Anterograde and retrograde memory impairment in chronic amnesia.

-Tests of new learning capacity and remote memory were given to the chronic amnesic patient (N.A.) who sustained a stab wound to the basal brain in 1960. N.A.‘s persisting defect in new learning was demonstrated with several tests, including a distractor test of short-term memory. These results are discussed in the light of previous findings in amnesic patients with distractor tests. N.A.‘s remote memory was markedly impaired for the period since 1960, but normal for the period prior to 1960. This discontinuity between premorbid and postmorbid memory, also reported for the well-known amnesic H.M., favors the view that amnesia represents a defect in the formation of enduring memory rather than a general defect in retrieval. HRAIN injury or disease can sometimes affect human memory in a relatively circumscribed way, without apparent loss in other cognitive functions. Such instances of amnesia have consequently been of special interest in discussions of the structure of human memory and its neurologic basis. In recent years there has been disagreement about what constitutes the correct description of some aspects of amnesia. For example, amnesic patients with Korsakoff psychosis have sometimes been described as normal and sometimes as deficient in short-term memory tasks [l, 21. There have also been divergent findings concerning the status of memory for events that occurred long before the onset of amnesia. In the case of remote memory, newly developed tests [3-51 indicate that loss of memories acquired many years before the onset of amnesia can occur in Korsakoff patients [6], in psychiatric patients receiving electroconvulsive therapy (ECT) [7-91, and in patients with diencephalic tumor [lo]. Yet, on the basis of informal interviews, the noted patient H.M. [ 1 l] appears to have normal premorbid memory, except for the period l-3 yr prior to the onset of his amnesia in 1953 [12]. Recently, objective remote-memory tests have confirmed that H.M. has good remote memory for events of the 192Os, 193Os, and 1940s [I 31. These results, taken together, suggest that H.M. may differ from other groups of amnesic patients with respect to premorbid memory. H.M. has long been considered a paradigmatic example of the amnesic syndrome, because of the remarkably circumscribed nature of his memory impairment. In view of the apparent differences between H.M. and other amnesic populations in premorbid memory, it would be of considerable interest to evaluate this dimension of memory in other patients whose amnesia is relatively pure. Finally, in view of the conflicting findings with shortterm memory tasks among different populations of Korsakoff patients [I, 21, it would also be of interest to evaluate short-term memory in other amnesic patients. We have therefore evaluated the performance of the patient N.A., originally described by TEUBER, MILNER and VAUGHAN [14]. N.A. has been amnesic since incurring a stab