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

Researchers used brain scans to study how autistic and non-autistic young people process speech that they both see and hear. Non-autistic youth showed brain activity similar to adults in areas important for combining sight and sound. Autistic youth showed different patterns, with activity mainly in areas that process vision and movement. Interestingly, older autistic participants showed more typical brain responses than younger ones, suggesting development may play a role.

This fMRI study examined neural mechanisms of audiovisual speech processing in 18 autistic youth compared to 20 non-autistic controls using a simultaneity-judgment task. Non-autistic youth showed brain activation patterns similar to previous adult studies, including regions like the superior temporal sulcus and insula. Autistic youth demonstrated responses in fewer multisensory regions, with activation limited primarily to visual and motor cortices. Age-related differences emerged in the middle temporal gyrus, where younger autistic individuals showed reduced responses compared to controls, while older autistic participants showed comparable responses.

Task accuracy correlated with precuneus activity across groups, and nonverbal IQ correlated with anterior temporal and insula responses.

Findings suggest autistic youth may use different neural pathways for processing audiovisual speech, with potential age-related improvements. This could inform timing and targets for interventions addressing multisensory processing difficulties, particularly considering developmental factors in treatment planning.

Small sample size (18 autistic, 20 control participants). Study described as providing 'preliminary findings' requiring larger-scale replication. Limited to simultaneity-judgment task which may not capture full range of multisensory processing differences.

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.