For the first time, neuroscientists at MIT and Harvard have linked differences in neurotransmitter activity, GABA, and symptoms of autism hypersensitivity in people who have autism, reports the Huffington Post. Caroline Robertson, PhD of Harvard University and her colleagues carried out a study in which they measured a type of visual function called binocular rivalry in 20 adults who have autism and 21 controls. During the study, two images were presented to each eye and were in competition for dominance of perception in the brain. In a press release announcing the study, Robertson said the following.
“This is the first connection in humans between a neurotransmitter in the brain and an autistic behavioral symptom. GABA is responsible for signaling that neurons should turn off, or stop firing. It tends to come into play… when information is being transmitted and it needs to be shut down or filtered out. It’s necessary to filter out signals in the external world that aren’t relevant to the task at hand. GABA helps us in this kind of inhibition.”
Robertson says that those who have autism are, of course, known to have a very detailed visual perception, illustrating great attention to detail, and have a difficult time excluding any irrelevant sensory information.
“It’s long been thought this might have something to do with inhibition in the brain, and our findings lend support to this notion,” Robertson said.
The authors of the study did specify, however, that the GABA dysfunction that they stumbled upon may vary, to a large degree, among those on the autism spectrum. In the behavioral manifestation of autism, there are additional neurotransmitters that could serve key roles.
Robertson and her colleagues hope these new findings will aid some researchers in developing more advanced diagnostic tools for autism, which is now diagnosed by studying children’s social interactions. Robertson told MedPage Today that additional research should figure out whether or not using EEG scans to measure brain responses during the binocular rivalry task is possible. Robertson added that if autism is linked to circuitry differences that end up affecting the visual cortex, these can be measured in nonverbal subjects, as long as they are able to see, and would become quite useful for early diagnostic screenings.
“This is a really great piece of work,” Richard Edden, associate professor of radiology at the Johns Hopkins University School of Medicine, says. “The role of inhibitory dysfunction in autism is strongly debated, with different camps arguing for elevated and reduced inhibition. This kind of study, which seeks to relate measures of inhibition directly to quantitative measures of function, is what we really to need to tease things out.”
Across the globe, autism is estimated to affect 21.7 million people as of 2013. Three years before that, the amount of people affected by autism was around 1–2 per 1,000 worldwide. Boys are four to five times more likely to develop autism than girls. About 1.5 percent of children in America, one in 68, are diagnosed with ASD as of last year, which is a 30 percent rise from one in 88 in 2012.
“If autism does trace back on some level to circuitry differences that affect the visual cortex, you can measure those things in a kid who’s even nonverbal, as long as he can see,” Robertson says. “We’d like it to move toward being useful for early diagnostic screenings. GABA is not reduced in the autistic brain, but the action of this inhibitory pathway is reduced. The next step is figuring out which part of the pathway is disrupted.”
[Photo by Dan Kitwood/Getty Images]