Two forms of human amnesia: an analysis of forgetting.

An analysis of forgetting was applied to patients with Korsakoff's syndrome, patients receiving bilateral electroconvulsive therapy (ECT), and case N. A. who has chronic amnesia for verbal material. Patients with Korsakoff's syndrome and case N. A. exhibited a normal forgetting rate, whereas patients receiving ECT exhibited abnormally rapid forgetting. Based on previous findings for the patient H. M., on indirect evidence that the amnesia associated with ECT might be related to temporal lobe dysfunction, and on the diencephalic distribution of lesions in case N. A. and in Korsakoff's syndrome, these results support the hypothesis that these amnesias are distinct syndromes of memory dysfunction. Thus, the stage of memory function disrupted may be different in the two circumstances, and medial temporal and diencephalic brain regions may normally contribute in different ways to the formation of memory.