Functional neuroimaging of autistic disorders

Functional neuroimaging methods hold promise for elucidating the neurobiolo gy of autistic disorders, yet they present difficult practical and scientif ic challenges when applied to these complex and heterogeneous syndromes. Si ngle-state studies of brain metabolism and blood flow thus far have failed to yield consistent findings, but suggest considerable variability in regio nal patterns of cerebral synaptic activity. Patients with idiopathic autism are less likely to show abnormalities than are patients with comorbid illn ess or epilepsy. Activation studies have begun to suggest alterations in br ain organization for language and cognition. Neurotransmitter studies using positron emission tomography (PET) suggest abnormalities of serotonergic a cid dopaminergic function. Studies using magnetic resonance spectroscopy (M RS) have begun to document metabolic deficits in the frontal cortex and cer ebellum. A single study using magnetoencephalography suggests a high incide nce of epileptiform activity in children with autistic regression. Research needs include well-controlled developmental studies, particularly of young subjects and relatively homogeneous subgroups, which balance scientific ri gor with ethical constraints. Investigations of the serotonergic and dopami nergic systems, limbic-based memory and emotional systems, and the role of epileptiform activity in autism represent priorities for future research. P ublished 2000 Wiley-Liss, Inc.(dagger)