Objectives: We examined differences in brain activation in the recently described salience detection network between ASD and typically developing (TD) subjects using fMRI and a visual oddball task to assess whether a core deficit exists in autism related to extracting salient information from sensory stimuli.
Methods: Subjects participated in a visual oddball task wherein uniformly colored circles (blue) flashed onto a screen at two second intervals, with 15% of the stimuli displaying a variant color (green). Subjects were instructed to depress a button for each variant stimulus. A total of 40 subjects were tested, 25 ASD, 15 TD. Subjects were all males, group-matched for age and IQ.
Results: TD and ASD populations showed significant activation of the salience detection network including bilateral fronto-insular cortex, anterior cingulate cortex, left posterior temporal, bilateral dorsolateral prefrontal, as well as primary motor cortex. ASD subject data demonstrated a significantly reduced activation of the right fronto-insular cortex when compared to TD activation (p=0.001 uncorrected).
Conclusions: The right fronto-insular cortex is hypoactive in ASD subjects relative to TD subjects during detection of novel visual stimuli. This area has been hypothesized to play a pivotal role in the allocation of attentional resources, more specifically, in switching between default-mode and attentional networks. This finding may contribute to a neurological basis for impaired extraction of salient information in individuals with autism.
Acknowledgements and Disclaimer. The project described was supported in part by Grant Number R01 MH080826 and R01 MH084795 from the National Institute Of Mental Health. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute Of Mental Health or the National Institutes of Health.