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Michael-Paul Schallmo, Alex Kale, Tamar Kolodny, Rachel Millin, Raphael Bernier, Scott Murray; Weaker neural suppression in autism spectrum disorder. Journal of Vision 2018;18(10):548. doi: https://doi.org/10.1167/18.10.548.
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Autism spectrum disorder (ASD) is often hypothesized to stem from a dysregulation of neural activity resulting in an imbalance of excitation and inhibition. While this is supported by specific animal models of ASD, there is little direct experimental support for this hypothesis from human studies. Using a visual paradigm, we tested whether mechanisms that regulate neural activity may be disrupted in individuals with ASD. Specifically, within the visual system, a powerful suppressive regulatory effect occurs in neurons when a stimulus is presented that is larger than the neuron's classical receptive field – information from the surround suppresses the neural response to the stimulus in the center. We used a well-known psychophysical paradigm that reflects this spatial suppression by measuring the amount of time required to perceive the motion direction of stimuli at various sizes. In addition, we used fMRI to measure neural suppression in the motion sensitive region called human MT complex (hMT+). In both the psychophysical and fMRI measurements, we found strong evidence of reduced suppression in individuals with ASD compared to neurotypical controls. We further tested the mechanism of impaired suppression by measuring GABA levels in hMT+ using MR spectroscopy, and observed no difference in GABA levels between ASD and control groups. Our results suggest that differences in suppressive regulatory mechanisms in ASD may result from altered neural responses, but not from a specific difference in GABA levels.
Meeting abstract presented at VSS 2018
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