title: Memory for past public events depends on retrieval frequency but not memory age in Alzheimer's disease.
abstract: Alzheimer's disease (AD) is characterized by retrograde memory deficits primarily caused by dysfunction of the hippocampal complex. Unresolved questions exist concerning the time course of hippocampal involvement in conscious recollection of declarative knowledge, as reports of temporal gradients of retrograde amnesia have been inconclusive. The aim of this study was to examine whether the extent and severity of retrograde amnesia is mediated by retrieval frequency or, in contrast, whether it depends on the age of the memory according to the assumptions of the main current theories of memory formation. We compared recall of past public events in patients with AD and healthy control (HC) individuals using the Historic Events Test (HET). The HET assesses knowledge about famous public events of the past 60 years divided into four time segments and consists of subjective memory rating, dating accuracy, and contextual memory tasks. Although memory for public events was impaired in AD patients, there was a strong effect of retrieval frequency across all time segments and both groups. As AD and HC groups derived similar benefits from greater retrieval frequency, cortical structures other than the hippocampal complex may mediate memory retrieval. These findings suggest that more frequently retrieved events and facts become more independent of the hippocampal complex and thus better protected against early damage of AD. This could explain why cognitive activity may delay the onset of memory decline in persons who develop AD.
authors: Department of Psychiatry and Psychotherapy, Eberhard Karls University, Tübingen, Germany Geriatric Center at the University Hospital, Eberhard Karls University, Tübingen, Germany.
authors: Stephan
authors: S
authors: Müller
authors: Christian
authors: C
authors: Mychajliw
authors: Martin
authors: M
authors: Hautzinger
authors: Andreas J
authors: AJ
authors: Fallgatter
authors: Ralf
authors: R
authors: Saur
authors: Thomas
authors: T
authors: Leyhe
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000150:complications* / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis / Q000209:etiology*; D011939:Mental Recall / Q000502:physiology*; D009483:Neuropsychological Tests; D013997:Time Factors
keywords: Alzheimer's disease; cognitive impairment; historic events test; multiple trace theory; retrieval frequency; standard model of memory consolidation