Temporally-graded retrograde memory loss in semantic dementia, medial temporal lobe amnesia and Alzheimer's dementia, reconciling the hippocampal consolidation and multiple trace theories of long-term memory storage

grantor: University of TorontoPatterns of retrograde memory loss associated with semantic dementia, amnesia and Alzheimer's dementia were examined by assessing knowledge of 20th century famous names and English vocabulary. The amnesic and Alzheimer's patients demonstrated temporally-graded semantic memory such that recent items were disproportionately impaired; conversely, the semantic dementia patient, D.K., demonstrated the reverse pattern. D.K.'s memory for autobiographical episodes was contrasted with that of one amnesic patient, K.C. Consistent with previous findings, K.C. demonstrated preserved personal semantics with a complete loss of personal episodes. In contrast, D.K. demonstrated a relatively complete preservation of autobiographical episodes with a loss of remote personal semantics. Findings are discussed in the context of two competing neuropsychological theories of long-term memory--hippocampal consolidation (Squire, 1992) and multiple trace theory (Nadel & Moscovitch, 1997). Combining ideas from both theories, a new model is proposed highlighting the importance of autobiographical significance in the representation of semantic knowledge.M.A