Frontal-subcortical circuits and human behavior.

This synthetic review was performed to demonstrate the utility of frontal-subcortical circuits in the explanation of a wide range of human behavioral disorders. Reports of patients with degenerative disorders or focal lesions involving frontal lobe or linked subcortical structures were chosen from the English literature. Individual case reports and group investigations from peer-reviewed journals were evaluated. Studies were included if they described patient behavior in detail or reported pertinent neuropsy-chological findings and had compelling evidence of a disorder affecting frontal-subcortical circuits. Information was used if the report from which it was taken met study selection criteria. Five parallel segregated circuits link the frontal lobe and subcortical structures. Clinical syndromes observed with frontal lobe injury are recapitulated with lesions of subcortical member structures of the circuits. Each prefrontal circuit has a signature behavioral syndrome: executive function deficits occur with lesions of the dorsolateral prefrontal circuit, disinhibition with lesions of the orbitofrontal circuit, and apathy with injury to the anterior cingulate circuit. Depression, mania, and obsessive-compulsive disorder may also be mediated by frontal-subcotical circuits. Movement disorders identify involvement of the basal ganglia component of frontal-subcortical circuits. Frontal-subcortical circuits mediate many aspects of human behavior.