Excess noise or light touches might feel like run-of-the-mill sensory experiences for most, but new research has found that the brains of people with autism spectrum disorders (ASD) are more reactive to sensory stimuli—that is, they do not filter out extraneous information as efficiently as neurotypical people. The findings come from research out of the University of California, San Francisco that compared brain activity in boys with autism, boys with sensory processing disorder (SPD), and typically developing boys when exposed to sensory stimuli.

The researchers used magnetoencephalographic (MEG) imaging on school-aged boys—18 typically developing, 17 with ASD, and ten with SPD—while exposing them to a short tone and a finger touch at one-minute intervals. In some instances, either the tone or the finger touch was longer, creating ‘oddball’ neural stimuli. This process allowed the research team to collect data on how much neural activity was present when boys of each group were exposed to the stimuli. Once the imaging was finished, the researchers calculated the difference between brain activity when actively and passively listening. This allowed them to measure the boys’ ability to modulate attention.

The brains of the ASD children exhibited more activity when exposed to the oddball stimulus than the control children’s brains. Interestingly, the SPD children were able to ignore the irrelevant sensory data as effectively as the neurotypical children; however, when the SPD boys had to press a button while hearing an oddball tone, their brain activity was comparably less.

A correlation between abnormal scores on sensory profile tests and a smaller difference between active and passive brain activity was also observed.

While this study did not identify which regions of the brain are affected by the higher levels of neural activity, the researchers state that will be the subject of their next inquiry.

Theodore Zanto, assistant adjunct professor of neurology at UC San Francisco, who presented the findings, explained that the children with autism are “over-processing stimuli they should be ignoring.” This is problematic since “most of what we’re experiencing in the world is irrelevant information.” These findings may have the potential to explain why people with autism spectrum disorders have problems with learning and memory.

This research was presented at the 2013 Society for Neuroscience Annual Meeting in San Diego.

Previous news in autism: