Abnormal sensory processing has been observed in autism, including superior visual motion discrimination, but the neural basis for these sensory changes remains unknown. Leveraging well-characterized suppressive neural circuits in the visual system, we used behavioral and fMRI tasks to demonstrate a significant reduction in neural suppression in young adults with autism spectrum disorder (ASD) compared to neurotypical controls. MR spectroscopy measurements revealed no group differences in neurotransmitter signals. We show how a computational model that incorporates divisive normalization, as well as narrower top-down gain (that could result, for example, from a narrower window of attention), can explain our observations and divergent previous findings. Thus, weaker neural suppression is reflected in visual task performance and fMRI measures in ASD, and may be attributable to differences in top-down processing.
Bibliographical noteFunding Information:
We thank Brenna Boyd, Judy Han, Ly Nguyen, Heena Panjwani, Micah Pepper, Mea-ghan Thompson, Anne Wolken, and the UW Diagnostic Imaging Center for help with recruitment and/or data collection. We thank Geoffrey M. Boynton for providing the original MATLAB functions for the computational model and Mark Mikkelsen for help with MRS quantification. This work was supported by funding from the National Institutes of Health (F32 EY025121 to M.-P.S., R01 MH106520 to S.O.M., T32 EY00703). This work applies tools developed under NIH grants R01 MH098228, R01 EB016089, and P41 EB015909; R.A.E.E. also receives support from these grants.