For the study, Piven's team conducted MRI scans of 50 autistic children and 33 children without the condition. The children had brain scans and testing of certain behavioral features of autism at 2 and 4.
The researchers found autistic children were more likely to have an enlarged amygdala at 2 and 4.
However, the researchers did not find a relationship between amygdala size and other social behaviors at this age, such as social gestures or ritualistic/repetitive behavior, Piven said.
"We have found a very specific behavior, social-orienting, known to be a core neuropsychological mechanism in autism, to have a specific relationship to a very early change in a selected brain structure in autistic individuals," Piven said. The finding identifies "an important potential, fundamental mechanism underlying the development of autism," he added.
"Studying this relationship as these children develop -- does the amygdala continue to enlarge, stay the same or get smaller -- will shed important light on the neurobiological basis of autism," Piven said.
Dr. Jon Shaw, chief of the division of child & adolescent psychiatry at the University of Miami Miller School of Medicine, believes the study adds a potential new understanding to some of the social problems associated with autism.
"The number of studies that have suggested various neurobiological pathways to autism are almost infinite, confirming the complex neurodevelopmental processes intrinsic to the disorder and suggest the need for humility in interpreting neurobiological findings," Shaw said.
This study, however, suggests that one of the important facets in the neurodevelopmental mosaic that makes up autism is an alteration in amygdala functioning, Shaw said.
"The authors, taking a developmental approach, suggest that increased bilateral amygdala volume with alterations in functioning occurs early in a
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