An overview of autism-related content on Genes to Cognition Online.
There are 3 primary symptoms of autism – social difficulties, communication difficulties, and repetitive behaviors. These may reflect abnormalities in brain areas, including the frontal cortex, amygdala, and cerebellum. At the cellular level, the brain’s mirror neuron system may be dysfunctional. Within these cells, abnormalities in the levels of biochemicals such as GABA, serotonin and, glutamate, have been reported. Many genes, which interact in complex ways, have been associated with autism. Evidence linking vaccinations to autism has been widely dismissed by the scientific community.
Selected items on the Genes to Cognition Online “subway line” explore key areas in autism research.
Research from twin studies provides compelling evidence that autism is a highly genetic disorder. A study by Bailey and Colleagues (1995) found that if an identical (monozygotic) twin had autism, there was a 60% likelihood that the other twin also had autism. For non-identical (dizygotic) twins this figure dropped to 0%. The search for genes for autism has been difficult however, and there is no one single gene that has been definitively linked to the disorder. Instead, it seems that a number of interacting genes are involved in the disorder. Use the Chromosome Map of Disorders and Processes to explore some of the prominent genes associated with autism.
One of the genes associated with autism is GABRB3, a GABA receptor gene. GABA is the primary inhibitory neurotransmitter in the brain, and a number of studies have found an association between autism and abnormalities in GABA levels. Serotonin and glutamate are other neurotransmitters linked to autism. Researchers have struggled to understand autism at a biochemical level, and a potentially promising avenue of research is to explore the biochemistry of mirror neurons.
Mirror neurons have elicited a lot of research attention as potentially important components in understanding the biological basis of autism. Mirror neurons have been called “empathy neurons” because they fire when we witness others perform particular actions and experience emotions. Individuals with autism have been found to have problems with empathy, and a dysfunctional mirror neuron system may be involved as a source of this problem. Mirror neurons have also been linked to language acquisition, and autistic individuals often have language impairments.
The frontal lobe (namely the inferior frontal gyrus) is thought to be part of the mirror neuron system. Abnormal activity in this area has been found in individuals with autism. Other neuroanatomical areas that have been linked to autism include the amygdala, which is involved in processing emotions; an enlarged brain; and abnormalities in the cerebellum. Explore these areas using the 3D brain.
Autism is a spectrum disorder, which means there are different levels and forms of autism. It is difficult to define exactly what constitutes autistic behavior, and the threshold between “normal” and “autistic” is often not clear. The Diagnostic and Statistical Manual of Mental disorders (DSM) focuses on 3 primary symptoms of autism – social difficulties, communication difficulties, and repetitive behaviors. One of the social difficulties is an inability to interpret facial expressions. Use the Reading Faces tool to explore your own ability to read facial expressions. Individuals will differ in how well they perform on this tool, just as autistic individuals differ in where they fall on the autistic spectrum.
A very controversial hypothesis about the causes of autism focuses on mercury levels in vaccines. Although this hypothesis has been widely dismissed by the scientific community, the fact that we still struggle to find specific causes for autism means the hypothesis retains advocates. The environment section also focuses on myths relating to bad parenting and social interest. You can also listen to an interview with Mark Haddon, author of the Curious Incident of the Dog in the Night-time.
autism, symptoms, research, mirror neuron system, inhibitory neurotransmitter, frontal cortex, gaba receptor, biochemical level, social difficulties, research attention, communication difficulties