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.

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.

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.

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: Differences in Multisensory Integration Covary with Sensory Responsiveness in Children with and without Autism Spectrum Disorder.

Research shows that children with autism spectrum disorder (ASD) differ in their behavioral patterns of responding to sensory stimuli (i.e., sensory responsiveness) and in various other aspects of sensory functioning relative to typical peers. This study explored relations between measures of sensory responsiveness and multisensory speech perception and integration in children with and without ASD. Participants were 8-17 year old children, 18 with ASD and 18 matched typically developing controls. Participants completed a psychophysical speech perception task, and parents reported on children's sensory responsiveness. Psychophysical measures (e.g., audiovisual accuracy, temporal binding window) were associated with patterns of sensory responsiveness (e.g., hyporesponsiveness, sensory seeking). Results indicate that differences in multisensory speech perception and integration covary with atypical patterns of sensory responsiveness.