What Causes Autism?

2008 March 17 by: Scott

Different parts of the brain have different functions:

The hippocampus makes it possible to recall recent experience and new information

The amygdala directs our emotional responses

The frontal lobes of the cerebrum allow us to solve problems, plan ahead, understand the behavior of others, and restrain our impulses

The parietal areas control hearing, speech, and language

The cerebellum regulates balance, body movements, coordination, and the muscles used in speaking

The corpus callossum passes information from one side of the brain to the other

But brain development does not stop at birth. The brain continues to change during the first few years of life, as new neurotransmitters become activated and additional lines of communication are established. Neural networks are forming and creating a foundation for processing language, emotions, and thought.

However, scientists now know that a number of problems may interfere with normal brain development. Cells may migrate to the wrong place in the brain. Or, due to problems with the neural pathways or the neurotransmitters, some parts of the communication network may fail to perform. A problem with the communication network may interfere with the overall task of coordinating sensory information, thoughts, feelings, and actions.

Researchers supported by NIMH and other NIH Institutes are scrutinizing the structures and functions of the brain for clues as to how a brain with autism differs from the normal brain. In one line of study, researchers are investigating potential defects that occur during initial brain development. Other researchers are looking for defects in the brains of people already known to have autism.

Scientists are also looking for abnormalities in the brain structures that make up the limbic system. Inside the limbic system, an area called the amygdala is known to help regulate aspects of social and emotional behavior. One study of high-functioning children with autism found that the amygdala was indeed impaired but that another area of the brain, the hippocampus, was not. In another study, scientists followed the development of monkeys whose amygdala was disrupted at birth. Like children with autism, as the monkeys grew, they became increasingly withdrawn and avoided social contact.