There are many articles and books written on the causes of autism. Many are written on a medical level that makes them difficult to read or understand. Research journal articles are also often difficult to decipher and navigate through the data. Child development, child psychology and child behavior experts share common ground in their discussions of autism and the challenges facing parents today. Cross Creek Family Counseling Online recently publish an article that outlines the causes of autism in a manner that the general public will understand. Parents searching for answers on the causes of autism will find this article very helpful.
The Causes of Autism
It is generally accepted that autism is caused by abnormalities in brain structures or functions. Using a variety of new research tools to study human and animal brain growth, scientists are discovering more about normal development and how abnormalities occur.
The brain of a fetus develops throughout pregnancy. Starting out with a few cells, the cells grow and divide until the brain contains billions of specialized cells, called neurons. Research sponsored by NIMH and other components at the National Institutes of Health is playing a key role in showing how cells find their way to a specific area of the brain and take on special functions. Once in place, each neuron sends out long fibers that connect with other neurons. In this way, lines of communication are established between various areas of the brain and between the brain and the rest of the body. As each neuron receives a signal it releases chemicals called neurotransmitters, which pass the signal to the next neuron. By birth, the brain has evolved into a complex organ with several distinct regions and subregions, each with a precise set of functions and responsibilities.
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.
Differences in neurotransmitters, the chemical messengers of the nervous system, are also being explored. For example, high levels of the neurotransmitter serotonin have been found in a number of people with autism. Since neurotransmitters
are responsible for passing nerve impulses in the brain and nervous system, it is possible that they are involved in the distortion of sensations that accompanies autism.
NIMH grantees are also exploring differences in overall brain function, using a technology called magnetic resonance imaging (MRI) to identify which parts of the brain are energized during specific mental tasks. In a study of adolescent boys, NIMH researchers observed that during problem-solving and language tasks, teenagers with autism were not only less successful than peers without autism, but the MRI images of their brains showed less activity. In a study of younger children, researcers observed low levels of activity in the parietal areas and the corpus callosum. Such research may help scientists determine whether autism reflects a problem with specific areas of the brain or with the transmission of signals from one part of the brain to another.
Each of these differences has been seen in some but not all the people with autism who were tested. What could this mean? Perhaps the term autism actually covers several different disorders, each caused by a different problem in the brain. Or perhaps the various brain differences are themselves caused by a single underlying disorder that scientists have not yet identified. Discovering the physical basis of autism should someday allow us to better identify, treat, and possibly prevent it.
