Multisensory speech perception in children with autism spectrum disorders

Differences Between Autistic and Non-Autistic Individuals in Audiovisual Speech Integration: A Systematic Review and Meta-analysis

Research has indicated unique challenges in audiovisual integration of speech among autistic individuals, although methodological differences have led to divergent findings. We conducted a systematic literature search to identify studies that measured audiovisual speech integration among both autistic and non-autistic individuals. Across the 18 identified studies (combined N = 952), autistic individuals showed impaired audiovisual integration compared to their non-autistic peers (g = 0.69, 95% CI [0.53, 0.85], p <.001). This difference was not found to be influenced by participants' mean ages, studies' sample sizes, risk-of-bias scores, or paradigms investigated. However, a subgroup analysis suggested that child studies may show larger between-group differences than adult ones. The prevailing pattern of impaired audiovisual speech integration in autism may have cascading effects on communicative and social behavior. However, small samples and inconsistency in design/analysis translated into considerable heterogeneity in findings and opacity regarding the influence of underlying unisensory and attentional factors. We recommend three key directions for future research: larger samples, more research with adults, and standardization of methodology and analytical approaches.

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 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 Relationship Between Social Skills and Sensory Profile, Emotion Regulation, and Empathizing/Systemizing in Adolescents on the Autism Spectrum

This study aims to evaluate the relationship between social skills and sensory features, emotion regulation, and empathy in adolescents on the autism spectrum. One hundred and twenty-three adolescents were included in the study (50 autistic, 73 typically developing-TD adolescents). The participants filled out the Adolescent/Adult Sensory Profile (AASP) and Emotion Regulation Questionnaire. Parents of the participants completed the Child Empathy and Systemizing Quotient (EQ-C/SQ-C) and Autism-Social Skills Profile (ASSP) scales. Social reciprocity, social participation/avoidance, ASSP total scores, empathy and systemizing scores were lower, and detrimental social behaviors, low registration sensory profile scores were higher in the autism spectrum group. While a difference between genders was observed in sensory sensitivity, sensation avoiding, low registration quadrants and empathy scores, no gender and group interaction was found in any domain. Social skill total scores were correlated to sensation seeking and low registration sensory features, empathy, systemizing, and reappraisal emotion regulation scores. A hierarchical multiple linear regression analysis was conducted controlling for group and gender, sensation seeking (p = .032, β = 0.138), low registration (p = .012, β = - 0.215) of the AASP, and empathy (p < .001, β = 0.555) and systemizing (p = .033, β = 0.138) scores of the EQ/SQ-C was found to significantly predict social skill total scores. Although emotional regulation strategies may play a role, sensory processing features and empathy and systemizing skills seem to be the more significant contributors to social skills during adolescence. Interventions targeting sensory processing and especially improving empathy and systematization skills may positively affect social skills in adolescents on the autism spectrum.

Individual Differences in Multisensory Attention Skills in Children with Autism Spectrum Disorder Predict Language and Symptom Severity: Evidence from the Multisensory Attention Assessment Protocol (MAAP)

Children with autism spectrum disorders (ASD) show atypical attention, particularly for social events. The new Multisensory Attention Assessment Protocol (MAAP) assesses fine-grained individual differences in attention disengagement, maintenance, and audiovisual matching for social and nonsocial events. We investigated the role of competing stimulation on attention, and relations with language and symptomatology in children with ASD and typical controls. Findings revealed: (1) the MAAP differentiated children with ASD from controls, (2) greater attention to social events predicted better language for both groups and lower symptom severity in children with ASD, (3) different pathways from attention to language were evident in children with ASD versus controls. The MAAP provides an ideal attention assessment for revealing diagnostic group differences and relations with outcomes.

A Randomized Controlled Trial for Audiovisual Multisensory Perception in Autistic Youth

Differences in audiovisual integration are commonly observed in autism. Temporal binding windows (TBWs) of audiovisual speech can be trained (i.e., narrowed) in non-autistic adults; this study evaluated a computer-based perceptual training in autistic youth and assessed whether treatment outcomes varied according to individual characteristics. Thirty autistic youth aged 8-21 were randomly assigned to a brief perceptual training (n = 15) or a control condition (n = 15). At post-test, the perceptual training group did not differ, on average, on TBWs for trained and untrained stimuli and perception of the McGurk illusion compared to the control group. The training benefited youth with higher language and nonverbal IQ scores; the training caused widened TBWs in youth with co-occurring cognitive and language impairments.

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.

Multisensory integration in the mammalian brain: diversity and flexibility in health and disease

Multisensory integration (MSI) occurs in a variety of brain areas, spanning cortical and subcortical regions. In traditional studies on sensory processing, the sensory cortices have been considered for processing sensory information in a modality-specific manner. The sensory cortices, however, send the information to other cortical and subcortical areas, including the higher association cortices and the other sensory cortices, where the multiple modality inputs converge and integrate to generate a meaningful percept. This integration process is neither simple nor fixed because these brain areas interact with each other via complicated circuits, which can be modulated by numerous internal and external conditions. As a result, dynamic MSI makes multisensory decisions flexible and adaptive in behaving animals. Impairments in MSI occur in many psychiatric disorders, which may result in an altered perception of the multisensory stimuli and an abnormal reaction to them. This review discusses the diversity and flexibility of MSI in mammals, including humans, primates and rodents, as well as the brain areas involved. It further explains how such flexibility influences perceptual experiences in behaving animals in both health and disease. This article is part of the theme issue 'Decision and control processes in multisensory perception'.

The Processing of Audiovisual Speech Is Linked with Vocabulary in Autistic and Nonautistic Children: An ERP Study

Explaining individual differences in vocabulary in autism is critical, as understanding and using words to communicate are key predictors of long-term outcomes for autistic individuals. Differences in audiovisual speech processing may explain variability in vocabulary in autism. The efficiency of audiovisual speech processing can be indexed via amplitude suppression, wherein the amplitude of the event-related potential (ERP) is reduced at the P2 component in response to audiovisual speech compared to auditory-only speech. This study used electroencephalography (EEG) to measure P2 amplitudes in response to auditory-only and audiovisual speech and norm-referenced, standardized assessments to measure vocabulary in 25 autistic and 25 nonautistic children to determine whether amplitude suppression (a) differs or (b) explains variability in vocabulary in autistic and nonautistic children. A series of regression analyses evaluated associations between amplitude suppression and vocabulary scores. Both groups demonstrated P2 amplitude suppression, on average, in response to audiovisual speech relative to auditory-only speech. Between-group differences in mean amplitude suppression were nonsignificant. Individual differences in amplitude suppression were positively associated with expressive vocabulary through receptive vocabulary, as evidenced by a significant indirect effect observed across groups. The results suggest that efficiency of audiovisual speech processing may explain variance in vocabulary in autism.

Perception of audio-visual synchrony in infants at elevated likelihood of developing autism spectrum disorder

The inability to perceive audio-visual speech as a unified event may contribute to social impairments and language deficits in children with autism spectrum disorder (ASD). In this study, we examined and compared two groups of infants on their sensitivity to audio-visual asynchrony for a social (speaking face) and non-social event (bouncing ball) and assessed the relations between multisensory integration and language production. Infants at elevated likelihood of developing ASD were less sensitive to audio-visual synchrony for the social event than infants without elevated likelihood. Among infants without elevated likelihood, greater sensitivity to audio-visual synchrony for the social event was associated with a larger productive vocabulary.

CONCLUSION

Findings suggest that early deficits in multisensory integration may impair language development among infants with elevated likelihood of developing ASD.

WHAT IS KNOWN

•Perceptual integration of auditory and visual cues within speech is important for language development. •Prior work suggests that children with ASD are less sensitive to the temporal synchrony within audio-visual speech.

WHAT IS NEW

•In this study, infants at elevated likelihood of developing ASD showed a larger temporal binding window for adynamic social event (Speaking Face) than TD infants, suggesting less efficient multisensory integration.

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.

Neural Correlates of Audiovisual Speech Processing in Autistic and Non-Autistic Youth

Autistic youth demonstrate differences in processing multisensory information, particularly in temporal processing of multisensory speech. Extensive research has identified several key brain regions for multisensory speech processing in non-autistic adults, including the superior temporal sulcus (STS) and insula, but it is unclear to what extent these regions are involved in temporal processing of multisensory speech in autistic youth. As a first step in exploring the neural substrates of multisensory temporal processing in this clinical population, we employed functional magnetic resonance imaging (fMRI) with a simultaneity-judgment audiovisual speech task. Eighteen autistic youth and a comparison group of 20 non-autistic youth matched on chronological age, biological sex, and gender participated. Results extend prior findings from studies of non-autistic adults, with non-autistic youth demonstrating responses in several similar regions as previously implicated in adult temporal processing of multisensory speech. Autistic youth demonstrated responses in fewer of the multisensory regions identified in adult studies; responses were limited to visual and motor cortices. Group responses in the middle temporal gyrus significantly interacted with age; younger autistic individuals showed reduced MTG responses whereas older individuals showed comparable MTG responses relative to non-autistic controls. Across groups, responses in the precuneus covaried with task accuracy, and anterior temporal and insula responses covaried with nonverbal IQ. These preliminary findings suggest possible differences in neural mechanisms of audiovisual processing in autistic youth while highlighting the need to consider participant characteristics in future, larger-scale studies exploring the neural basis of multisensory function in autism.

An auditory processing advantage enables communication in less complex social settings: Signs of an extreme female brain in children and adolescents being assessed for Autism Spectrum Disorders

Background

The underlying factors of the male predominance in Autism Spectrum Disorders (ASD) are largely unknown, although a female advantage in social communication has been pointed out as a potential factor. Recently, attention has been given to ASD as a sensory processing disorder, focusing on the audio-visual temporal processing paramount for the development of communication. In ASD, a deviant audio-visual processing has been noted, resulting in difficulties interpreting multisensory information. Typically Developed (TD) females have shown an enhanced language processing in unisensory situations compared to multisensory situations. We aim to find out whether such an advantage also can be seen in girls within the ASD population, and if so, is it related to social communication skills?

Method

Forty children (IQ > 85), 20 females (mean age = 13.90 years, SD = 2.34) and 20 males (mean age = 12.15 years, SD = 2.83) triaged for an ASD assessment were recruited from a child and youth psychiatric clinic in Sweden. Using The Social Responsiveness Scale (SRS) we looked at associations with child performance on the Integrated Visual and Auditory Continuous Performance Test (IVA-2).

Results

An auditory advantage in the female group was associated with less rated problems in social communications in unisensory processing whereas in multisensory processing an auditory dominance was associated with more rated problems in Social Awareness. In the male group, a visual dominance was associated with more rated problems in Social Rigidity.

Conclusion

A female unisensory processing advantage in ASD could very well be explaining the male domination in ASD. However, the social difficulties related to multisensory processing indicate that ASD females might be struggling as hard as males in more complex settings. Implications on the assessment procedure are discussed.

Temporal processing deficit in children and adolescents with autism spectrum disorder: An online assessment

Objective

The sensory deficit has been considered as one of the core features in children and adolescents with autism spectrum disorder (ASD). The present study aimed to examine the temporal processing of simple and more complex auditory inputs in ASD children and adolescents with an online assessment that can be conducted remotely.

Methods

One hundred fifty-eight children and adolescents aged 5-17 years participated in this study, including 79 ASD participants and 79 typically developing (TD) participants. The online assessment consisted of two temporal-order judgment tasks that required repeating the sequence of two pure tones or consonant-vowel (CV) syllabic pairs at varying interstimulus intervals (ISIs).

Results

Significantly lower accuracy rates were found in ASD than TD participants in the pure tone and the CV conditions with both short and long ISI. In addition, ASD participants (M  =  245.97 ms) showed a significantly higher passing threshold than TD participants (M  =  178.84 ms) in the CV task. Receiver operating characteristic analysis found that the age × ISI passing threshold composite yielded a sensitivity of 74.7% and a specificity of 50.6% at the cutoff point of -0.307 in differentiating ASD participants from TD participants.

Conclusion

In sum, children and adolescents with ASD showed impaired temporal processing of both simple and more complex auditory stimuli, and the online assessment seems to be sensitive in differentiating individuals with ASD from those with TD.

The Impact of Singing on Visual and Multisensory Speech Perception in Children on the Autism Spectrum

Autistic children show reduced multisensory integration of audiovisual speech stimuli in response to the McGurk illusion. Previously, it has been shown that adults can integrate sung McGurk tokens. These sung speech tokens offer more salient visual and auditory cues, in comparison to the spoken tokens, which may increase the identification and integration of visual speech cues in autistic children. Forty participants (20 autism, 20 non-autistic peers) aged 7-14 completed the study. Participants were presented with speech tokens in four modalities: auditory-only, visual-only, congruent audiovisual, and incongruent audiovisual (i.e., McGurk; auditory 'ba' and visual 'ga'). Tokens were also presented in two formats: spoken and sung. Participants indicated what they perceived via a four-button response box (i.e., 'ba', 'ga', 'da', or 'tha'). Accuracies and perception of the McGurk illusion were calculated for each modality and format. Analysis of visual-only identification indicated a significant main effect of format, whereby participants were more accurate in sung versus spoken trials, but no significant main effect of group or interaction effect. Analysis of the McGurk trials indicated no significant main effect of format or group and no significant interaction effect. Sung speech tokens improved identification of visual speech cues, but did not boost the integration of visual cues with heard speech across groups. Additional work is needed to determine what properties of spoken speech contributed to the observed improvement in visual accuracy and to evaluate whether more prolonged exposure to sung speech may yield effects on multisensory integration.

No differences between adults with and without autism in audiovisual synchrony perception

LAY ABSTRACT

It has been known for a long time that individuals diagnosed with autism spectrum disorder perceive the world differently. In this study, we investigated how people with or without autism perceive visual and auditory information. We know that an auditory and a visual stimulus do not have to be perfectly synchronous for us to perceive them as synchronous: first, when the two are within a certain time window (temporal binding window), the brain will tell us that they are synchronous. Second, the brain can also adapt quickly to audiovisual asynchronies (rapid recalibration). Although previous studies have shown that people with autism spectrum disorder have different temporal binding windows, and less rapid recalibration, we did not find these differences in our study. However, we did find that both processes develop over age, and since previous studies tested only young people (children, adolescents, and young adults), and we tested adults from 18 to 55 years, this might explain the different findings. In the end, there might be quite a complex story, where people with and without autism spectrum disorder perceive the world differently, even dependent on how old they are.

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.

Autism and the Sensory Disruption of Social Experience

Autism research has recently witnessed an embodied turn. In response to the cognitivist approaches dominating the field, phenomenological scholars have suggested a reconceptualization of autism as a disorder of embodied intersubjectivity. Part of this interest in autistic embodiment concerns the role of sensory differences, which have recently been added to the diagnostic criteria of autism. While research suggests that sensory differences are implicated in a wide array of autistic social difficulties, it has not yet been explored how sensory and social experience in autism relate on a phenomenological level. Given the importance of the sensory dimension of social encounters in phenomenological analyses of autism, this question must be considered crucial. This article investigates the role played by sensory differences in autistic social experience. Through a phenomenological analysis informed primarily by the philosophy of Maurice Merleau-Ponty with particular emphasis on the relation between intersubjectivity and perception, I argue that sensory differences affect the way other people appear in autistic experience on a pre-reflective level. By drawing on autistic young adults’ experiential descriptions of social encounters, this article identifies three aspects of how sensory differences affect social experiences in autism. First, social encounters manifested as sensorially disturbing, chaotic, and unpredictable events. Second, the embodied expressions of others appeared unfamiliar, threatening, and promoted a sense of detachment from the social world. Third, deliberate practices were employed to actively seek perceptual and social meaning in these disorienting social encounters. This analysis stresses the importance of understanding embodied intersubjectivity through its sensory dimensions. In addition, it indicates an important avenue for future research in exploring the potential role of practice in maintaining an intuitive grip on social meaning. By approaching social encounters as sensory and perceptual events, I emphasize how social difficulties in autism are inherently world-involving phenomena rather than a cognitive deficit reducible to the autistic person.

The relationship between multisensory associative learning and multisensory integration

Integrating sensory information from multiple modalities leads to more precise and efficient perception and behaviour. The process of determining which sensory information should be perceptually bound is reliant on both low-level stimulus features, as well as multisensory associations learned throughout development based on the statistics of our environment. Here, we explored the relationship between multisensory associative learning and multisensory integration using encephalography (EEG) and behavioural measures. Sixty-one participants completed a three-phase study. First, participants were exposed to novel audiovisual shape-tone pairings with frequent and infrequent stimulus pairings and complete a target detection task. EEG recordings of the mismatch negativity (MMN) and P3 were calculated as neural indices of multisensory associative learning. Next, the same learned stimulus pairs were presented in audiovisual as well as unisensory auditory and visual modalities while both early (<120 ms) and late neural indices of multisensory integration were recorded. Finally, participants completed an analogous behavioural speeded-response task, with behavioural indices of multisensory gain calculated using the Race Model. Significant relationships were found in fronto-central and occipital areas between neural measures of associative learning and both early and late indices of multisensory integration in frontal and centro-parietal areas, respectively. Participants who showed stronger indices of associative learning also exhibited stronger indices of multisensory integration of the stimuli they learned to associate. Furthermore, a significant relationship was found between neural index of early multisensory integration and behavioural indices of multisensory gain. These results provide insight into the neural underpinnings of how higher-order processes such as associative learning guide multisensory integration.

Abnormal sensory perception masks behavioral performance of Grin1 knockdown mice

The development and function of sensory systems require intact glutamatergic neurotransmission. Changes in touch sensation and vision are common symptoms in autism spectrum disorders, where altered glutamatergic neurotransmission is strongly implicated. Further, cortical visual impairment is a frequent symptom of GRIN disorder, a rare genetic neurodevelopmental disorder caused by pathogenic variants of GRIN genes that encode NMDA receptors. We asked if Grin1 knockdown mice (Grin1KD), as a model of GRIN disorder, had visual impairments resulting from NMDA receptor deficiency. We discovered that Grin1KD mice had deficient visual depth perception in the visual cliff test. Since Grin1KD mice are known to display robust changes in measures of learning, memory, and emotionality, we asked whether deficits in these higher-level processes could be partly explained by their visual impairment. By changing the experimental conditions to improve visual signals, we observed significant improvements in the performance of Grin1KD mice in tests that measure spatial memory, executive function, and anxiety. We went further and found destabilization of the outer segment of retina together with the deficient number and size of Meissner corpuscles (mechanical sensor) in the hind paw of Grin1KD mice. Overall, our findings suggest that abnormal sensory perception can mask the expression of emotional, motivational and cognitive behavior of Grin1KD mice. This study demonstrates new methods to adapt routine behavioral paradigms to reveal the contribution of vision and other sensory modalities in cognitive performance.

Aberrant causal inference and presence of a compensatory mechanism in autism spectrum disorder

Autism spectrum disorder (ASD) is characterized by a panoply of social, communicative, and sensory anomalies. As such, a central goal of computational psychiatry is to ascribe the heterogenous phenotypes observed in ASD to a limited set of canonical computations that may have gone awry in the disorder. Here, we posit causal inference - the process of inferring a causal structure linking sensory signals to hidden world causes - as one such computation. We show that audio-visual integration is intact in ASD and in line with optimal models of cue combination, yet multisensory behavior is anomalous in ASD because this group operates under an internal model favoring integration (vs. segregation). Paradoxically, during explicit reports of common cause across spatial or temporal disparities, individuals with ASD were less and not more likely to report common cause, particularly at small cue disparities. Formal model fitting revealed differences in both the prior probability for common cause (p-common) and choice biases, which are dissociable in implicit but not explicit causal inference tasks. Together, this pattern of results suggests (i) different internal models in attributing world causes to sensory signals in ASD relative to neurotypical individuals given identical sensory cues, and (ii) the presence of an explicit compensatory mechanism in ASD, with these individuals putatively having learned to compensate for their bias to integrate in explicit reports.

Individual differences in beta frequency correlate with the audio-visual fusion illusion

Presenting one flash with two beeps induces a perception of two flashes (audio-visual [AV] fission illusion), while presenting two flashes with one beep induces a perception of one flash (fusion illusion). Although previous studies showed a relationship between the frequency of the alpha rhythm (alpha cycle) and one's susceptibility to the fission illusion, the relationship between neural oscillations and the fusion illusion is unknown. Using electroencephalography, here I investigated the frequency of oscillatory signals in the pre-stimulus period and found a significant correlation between the beta rhythm and the fusion illusion; specifically, participants with a lower beta frequency showed a larger fusion illusion. These data indicate two separate time windows of AV integration in the human brain, one defined by the alpha cycle (fission) and another defined by the beta cycle (fusion).

Multisensory integration and maternal sensitivity are related to each other and predictive of expressive vocabulary in 24-month-olds

Multisensory integration (MSI) is the ability to combine temporally synchronous, amodally specified sensory information to create rich, coordinated perceptual experiences. In early development, attention is directed toward such information in both social contexts (e.g., human speakers) and nonsocial contexts (e.g., multimodal toys). Parenting behaviors may support and sculpt multisensory integration by providing children with opportunities to experience amodally specified information (e.g., contingent face-to-face interactions). This study examined (a) whether 24-month-olds' MSI abilities differed as a function of context (social or nonsocial) and competition for attention (low or high), (b) whether MSI predicted expressive vocabulary, and (c) whether maternal sensitivity (MS) was related to both MSI and language. A total of 32 24-month-olds were tested in the Multisensory Attention Assessment Protocol, an audiovisual task that presents laterally positioned social/nonsocial events with and without a central distractor. Their mothers completed the MacArthur-Bates Communicative Development Inventories and participated in a free-play period with their children for MS coding. Results showed MSI in both social and nonsocial conditions (i.e., toddlers paid more attention to the "match"), but only the ability to maintain attention to the social match was related to toddlers' expressive vocabulary. In addition, MS was positively correlated with toddlers' expressive language and social MSI performance. Taken together, the pattern of results shows important relations between emerging integration abilities and parenting behavior as well as the ability of both factors to positively influence word learning during early toddlerhood.

Functional localization of audiovisual speech using near infrared spectroscopy

Visual cues are especially vital for hearing impaired individuals such as cochlear implant (CI) users to understand speech in noise. Functional Near Infrared Spectroscopy (fNIRS) is a light-based imaging technology that is ideally suited for measuring the brain activity of CI users due to its compatibility with both the ferromagnetic and electrical components of these implants. In a preliminary step toward better elucidating the behavioral and neural correlates of audiovisual (AV) speech integration in CI users, we designed a speech-in-noise task and measured the extent to which 24 normal hearing individuals could integrate the audio of spoken monosyllabic words with the corresponding visual signals of a female speaker. In our behavioral task, we found that audiovisual pairings provided average improvements of 103% and 197% over auditory-alone listening conditions in -6 and -9 dB signal-to-noise ratios consisting of multi-talker background noise. In an fNIRS task using similar stimuli, we measured activity during auditory-only listening, visual-only lipreading, and AV listening conditions. We identified cortical activity in all three conditions over regions of middle and superior temporal cortex typically associated with speech processing and audiovisual integration. In addition, three channels active during the lipreading condition showed uncorrected correlations associated with behavioral measures of audiovisual gain as well as with the McGurk effect. Further work focusing primarily on the regions of interest identified in this study could test how AV speech integration may differ for CI users who rely on this mechanism for daily communication.

The enfacement illusion in autism spectrum disorder: How interpersonal multisensory stimulation influences facial recognition of the self

At its most basic level, the sense of self is built upon awareness of one's body and the face holds special significance as the individual's most important and distinctive physical feature. Multimodal sensory integration is pivotal to experiencing one's own body as a coherent visual "self" representation is formed and maintained by matching felt and observed sensorimotor experiences in the mirror. While difficulties in individual facial identity recognition and in both self-referential cognition and empathy are frequently reported in individuals with autism spectrum disorder (ASD), studying the effect of multimodal sensory stimulation in this population is of relevant interest. The present study investigates for the first time the specific effect on Interpersonal Multisensory Stimulation (IMS) on face self-recognition in a sample of 30 adults with (n = 15) and without (n = 15) ASD, matched on age and sex. The results demonstrate atypical self-face recognition and absence of IMS effects (enfacement illusion) in adults with ASD compared to controls, indicating that multisensory integration failed in updating cognitive representations of one's own face among persons with this disorder. The results are discussed in the light of other findings indicating alterations in body enfacement illusion and automatic imitation in ASD as well as in the context of the theories of procedural perception and multisensory integration alterations.

Remote Microphone Systems Can Improve Listening-in-Noise Accuracy and Listening Effort for Youth With Autism

OBJECTIVES

This study examined whether remote microphone (RM) systems improved listening-in-noise performance in youth with autism. We explored effects of RM system use on both listening-in-noise accuracy and listening effort in a well-characterized sample of participants with autism. We hypothesized that listening-in-noise accuracy would be enhanced and listening effort reduced, on average, when participants used the RM system. Furthermore, we predicted that effects of RM system use on listening-in-noise accuracy and listening effort would vary according to participant characteristics. Specifically, we hypothesized that participants who were chronologically older, had greater nonverbal cognitive and language ability, displayed fewer features of autism, and presented with more typical sensory and multisensory profiles might exhibit greater benefits of RM system use than participants who were younger, had less nonverbal cognitive or language ability, displayed more features of autism, and presented with greater sensory and multisensory disruptions.

DESIGN

We implemented a within-subjects design to investigate our hypotheses, wherein 32 youth with autism completed listening-in-noise testing with and without an RM system. Listening-in-noise accuracy and listening effort were evaluated simultaneously using a dual-task paradigm for stimuli varying in complexity (i.e., syllable-, word-, sentence-, and passage-level). In addition, several putative moderators of RM system effects (i.e., sensory and multisensory function, language, nonverbal cognition, and broader features of autism) on outcomes of interest were evaluated.

RESULTS

Overall, RM system use resulted in higher listening-in-noise accuracy in youth with autism compared with no RM system use. The observed benefits were all large in magnitude, although the benefits on average were greater for more complex stimuli (e.g., key words embedded in sentences) and relatively smaller for less complex stimuli (e.g., syllables). Notably, none of the putative moderators significantly influenced the effects of the RM system on listening-in-noise accuracy, indicating that RM system benefits did not vary according to any of the participant characteristics assessed. On average, RM system use did not have an effect on listening effort across all youth with autism compared with no RM system use but instead yielded effects that varied according to participant profile. Specifically, moderated effects indicated that RM system use was associated with increased listening effort for youth who had (a) average to below-average nonverbal cognitive ability, (b) below-average language ability, and (c) reduced audiovisual integration. RM system use was also associated with decreased listening effort for youth with very high nonverbal cognitive ability.

CONCLUSIONS

This study extends prior work by showing that RM systems have the potential to boost listening-in-noise accuracy for youth with autism. However, this boost in accuracy was coupled with increased listening effort, as indexed by longer reaction times while using an RM system, for some youth with autism, perhaps suggesting greater engagement in the listening-in-noise tasks when using the RM system for youth who had lower cognitive abilities, were less linguistically able, and/or have difficulty integrating seen and heard speech. These findings have important implications for clinical practice, suggesting RM system use in classrooms could potentially improve listening-in-noise performance for some youth with autism.

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.

Face-viewing patterns predict audiovisual speech integration in autistic children

Autistic children show audiovisual speech integration deficits, though the underlying mechanisms remain unclear. The present study examined how audiovisual speech integration deficits in autistic children could be affected by their looking patterns. We measured audiovisual speech integration in 26 autistic children and 26 typically developing (TD) children (4- to 7-year-old) employing the McGurk task (a videotaped speaker uttering phonemes with her eyes open or closed) and tracked their eye movements. We found that, compared with TD children, autistic children showed weaker audiovisual speech integration (i.e., the McGurk effect) in the open-eyes condition and similar audiovisual speech integration in the closed-eyes condition. Autistic children viewed the speaker's mouth less in non-McGurk trials than in McGurk trials in both conditions. Importantly, autistic children's weaker audiovisual speech integration could be predicted by their reduced mouth-looking time. The present study indicated that atypical face-viewing patterns could serve as one of the cognitive mechanisms of audiovisual speech integration deficits in autistic children. LAY SUMMARY: McGurk effect occurs when the visual part of a phoneme (e.g., "ga") and the auditory part of another phoneme (e.g., "ba") uttered by a speaker were integrated into a fused perception (e.g., "da"). The present study examined how McGurk effect in autistic children could be affected by their looking patterns for the speaker's face. We found that less looking time for the speaker's mouth in autistic children could predict weaker McGurk effect. As McGurk effect manifests audiovisual speech integration, our findings imply that we could improve audiovisual speech integration in autistic children by directing them to look at the speaker's mouth in future intervention.

Temporal Synchrony in Autism: a Systematic Review

Temporal synchrony is the alignment of processes in time within or across individuals in social interaction and is observed and studied in various domains using wide-ranging paradigms. Evidence suggesting reduced temporal synchrony in autism (e.g. compared to neurotypicals) has hitherto not been reviewed. To systematically review the magnitude and generalisability of the difference across different tasks and contexts, EBSCO, OVID, Web of Science, and Scopus databases were searched. Thirty-two studies were identified that met our inclusion criteria in audio-visual, audio-motor, visuo-tactile, visuo-motor, social motor, and conversational synchrony domains. Additionally, two intervention studies were included. The findings suggest that autistic participants showed reduced synchrony tendencies in every category of temporal synchrony reviewed. Implications, methodological weaknesses, and evidence gaps are discussed.

Relations Between the McGurk Effect, Social and Communication Skill, and Autistic Features in Children with and without Autism

Children with autism show alterations in multisensory integration that have been theoretically and empirically linked with the core and related features of autism. It is unclear, however, to what extent multisensory integration maps onto features of autism within children with and without autism. This study, thus, evaluates relations between audiovisual integration and core and related autism features across children with and without autism. Thirty-six children reported perceptions of the McGurk illusion during a psychophysical task. Parents reported on participants' autistic features. Increased report of illusory percepts tended to covary with reduced autistic features and greater communication skill. Some relations, though, were moderated by group. This work suggests that associations between multisensory integration and higher-order skills are present, but in some instances vary according to diagnostic group.

Inflexible Updating of the Self-Other Divide During a Social Context in Autism: Psychophysical, Electrophysiological, and Neural Network Modeling Evidence

BACKGROUND

Autism spectrum disorder (ASD) affects many aspects of life, from social interactions to (multi)sensory processing. Similarly, the condition expresses at a variety of levels of description, from genetics to neural circuits and interpersonal behavior. We attempt to bridge between domains and levels of description by detailing the behavioral, electrophysiological, and putative neural network basis of peripersonal space (PPS) updating in ASD during a social context, given that the encoding of this space relies on appropriate multisensory integration, is malleable by social context, and is thought to delineate the boundary between the self and others.

METHODS

Fifty (20 male/30 female) young adults, either diagnosed with ASD or age- and sex-matched individuals, took part in a visuotactile reaction time task indexing PPS, while high-density electroencephalography was continuously recorded. Neural network modeling was performed in silico.

RESULTS

Multisensory psychophysics demonstrates that while PPS in neurotypical individuals shrinks in the presence of others-as to "give space"-this does not occur in ASD. Likewise, electroencephalography recordings suggest that multisensory integration is altered by social context in neurotypical individuals but not in individuals with ASD. Finally, a biologically plausible neural network model shows, as a proof of principle, that PPS updating may be inflexible in ASD owing to the altered excitatory/inhibitory balance that characterizes neural circuits in animal models of ASD.

CONCLUSIONS

Findings are conceptually in line with recent statistical inference accounts, suggesting diminished flexibility in ASD, and further these observations by suggesting within an example relevant for social cognition that such inflexibility may be due to excitatory/inhibitory imbalances.

Impaired Audiovisual Representation of Phonemes in Children with Developmental Language Disorder

We examined whether children with developmental language disorder (DLD) differed from their peers with typical development (TD) in the degree to which they encode information about a talker’s mouth shape into long-term phonemic representations. Children watched a talker’s face and listened to rare changes from [i] to [u] or the reverse. In the neutral condition, the talker’s face had a closed mouth throughout. In the audiovisual violation condition, the mouth shape always matched the frequent vowel, even when the rare vowel was played. We hypothesized that in the neutral condition no long-term audiovisual memory traces for speech sounds would be activated. Therefore, the neural response elicited by deviants would reflect only a violation of the observed audiovisual sequence. In contrast, we expected that in the audiovisual violation condition, a long-term memory trace for the speech sound/lip configuration typical for the frequent vowel would be activated. In this condition then, the neural response elicited by rare sound changes would reflect a violation of not only observed audiovisual patterns but also of a long-term memory representation for how a given vowel looks when articulated. Children pressed a response button whenever they saw a talker’s face assume a silly expression. We found that in children with TD, rare auditory changes produced a significant mismatch negativity (MMN) event-related potential (ERP) component over the posterior scalp in the audiovisual violation condition but not in the neutral condition. In children with DLD, no MMN was present in either condition. Rare vowel changes elicited a significant P3 in both groups and conditions, indicating that all children noticed auditory changes. Our results suggest that children with TD, but not children with DLD, incorporate visual information into long-term phonemic representations and detect violations in audiovisual phonemic congruency even when they perform a task that is unrelated to phonemic processing.

Weaker McGurk Effect for Rubin's Vase-Type Speech in People With High Autistic Traits

While visual information from facial speech modulates auditory speech perception, it is less influential on audiovisual speech perception among autistic individuals than among typically developed individuals. In this study, we investigated the relationship between autistic traits (Autism-Spectrum Quotient; AQ) and the influence of visual speech on the recognition of Rubin's vase-type speech stimuli with degraded facial speech information. Participants were 31 university students (13 males and 18 females; mean age: 19.2, SD: 1.13 years) who reported normal (or corrected-to-normal) hearing and vision. All participants completed three speech recognition tasks (visual, auditory, and audiovisual stimuli) and the AQ-Japanese version. The results showed that accuracies of speech recognition for visual (i.e., lip-reading) and auditory stimuli were not significantly related to participants' AQ. In contrast, audiovisual speech perception was less susceptible to facial speech perception among individuals with high rather than low autistic traits. The weaker influence of visual information on audiovisual speech perception in autism spectrum disorder (ASD) was robust regardless of the clarity of the visual information, suggesting a difficulty in the process of audiovisual integration rather than in the visual processing of facial speech.

Greater functional connectivity between sensory networks is related to symptom severity in toddlers with autism spectrum disorder

BACKGROUND

Symptoms of autism spectrum disorder (ASD) emerge in the first years of life. Yet, little is known about the organization and development of functional brain networks in ASD proximally to the symptom onset. Further, the relationship between brain network connectivity and emerging ASD symptoms and overall functioning in early childhood is not well understood.

METHODS

Resting-state fMRI data were acquired during natural sleep from 24 young children with ASD and 23 typically developing (TD) children, aged 17-45 months. Intrinsic functional connectivity (iFC) within and between resting-state functional networks was derived with independent component analysis (ICA).

RESULTS

Increased iFC between visual and sensorimotor networks was found in young children with ASD compared to TD participants. Within the ASD group, the degree of overconnectivity between visual and sensorimotor networks was associated with greater autism symptoms. Age-related weakening of the visual-auditory between-network connectivity was observed in the ASD but not the TD group.

CONCLUSIONS

Taken together, these results provide evidence for disrupted functional network maturation and differentiation, particularly involving visual and sensorimotor networks, during the first years of life in ASD. The observed pattern of greater visual-sensorimotor between-network connectivity associated with poorer clinical outcomes suggests that disruptions in multisensory brain circuitry may play a critical role for early development of behavioral skills and autism symptomatology in young children with ASD.

Reduced multisensory facilitation exists at different periods of development in autism

Atypical sensory processing is now recognised as a key component of an autism diagnosis. The integration of multiple sensory inputs (multisensory integration (MSI)) is thought to be idiosyncratic in autistic individuals and may have cascading effects on the development of higher-level skills such as social communication. Multisensory facilitation was assessed using a target detection paradigm in 45 autistic and 111 neurotypical individuals, matched on age and IQ. Target stimuli were: auditory (A; 3500 Hz tone), visual (V; white disk 'flash') or audiovisual (AV; simultaneous tone and flash), and were presented on a dark background in a randomized order with varying stimulus onset delays. Reaction time (RT) was recorded via button press. In order to assess possible developmental effects, participants were divided into younger (age 14 or younger) and older (age 15 and older) groups. Redundancy gain (RG) was significantly greater in neurotypical, compared to autistic individuals. No significant effect of age or interaction was found. Race model analysis was used to compute a bound value that represented the facilitation effect provided by MSI. Our results revealed that MSI facilitation occurred (violation of the race model) in neurotypical individuals, with more efficient MSI in older participants. In both the younger and older autistic groups, we found reduced MSI facilitation (no or limited violation of the race model). Autistic participants showed reduced multisensory facilitation compared to neurotypical participants in a simple target detection task, void of social context. This remained consistent across age. Our results support evidence that autistic individuals may not integrate low-level, non-social information in a typical fashion, adding to the growing discussion around the influential effect that basic perceptual atypicalities may have on the development of higher-level, core aspects of autism.

Visual-Tactile Spatial Multisensory Interaction in Adults With Autism and Schizophrenia

Background: Individuals with autism spectrum disorder (ASD) and schizophrenia (SZ) exhibit multisensory processing difficulties and social impairments, with growing evidence that the former contributes to the latter. However, this work has largely reported on separate cohorts, introducing method variance as a barrier to drawing broad conclusions across studies. Further, very few studies have addressed touch, resulting in sparse knowledge about how these two clinical groups may integrate somatic information with other senses. Methods: In this study, we compared adults with ASD (n = 29), SZ (n = 24), and typical developmental histories (TD, n = 37) on two tasks requiring visual-tactile spatial multisensory processing. In the first task (crossmodal congruency), participants judged the location of a tactile stimulus in the presence or absence of simultaneous visual input that was either spatially congruent or incongruent, with poorer performance for incongruence an index of spatial multisensory interaction. In the second task, participants reacted to touch in the presence or absence of dynamic visual stimuli that appeared to approach or recede from the body. Within a certain radius around the body, defined as peripersonal space (PPS), an approaching visual or auditory stimulus reliably speeds reaction times (RT) to touch; outside of this radius, in extrapersonal space (EPS), there is no multisensory effect. PPS can be defined both by its size (radius) and slope (sharpness of the PPS-EPS boundary). Clinical measures were administered to explore relations with visual-tactile processing. Results: Neither clinical group differed from controls on the crossmodal congruency task. The ASD group had significantly smaller and more sharply-defined PPSs compared to the other two groups. Small PPS size was related to social symptom severity across groups, but was largely driven by the TD group, without significant effects in either clinical group. Conclusions: These results suggest that: (1) spatially static visual-tactile facilitation is intact in adults with ASD and SZ, (2) spatially dynamic visual-tactile facilitation impacting perception of the body boundary is affected in ASD but not SZ, and (3) body boundary perception is related to social-emotional function, but not in a way that maps on to clinical status.

Late attentional processes potentially compensate for early perceptual multisensory integration deficits in children with autism: evidence from evoked potentials

Sensory processing deficits and altered long-range connectivity putatively underlie Multisensory Integration (MSI) deficits in Autism Spectrum Disorder (ASD). The present study set out to investigate non-social MSI stimuli and their electrophysiological correlates in young neurotypical adolescents and adolescents with ASD. We report robust MSI effects at behavioural and electrophysiological levels. Both groups demonstrated normal behavioural MSI. However, at the neurophysiological level, the ASD group showed less MSI-related reduction of the visual P100 latency, greater MSI-related slowing of the auditory P200 and an overall temporally delayed and spatially constrained onset of MSI. Given the task design and patient sample, and the age of our participants, we argue that electro-cortical indices of MSI deficits in ASD: (a) can be detected in early-adolescent ASD, (b) occur at early stages of perceptual processing, (c) can possibly be compensated by later attentional processes, (d) thus leading to normal MSI at the behavioural level.

Correlations Between Audiovisual Temporal Processing and Sensory Responsiveness in Adolescents with Autistic Traits

Atypical sensory processing has recently gained much research interest as a key domain of autistic symptoms. Individuals with autism spectrum disorder (ASD) exhibit difficulties in processing the temporal aspects of sensory inputs, and show altered behavioural responses to sensory stimuli (i.e., sensory responsiveness). The present study examined the relation between sensory responsiveness (assessed by the Adult/Adolescent Sensory Profile) and audiovisual temporal integration (measured by unisensory temporal order judgement (TOJ) tasks and audiovisual simultaneity judgement (SJ) tasks) in typically-developing adolescents (n = 94). We found that adolescents with higher levels of autistic traits exhibited more difficulties in separating visual stimuli in time (i.e., larger visual TOJ threshold) and showed a stronger bias to perceive sound-leading audiovisual pairings as simultaneous. Regarding the associations between different measures of sensory function, reduced visual temporal acuity, but not auditory or multisensory temporal processing, was significantly correlated with more atypical patterns of sensory responsiveness. Furthermore, the positive correlation between visual TOJ thresholds and sensory avoidance was only found in adolescents with relatively high levels of autistic traits, but not in those with relatively low levels of autistic traits. These findings suggest that reduced visual temporal acuity may contribute to altered sensory experiences and may be linked to broader behavioural characteristics of ASD.

Approaches to Understanding Multisensory Dysfunction in Autism Spectrum Disorder

Abnormal sensory responses are a DSM-5 symptom of autism spectrum disorder (ASD), and research findings demonstrate altered sensory processing in ASD. Beyond difficulties with processing information within single sensory domains, including both hypersensitivity and hyposensitivity, difficulties in multisensory processing are becoming a core issue of focus in ASD. These difficulties may be targeted by treatment approaches such as "sensory integration," which is frequently applied in autism treatment but not yet based on clear evidence. Recently, psychophysical data have emerged to demonstrate multisensory deficits in some children with ASD. Unlike deficits in social communication, which are best understood in humans, sensory and multisensory changes offer a tractable marker of circuit dysfunction that is more easily translated into animal model systems to probe the underlying neurobiological mechanisms. Paralleling experimental paradigms that were previously applied in humans and larger mammals, we and others have demonstrated that multisensory function can also be examined behaviorally in rodents. Here, we review the sensory and multisensory difficulties commonly found in ASD, examining laboratory findings that relate these findings across species. Next, we discuss the known neurobiology of multisensory integration, drawing largely on experimental work in larger mammals, and extensions of these paradigms into rodents. Finally, we describe emerging investigations into multisensory processing in genetic mouse models related to autism risk. By detailing findings from humans to mice, we highlight the advantage of multisensory paradigms that can be easily translated across species, as well as the potential for rodent experimental systems to reveal opportunities for novel treatments. LAY SUMMARY: Sensory and multisensory deficits are commonly found in ASD and may result in cascading effects that impact social communication. By using similar experiments to those in humans, we discuss how studies in animal models may allow an understanding of the brain mechanisms that underlie difficulties in multisensory integration, with the ultimate goal of developing new treatments. Autism Res 2020, 13: 1430-1449. © 2020 International Society for Autism Research, Wiley Periodicals, Inc.

Intranasal oxytocin modulates brain responses to voice-identity recognition in typically developing individuals, but not in ASD

Faces and voices are prominent cues for person-identity recognition. Face recognition behavior and associated brain responses can be enhanced by intranasal administration of oxytocin. It is unknown whether oxytocin can also augment voice-identity recognition mechanisms. To find it out is particularly relevant for individuals who have difficulties recognizing voice identity such as individuals diagnosed with autism spectrum disorder (ASD). We conducted a combined behavioral and functional magnetic resonance imaging (fMRI) study to investigate voice-identity recognition following intranasal administration of oxytocin or placebo in a group of adults diagnosed with ASD (full-scale intelligence quotient > 85) and pairwise-matched typically developing (TD) controls. A single dose of 24 IU oxytocin was administered in a randomized, double-blind, placebo-controlled and cross-over design. In the control group, but not in the ASD group, administration of oxytocin compared to placebo increased responses to recognition of voice identity in contrast to speech in the right posterior superior temporal sulcus/gyrus (pSTS/G) - a region implicated in the perceptual analysis of voice-identity information. In the ASD group, the right pSTS/G responses were positively correlated with voice-identity recognition accuracy in the oxytocin condition, but not in the placebo condition. Oxytocin did not improve voice-identity recognition performance at the group level. The ASD compared to the control group had lower right pSTS/G responses to voice-identity recognition. Since ASD is known to have atypical pSTS/G, the results indicate that the potential of intranasal oxytocin to enhance mechanisms for voice-identity recognition might be variable and dependent on the functional integrity of this brain region.

Stability of Variables Derived From Measures of Multisensory Function in Children With Autism Spectrum Disorder

Children with autism spectrum disorder (ASD) display differences in multisensory function as quantified by several different measures. This study estimated the stability of variables derived from commonly used measures of multisensory function in school-aged children with ASD. Participants completed: a simultaneity judgment task for audiovisual speech, tasks designed to elicit the McGurk effect, listening-in-noise tasks, electroencephalographic recordings, and eye-tracking tasks. Results indicate the stability of indices derived from tasks tapping multisensory processing is variable. These findings have important implications for measurement in future research. Averaging scores across repeated observations will often be required to obtain acceptably stable estimates and, thus, to increase the likelihood of detecting effects of interest, as it relates to multisensory processing in children with ASD.

Plasticity of Temporal Binding in Children with Autism Spectrum Disorder:A Single Case Experimental Design Perceptual Training Study

BACKGROUND

Many children with autism spectrum disorder (ASD) demonstrate atypical responses to multisensory stimuli. These disruptions, which are frequently seen in response to audiovisual speech, may produce cascading effects on the broader development of children with ASD. Perceptual training has been shown to enhance multisensory speech perception in typically developed adults. This study was the first to examine the effects of perceptual training on audiovisual speech perception in children with ASD.

METHOD

A multiple baseline across participants design was utilized with four 7- to 13-year-old children with ASD. The dependent variable, which was probed outside the training task each day using a simultaneity judgment task in baseline, intervention, and maintenance conditions, was audiovisual temporal binding window (TBW), an index of multisensory temporal acuity. During perceptual training, participants completed the same simultaneity judgment task with feedback on their accuracy after each trial in easy-, medium-, and hard-difficulty blocks.

RESULTS

A functional relation between the multisensory perceptual training program and TBW size was not observed. Of the three participants who were entered into training, one participant demonstrated a strong effect, characterized by a fairly immediate change in TBW trend. The two remaining participants demonstrated a less clear response (i.e., longer latency to effect, lack of functional independence). The first participant to enter the training condition demonstrated some maintenance of a narrower TBW post-training.

CONCLUSIONS

Results indicate TBWs in children with ASD may be malleable, but additional research is needed and may entail further adaptation to the multisensory perceptual training paradigm.

Brief Report: Speech-in-Noise Recognition and the Relation to Vocal Pitch Perception in Adults with Autism Spectrum Disorder and Typical Development

We tested the ability to recognise speech-in-noise and its relation to the ability to discriminate vocal pitch in adults with high-functioning autism spectrum disorder (ASD) and typically developed adults (matched pairwise on age, sex, and IQ). Typically developed individuals understood speech in higher noise levels as compared to the ASD group. Within the control group but not within the ASD group, better speech-in-noise recognition abilities were significantly correlated with better vocal pitch discrimination abilities. Our results show that speech-in-noise recognition is restricted in people with ASD. We speculate that perceptual impairments such as difficulties in vocal pitch perception might be relevant in explaining these difficulties in ASD.

Audiovisual temporal integration: Cognitive processing, neural mechanisms, developmental trajectory and potential interventions

To integrate auditory and visual signals into a unified percept, the paired stimuli must co-occur within a limited time window known as the Temporal Binding Window (TBW). The width of the TBW, a proxy of audiovisual temporal integration ability, has been found to be correlated with higher-order cognitive and social functions. A comprehensive review of studies investigating audiovisual TBW reveals several findings: (1) a wide range of top-down processes and bottom-up features can modulate the width of the TBW, facilitating adaptation to the changing and multisensory external environment; (2) a large-scale brain network works in coordination to ensure successful detection of audiovisual (a)synchrony; (3) developmentally, audiovisual TBW follows a U-shaped pattern across the lifespan, with a protracted developmental course into late adolescence and rebounding in size again in late life; (4) an enlarged TBW is characteristic of a number of neurodevelopmental disorders; and (5) the TBW is highly flexible via perceptual and musical training. Interventions targeting the TBW may be able to improve multisensory function and ameliorate social communicative symptoms in clinical populations.

Brief Sensory Training Narrows the Temporal Binding Window and Enhances Long-Term Multimodal Speech Perception

Our ability to integrate multiple sensory-based representations of our surrounding supplies us with a more holistic view of our world. There are many complex algorithms our nervous system uses to construct a coherent perception. An indicator to solve this 'binding problem' are the temporal characteristics with the specificity that environmental information has different propagation speeds (e.g., sound and electromagnetic waves) and sensory processing time and thus the temporal relationship of a stimulus pair derived from the same event must be flexibly adjusted by our brain. This tolerance can be conceptualized in the form of the cross-modal temporal binding window (TBW). Several studies showed the plasticity of the TBW and its importance concerning audio-visual illusions, synesthesia, as well as psychiatric disturbances. Using three audio-visual paradigms, we investigated the importance of length (short vs. long) as well as modality (uni- vs. multimodal) of a perceptual training aiming at reducing the TBW in a healthy population. We also investigated the influence of the TBW on speech intelligibility, where participants had to integrate auditory and visual speech information from a videotaped speaker. We showed that simple sensory trainings can change the TBW and are capable of optimizing speech perception at a very naturalistic level. While the training-length had no different effect on the malleability of the TBW, the multisensory trainings induced a significantly stronger narrowing of the TBW than their unisensory counterparts. Furthermore, a narrowing of the TBW was associated with a better performance in speech perception, meaning that participants showed a greater capacity for integrating informations from different sensory modalities in situations with one modality impaired. All effects persisted at least seven days. Our findings show the significance of multisensory temporal processing regarding ecologically valid measures and have important clinical implications for interventions that may be used to alleviate debilitating conditions (e.g., autism, schizophrenia), in which multisensory temporal function is shown to be impaired.

Auditory Deficits in Audiovisual Speech Perception in Adult Asperger's Syndrome: fMRI Study

Audiovisual (AV) integration deficits have been proposed to underlie difficulties in speech perception in Asperger’s syndrome (AS). It is not known, if the AV deficits are related to alterations in sensory processing at the level of unisensory processing or at levels of conjoint multisensory processing. Functional Magnetic-resonance images (MRI) was performed in 16 adult subjects with AS and 16 healthy controls (HC) matched for age, gender, and verbal IQ as they were exposed to disyllabic AV congruent and AV incongruent nouns. A simple semantic categorization task was used to ensure subjects’ attention to the stimuli. The left auditory cortex (BA41) showed stronger activation in HC than in subjects with AS with no interaction regarding AV congruency. This suggests that alterations in auditory processing in unimodal low-level areas underlie AV speech perception deficits in AS. Whether this is signaling a difficulty in the deployment of attention remains to be demonstrated.

Within- and Cross-Modal Integration and Attention in the Autism Spectrum

Although impairment in sensory integration is suggested in the autism spectrum (AS), empirical evidences remain equivocal. We assessed the integration of low-level visual and tactile information within and across modalities in AS and typically developing (TD) individuals. TD individuals demonstrated increased redundancy gain for cross-modal relative to double tactile or visual stimulation, while AS individuals showed similar redundancy gain between cross-modal and double tactile conditions. We further observed that violation of the race model inequality for cross-modal conditions was observed over a wider proportion of the reaction times distribution in TD than AS individuals. Importantly, the reduced cross-modal integration in AS individuals was not related to atypical attentional shift between modalities. We conclude that AS individuals displays selective decrease of cross-modal integration of low-level information.

Reduced multisensory facilitation in adolescents and adults on the Autism Spectrum

Individuals with autism are reported to integrate information from visual and auditory channels in an idiosyncratic way. Multisensory integration (MSI) of simple, non-social stimuli (i.e., flashes and beeps) was evaluated in adolescents and adults with (n = 20) and without autism (n = 19) using a reaction time (RT) paradigm using audio, visual, and audiovisual stimuli. For each participant, the race model analysis compares the RTs on the audiovisual condition to a bound value computed from the unimodal RTs that reflects the effect of redundancy. If the actual audiovisual RTs are significantly faster than this bound, the race model is violated, indicating evidence of MSI. Our results show that the race model violation occurred only for the typically-developing (TD) group. While the TD group shows evidence of MSI, the autism group does not. These results suggest that multisensory integration of simple information, void of social content or complexity, is altered in autism. Individuals with autism may not benefit from the advantage conferred by multisensory stimulation to the same extent as TD individuals. Altered MSI for simple, non-social information may have cascading effects on more complex perceptual processes related to language and behaviour in autism.