Something strange is going on in the amygdala - an almond-shaped structure deep in the human brain - among people with autism.
Researchers at the University of Washington have discovered an increased pattern of brain activity in the amygdalas of adults with autism that may be linked to the social deficits that typically are associated with the disorder. Previous research at the UW and elsewhere has shown that abnormal growth patterns in the amygdala are commonly found among young children diagnosed with autism.
The amygdala is popularly associated with the "fight-or-flight response" in dangerous situations. But it has other functions, including identifying faces and situations and evaluating social information such as emotions.
The new research shows that brain activation in adults with autism remains elevated long after similar brain regions of typically developed adults have stopped being activated when exposed to a series of pictures of human faces. A decrease in activation over time to the same type of information is called neural habituation and is connected with learning, according to Natalia Kleinhans, lead author of the new study and a UW research assistant professor of radiology.
"What we are seeing is hyperexcitability or overarousal of the amygdala, which suggests that neurons in the amygdala are firing more than expected," said Kleinhans, who is associated with the UW Autism Center.
"If you consider that habituation reflects learning in as simple a task as looking at a face, slowness to habituate in people with autism may contribute even more markedly to difficulty with more complex social interactions and social cognition. If the brain is not reacting typically to a static face with a neutral expression, you can imagine how difficult it may be for someone with autism to pick up more subtle social cues."
The National Institute of Child Health and Human Development and the National Institute of Mental Health funded the research, which appears in the online edition of The American Journal of Psychiatry .