Children with autism can detect simple movements twice as fast as typically developing children, and this hypersensitivity to motion may provide insight into the workings behind the disorder, according to a new study published in the Journal of Neuroscience.
This heightened sensory perception may help explain why some people with autism are painfully sensitive to noise and bright lights.
It also may be connected to some of the complex social and behavioral deficits found in the disorder, said Duje Tadin, Ph.D., one of the lead authors on the study and an assistant professor of brain and cognitive sciences at the University of Rochester.
“We think of autism as a social disorder because children with this condition often struggle with social interactions, but what we sometimes neglect is that almost everything we know about the world comes from our senses. Abnormalities in how a person sees or hears can have a profound effect on social communication,” said Tadin.
Prior research has shown that people with autism have enhanced visual abilities with static images, but this is the first study to uncover a sharper awareness of motion, said the authors.
The study involved 20 children with autism and 26 typically developing children, ages 8 to 17. They were asked to look at brief video clips of moving black and white bars and to indicate which direction the bars were heading, right or left.
Each time a participant made a correct guess, the next video clip became slightly shorter and a little more difficult. If the subjects made a mistake, the next video became slightly longer and therefore easier to see. In this way, the researchers were able to determine how quickly children with autism can perceive motion.
The findings showed that when the bars in the image were just barely visible, both groups of children performed identically.
Similarly, when the contrast or darkness of the bars was increased, all participants in the study got better at perceiving the direction of movement.
“But kids with autism, got much, much better — performing twice as well as their peers,” said Jennifer Foss-Feig, Ph.D., a postdoctoral fellow at the Child Study Center at Yale University, and colleagues at Vanderbilt University.
In fact, the worst performing participant with autism was about equal to the average of the participants without autism.
“This dramatically enhanced ability to perceive motion is a hint that the brains of individuals with autism keep responding more and more as intensity increases. Although this could be considered advantageous, in most circumstances if the neural response doesn’t stop at the right level it could lead to sensory overload,” said Foss-Feig.
The authors noted that such hypersensitive perception is the neural signature for a brain that is unable to dampen its response to sensory information. This same increase in neural “excitability” is also found in epilepsy, which is strongly linked to autism.
In fact, up to one-third of individuals with autism also have epilepsy. Normally, the brain has the ability to slow down its responses to sound, taste, touch, and other stimuli when they become too intense.
“If the processing of our vision, hearing, and other sensory systems is abnormal in some way, it will have a cascading effect on other brain functions,” said Carissa Cascio, Ph.D., assistant professor of psychiatry at Vanderbilt University, in whose lab the study was conducted.
“You may be able to see better, but at some point the brain really is over-responding. A strong response to high intensity stimuli in autism could be one reason for withdrawal.”
Source: University of Rochester