speech processing in autism would be characterized by activation differences in brain regions well known to be associated with audiovisual enhancement in neurotypicals. However, our results did not provide evidence for altered processing of auditory alone, visual alone, audiovisual conditions or AV- gain in regions associated with the respective task when comparing activation patterns between groups. Instead, we found that autistic individuals responded with higher activations in mostly frontal regions where the activation to the experimental conditions was below baseline (de-activations) in the control group. These frontal effects were observed in both unisensory and audiovisual conditions, suggesting that these altered activations were not specific to multisensory processing but reflective of more general mechanisms such as an altered disengagement of Default Mode Network processes during the observation of the language stimulus across conditions.

Multisensory integration deficits in Schizophrenia and Autism evidenced in behaviour but not event related potentials

The process of integrating information from different sensory channels, known as multisensory integration (MSI) was assessed in two disorders, Autism Spectrum Disorder (ASD) and Schizophrenia (SCZ). 32 healthy controls (HC), 35 SCZ patients, and 23 ASD patients performed an audiovisual (AV) synchronous target detection task while reaction time (RT) and scalp recorded electrophysiological (EEG) activity were measured. MSI in the AV condition resulted in faster and less variable RTs compared to the unimodal conditions. Using our novel bootstrap method, MSI gain was observed in 78 % of HC, 26 % of ASD, and 48 % of SCZ patients. At the neural level, MSI in the AV condition resulted in larger amplitude of sensory evoked responses and cognitive P3 response compared to the corresponding unimodal conditions. These neural effects of MSI were not related to the behavioural MSI gain identified at the individual level and could not explain the deficits in behavioural MSI of patient groups. In conclusion, a robust MSI gain deficit in RT was observed in both patient groups that was not reflected in early perceptual and cognitive electro-cortical responses, suggesting that behavioural MSI deficits in ASD and SCZ may arise at late processing stages such as response selection.

Probing a neural unreliability account of auditory sensory processing atypicalities in Rett Syndrome

Background In the search for objective tools to quantify neural function in Rett Syndrome (RTT), which are crucial in the evaluation of therapeutic efficacy in clinical trials, recordings of sensory-perceptual functioning using event-related potential (ERP) approaches have emerged as potentially powerful tools. Considerable work points to highly anomalous auditory evoked potentials (AEPs) in RTT. However, an assumption of the typical signal-averaging method used to derive these measures is "stationarity" of the underlying responses - i.e. neural responses to each input are highly stereotyped. An alternate possibility is that responses to repeated stimuli are highly variable in RTT. If so, this will significantly impact the validity of assumptions about underlying neural dysfunction, and likely lead to overestimation of underlying neuropathology. To assess this possibility, analyses at the single-trial level assessing signal-to-noise ratios (SNR), inter-trial variability (ITV) and inter-trial phase coherence (ITPC) are necessary. Methods AEPs were recorded to simple 100Hz tones from 18 RTT and 27 age-matched controls (Ages: 6-22 years). We applied standard AEP averaging, as well as measures of neuronal reliability at the single-trial level (i.e. SNR, ITV, ITPC). To separate signal-carrying components from non-neural noise sources, we also applied a denoising source separation (DSS) algorithm and then repeated the reliability measures. Results Substantially increased ITV, lower SNRs, and reduced ITPC were observed in auditory responses of RTT participants, supporting a "neural unreliability" account. Application of the DSS technique made it clear that non-neural noise sources contribute to overestimation of the extent of processing deficits in RTT. Post-DSS, ITV measures were substantially reduced, so much so that pre-DSS ITV differences between RTT and TD populations were no longer detected. In the case of SNR and ITPC, DSS substantially improved these estimates in the RTT population, but robust differences between RTT and TD were still fully evident. Conclusions To accurately represent the degree of neural dysfunction in RTT using the ERP technique, a consideration of response reliability at the single-trial level is highly advised. Non-neural sources of noise lead to overestimation of the degree of pathological processing in RTT, and denoising source separation techniques during signal processing substantially ameliorate this issue.

Probing a neural unreliability account of auditory sensory processing atypicalities in Rett Syndrome

Background

In the search for objective tools to quantify neural function in Rett Syndrome (RTT), which are crucial in the evaluation of therapeutic efficacy in clinical trials, recordings of sensory-perceptual functioning using event-related potential (ERP) approaches have emerged as potentially powerful tools. Considerable work points to highly anomalous auditory evoked potentials (AEPs) in RTT. However, an assumption of the typical signal-averaging method used to derive these measures is "stationarity" of the underlying responses - i.e. neural responses to each input are highly stereotyped. An alternate possibility is that responses to repeated stimuli are highly variable in RTT. If so, this will significantly impact the validity of assumptions about underlying neural dysfunction, and likely lead to overestimation of underlying neuropathology. To assess this possibility, analyses at the single-trial level assessing signal-to-noise ratios (SNR), inter-trial variability (ITV) and inter-trial phase coherence (ITPC) are necessary.

Methods

AEPs were recorded to simple 100Hz tones from 18 RTT and 27 age-matched controls (Ages: 6-22 years). We applied standard AEP averaging, as well as measures of neuronal reliability at the single-trial level (i.e. SNR, ITV, ITPC). To separate signal-carrying components from non-neural noise sources, we also applied a denoising source separation (DSS) algorithm and then repeated the reliability measures.

Results

Substantially increased ITV, lower SNRs, and reduced ITPC were observed in auditory responses of RTT participants, supporting a "neural unreliability" account. Application of the DSS technique made it clear that non-neural noise sources contribute to overestimation of the extent of processing deficits in RTT. Post-DSS, ITV measures were substantially reduced, so much so that pre-DSS ITV differences between RTT and TD populations were no longer detected. In the case of SNR and ITPC, DSS substantially improved these estimates in the RTT population, but robust differences between RTT and TD were still fully evident.

Conclusions

To accurately represent the degree of neural dysfunction in RTT using the ERP technique, a consideration of response reliability at the single-trial level is highly advised. Non-neural sources of noise lead to overestimation of the degree of pathological processing in RTT, and denoising source separation techniques during signal processing substantially ameliorate this issue.

Assessing the integrity of auditory sensory memory processing in CLN3 disease (Juvenile Neuronal Ceroid Lipofuscinosis (Batten disease)): an auditory evoked potential study of the duration-evoked mismatch negativity (MMN)

BACKGROUND

We interrogated auditory sensory memory capabilities in individuals with CLN3 disease (juvenile neuronal ceroid lipofuscinosis), specifically for the feature of "duration" processing. Given decrements in auditory processing abilities associated with later-stage CLN3 disease, we hypothesized that the duration-evoked mismatch negativity (MMN) of the event related potential (ERP) would be a marker of progressively atypical cortical processing in this population, with potential applicability as a brain-based biomarker in clinical trials.

METHODS

We employed three stimulation rates (fast: 450 ms, medium: 900 ms, slow: 1800 ms), allowing for assessment of the sustainability of the auditory sensory memory trace. The robustness of MMN directly relates to the rate at which the regularly occurring stimulus stream is presented. As presentation rate slows, robustness of the sensory memory trace diminishes. By manipulating presentation rate, the strength of the sensory memory trace is parametrically varied, providing greater sensitivity to detect auditory cortical dysfunction. A secondary hypothesis was that duration-evoked MMN abnormalities in CLN3 disease would be more severe at slower presentation rates, resulting from greater demand on the sensory memory system.

RESULTS

Data from individuals with CLN3 disease (N = 21; range 6-28 years of age) showed robust MMN responses (i.e., intact auditory sensory memory processes) at the medium stimulation rate. However, at the fastest rate, MMN was significantly reduced, and at the slowest rate, MMN was not detectable in CLN3 disease relative to neurotypical controls (N = 41; ages 6-26 years).

CONCLUSIONS

Results reveal emerging insufficiencies in this critical auditory perceptual system in individuals with CLN3 disease.

Enhanced sensitivity to pitch perception and its possible relation to language acquisition in autism

Background and aims

Fascinations for or aversions to particular sounds are a familiar feature of autism, as is an ability to reproduce another person's utterances, precisely copying the other person's prosody as well as their words. Such observations seem to indicate not only that autistic people can pay close attention to what they hear, but also that they have the ability to perceive the finer details of auditory stimuli. This is consistent with the previously reported consensus that absolute pitch is more common in autistic individuals than in neurotypicals. We take this to suggest that autistic people have perception that allows them to pay attention to fine details. It is important to establish whether or not this is so as autism is often presented as a deficit rather than a difference. We therefore undertook a narrative literature review of studies of auditory perception, in autistic and nonautistic individuals, focussing on any differences in processing linguistic and nonlinguistic sounds.

Main contributions

We find persuasive evidence that nonlinguistic auditory perception in autistic children differs from that of nonautistic children. This is supported by the additional finding of a higher prevalence of absolute pitch and enhanced pitch discriminating abilities in autistic children compared to neurotypical children. Such abilities appear to stem from atypical perception, which is biased toward local-level information necessary for processing pitch and other prosodic features. Enhanced pitch discriminating abilities tend to be found in autistic individuals with a history of language delay, suggesting possible reciprocity. Research on various aspects of language development in autism also supports the hypothesis that atypical pitch perception may be accountable for observed differences in language development in autism.

Conclusions

The results of our review of previously published studies are consistent with the hypothesis that auditory perception, and particularly pitch perception, in autism are different from the norm but not always impaired. Detail-oriented pitch perception may be an advantage given the right environment. We speculate that unusually heightened sensitivity to pitch differences may be at the cost of the normal development of the perception of the sounds that contribute most to early language development.

Implications

The acquisition of speech and language may be a process that normally involves an enhanced perception of speech sounds at the expense of the processing of nonlinguistic sounds, but autistic children may not give speech sounds this same priority.

The Development of Multisensory Integration at the Neuronal Level

Multisensory integration is a fundamental function of the brain. In the typical adult, multisensory neurons' response to paired multisensory (e.g., audiovisual) cues is significantly more robust than the corresponding best unisensory response in many brain regions. Synthesizing sensory signals from multiple modalities can speed up sensory processing and improve the salience of outside events or objects. Despite its significance, multisensory integration is testified to be not a neonatal feature of the brain. Neurons' ability to effectively combine multisensory information does not occur rapidly but develops gradually during early postnatal life (for cats, 4-12 weeks required). Multisensory experience is critical for this developing process. If animals were restricted from sensing normal visual scenes or sounds (deprived of the relevant multisensory experience), the development of the corresponding integrative ability could be blocked until the appropriate multisensory experience is obtained. This section summarizes the extant literature on the development of multisensory integration (mainly using cat superior colliculus as a model), sensory-deprivation-induced cross-modal plasticity, and how sensory experience (sensory exposure and perceptual learning) leads to the plastic change and modification of neural circuits in cortical and subcortical areas.

Multisensory Integration and Causal Inference in Typical and Atypical Populations

Multisensory perception is critical for effective interaction with the environment, but human responses to multisensory stimuli vary across the lifespan and appear changed in some atypical populations. In this review chapter, we consider multisensory integration within a normative Bayesian framework. We begin by outlining the complex computational challenges of multisensory causal inference and reliability-weighted cue integration, and discuss whether healthy young adults behave in accordance with normative Bayesian models. We then compare their behaviour with various other human populations (children, older adults, and those with neurological or neuropsychiatric disorders). In particular, we consider whether the differences seen in these groups are due only to changes in their computational parameters (such as sensory noise or perceptual priors), or whether the fundamental computational principles (such as reliability weighting) underlying multisensory perception may also be altered. We conclude by arguing that future research should aim explicitly to differentiate between these possibilities.

The dissociation of semantically congruent and incongruent cross-modal effects on the visual attentional blink

Introduction

Recent studies have found that the sound-induced alleviation of visual attentional blink, a well-known phenomenon exemplifying the beneficial influence of multisensory integration on time-based attention, was larger when that sound was semantically congruent relative to incongruent with the second visual target (T2). Although such an audiovisual congruency effect has been attributed mainly to the semantic conflict carried by the incongruent sound restraining that sound from facilitating T2 processing, it is still unclear whether the integrated semantic information carried by the congruent sound benefits T2 processing.

Methods

To dissociate the congruence-induced benefit and incongruence-induced reduction in the alleviation of visual attentional blink at the behavioral and neural levels, the present study combined behavioral measures and event-related potential (ERP) recordings in a visual attentional blink task wherein the T2-accompanying sound, when delivered, could be semantically neutral in addition to congruent or incongruent with respect to T2.

Results

The behavioral data clearly showed that compared to the neutral sound, the congruent sound improved T2 discrimination during the blink to a higher degree while the incongruent sound improved it to a lesser degree. The T2-locked ERP data revealed that the early occipital cross-modal N195 component (192-228 ms after T2 onset) was uniquely larger in the congruent-sound condition than in the neutral-sound and incongruent-sound conditions, whereas the late parietal cross-modal N440 component (400-500 ms) was prominent only in the incongruent-sound condition.

Discussion

These findings provide strong evidence that the modulating effect of audiovisual semantic congruency on the sound-induced alleviation of visual attentional blink contains not only a late incongruence-induced cost but also an early congruence-induced benefit, thereby demonstrating for the first time an unequivocal congruent-sound-induced benefit in alleviating the limitation of time-based visual attention.

Sensory Phenotypes in Autism: Making a Case for the Inclusion of Sensory Integration Functions

Sensory features are part of the diagnostic criteria for autism and include sensory hypo/hyper reactivity and unusual sensory interest; however, additional sensory differences, namely differences in sensory integration, have not been routinely explored. This study characterized sensory integration differences in a cohort of children (n = 93) with a confirmed diagnosis of autism (5-9 years) using a standardized, norm-referenced battery. Mean z scores, autism diagnostic scores, and IQ are reported. Participants showed substantial deficits in tactile perception, praxis, balance, visual perception, and visual-motor skills. Relationship with autism diagnostic test scores were weak or absent. Findings suggest additional sensory difficulties that are not typically assessed or considered when characterizing sensory features in autism. These data have implications for a greater understanding of the sensory features in the autism phenotype and the development of personalized treatments.

Atypical development of causal inference in autism inferred through a neurocomputational model

In everyday life, the brain processes a multitude of stimuli from the surrounding environment, requiring the integration of information from different sensory modalities to form a coherent perception. This process, known as multisensory integration, enhances the brain's response to redundant congruent sensory cues. However, it is equally important for the brain to segregate sensory inputs from distinct events, to interact with and correctly perceive the multisensory environment. This problem the brain must face, known as the causal inference problem, is strictly related to multisensory integration. It is widely recognized that the ability to integrate information from different senses emerges during the developmental period, as a function of our experience with multisensory stimuli. Consequently, multisensory integrative abilities are altered in individuals who have atypical experiences with cross-modal cues, such as those on the autistic spectrum. However, no research has been conducted on the developmental trajectories of causal inference and its relationship with experience thus far. Here, we used a neuro-computational model to simulate and investigate the development of causal inference in both typically developing children and those in the autistic spectrum. Our results indicate that higher exposure to cross-modal cues accelerates the acquisition of causal inference abilities, and a minimum level of experience with multisensory stimuli is required to develop fully mature behavior. We then simulated the altered developmental trajectory of causal inference in individuals with autism by assuming reduced multisensory experience during training. The results suggest that causal inference reaches complete maturity much later in these individuals compared to neurotypical individuals. Furthermore, we discuss the underlying neural mechanisms and network architecture involved in these processes, highlighting that the development of causal inference follows the evolution of the mechanisms subserving multisensory integration. Overall, this study provides a computational framework, unifying causal inference and multisensory integration, which allows us to suggest neural mechanisms and provide testable predictions about the development of such abilities in typically developed and autistic children.

The Impact of Audio-Visual, Visual and Auditory Cues on Multiple Object Tracking Performance in Children with Autism

Previous studies have documented differences in processing multisensory information by children with autism compared to typically developing children. Furthermore, children with autism have been found to track fewer multiple objects on a screen than those without autism, suggesting reduced attentional control. In the present study, we investigated whether children with autism (n = 33) and children without autism (n = 33) were able to track four target objects moving amongst four indistinguishable distractor objects while sensory cues were presented. During tracking, we presented various types of cues - auditory, visual, or audio-visual or no cues while target objects bounced off the inner boundary of a centralized circle. We found that children with autism tracked fewer targets than children without autism. Furthermore, children without autism showed improved tracking performance in the presence of visual cues, whereas children with autism did not benefit from sensory cues. Whereas multiple object tracking performance improved with increasing age in children without autism, especially when using audio-visual cues, children with autism did not show age-related improvement in tracking. These results are in line with the hypothesis that attention and the ability to integrate sensory cues during tracking are reduced in children with autism. Our findings could contribute valuable insights for designing interventions that incorporate multisensory information.

Cross-modal enhancement of spatially unpredictable visual target discrimination during the attentional blink

The attentional blink can be substantially reduced by delivering a task-irrelevant sound synchronously with the second target (T2) embedded in a rapid serial visual presentation stream, which is further modulated by the semantic congruency between the sound and T2. The present study extended the cross-modal boost during attentional blink and the modulation of audiovisual semantic congruency in the spatial domain by showing that a spatially uninformative, semantically congruent (but not incongruent) sound could even improve the discrimination of spatially unpredictable T2 during attentional blink. T2-locked event-related potential (ERP) data yielded that the early cross-modal P195 difference component (184-234 ms) over the occipital scalp contralateral to the T2 location was larger preceding accurate than inaccurate discriminations of semantically congruent, but not incongruent, audiovisual T2s. Interestingly, the N2pc component (194-244 ms) associated with visual-spatial attentional allocation was enlarged for incongruent audiovisual T2s relative to congruent audiovisual and unisensory visual T2s only when they were accurately discriminated. These ERP findings suggest that the spatially extended cross-modal boost during attentional blink involves an early cross-modal interaction strengthening the perceptual processing of T2, without any sound-induced enhancement of visual-spatial attentional allocation toward T2. In contrast, the absence of an accuracy decrease in response to semantically incongruent audiovisual T2s may originate from the semantic mismatch capturing extra visual-spatial attentional resources toward T2.

Sensory Processing Differences in Individuals With Autism Spectrum Disorder: A Narrative Review of Underlying Mechanisms and Sensory-Based Interventions

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by difficulties with social interaction and restricted, repetitive patterns of behavior. Altered sensory processing and perception are considered characteristics of ASD. Sensory processing differences (SPDs) are commonly observed in individuals with ASD, leading to atypical responses to sensory stimuli. SPDs refer to the way in which individuals receive, process, and respond to sensory information from the environment. People with SPDs may be hypersensitive (over-reactive) or hyposensitive (under-reactive) to sensory input, or they may experience fragmented or distorted perceptions. These differences can make it difficult for individuals with SPDs to filter out irrelevant sensory information, and to integrate sensory information from different sources. This study intends to investigate the underlying mechanisms contributing to SPDs in individuals with autism and determine the effectiveness of sensory-based therapies in addressing these challenges. The literature suggests that altered neural pathways, sensory gating dysfunction, and atypical sensory modulation contribute to SPDs in individuals with ASD. Assistive technology, environmental changes, and sensory-based interventions like sensory integration therapy (SIT) have all shown promise in improving sensory functioning and reducing associated behavioral issues. However, further research is needed to improve our understanding of sensory processing in autism and to optimize interventions for individuals with ASD.

An imbalance of excitation and inhibition in the multisensory cortex impairs the temporal acuity of audiovisual processing and perception

The neural integration of closely timed auditory and visual stimuli can offer several behavioral advantages; however, an overly broad window of temporal integration-a phenomenon observed in various neurodevelopmental disorders-could have far-reaching perceptual consequences. Non-invasive studies in humans have suggested that the level of GABAergic inhibition in the multisensory cortex influences the temporal window over which auditory and visual stimuli are bound into a unified percept. Although this suggestion aligns with the theory that an imbalance of cortical excitation and inhibition alters multisensory processing, no prior studies have performed experimental manipulations to determine the causal effects of a reduction of GABAergic inhibition on audiovisual temporal perception. To that end, we used a combination of in vivo electrophysiology, neuropharmacology, and translational behavioral testing in rats to provide the first mechanistic evidence that a reduction of GABAergic inhibition in the audiovisual cortex is sufficient to disrupt unisensory and multisensory processing across the cortical layers, and ultimately impair the temporal acuity of audiovisual perception and its rapid adaptation to recent sensory experience. Looking forward, our findings provide support for using rat models to further investigate the neural mechanisms underlying the audiovisual perceptual alterations observed in neurodevelopmental disorders, such as autism, schizophrenia, and dyslexia.

Assessing the integrity of auditory sensory memory processing in CLN3 disease (Juvenile Neuronal Ceroid Lipofuscinosis (Batten disease)): An auditory evoked potential study of the duration-evoked mismatch negativity (MMN)

Background

We interrogated auditory sensory memory capabilities in individuals with CLN3 disease (juvenile neuronal ceroid lipofuscinosis), specifically for the feature of "duration" processing, a critical cue in speech perception. Given decrements in speech and language skills associated with later-stage CLN3 disease, we hypothesized that the duration-evoked mismatch negativity (MMN) of the event related potential (ERP) would be a marker of progressively atypical cortical processing in this population, with potential applicability as a brain-based biomarker in clinical trials.

Methods

We employed three stimulation rates (fast: 450 ms, medium: 900 ms, slow: 1800 ms), allowing for assessment of the sustainability of the auditory sensory memory trace. The robustness of MMN directly relates to the rate at which the regularly occurring stimulus stream is presented. As presentation rate slows, robustness of the sensory memory trace diminishes. By manipulating presentation rate, the strength of the sensory memory trace is parametrically varied, providing greater sensitivity to detect auditory cortical dysfunction. A secondary hypothesis was that duration-evoked MMN abnormalities in CLN3 disease would be more severe at slower presentation rates, resulting from greater demand on the sensory memory system.

Results

Data from individuals with CLN3 disease (N=21; range 6-28 years of age) showed robust MMN responses (i.e., intact auditory sensory memory processes) at the medium stimulation rate. However, at the fastest rate, MMN was significantly reduced, and at the slowest rate, MMN was not detectable in CLN3 disease relative to neurotypical controls (N=41; ages 6-26 years).

Conclusions

Results reveal emerging insufficiencies in this critical auditory perceptual system in individuals with CLN3 disease.

Cued motor processing in autism and typical development: A high-density electrical mapping study of response-locked neural activity in children and adolescents

Motor atypicalities are common in autism spectrum disorder (ASD) and are often evident prior to classical ASD symptoms. Despite evidence of differences in neural processing during imitation in autistic individuals, research on the integrity and spatiotemporal dynamics of basic motor processing is surprisingly sparse. To address this need, we analysed electroencephalography (EEG) data recorded from a large sample of autistic (n = 84) and neurotypical (n = 84) children and adolescents while they performed an audiovisual speeded reaction time (RT) task. Analyses focused on RTs and response-locked motor-related electrical brain responses over frontoparietal scalp regions: the late Bereitschaftspotential, the motor potential and the reafferent potential. Evaluation of behavioural task performance indicated greater RT variability and lower hit rates in autistic participants compared to typically developing age-matched neurotypical participants. Overall, the data revealed clear motor-related neural responses in ASD, but with subtle differences relative to typically developing participants evident over fronto-central and bilateral parietal scalp sites prior to response onset. Group differences were further parsed as a function of age (6-9, 9-12 and 12-15 years), sensory cue preceding the response (auditory, visual and bi-sensory audiovisual) and RT quartile. Group differences in motor-related processing were most prominent in the youngest group of children (age 6-9), with attenuated cortical responses observed for young autistic participants. Future investigations assessing the integrity of such motor processes in younger children, where larger differences may be present, are warranted.

Why do children with autism spectrum disorder have abnormal visual perception?

Autism spectrum disorder (ASD) is associated with severe impairment in social functioning. Visual information processing provides nonverbal cues that support social interactions. ASD children exhibit abnormalities in visual orientation, continuous visual exploration, and visual-spatial perception, causing social dysfunction, and mechanisms underlying these abnormalities remain unclear. Transmission of visual information depends on the retina-lateral geniculate nucleus-visual cortex pathway. In ASD, developmental abnormalities occur in rapid expansion of the visual cortex surface area with constant thickness during early life, causing abnormal transmission of the peak of the visual evoked potential (P100). We hypothesized that abnormal visual perception in ASD are related to the abnormal visual information transmission and abnormal development of visual cortex in early life, what's more, explored the mechanisms of abnormal visual symptoms to provide suggestions for future research.

Neurophysiological measures of auditory sensory processing are associated with adaptive behavior in children with Autism Spectrum Disorder

BACKGROUND

Atypical auditory cortical processing is consistently found in scalp electrophysiological and magnetoencephalographic studies of Autism Spectrum Disorder (ASD), and may provide a marker of neuropathological brain development. However, the relationship between atypical cortical processing of auditory information and adaptive behavior in ASD is not yet well understood.

METHODS

We sought to test the hypothesis that early (100-175 ms) auditory processing in ASD is related to everyday adaptive behavior through the examination of auditory event-related potentials (AEPs) in response to simple tones and Vineland Adaptive Behavior Scales in a large cohort of children with ASD (N = 84), aged 6-17, and in age- and IQ- matched neurotypically (NT) developing controls (N = 132).

RESULTS

Statistical analyses revealed significant group differences in early AEPs over temporal scalp regions (150-175 ms), and the expected rightward lateralization of the AEP (100-125 ms and 150-175 ms) to tonal stimuli in both groups. Lateralization of the AEP (150-175 ms) was significantly associated with adaptive functioning in the socialization domain.

CONCLUSIONS

These results lend support to the hypothesis that atypical processing of sensory information is related to everyday adaptive behavior in autism.

Severely Attenuated Visual Feedback Processing in Children on the Autism Spectrum

Individuals on the autism spectrum often exhibit atypicality in their sensory perception, but the neural underpinnings of these perceptual differences remain incompletely understood. One proposed mechanism is an imbalance in higher-order feedback re-entrant inputs to early sensory cortices during sensory perception, leading to increased propensity to focus on local object features over global context. We explored this theory by measuring visual evoked potentials during contour integration as considerable work has revealed that these processes are largely driven by feedback inputs from higher-order ventral visual stream regions. We tested the hypothesis that autistic individuals would have attenuated evoked responses to illusory contours compared with neurotypical controls. Electrophysiology was acquired while 29 autistic and 31 neurotypical children (7-17 years old, inclusive of both males and females) passively viewed a random series of Kanizsa figure stimuli, each consisting of four inducers that were aligned either at random rotational angles or such that contour integration would form an illusory square. Autistic children demonstrated attenuated automatic contour integration over lateral occipital regions relative to neurotypical controls. The data are discussed in terms of the role of predictive feedback processes on perception of global stimulus features and the notion that weakened "priors" may play a role in the visual processing anomalies seen in autism.SIGNIFICANCE STATEMENT Children on the autism spectrum differ from typically developing children in many aspects of their processing of sensory stimuli. One proposed mechanism for these differences is an imbalance in higher-order feedback to primary sensory regions, leading to an increased focus on local object features rather than global context. However, systematic investigation of these feedback mechanisms remains limited. Using EEG and a visual illusion paradigm that is highly dependent on intact feedback processing, we demonstrated significant disruptions to visual feedback processing in children with autism. This provides much needed experimental evidence that advances our understanding of the contribution of feedback processing to visual perception in autism spectrum disorder.

In-Memory Tactile Sensor with Tunable Steep-Slope Region for Low-Artifact and Real-Time Perception of Mechanical Signals

A tactile sensor needs to perceive static pressures and dynamic forces in real-time with high accuracy for early diagnosis of diseases and development of intelligent medical prosthetics. However, biomechanical and external mechanical signals are always aliased (including variable physiological and pathological events and motion artifacts), bringing great challenges to precise identification of the signals of interest (SOI). Although the existing signal segmentation methods can extract SOI and remove artifacts by blind source separation and/or additional filters, they may restrict the recognizable patterns of the device, and even cause signal distortion. Herein, an in-memory tactile sensor (IMT) with a dynamically adjustable steep-slope region (SSR) and nanocavity-induced nonvolatility (retention time >1000 s) is proposed on the basis of a machano-gated transistor, which directly transduces the tactile stimuli to various dope states of the channel. The programmable SSR endows the sensor with a critical window of responsiveness, realizing the perception of signals on demand. Owing to the nonvolatility of the sensor, the mapping of mechanical cues with high spatiotemporal accuracy and associative learning between two physical inputs are realized, contributing to the accurate assessment of the tissue health status and ultralow-power (about 25.1 μW) identification of an occasionally occurring tremor.

Audiovisual temporal binding window narrows with age in autistic individuals

Atypical sensory perception has been recognized in autistic individuals since its earliest descriptions and is now considered a key characteristic of autism. Although the integration of sensory information (multisensory integration; MSI) has been demonstrated to be altered in autism, less is known about how this perceptual process differs with age. This study aimed to assess the integration of audiovisual information across autistic children and adolescents. MSI was measured using a non-social, simultaneity judgment task. Variation in temporal sensitivity was evaluated via Gaussian curve fitting procedures, allowing us to compare the width of temporal binding windows (TBWs), where wider TBWs indicate less sensitivity to temporal alignment. We compared TBWs in age and IQ matched groups of autistic (n = 32) and neurotypical (NT; n = 73) children and adolescents. The sensory profile of all participants was also measured. Across all ages assessed (i.e., 6 through 18 years), TBWs were negatively correlated with age in the autistic group. A significant correlation was not found in the NT group. When compared as a function of child (6-12 years) and adolescent (13-18 years) age groups, a significant interaction of group (autism vs NT) by age group was found, whereby TBWs became narrower with age in the autistic, but not neurotypical group. We also found a significant main effect of age and no significant main effect of group. Results suggest that TBW differences between autistic and neurotypical groups diminishes with increasing age, indicating an atypical developmental profile of MSI in autism which ameliorates across development.

Impairments in recognition of emotional facial expressions, affective prosody, and multisensory facilitation of response time in high-functioning autism

Introduction

Deficits in emotional perception are common in autistic people, but it remains unclear to which extent these perceptual impairments are linked to specific sensory modalities, specific emotions or multisensory facilitation.

Methods

This study aimed to investigate uni- and bimodal perception of emotional cues as well as multisensory facilitation in autistic (n = 18, mean age: 36.72 years, SD: 11.36) compared to non-autistic (n = 18, mean age: 36.41 years, SD: 12.18) people using auditory, visual and audiovisual stimuli.

Results

Lower identification accuracy and longer response time were revealed in high-functioning autistic people. These differences were independent of modality and emotion and showed large effect sizes (Cohen's d 0.8-1.2). Furthermore, multisensory facilitation of response time was observed in non-autistic people that was absent in autistic people, whereas no differences were found in multisensory facilitation of accuracy between the two groups.

Discussion

These findings suggest that processing of auditory and visual components of audiovisual stimuli is carried out more separately in autistic individuals (with equivalent temporal demands required for processing of the respective unimodal cues), but still with similar relative improvement in accuracy, whereas earlier integrative multimodal merging of stimulus properties seems to occur in non-autistic individuals.

Aberrant neural correlates of multisensory processing of audiovisual social cues related to social anxiety: An electrophysiological study

BACKGROUND

Social anxiety disorder (SAD) is characterized by abnormal fear to social cues. Although unisensory processing to social stimuli associated with social anxiety (SA) has been well described, how multisensory processing relates to SA is still open to clarification. Using electroencephalography (EEG) measurement, we investigated the neural correlates of multisensory processing and related temporal dynamics in social anxiety disorder (SAD).

METHODS

Twenty-five SAD participants and 23 healthy control (HC) participants were presented with angry and neutral faces, voices and their combinations with congruent emotions and they completed an emotional categorization task.

RESULTS

We found that face-voice combinations facilitated auditory processing in multiple stages indicated by the acceleration of auditory N1 latency, attenuation of auditory N1 and P250 amplitudes, and decrease of theta power. In addition, bimodal inputs elicited cross-modal integrative activity which is indicated by the enhancement of visual P1, N170, and P3/LPP amplitudes and superadditive response of P1 and P3/LPP. More importantly, excessively greater integrative activity (at P3/LPP amplitude) was found in SAD participants, and this abnormal integrative activity in both early and late temporal stages was related to the larger interpretation bias of miscategorizing neutral face-voice combinations as angry.

CONCLUSION

The study revealed that neural correlates of multisensory processing was aberrant in SAD and it was related to the interpretation bias to multimodal social cues in multiple processing stages. Our findings suggest that deficit in multisensory processing might be an important factor in the psychopathology of SA.

Effects of Integrative Autism Therapy on Multiple Physical, Sensory, Cognitive, and Social Integration Domains in Children and Adolescents with Autism Spectrum Disorder: A 4-Week Follow-Up Study

This study aimed to compare the effects of conventional autism therapy (CAT) and integrative autism therapy (IAT) in children and adolescents with autism spectrum disorder (ASD). A convenience sample of 24 children with ASD was recruited and underwent either CAT or IAT for 60 min/day, twice a week, for 20 sessions over 10 weeks. Outcome measures included the following: (1) physical domain (pediatric balance scale, PBS), (2) sensory domain (short sensory profile), (3) cognitive domains (functional independence measure, FIM; and childhood autism rating scale), and (4) social integration domain (Canadian occupational performance measure, COPM; short falls efficacy scale; and pediatrics quality of life questionnaire). Two-way repeated analysis of variance (ANOVA) was used to determine the intervention-related changes in the four domains across the pre-test, post-test, and follow-up test at p < 0.05. ANOVA showed significant interaction effects on the PBS, FIM, and COPM (p < 0.05) variables. Moreover, time main effects (p < 0.05) were observed in all four domain variables, but no group main effect was noted. This study provides promising evidence that IAT is more effective than CAT for managing children and adolescents with ASD.

Multisensory integration and interactions across vision, hearing, and somatosensation in autism spectrum development and typical development

Most prior studies of multisensory integration (MSI) in autism have measured MSI in only a single combination of modalities - typically audiovisual integration. The present study used onset reaction times (RTs) and 125-channel electroencephalography (EEG) to examine different forms of bimodal and trimodal MSI based on combinations of auditory (noise burst), somatosensory (finger tap), and visual (flash) stimuli presented in a spatially-aligned manner using a custom desktop apparatus. A total of 36 autistic and 19 non-autistic adolescents between the ages of 11-14 participated. Significant RT multisensory facilitation relative to summed unisensory RT was observed in both groups, as were significant differences between summed unisensory and multisensory ERPs. Although the present study's statistical approach was not intended to test effect latencies, these interactions may have begun as early as ∼45 ms, constituting "early" (<100 ms) MSI. RT and ERP measurements of MSI appeared independent of one another. Groups did not significantly differ in multisensory RT facilitation, but we found exploratory evidence of group differences in the magnitude of audiovisual interactions in ERPs. Future research should make greater efforts to explore MSI in under-represented populations, especially autistic people with intellectual disabilities and nonspeaking/minimally-verbal autistic people.

Altered EEG variability on different time scales in participants with autism spectrum disorder: an exploratory study

One of the great challenges in psychiatry is finding reliable biomarkers that may allow for more accurate diagnosis and treatment of patients. Neural variability received increasing attention in recent years as a potential biomarker. In the present explorative study we investigated temporal variability in visually evoked EEG activity in a cohort of 16 adult participants with Asperger Syndrome (AS) and 19 neurotypical (NT) controls. Participants performed a visual oddball task using fine and coarse checkerboard stimuli. We investigated various measures of neural variability and found effects on multiple time scales. (1) As opposed to the previous studies, we found reduced inter-trial variability in the AS group compared to NT. (2) This effect builds up over the entire course of a 5-min experiment and (3) seems to be based on smaller variability of neural background activity in AS compared to NTs. The here reported variability effects come with considerably large effect sizes, making them promising candidates for potentially reliable biomarkers in psychiatric diagnostics. The observed pattern of universality across different time scales and stimulation conditions indicates trait-like effects. Further research with a new and larger set of participants are thus needed to verify or falsify our findings.

Resolution of impaired multisensory processing in autism and the cost of switching sensory modality

Children with autism spectrum disorders (ASD) exhibit alterations in multisensory processing, which may contribute to the prevalence of social and communicative deficits in this population. Resolution of multisensory deficits has been observed in teenagers with ASD for complex, social speech stimuli; however, whether this resolution extends to more basic multisensory processing deficits remains unclear. Here, in a cohort of 364 participants we show using simple, non-social audiovisual stimuli that deficits in multisensory processing observed in high-functioning children and teenagers with ASD are not evident in adults with the disorder. Computational modelling indicated that multisensory processing transitions from a default state of competition to one of facilitation, and that this transition is delayed in ASD. Further analysis revealed group differences in how sensory channels are weighted, and how this is impacted by preceding cross-sensory inputs. Our findings indicate that there is a complex and dynamic interplay among the sensory systems that differs considerably in individuals with ASD.

Crosse et al. study a cohort of 364 participants with autism spectrum disorders (ASD) and matched controls, and show that deficits in multisensory processing observed in high-functioning children and teenagers with ASD are not evident in adults with the disorder. Using computational modelling they go on to demonstrate that there is a delayed transition of multisensory processing from a default state of competition to one of facilitation in ASD, as well as differences in sensory weighting and the ability to switch between sensory modalities, which sheds light on the interplay among sensory systems that differ in ASD individuals.

Source Localization of Audiovisual Multisensory Neural Generators in Young Adults with Attention-Deficit/Hyperactivity Disorder

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that exhibits unique neurological and behavioural characteristics. Our previous work using event-related potentials demonstrated that adults with ADHD process audiovisual multisensory stimuli somewhat differently than neurotypical controls. This study utilised an audiovisual multisensory two-alternative forced-choice discrimination task. Continuous whole-head electroencephalography (EEG) was recorded. Source localization (sLORETA) software was utilised to determine differences in the contribution made by sources of neural generators pertinent to audiovisual multisensory processing in those with ADHD versus neurotypical controls. Source localization techniques elucidated that the controls had greater neural activity 164 ms post-stimulus onset when compared to the ADHD group, but only when responding to audiovisual stimuli. The source of the increased activity was found to be Brodmann Area 2, postcentral gyrus, right-hemispheric parietal lobe referenced to Montreal Neurological Institute (MNI) coordinates of X = 35, Y = −40, and Z = 70 (p < 0.05). No group differences were present during either of the unisensory conditions. Differences in the integration areas, particularly in the right-hemispheric parietal brain regions, were found in those with ADHD. These alterations may correspond to impaired attentional capabilities when presented with multiple simultaneous sensory inputs, as is the case during a multisensory condition.

The interplay between audiovisual temporal synchrony and semantic congruency in the cross-modal boost of the visual target discrimination during the attentional blink

The visual attentional blink can be substantially reduced by delivering a task-irrelevant sound synchronously with the second visual target (T2), and this effect is further modulated by the semantic congruency between the sound and T2. However, whether the cross-modal benefit originates from audiovisual interactions or sound-induced alertness remains controversial, and whether the semantic congruency effect is contingent on audiovisual temporal synchrony needs further investigation. The current study investigated these questions by recording event-related potentials (ERPs) in a visual attentional blink task wherein a sound could either synchronize with T2, precede T2 by 200 ms, be delayed by 100 ms, or be absent, and could be either semantically congruent or incongruent with T2 when delivered. The behavioral data showed that both the cross-modal boost of T2 discrimination and the further semantic modulation were the largest when the sound synchronized with T2. In parallel, the ERP data yielded that both the early occipital cross-modal P195 component (192-228 ms after T2 onset) and late parietal cross-modal N440 component (424-448 ms) were prominent only when the sound synchronized with T2, with the former being elicited solely when the sound was further semantically congruent whereas the latter occurring only when that sound was incongruent. These findings demonstrate not only that the cross-modal boost of T2 discrimination during the attentional blink stems from early audiovisual interactions and the semantic congruency effect depends on audiovisual temporal synchrony, but also that the semantic modulation can unfold at the early stage of visual discrimination processing.

Abnormal cortical responses elicited by audiovisual movies in patients with autism spectrum disorder with atypical sensory behavior: A magnetoencephalographic study

BACKGROUND

Atypical sensory behavior disrupts behavioral adaptation in children with autism spectrum disorder (ASD); however, neural correlates of sensory dysfunction using magnetoencephalography (MEG) remain unclear.

METHOD

We used MEG to measure the cortical activation elicited by visual (uni)/audiovisual (multisensory) movies in 46 children (7-14 years) were included in final analysis: 13 boys with atypical audiovisual behavior in ASD (AAV+), 10 without this condition, and 23 age-matched typically developing boys.

RESULTS

The AAV+ group demonstrated an increase in the cortical activation in the bilateral insula in response to unisensory movies and in the left occipital, right superior temporal sulcus (rSTS), and temporal regions to multisensory movies. These increased responses were correlated with severity of the sensory impairment. Increased theta-low gamma oscillations were observed in the rSTS in AAV+.

CONCLUSION

The findings suggest that AAV is attributed to atypical neural networks centered on the rSTS.

Oscillatory entrainment mechanisms and anticipatory predictive processes in children with autism spectrum disorder

Anticipating near-future events is fundamental to adaptive behavior, whereby neural processing of predictable stimuli is significantly facilitated relative to nonpredictable events. Neural oscillations appear to be a key anticipatory mechanism by which processing of upcoming stimuli is modified, and they often entrain to rhythmic environmental sequences. Clinical and anecdotal observations have led to the hypothesis that people with autism spectrum disorder (ASD) may have deficits in generating predictions, and as such, a candidate neural mechanism may be failure to adequately entrain neural activity to repetitive environmental patterns, to facilitate temporal predictions. We tested this hypothesis by interrogating temporal predictions and rhythmic entrainment using behavioral and electrophysiological approaches. We recorded high-density electroencephalography in children with ASD and typically developing (TD) age- and IQ-matched controls, while they reacted to an auditory target as quickly as possible. This auditory event was either preceded by predictive rhythmic visual cues or was not preceded by any cue. Both ASD and control groups presented comparable behavioral facilitation in response to the Cue versus No-Cue condition, challenging the hypothesis that children with ASD have deficits in generating temporal predictions. Analyses of the electrophysiological data, in contrast, revealed significantly reduced neural entrainment to the visual cues and altered anticipatory processes in the ASD group. This was the case despite intact stimulus-evoked visual responses. These results support intact behavioral temporal prediction in response to a cue in ASD, in the face of altered neural entrainment and anticipatory processes.NEW & NOTEWORTHY We examined behavioral and EEG indices of predictive processing in children with ASD to rhythmically predictable stimuli. Although behavioral measures of predictive processing and evoked neural responses were intact in the ASD group, neurophysiological measures of preparatory activity and entrainment were impaired. When sensory events are presented in a predictable temporal pattern, performance and neuronal responses in ASD may be governed more by the occurrence of the events themselves and less by their anticipated timing.

Enhanced attentional processing during speech perception in adult high-functioning autism spectrum disorder: An ERP-study

Deficits in audiovisual speech perception have consistently been detected in patients with Autism Spectrum Disorder (ASD). Especially for patients with a highly functional subtype of ASD, it remains uncertain whether these deficits and underlying neural mechanisms persist into adulthood. Research indicates differences in audiovisual speech processing between ASD and healthy controls (HC) in the auditory cortex. The temporal dynamics of these differences still need to be characterized. Thus, in the present study we examined 14 adult subjects with high-functioning ASD and 15 adult HC while they viewed visual (lip movements) and auditory (voice) speech information that was either superimposed by white noise (condition 1) or not (condition 2). Subject's performance was quantified by measuring stimulus comprehension. In addition, event-related brain potentials (ERPs) were recorded. Results demonstrated worse speech comprehension for ASD subjects compared to HC under noisy conditions. Moreover, ERP-analysis revealed significantly higher P2 amplitudes over parietal electrodes for ASD subjects compared to HC.

Monochannel Preference in Autism Spectrum Conditions Revealed by a Non-Visual Variant of Rubber Hand Illusion

Individuals with autism spectrum conditions (ASC) are less susceptible to multisensory delusions, such as rubber hand illusion (RHI). Here, we investigate whether a monochannel variant of RHI is more effective in inducing an illusory feeling of ownership in ASC. To this aim, we exploit a non-visual variant of the RHI that, excluding vision, leverages only on the somatosensory channel. While the visual-tactile RHI does not alter the perceived hand position in ASC individuals, the tacto-tactile RHI effectively modulates proprioception to a similar extent as that found in typical development individuals. These findings suggest a more effective integration of multiple inputs originating from the same sensory channel in ASC, revealing a monochannel preference in this population.

Looking for consistency in an uncertain world: test-retest reliability of neurophysiological and behavioral readouts in autism

BACKGROUND

Autism spectrum disorders (ASD) are associated with altered sensory processing and perception. Scalp recordings of electrical brain activity time-locked to sensory events (event-related potentials; ERPs) provide precise information on the time-course of related altered neural activity, and can be used to model the cortical loci of the underlying neural networks. Establishing the test-retest reliability of these sensory brain responses in ASD is critical to their use as biomarkers of neural dysfunction in this population.

METHODS

EEG and behavioral data were acquired from 33 children diagnosed with ASD aged 6-9.4 years old, while they performed a child-friendly task at two different time-points, separated by an average of 5.2 months. In two blocked conditions, participants responded to the occurrence of an auditory target that was either preceded or not by repeating visual stimuli. Intraclass correlation coefficients (ICCs) were used to assess test-retest reliability of measures of sensory (auditory and visual) ERPs and performance, for the two experimental conditions. To assess the degree of reliability of the variability of responses within individuals, this analysis was performed on the variance of the measurements, in addition to their means. This yielded a total of 24 measures for which ICCs were calculated.

RESULTS

The data yielded significant good ICC values for 10 of the 24 measurements. These spanned across behavioral and ERPs data, experimental conditions, and mean as well as variance measures. Measures of the visual evoked responses accounted for a disproportionately large number of the significant ICCs; follow-up analyses suggested that the contribution of a greater number of trials to the visual compared to the auditory ERP partially accounted for this.

CONCLUSIONS

This analysis reveals that sensory ERPs and related behavior can be highly reliable across multiple measurement time-points in ASD. The data further suggest that the inter-trial and inter-participant variability reported in the ASD literature likely represents replicable individual participant neural processing differences. The stability of these neuronal readouts supports their use as biomarkers in clinical and translational studies on ASD. Given the minimum interval between test/retest sessions across our cohort, we also conclude that for the tested age-range of ~ 6 to 9.4 years, these reliability measures are valid for at least a 3-month interval. Limitations related to EEG task demands and study length in the context of a clinical trial are considered.

Cortical Auditory Processing of Simple Stimuli Is Altered in Autism: A Meta-analysis of Auditory Evoked Responses

BACKGROUND

Auditory perceptual abnormalities are common in persons on the autism spectrum. The neurophysiologic underpinnings of these differences have frequently been studied using auditory event-related potentials (ERPs) and event-related magnetic fields (ERFs). However, no study to date has quantitatively synthesized this literature to determine whether early auditory ERP/ERF latencies or amplitudes in autistic persons differ from those of typically developing control subjects.

METHODS

We searched PubMed and ProQuest for studies comparing 1) latencies/amplitudes of P1/M50, N1b, N1c, M100, P2/M200, and/or N2 ERP/ERF components evoked by pure tones and 2) paired-click sensory gating (P1/N1b amplitude suppression) in autistic individuals and typically developing control subjects. Effects were synthesized using Bayesian 3-level meta-analysis.

RESULTS

In response to pure tones, autistic individuals exhibited prolonged P1/M50 latencies (g = 0.341 [95% credible interval = 0.166, 0.546]), prolonged M100 latencies (g = 0.319 [0.093, 0.550]), reduced N1c amplitudes (g = -0.812 [-1.278, -0.187]), and reduced N2 amplitudes (g = -0.374 [-0.633, -0.179]). There were no practically significant group differences in P2/M200 latencies, N2 latencies, P1/M50 amplitudes, N1b amplitudes, M100 amplitudes, or P2/M200 amplitudes. Paired-click sensory gating was also reduced in autistic individuals (g = -0.389 [-0.619, -0.112]), although this effect was primarily driven by smaller responses to the first click stimulus.

CONCLUSIONS

Relative to typically developing control subjects, autistic individuals demonstrate multiple alterations in early cortical auditory processing of simple stimuli. However, most group differences were modest in size and based on small numbers of heterogeneous studies with variable quality. Future work is necessary to understand whether these neurophysiologic measures can predict clinically meaningful outcomes or serve as stratification biomarkers for the autistic population.

Multisensory enhancement of overt behavior requires multisensory experience

The superior colliculus (SC) is richly endowed with neurons that integrate cues from different senses to enhance their physiological responses and the overt behaviors they mediate. However, in the absence of experience with cross-modal combinations (e.g., visual-auditory), they fail to develop this characteristic multisensory capability: Their multisensory responses are no greater than their most effective unisensory responses. Presumably, this impairment in neural development would be reflected as corresponding impairments in SC-mediated behavioral capabilities such as detection and localization performance. Here, we tested that assumption directly in cats raised to adulthood in darkness. They, along with a normally reared cohort, were trained to approach brief visual or auditory stimuli. The animals were then tested with these stimuli individually and in combination under ambient light conditions consistent with their rearing conditions and home environment as well as under the opposite lighting condition. As expected, normally reared animals detected and localized the cross-modal combinations significantly better than their individual component stimuli. However, dark-reared animals showed significant defects in multisensory detection and localization performance. The results indicate that a physiological impairment in single multisensory SC neurons is predictive of an impairment in overt multisensory behaviors.

A case-control study of visual, auditory and audio-visual sensory interactions in children with autism spectrum disorder

To assess the relative integrity of early visual and auditory processes in autism spectrum disorder (ASD), we used frequency-tagged visual and auditory stimulation and high-density electroencephalogram recordings of unimodal and dual-modality responses in a case-control design. To test for the specificity of effects on ASD, we recorded from a smaller group of children with attention-deficit hyperactivity disorder (ADHD). Horizontal 3 cycle per degree (cpd) gratings were presented at 5 Hz, and a random stream of /ba/, /da/, /ga/ syllables was presented at 6 Hz. Grating contrast response functions were measured unimodally and in the presence of a 64-dB auditory input. Auditory response functions were measured unimodally and in the presence of a 40% contrast grating. Children with ASD (n = 34) and ADHD (n = 13) showed a common lack of audio-visual interaction compared to typically developing children (n = 40) when measured at the first harmonic of the visual stimulus frequency. Both patient groups also showed depressed first harmonic responses at low contrast, but the ADHD group had consistently higher first-harmonic responses at high contrast. Children with ASD had a preferential loss of second-harmonic (transient) responses. The alteredtransient responses in ASD are likely to arise very early in the visual pathway and could thus have downstream consequences for many other visual mechanisms and processes. The alteration in audio-visual interaction could be a signature of a comorbid phenotype shared by ASD and ADHD, possibly due to alterations in attentional selection systems.

Effects of age on loudness-dependent auditory ERPs in young autistic and typically-developing children

Limited research has investigated the development of auditory ERPs in young children, and particularly how stimulus intensity may affect these auditory ERPs. Previous research has also yielded inconsistent findings regarding differences in the development of auditory ERPs in autism and typical development. Furthermore, stimulus intensity may be of particular interest in autism insofar as autistic people may have atypical experiences of sound intensity (e.g., hyperacusis). Therefore, the present study examined associations between age and ERPs evoked by tones of differing intensities (50, 60, 70, and 80 dB SPL) in a large sample of young children (2-5 years) with and without an autism diagnosis. Correlations between age and P1 latencies were examined, while cluster-based permutation testing was used to examine associations between age and neural response amplitudes, as well as group differences in amplitude, over all electrode sites in the longer time window of 1-350 ms. Older autistic participants had faster P1 latencies, but these effects only attained significance over the right hemisphere in response to soft 50 dB sounds. Autistic participants had slower P1 responses to 80 dB sounds over the right hemisphere. Over the scalp regions associated with the later N2 response, more negative response amplitudes (that is, larger N2 responses) were observed in typically-developing than autistic participants. Furthermore, continuous associations between response amplitudes and age suggested that older typically-developing participants exhibited stronger N2 responses to all intensities, though this effect may have at least in part reflected the absence of small positive voltage deflections in the N2 latency window. Age was associated with amplitudes of responses to 50 dB through 70 dB sounds in autism, but in contrast to Typical Development (TD), little evidence of relationships between age and amplitudes in the N2 latency window was found in autism in the 80 dB condition. Although caution should be exercised in interpretation due to the cross-sectional nature of this study, these findings suggest that developmental changes in auditory responses may differ across diagnostic groups in a manner that depends on perceived loudness and/or stimulus intensity.

Atypical Multisensory Integration and the Temporal Binding Window in Autism Spectrum Disorder

The present study examined the relationship between multisensory integration and the temporal binding window (TBW) for multisensory processing in adults with Autism spectrum disorder (ASD). The ASD group was less likely than the typically developing group to perceive an illusory flash induced by multisensory integration during a sound-induced flash illusion (SIFI) task. Although both groups showed comparable TBWs during the multisensory temporal order judgment task, correlation analyses and Bayes factors provided moderate evidence that the reduced SIFI susceptibility was associated with the narrow TBW in the ASD group. These results suggest that the individuals with ASD exhibited atypical multisensory integration and that individual differences in the efficacy of this process might be affected by the temporal processing of multisensory information.

Neural Basis of Semantically Dependent and Independent Cross-Modal Boosts on the Attentional Blink

The present study recorded event-related potentials (ERPs) in a visual object-recognition task under the attentional blink paradigm to explore the temporal dynamics of the cross-modal boost on attentional blink and whether this auditory benefit would be modulated by semantic congruency between T2 and the simultaneous sound. Behaviorally, the present study showed that not only a semantically congruent but also a semantically incongruent sound improved T2 discrimination during the attentional blink interval, whereas the enhancement was larger for the congruent sound. The ERP results revealed that the behavioral improvements induced by both the semantically congruent and incongruent sounds were closely associated with an early cross-modal interaction on the occipital N195 (192–228 ms). In contrast, the lower T2 accuracy for the incongruent than congruent condition was accompanied by a larger late occurring cento-parietal N440 (424–448 ms). These findings suggest that the cross-modal boost on attentional blink is hierarchical: the task-irrelevant but simultaneous sound, irrespective of its semantic relevance, firstly enables T2 to escape the attentional blink via cross-modally strengthening the early stage of visual object-recognition processing, whereas the semantic conflict of the sound begins to interfere with visual awareness only at a later stage when the representation of visual object is extracted.

Individuals With Autism Have No Detectable Deficit in Neural Markers of Prediction Error When Presented With Auditory Rhythms of Varied Temporal Complexity

The brain's ability to encode temporal patterns and predict upcoming events is critical for speech perception and other aspects of social communication. Deficits in predictive coding may contribute to difficulties with social communication and overreliance on repetitive predictable environments in individuals with autism spectrum disorder (ASD). Using a mismatch negativity (MMN) task involving rhythmic tone sequences of varying complexity, we tested the hypotheses that (1) individuals with ASD have reduced MMN response to auditory stimuli that deviate in presentation timing from expected patterns, particularly as pattern complexity increases and (2) amplitude of MMN signal is inversely correlated with level of impairment in social communication and repetitive behaviors. Electroencephalography was acquired as individuals (age 6-21 years) listened to repeated five-rhythm tones that varied in the Shannon entropy of the rhythm across three conditions (zero, medium-1 bit, and high-2 bit entropy). The majority of the tones conformed to the established rhythm (standard tones); occasionally the fourth tone was temporally shifted relative to its expected time of occurrence (deviant tones). Social communication and repetitive behaviors were measured using the Social Responsiveness Scale and Repetitive Behavior Scale-Revised. Both neurotypical controls (n = 19) and individuals with ASD (n = 21) show stepwise decreases in MMN as a function of increasing entropy. Contrary to the result forecasted by a predictive coding hypothesis, individuals with ASD do not differ from controls in these neural mechanisms of prediction error to auditory rhythms of varied temporal complexity, and there is no relationship between these signals and social communication or repetitive behavior measures. LAY SUMMARY: We tested the idea that the brain's ability to use previous experience to influence processing of sounds is weaker in individuals with autism spectrum disorder (ASD) than in neurotypical individuals. We found no difference between individuals with ASD and neurotypical controls in brain wave responses to sounds that occurred earlier than expected in either simple or complex rhythms. There was also no relationship between these brain waves and social communication or repetitive behavior scores.