In the first study of its kind, researchers from a collaboration of Cedars-Sinai Medical Center, California Institute of Technology, and Huntington Memorial Hospital recorded real-time neural responses to stimuli in a group of people with autism spectrum disorders (ASD). They found a difference in the neurological response to depictions of emotion in a particular type of neuron in the amygdala. These findings help further the neurological community’s understanding of ASD and suggest avenues for future research.

The study was comprised of two people with high-functioning autism (HFA) and a control group. Real-time neural data was gathered via intracranial electroencephalogram (EEG), which is a procedure that involves implanting electrodes directly into the brain. While this tactic would be considered invasive under normal circumstances, all of the participants in this study were already receiving treatment via depth electrodes for seizure-related disorders; two of them happened to have HFA in addition to epilepsy. The presence of electrodes in the brain allowed the researchers to record chemical and electrical changes when the neurons in the amygdala fired.

The researchers showed pictures of faces or parts of faces depicting emotions to the participants who were asked to observe and report the emotion being expressed in the image. The EEG data indicated the presence of two types of neurons in the amygdala—part of the brain that is important in processing emotions—firing in response to the images. The “whole-face” neurons responded similarly in the people with HFA and the control group. However, there were differences in how the “face-part” neurons responded in the two groups. The HFA subjects’ neurons were more active when shown the mouth region of a face than the eye region. Since the amygdala’s neurons appear normal in the people with HFA, the researchers conclude that it is the face-part-sensitive neurons that are abnormal in people with autism spectrum disorders.

For lead study author Dr. Ueli Ruthishauser, PhD, assistant professor of neuropsychology and director of Human Neurophysiology Research at Cedars-Sinai, the findings raise more questions than they answer. He states, “Are there genetic mutations that lead to changes in this one population of neurons? Do the cell abnormalities originate in the amygdala or are they the result of processing abnormalities elsewhere in the brain? There are many questions yet to be answered, but this study points us in a specific direction that we believe will help understand autism.”

This research is published in the journal Neuron.

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