Double dissociation of frontal dysfunction in organic amnesia.

Subjects with either diencephalic or bilateral medial temporal lobe amnesia were examined on the Wisconsin Card Sorting Test (WCST) and Cognitive Estimation Test (CET). Alcoholic Korsakoff patients performed more poorly on the WCST but normally on the CET, whereas post-encephalitic patients performed normally on the WCST but poorly on the CET. This double dissociation is interpreted as reflecting different patterns of frontal dysfunction in Korsakoff and post-encephalitic amnesia.