Using a visual test that is known to prompt different reactions in autistic and normal brains, a research team led by Caroline Robertson, a Junior Fellow of the Harvard Society of Fellows, was able to show that those differences were associated with a breakdown in the signaling pathway used by GABA, one of the brain’s chief inhibitory neurotransmitters.
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They also found the autistic brains to contain greater levels of nestin and CD34- proteins that control the angiogenesis process- compared to the typical brains.
GABA is an inhibitory neurotransmitter, which means it calms the brain, and opposes the action of exitatory neurotransmitters, which fire it up. It tends to come into play… when information is being transmitted and it needs to be shut down or filtered out. GABA is one of the brain’s neurotransmitters.
“It’s always been thought this might have something to do with inhibition in the brain, and our findings lend support to this notion”, Robertson said. “But this is one, and we feel good about this one”.
An estimated one in 100 children has autism spectrum disorder, a condition that affects social interaction, communication, interests and behaviour.
“This theory that the GABA signaling pathway plays a role in autism has been shown in animal models, but until now we never had evidence for it actually causing autistic differences in humans”.
“Individuals with autism are known to have detail-oriented visual perception – exhibiting remarkable attention to small details in the sensory environment and difficulty filtering out or suppressing irrelevant sensory information”, Robertson said in a press release announcing the study results.
Further studies by the researchers will examine the genetic basis of the GABA imbalance.
Robertson explained that what happens is that one image gets suppressed from visual awareness for a short period of time, then as the neurons that suppress the image get exhausted, vision will switch to the other image.
She said: ‘It’s not that there’s no GABA in the brain…it’s that there’s some step along that pathway that’s broken’. “It’s not in lower concentration, it’s just not relating to visual perception”.
Currently, doctors can not diagnose autism in children who can not speak, which is exactly when early intervention would be most effective, she continued. 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.
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“It’ll be a longer story than just, Aha!” This suggests that the autistic brain is repeatedly producing blood vessels, with constant fluctuations that cause instability in blood flow to the brain. While half of the participants had autism, the other half had no symptoms of the disease.
