Memory for Remote Events in Amnesic Patients

THE amnesic syndrome is characterized by a gross memory impairment in patients with intact intellectual functions and intact immediate memory span. Defective learning and retention of on-going events is the central component of the syndrome. Some degree of retrograde amnesia, loss of memory for events antedating the onset of the illness, is a constant feature (Talland, 1965; Zangwill, 1966). Estimates of its duration have been very variable. A patient with bilateral hippocampal lesions (P. B.) reported by Penfield and Milner (1958) had a retrograde amnesia extending three months prior to operation. Retrograde amnesia following a bitemporal lobectomy (H. M.) was estimated to be of some three years ' duration (Scoville and Milner, 1957). Assessment twelve years later suggested some shrinking of the retro-grade defect which was then considered to be patchy for one year prior to operation (Milner, Corkin and Teuber, 1968). Dimsdale et al. (1964) reported a patient (N. T.) in whom a right temporal lobectomy resulted in a severe amnesic syndrome with a retrograde amnesia for ten years prior to operation. In post-encephalitic patients with marked amnesia syndromes the retrograde amnesia was estimated to range from