Two inner-brain structures show signs of unusual development in autistic children and teenagers, according to a new brain-scan investigation.
The imagery reveals that boys between ages 7 and 12 diagnosed with autism have larger amygdalas than neurologically healthy boys do, say David G. Amaral of the University of California, Davis and his coworkers. The amygdala is associated with emotional responses to social situations.
This finding held regardless of whether autism was accompanied by mental retardation, as often occurs. However, amygdala volume expanded markedly by age 18 in the healthy youths while remaining the same in those with autism. As a result, amygdala size ultimately wound up about equal for both groups, Amaral's team reports in the July 14 Journal of Neuroscience.