Autism is often described as the ‘intense world syndrome,’ referring to the observation that individuals with autism experience sensory input as too intense. This has led to the hypothesis that excitability is too high in the brains of those with autism, possibly as a result of impaired pruning of synapses during development.
The way a child with autism communicates through speech plays a significant role in educational, psychosocial and eventual vocational aspects of quality of life. Some children with autism, both with and without language impairment, have challenges acquiring articulate speech and mastering the prosodic features expected when speaking in different situations.
Autism can be thought of as a disconnection syndrome, in which the normal interactions between areas of the cerebral cortex are disrupted. Information flows between cortical areas along a hierarchy. Of particular interest is the influence of cortical areas that are higher in the hierarchy on early stages of sensory processing. This hierarchy is referred to as top-down control. Such interactions facilitate our interpretation of our external environment, by segmenting visual scenes into objects and their backgrounds. They play a role in object recognition, and they provide the necessary selection of scene elements that are relevant to perceptual tasks as opposed to those that are irrelevant.
David Heeger, André Fenton and Robert Froemke of New York University, in collaboration with Marlene Behrmann of Carnegie Mellon University in Pittsburgh, are investigating the possibility that generic, brain-wide circuit malfunctions lie at the root of autism spectrum disorders. They posit that if we understood these malfunctions better, both diagnosis and intervention might be optimized.
Duplication of a small region on chromosome 22, resulting in 22q11.2 duplication syndrome, has been associated with autism, but to date there has not been a large-scale cohort study of this association.
The causes of social dysfunction in autism, a core symptom of the disorder, remain unknown. Many genetic abnormalities seem to be involved in the disorder. Because behavioral problems are mediated by malfunctions in neural circuits, it is likely that diverse genetic defects converge to cause similar functional abnormalities at the neural circuit level. Therefore, understanding the neural circuit malfunctions may hold the key to understanding social dysfunction in autism.
Similar to the well-known critical period in development for language acquisition, there is likely to be a critical window during childhood for acquiring normal social behavior. An important goal in autism research is to identify this critical period, and possibly to manipulate the length of the window or reopen it in adulthood to help with the acquisition and maintenance of appropriate social behaviors.
The diagnosis of autism spectrum disorders is currently based on behavioral observations. As a result, many children with autism are not diagnosed until after their third birthday. This delay in diagnosis can be detrimental, as earlier interventions can significantly improve cognition, adaptive behavior and symptoms.
Autism appears to be caused by aberrant synapses, or connections between brain cells. A leading hypothesis is that a generalized hyper-excitability in the brains of individuals with autism impairs cognitive functions and increases seizure susceptibility.
Few robust biomarkers have been identified for autism, and there are no medications that treat the social deficits associated with the disorder. Progress has been impeded in part by the challenge of obtaining relevant tissue samples from people with autism and matched controls.