The amygdala is one of several brain regions suspected to be pathological in autism. Previously, we found that young children with autism have a larger amygdala than typically developing children. Past qualitative observations of the autistic brain suggest increased cell density in some nuclei of the postmortem autistic amygdala.
David Amaral, Ph.D., and Cynthia Mills Schumann at the University of California, Davis found that males with autism have fewer cells in amygdala - a part of the brain that has a key role in emotion and memory. This study provides the first scientific evidence that it is the number of cells in amygdala that is affected by the disorder and not the density of cells or volume of tissue.
The team used modern techniques to study the three-dimensional structure of brain areas known to show differences in autism. Comparing the postmortem brain tissue of nine males who had autism to 10 males who did not, the researchers counted and measured representative samples of cells in the amygdala. Based on their current findings, the researchers aim to determine why there are fewer cells and whether other brain areas are similarly affected in autism.
Autism is a developmental disorder that causes severe and pervasive impairment in thinking, feeling, language, and the ability to relate to others. The disorder develops in childhood and generally is diagnosed by age three. Autism is about four times more common in boys than girls.1 Girls with the disorder, however, tend to have more severe symptoms and greater cognitive impairment. [1,2]
Schumann CM, Amaral DG. Stereological Analysis of Amygdala Neuron Number in Autism. Journal of Neuroscience. 19 Jul 2006; 26(29): 7674-7679.
1Fombonne E. Epidemiology of autism and related conditions. In: Volkmar FR, ed. Autism and pervasive developmental disorders. Cambridge, England: Cambridge University Press, 1998; 32-63.
2Yeargin-Allsopp M, Rice C, Karapurkar T, Doernberg N, Boyle C, Murphy C. Prevalence of Autism in a US Metropolitan Area. The Journal of the American Medical Association. 2003 Jan 1;289(1):49-55.
Science Update Males with Autism Have Fewer Cells in Brain’s Emotional Memory Hub nimh July 26, 2006
