Understanding symptoms of medical frontal lobe disorder: A clinical case study.

A case of anterior communicating artery aneurysm with damage to inferior medial frontal areas (Brodmann areas 25, 32, 24-inferior) is presented. Four prominent deficits are discussed: (1) anterograde amnesia, (2) inert perseverative card sorting, (3) motor stereotypies, and (4) reduplicative paramnesia. These four deficits are discussed as negative or positive symptoms, related either to damage in inferior medial frontal (Brodmann areas 25, 32, 24-inferior) regions or release phenomena of superior medial frontal (Brodmann areas 6-medial and 24-superior) regions. It is concluded that the inferior and superior medial frontal regions act as opponent processors, with the inferior (B25, 32) area functioning to switch current mental set while the superior (B24-superior, 6-medial) region functions to maintain current mental set. Testable hypotheses about the opponent processor mechanism are suggested, as applied to neuropsychiatric disorders.