Causes of Autism

One theory on causes of autism is atypical brain development.

The thought is that with autism there's accelerated growth at a different time than a majority of the population. The consequences, in terms of early development, include differences within the cortex. The cortex is the part of the brain which is responsible for higher brain functions, including sensation, voluntary muscle movement, thought, reasoning, and memory. The result may be that autistic people perceive things differently and may have less ability to block sensory input.

The disadvantages of “atypical” wiring would be its affect on being able to integrate information the way a majority of the general population is accustomed to having people think. The symptoms are most prominent in social interaction and problem solving because those situations require a high degree of interaction and processing of information. Social situations cause sensory overload and as a result, confusion.

The benefits of “atypical” wiring is other abilities are enhanced. Autistic people have a greater ability to use the visual parts of the right side of the brain to compensate for problems with language processing. Autistic people are usually very aware of their physical surroundings and notice details. Autistic children can find Waldo much quicker than non-autistic children and enjoy the challenge.

Autistic people think logically and predictably, their logic is just different. Metaphors and symbolism are lost on them. It’s vitally important that teachers and parents understand that autistic children think literally. For example, if a teacher would say "ok close your books and hop over to the door" and the child hops, the teacher feels mocked. She hasn't been mocked, she has been obeyed.

Physical brain abnormalities
Researchers have discovered brain abnormalities in individuals with autism. The reasons for these abnormalities is not known nor is the influence they have on behavior. These abnormalities can be classified into two types--dysfunctions in the neural structure of the brain and abnormal biochemistry of the brain. It will be important for future researchers to examine the relationship between these two types of abnormalities to further associate this atypical brain development as one of the causes of autism.

With respect to brain structure, Drs. Bauman and Kemper examined post-mortem brains of several autistic individuals and have located two areas in the limbic system which are underdeveloped--the amygdala and the hippocampus. These two areas are responsible for emotions, aggression, sensory input, and learning. These researchers also found a deficiency of Purkinje cells in the cerebellum.

Using Magnetic Resonance Imaging, Dr. Courchesne has found two areas in the cerebellum, vermal lobules VI and VII, which are significantly smaller than normal in autistic individuals. Interestingly, there are a some autistic individuals whose vermal lobules VI and VII are larger than normal. One or both of these areas of the cerebellum are believed to be responsible for attention.

With respect to biochemistry, many autistic individuals have elevated levels of serotonin in their blood and cerebral spinal fluid, whereas others have relatively low levels of serotonin. There is also evidence that some autistic individuals have elevated levels of beta-endorphins, an endogenous opiate-like substance in the body. It is felt that those individuals who have an increased pain tolerance may likely be due to elevated levels of beta-endorphins.

Again, more research is needed to positively identify if atypical brain development contributes to autism. There continue to be many theories on the causes of autism with very little good statistical data to prove the theories to be true or false.

Go back to more causes of autism

Autism Home Page