Adaptive Neural Mechanisms in Individuals with Autism for Integrating Multisensory Real-World Stimuli
Objectives: We are using functional magnetic resonance imaging (fMRI) to characterize adaptive cortical mechanisms for processing audiovisual information in high-functioning individuals with autism. Neuroimaging results will be correlated with behavioral measures of sensory processing and integration. We also sought to use socially relevant stimuli in order to more precisely examine how the brain responds when processing real-world events in the environment.
Methods: While in the 3T MRI scanner, participants watched a video of someone bouncing a basketball (a socially relevant stimulus). Their task was to press a button when they perceived the ball to touch the ground. The video included an audiovisual condition (bi-modal; see and hear the action), a visual only condition (uni-modal; only see the ball dribbled), and a resting condition (baseline control; actor holding basketball). Participants included high-functioning individuals with autism (aged 18-28 years) as well as individuals without autism matched for age and gender. Brain regions activated during the unimodal and bimodal conditions, relative to the baseline condition, were modeled using multiple linear regression analyses (NIH AFNI software). Individual datasets were transformed into Talairach coordinate space, and groups were compared and contrasted across conditions using t-tests.
Results: Both groups showed similar activation in primary auditory and primary visual cortices when processing audiovisual information. However, differences were seen between the two groups across the two conditions (uni-modal vs. bi-modal; p<0.01, corrected). The group with autism revealed increased activation in portions of cingulate cortex and middle temporal gyrus compared to individuals without autism. Conversely, individuals without autism showed increased activation in left inferior medial-posterior insula, which persisted in all individual datasets.
Conclusions: The functional roles of the cortical regions differentially activated provide important clues as to possible adaptive mechanisms that high-functioning adults with autism are using at a systems level to cope with audiovisual interactions. Correlations between neuroimaging results and sensory profile sub-scores may reveal autism subtypes that can be explored further.