Retrograde amnesia in patients with diencephalic, temporal lobe or frontallesions

Patients with focal diencephalic, temporal lobe, or frontal lobe lesions we re examined on various measures of remote memory. Korsakoff patients showed a severe impairment with a characteristic 'temporal gradient', whereas two patients with focal diencephalic damage (and anterograde amnesia) were vir tually unimpaired on remote memory measures. Patients with frontal lobe pat hology were severely impaired in the recall of autobiographical incidents a nd famous news events. Patients with temporal lobe pathology showed severe impairment but a relatively 'flat' temporal gradient, largely attributable to herpes encephalitis patients. From recognition and cued recall tasks, it is argued that there is an important retrieval component to the remote mem ory deficit across all the lesion groups. In general, the pattern of perfor mance by the frontal lobe and temporal lobe groups was closely similar: and there was no evidence of any major access/storage difference between them. However, laterality comparisons across these groups indicated that the rig ht temporal and frontal lobe regions may make a greater contribution to the retrieval of past episodic (incident and event) memories, whereas the left temporal region is more closely involved in the lexical-semantic labelling of remote memories. (C) 1999 Elsevier Science Ltd. All rights reserved.