Researchers led by 2005 NARSAD Distinguished Investigator Grantee, Ralph Adolphs, Ph.D., of the California Institute of Technology have made the first recordings of the firings of single neurons in the brains of individuals with autism spectrum disorder (ASD). Their findings, published November 20th in Neuron, identify specific neurons in a region called the amygdala, known to play a key role in the processing of emotions, which show reduced processing of the eye region of faces and heightened responses to mouths. Previous studies have shown the social interaction difficulties typical of ASD to be related to differences in how the brain processes sensory information about faces, but it was not known how.
"We found that single brain cells in the amygdala of people with autism respond differently to faces in a way that explains many prior behavioral observations," says Dr. Adolphs, Bren Professor of Psychology and Neuroscience and Professor of Biology at Caltech. "We believe this shows that abnormal functioning in the amygdala is a reason that people with autism process faces abnormally."
Dr. Adolphs and a team of neuroscientists and neurosurgeons from multiple medical centers in California worked with patients with epilepsy who had electrodes implanted in their medial temporal lobes, the area of the brain where the amygdala is located. (The implants are used to help identify where seizures originate in the brain.) The researchers knew that epilepsy and ASD sometimes go together, and they identified two patients with both illnesses. They were then able to use the implanted electrodes to record the firings of individual neurons as the patients looked at different parts of human faces. The team discovered that in the control group of epilepsy patients without ASD, the neurons responded most strongly to the eye region of the face, whereas in the two patients with ASD, the neurons responded most strongly to the mouth region.
The researchers report that their findings are surprising, not only because they found highly specific abnormalities in single-cell responses, but also that only a certain subset of cells responded that way, while another set showed typical responses to faces. These findings suggest the existence of specific mechanisms for ASD that can potentially be traced back to their genetic and environmental causes, and could be targeted for novel treatments of the disorder.
“We can now ask how these cells change their responses with treatments, how they correspond to similar cell populations in animal models of autism and what genes this particular population of cells expresses,” says Dr. Adolphs.
To validate their results, the researchers hope to identify and test additional subjects, which is a challenge because it is very hard to find people with ASD who also have epilepsy and who have been implanted with electrodes in the amygdala for single-cell recordings, says Dr. Adolphs.
Read more about this autism research.
Watch a TEDx Presentation by Dr. Adolphs on "The Social Brain":