Neuroscience of Autism

Autism or, more appropriately, autistic spectrum disorders (ASDs) are a group of neurodevelopmental disorders with varying degrees of behavioral impairment. The cause(s) of autism are unknown, and the neuropathology has not yet been clearly established. Diagnosis is based on observing behavioral impairments in three categories: (1) social and emotional reciprocity; (2) communication and language development; (3) stereotyped, repetitive behaviors and interests (American Psychiatric Association 1994). As toddlers, children with autism may display unusual affective behavior, lack of interest in family members, poor eye contact, and lack of response, to name (Werner et al. 2000). Since Leo Kanner (1943) initially described the disorder over 60 years ago, the definition of the ASDs has evolved and now encompasses a wide spectrum of social and emotional abnormalities with varying levels of cognitive and linguistic functioning. The disorder ranges from the lower functioning end of the spectrum with mental retardation to the higher functioning end of the spectrum with normal IQ, and in the limit to Asperger syndrome with normal to high IQ and relatively normal language development. Comorbid conditions are present at all levels of the spectrum and include epilepsy, anxiety states, gastrointestinal and gross motor problems, and the inability to modulate sensory input. Current estimates of prevalence are of the order of 1:150 children. Males are four times as likely to have an ASD as females. Concordance in monozygotic twins is very high, and there have been numerous genes implicated as susceptibility factors. There is now a general consensus emerging that there may be several etiologies and several courses to ASDs.