Summary: Abnormal sensory processing associated with ASD has been linked to weaker neural suppression in the visual cortex.
Source: University of Minnesota
According to the National Autism Association, people with autism spectrum disorder (ASD) may experience sensory hypersensitivity. A University of Minnesota Medical School researcher recently published an article in Nature Communications that illustrates why that may be true by showing the differences in visual motion perception in ASD are accompanied by weaker neural suppression in the visual cortex of the brain.
While experts in neuroscience and psychiatry recognize that differences in sensory functioning are common among people with ASD, it is not currently understood what is happening differently in the brain on a neural level to cause the variations in sensory perception.
Using functional MRI and visual tasks, lead author Michael-Paul Schallmo, PhD, assistant professor in the Department of Psychiatry at the U of M Medical School, and a team of researchers at the University of Washington found:
People with ASD show enhanced perception of large moving stimuli compared to neuro-typical individuals;
Brain responses to these visual stimuli are different among young adults with ASD compared to neuro-typical individuals. In particular, brain responses in visual cortex show less neural suppression in ASD;
A computational model can describe the difference in brain responses.
“Our work suggests that there may be differences in how people with ASD focus their attention on objects in the visual world that could explain the difference in neural responses we are seeing and may be linked to symptoms like sensory hypersensitivity,” Schallmo said.
Schallmo is currently working with collaborators at the U of M on a follow-up study of visual and cognitive functioning in youth with ASD, Tourette syndrome, attention deficit hyperactivity disorder and obsessive-compulsive disorder. Having a better understanding of how these different disorders affect brain function could lead to new screenings to better identify kids who are at risk for ASD and related conditions. It may also help scientists to find new targets for studies seeking to improve treatments for sensory symptoms in these disorders.
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.
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.