Retrograde amnesia: a study of its relation to anterograde amnesia and semantic memory deficits

This group study of 24 amnesic patients and 40 control subjects examined the hypothesis that retrograde memory deficits result from a combination of two impairment mechanisms: (1) a deficit in the retrieval of contents that is related to dysfunctioning of the hippocampal anterograde memory system, and (2) a deficit in the storage and/or retrieval of contents that is related to concomitant neocortical lesions. Retrograde amnesia was evaluated with the use of new Famous Persons and Autobiographical Memory Tests. The postulated components of retrograde memory impairment were assessed using the Wechsler Memory Scale and a new Semantic Memory Test, respectively. Regression analyses showed that recent episodic autobiography was exclusively related to the hippocampal component, while memory for famous persons and childhood autobiography was related to the neocortical component. In the case of details concerning people of recent fame, both components were identified as independent determinants. The temporal gradient of patients' impairment at the Famous Persons Test was marked for detailed knowledge, but small for overlearned knowledge. The present results thus support the combination hypothesis. They conform to the view that the transition from a hippocampus-dependent to a neocortex-dependent mnemonic representation of new contents is mediated by reiteration, and occurs within 5-10 years.