The Short of It
Harvard scientists link a specific neurotransmitter with behavior associated with autism.
In a study published in the journal Current Biology, lead researcher Caroline Robertson, a junior fellow of the Harvard Society of Fellows, looked at how a normal brain and an autistic one process visual information. Specifically, researchers used a binocular-rivalry test, in which both eyes are forced to take in different information at one time.
Robertson explained the test this way:
"The end result is that one image is just suppressed entirely from visual awareness for a short period. So if I show you a picture of a horse and an apple, the horse will entirely go away, and you will just see the apple. Eventually, though, the neurons that are forcing that inhibitory signal get tired, and it will switch until you only see the horse. As that process repeats, the two images will rock back and forth. Where the average person might rock back and forth between the two images every three seconds, an autistic person might take twice as long. They spend the same amount of time in the steady state, where they see only one image, as the average person. It just takes them longer to switch between them, and the second image is not as deeply suppressed."
Researchers were able to determine the differences between a normal and autistic brain can be explained by a breakdown in the signaling pathway used by GABA, a chief inhibitory neurotransmitter. GABA was lower in autistic individuals.
"This is the first time, in humans, that a neurotransmitter in the brain has been linked to autistic behavior—full stop... What we think we're seeing is evidence of a deficit in the GABA-ergic signaling pathway. It's not that there's no GABA in the brain ... it's that there's some step along that pathway that's broken," Robertson says.
This new data may also help explain why people with autism sometimes have seizures.
Similar visual tests may help doctors evaluate younger children for autistic behavior, and then move forward with earlier intervention. As Robertson explains, "Before children can talk, they can see, so we may be able to use this type of visual task to screen children and see if there's something imbalanced in their brains."
It's unknown at this time if any treatments can make use of this discovery. But we are one step closer to understanding the disorder that affects one in 45 kids in the United States. Robertson cautions many other forces are likely at play when it comes to fully explaining what causes autism. I can only imagine how frustrating that must be for parents.