Autism Vox

The Shrinking Amygdala?

by Kristina Chew, PhD on December 4th, 2006

A new research study by Richard Davidson, Ph.D., and colleagues at the University of Wisconsin has found that the amygdala, the part of the brain that detects fear, actually shrinks in autistic persons who are “the most severely socially impaired.” As reported in today’s Eurekalert.org:

…..social fear in autism may initially trigger a hyperactive, abnormally enlarged amygdala, which eventually gives way to a toxic adaptation that kills amygdala cells and shrinks the structure…….

The researchers suggest that the amygdala in autism fits a model in which a brain structure adapts to chronic stress – in this case, fear of people – by first becoming hyperactive, but over time succumbing to a process of toxic cell death and atrophy, as has been proposed occurs in the hippocampus for some forms of depression.*** Children with autism who are least hypersensitive to interaction with people would thus show slower amygdala shrinkage while those who were most hypersensitive would begin to show amygdala changes early in life.

The researches note that these adaptations in the amygdala are most likely to “affect most people with autism by adulthood”; they are careful to note that such changes “account for slightly more than half of the variability in nonverbal social impairment” and that they are not behind all “autistic behavior.”

I do think these findings relevant for my son Charlie. He is indeed hypersensitive to interactions with other people, especially when these involve non-verbal communication (such as gestures, change in tone of voice) and changes in emotions (Charlie tenses his shoulders, looks worried, and speaks less clearly and more repetitively when I am worried or angry). On the one hand, this study leads me to suspect that Charlie’s adolescence will be interesting indeed should the change in amygdala size the researchers note occur for him…….and on the other hand, it paints a further portrait as to why Charlie can go into white-eyed, desperate panic by a misplaced green squishy ball; of something to comfort him.

Davidson is the Director of the Laboratory for Affective Neuroscience and the Waisman Laboratory for Brain Imaging & Behavior. Davidson et al.’s study is published in the December 2006 Archives of General Psychiatry.

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POSTED IN: Adulthood, Health, Neuroscience, Psychiatry, Science