Normal and abnormal forgetting in organic amnesia: effect of locus of lesion.

Speed of forgetting by the patient H.M. was examined in two experiments using picture recognition tests. In both experiments stimulus duration was manipulated to equalize initial performance by H.M. and others, and speed of forgetting was investigated over a period of one week. In the first experiment, where initial performance was high, H,M. appeared to forget faster than normal controls. In the second experiment, where initial performance was somewhat lower, H.M. was shown to forget faster than both controls and Korsakoff patients (who forget at a normal rate). These results suggest a functional difference between the amnesia with hippocampal lesions and the amnesia of Korsakoff's disease.