|Other Abstract||Temporal proximity is a basic and crucial cue to determine whether different sensory inputs belong to a single object or event. To integrate auditory and visual signals into a unified percept, the paired stimuli should be presented close in time and fall 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. From a developmental perspective, adolescence is the key developmental stage in which narrowing of TBW progresses to reach maturity. However, as most studies of the TBW are conducted in infants and adults, it remains unclear how the TBW width changes during childhood and adolescence.
Autism and schizophrenia are neurodevelopmental disorders that share overlapping features. Impaired audiovisual temporal integration, manifesting as abnormally widened TBW, is associated with both disorders and may cascade into aberrant perceptual experiences and social communicative difficulties. However, little is known about the similarities and differences of the underlying mechanisms of the widened TBW in these two clinical and subclinical groups. In this dissertation, we have con ducted four studies to systematically investigate audiovisual temporal integration in clinical and subclinical samples of individuals with autism and schizophrenia, and to explore the potential therapeutic effect of audiovisual trainings to improve social communicative function in 4 cases of autism spectrum disorder.
Study 1 examined audiovisual temporal integration ability in a group of typically developing adolescents and young adults. Results showed no significant difference in the width of audiovisual TBW between the two age groups, suggesting the ability to utilize temporal cues to separate and integrate multisensory information matures at the early adolescence
y 2 compared audiovisual temporal integration between individuals with autism and schizophrenia, and examined the correlations between audiovisual temporal processing and autistic and schizotypal traits in typically developing children and adolescents. Our results demonstrated both shared and distinct patterns of atypical temporal processing in individuals with early onset schizophrenia (EOS) and individuals with high functioning autism. Specifically, when complex linguistic stimuli were involved in the eye tracking paradigm , both groups of patients exhibited reduced sensitivity of detecting audiovisual speech asynchrony. However, reduced temporal acuity was a generalized impairment in patients with EOS, affecting unisensory and multisensory modalities, as w ell as non speech and speech stimuli . In contrast , individuals with autism only exnibited widened audiovisual TBW for speech stimuli, and their unisensory temporal acuity and the TBW for non-speech stimuli preserved well. Moreover, in the non-clinical child population, our results did not find any significant correlation between the TBW width and the levels of autistic or schizotypal traits.
Study 3 investigated the neural correlates of audiovisual TBW with resting state functional connectivity in young adults with different levels of autistic and schizotypal traits. T he resting state functional connectivity between some regions engaged in multisensory and timing tasks, including the superior temporal cortex, the cerebellum and the prefrontal cortex, may be the neural correlates underlying inter individual variability of the TBW width. Specifically, stronger resting state functional connectivity (rsFC) between the left superior temporal cortex and the left precuneus, and weaker rsFC between the left cerebellu m and the right dorsal lateral prefrontal cortex were correlated with a narrower TBW for speech stimuli. On the other hand , stronger rsFC between the left anterior superior temporal gyrus and the right inferior temporal gyrus was correlated with a wider audiovisual TBW for non speech stimuli. In addition, the TBW width and its related rsFC were not affected by levels of autistic or schizotypal traits, which was consistent with the findings of Study 2.|