CAMBRIDGE, Massachusetts – For the first time, a study of brain chemicals linked to autism disorder identifies a specific neurotransmitter directly related to the condition.
Harvard scientists found that, compared to normal brains, the signaling pathways of gamma-aminobutyric acid (GABA), one of the brain’s neurotransmitters, present a breakdown in autistic brains when exposed to the same stimulus. The research was published Thursday, Dec. 17, in the journal Current Biology.
There are many other brain chemicals known for their association with autism, but this study is the first study that identifies a specific neurotransmitter that works differently in autistic brains than in healthy ones. GABA’s signaling pathways had been previously observed in animals but this is the first time that evidence of different responses have been discovered in humans, according to researcher Caroline Robertson, a junior fellow at the Harvard Society of Fellows.
For this study, scientists used a test called “binocular rivalry” to stimulate responses in autistic and normal brains. Robertson explained in a press conference that the brain is exposed to two slightly differing images, one from each eye, forcing both human eyes to look at different images at the same time. Neurons suppress one of the images from visual awareness for a short period of time, but once they get tired, vision switches to the other image. This process repeats over and over again and images flash back and forth and researchers found that, whereas the “swtiching” took an average person about three seconds, it took a much longer time with an autistic person.
The GABA neurotransmitter is responsible of inhibiting brain cells from firing in response to signals coming from external stimulus. Even though levels of excitatory neurotransmitters were normal in autistic brains, through the visual test and brain imaging technology researchers found that they all had low levels of GABA, which means it does not its job properly.
“GABA is responsible for signaling that neurons should turn off, or stop firing,” as Robertson told Huffington Post. “It tends to come into play … when information is being transmitted and it needs to be shut down or filtered out.” She added that people need to block external signals that are not relevant to the task they are performing and that GABA help them in that inhibition process.
These findings explain why it is so difficult for autistic people to concentrate in a single task. They have a hard time when trying to turn off external world’s signals such as distracting sounds and other sensations that make them feel overwhelmed because they simply cannot block them. This condition is known as hypersensitivity and negatively influences social skills, communication and behavior.
Robertson, however, remarked that further research is needed in order to understand the cause of GABA’s disruption in autistic brains and what could be the effects of enhancing GABA levels in those patients. But still, this study is a step towards finding new treatments and even prevention of autism.
Source: Huffington Post