A stable impairment in remote memory following electroconvulsive therapy.

Psychiatric patients receiving a course of electroconvulsive therapy for relief of depressive illness were given a test of remote memory for public events covering the years 1940-1969. An impairment in remote memory, covering nearly the entire time period sampled by the test, developed during the tirst five treatments. This impairment was present during the first hour after the fifth treatment and persisted unchanged for at least twenty-four hours thereafter. Electroconvulsive therapy did not affect performance on the verbal portion of the Weschler Adult Intelligence Scale. Apparenny, the amnesia produced by electroconvulsive therapy can involve a large portion or perhaps all of remote memory, in addition to recent memory. The relevance of these results to the neural substrates underlying storage and recall is discussed. THE AMNESIC syndrome is characterized by both an anterograde loss of memory for events that occur after the onset of amnesia and by a retrograde memory loss for events that occurred before the onset of amnesia [l-3]. Most observations suggest that retrograde amnesia is brief. For example, in 81 per cent of a series of 1029 head injury cases, retrograde amnesia was estimated to involve only those events occurring within 30 min of the injury [4]. Loss of memory for events that took place months or years before the onset of amnesia can occur, but an impairment in remote memory has generally been associated with unusually severe head injury [4] and with chronic anterograde amnesia [5-71. It has also been reported that performance on personal data inventories, which probably involve remote memory to some degree, is impaired by electroconvulsive therapy (ECT) [g-lo]. However, since it is known that a course of ECT can impair performance in some tests of cognitive function [ll, 121, it is not clear whether these reports reflect a true defect in remote memory or a broad impairment of intellectual capacity. It has recently been reported that ECT treatment impaired performance on a test of remote memory for public events, without affecting intelligence test scores [13]. This impairment was observed shortly after the fifth ECT treatment and covered nearly the entire time period (1940-1969) sampled by the test. For these patients anterograde amnesia diminished markedly within a few hours after each ECT treatment [14] and it might be expected, therefore, that the remote memory impairment would diminish similarly during the hours after treatment. Indeed, retrograde amnesia typically shrinks following the precipitating incident [4, 6, 151, and in the case of head trauma, it is clear that considerable shrinkage of retrograde amnesia can occur before the anterograde amnesia has disappeared [4, 151. The present study assessed remote memory following ECT up to 24 h after the first and fifth treatments. The results indicated that remote memory was markedly impaired after a series of five ECT treatments and that this impairment did not change measurably between 40 min and 24 h after treatment.