As many as 90 percent of people with autism spectrum disorder (ASD) struggle with overwhelming sensory stimuli. A new study offers insight into the cause of autism’s sensory issues. The study demonstrated that people with ASD have abnormal brain signals when relaying sensory input. The findings contribute to the body of knowledge about ASD and may lead to more in-depth autism research.
The researchers measured the brain activity of 15 boys with ASD and 15 controls without ASD, all between 8 and 18 years old. They used magnetoencephalography (MEG) to monitor the participants’ brain activity. Many studies that investigate autism’s brain connectivity use fMRIs, but the researchers chose MEGs because they are better able to quickly track connections between neighboring brain regions.
While monitoring a participant’s brain activity, the researchers applied a 25-hertz vibration to his fingertips. According to a previous study, vibrations do not desensitize people with ASD to further touch. The vibration triggered brain activity in the primary somatosensory cortex (S1) and the secondary somatosensory cortex (S2), regions that govern tactile sensations. When a sensory signal comes through, it typically travels to the S1 and then gets relayed to S2, in a ‘feed-forward’ connection. The S2 can also send signals back to the S1, forming a ‘feedback’ connection.
In a typical brain, sensory stimuli are dampened by feedback connections, but for autistic brains, these connections behave abnormally. In the boys with ASD and the boys in the control group, brains responded with waves of the same frequency in both the S1 and S2. However, the boys with ASD had stronger S2 activity.
The findings indicate that people with ASD have overpowering feed-forward signals or weak feedback signals, resulting in sensory overload. The results could explain why so many people with ASD are sensitive to stimuli like light, sound, and touch.
This research is published in the journal Brain.
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