MECHANISM OF DISINHIBITION AFTER BRAIN-LESIONS

Disinhibition syndromes, ranging from mildly inappropriate social beha vior to full blown mania, may result from lesions to specific brain ar eas. Several studies in patients with closed head injuries, brain tumo rs, stroke lesions, and focal epilepsy have demonstrated a significant association between disinhibition syndromes and dysfunction of orbito frontal and basotemporal cortices of the right hemisphere. Based on th e phylogenetic origin of these cortical areas and their main connectio ns with dorsal regions related to visuospatial functions, somatosensat ion, and spatial memory, the orbitofrontal and basotemporal cortices m ay selectively inhibit or release motor, instinctive, affective, and i ntellectual behaviors elaborated in the dorsal cortex. Thus, dysfuncti on of these heteromodal ventral brain areas may result in disinhibited behaviors.