Summary: Abnormal sensory processing associated with autism spectrum disorder (ASD) is linked to reduced neural suppression in the visual cortex, which helps explain differences in visual motion perception.
Source: University of Minnesota
Overview: Many people with autism spectrum disorder (ASD) report heightened sensitivity to sensory input, including vision. A recent study led by researchers at the University of Minnesota Medical School, published in Nature Communications, provides evidence that differences in visual motion perception in ASD are accompanied by weaker neural suppression in visual cortex. The findings help clarify a neural mechanism that may underlie some sensory hypersensitivities experienced by people with ASD.
Although clinicians and neuroscientists have long recognized atypical sensory experiences as a common feature of ASD, the specific neural processes that produce those differences have not been fully understood. This study combines behavioral testing, functional magnetic resonance imaging (fMRI), magnetic resonance spectroscopy, and computational modeling to probe how the visual system functions differently in young adults with ASD compared with neurotypical controls.
Using visual tasks designed to engage suppressive neural circuits in the visual cortex, and measuring brain responses with fMRI, the research team—led by Michael-Paul Schallmo, PhD, assistant professor in the Department of Psychiatry at the University of Minnesota Medical School, in collaboration with investigators at the University of Washington—reported three main findings:
- Individuals with ASD demonstrated enhanced perception of large moving visual stimuli compared with neurotypical participants, indicating superior motion discrimination for certain stimulus sizes.
- fMRI responses in visual cortex differed between groups: young adults with ASD showed reduced neural suppression in response to those visual stimuli, reflecting altered cortical processing.
- A computational model that incorporates divisive normalization and a narrower top-down gain window—consistent with a more focused or narrower attentional window—can account for the observed behavioral and neural differences.
“Our work suggests there may be differences in how people with ASD allocate attention to objects in the visual environment,” Schallmo said. “Those differences could explain the altered neural responses we observe and may relate to sensory hypersensitivity symptoms commonly reported in autism.”
The study also used MR spectroscopy to measure neurotransmitter signals and found no clear group differences on those measures, suggesting that the reduced neural suppression observed in ASD is not explained by gross differences in measured neurotransmitter concentrations in the regions studied. Instead, the results point to altered circuit-level dynamics and top-down modulation as plausible contributors.
The computational modeling performed by the authors incorporates established principles of divisive normalization, a canonical computation in sensory cortex that governs how neural responses scale with stimulus strength and context. By adding the constraint of narrower top-down gain—a mechanism that could reflect a more focused attentional window—the model reproduces both the enhanced behavioral performance for large moving stimuli and the reduced fMRI suppression observed in participants with ASD. This approach helps reconcile divergent findings from earlier studies and frames testable hypotheses about attention and top-down control in autism.
Schallmo and colleagues are currently extending this line of research in a follow-up study examining visual and cognitive functioning across youth with ASD and other neurodevelopmental or neuropsychiatric conditions, including Tourette syndrome, attention deficit hyperactivity disorder (ADHD), and obsessive-compulsive disorder (OCD). Greater clarity about how these disorders differentially impact sensory processing and cortical dynamics could inform improved screening tools, earlier identification of children at risk, and the development of targeted interventions to reduce sensory symptoms.
Funding: This research was supported by the National Institutes of Health.
About this neuroscience research article
Source:
University of Minnesota
Media Contacts:
Kelly Glynn – University of Minnesota
Image Source:
The image is in the public domain.
Original Research: Open access. “Weaker neural suppression in autism” by Michael-Paul Schallmo, Tamar Kolodny, Alexander M. Kale, Rachel Millin, Anastasia V. Flevaris, Richard A. E. Edden, Jennifer Gerdts, Raphael A. Bernier, Scott O. Murray. Nature Communications. DOI: 10.1038/s41467-020-16495-z
Abstract
Weaker neural suppression in autism
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, the authors 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. A computational model that incorporates divisive normalization, along with narrower top-down gain (which could reflect a narrower window of attention), can explain these observations and help reconcile divergent prior findings. Thus, weaker neural suppression is evident in both visual task performance and fMRI measures in ASD, and may be attributable to differences in top-down processing.
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