People with an autism spectrum disorder, or ASD, may experience sensory hypersensitivity more often than people without ASD, according to the National Autism Association. Among other responses, this hypersensitivity can lead to “sensory overload,” when sensory systems like vision or hearing are “overwhelmed” by stimuli. Scientists do not fully understand the differences in how sensory systems perceive and process stimuli in people with ASD or the neurological and physiological changes to the brain that are associated with these differences.
In a paper published in Nature Communications, a team of scientists at the University of Washington, the University of Minnesota and the Johns Hopkins University report that differences in visual motion perception in ASD are accompanied by weaker neural “suppression” in the visual cortex of the brain.
“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,” said lead author Michael-Paul Schallmo, an assistant professor of psychiatry at the University of Minnesota.
Schallmo is a former UW postdoctoral researcher who worked on this study with co-author Scott Murray, a UW professor of psychology and a research affiliate with the UW Center on Human Development and Disability.
“One of the interesting aspects of our findings is that they show that the reduction in neural suppression actually results in better performance in the motion discrimination task,” said Murray. “So, a potential downside of reduced neural suppression is that it may lead to sensory hypersensitivity but it is also accompanied by a potential upside — enhanced visual motion perception.”
The team used functional MRI and visual tasks to study visual perception in 28 young adults with ASD and 35 without ASD. They found that participants with ASD showed the enhanced perception of large moving stimuli compared to those without ASD. Brain activity showed unique responses to visual stimuli in individuals with ASD: In particular, the visual cortex showed less neural “suppression,” meaning that levels of activity in this region of the brain were higher than in participants without ASD.
The researchers also demonstrated that a computational model of neural behavior can explain the differences in brain responses that they found. These methods can help scientists model the differences in sensory processing that occur in the brains of people with ASD that may underlie this visual hypersensitivity.
Schallmo is currently working on a follow-up study of visual and cognitive function 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 children who are at risk for ASD and other conditions. It may also help scientists to find new targets for studies seeking to improve treatments for sensory symptoms in these disorders.
Source: University of Washington