Autobiographical Memory Performance in Alzheimer’s Disease Depends on Retrieval Frequency

Abstract

Alzheimer's disease (AD) is characterized by memory disturbances primarily caused by pathogenic mechanisms affecting medial temporal lobe structures. As proposed by current theories of memory formation, this decrease is mediated by the age of the acquired knowledge. However, they cannot fully explain specific patterns of retrograde amnesia in AD. In the current study we examined an alternative approach and investigated whether the extent and severity of retrograde amnesia in AD is mediated by the frequency of memory retrieval or whether it depends on the mere age of knowledge. We compared recall of autobiographical incidents from three life periods in patients with amnestic mild cognitive impairment (aMCI), patients with early dementia of Alzheimer type (eDAT), and healthy control (HC) individuals using the Autobiographical Memory Interview. Retrieval frequency was operationalized by a paired comparison analysis. In contrast to HC individuals, recall of autobiographical incidents was impaired in patients with aMCI and eDAT following Ribot's gradient, with a reduced memory loss for remote compared to more recent life events. However, there was a strong effect of retrieval frequency on memory performance with frequently retrieved incidents memorized in more detail than less frequently retrieved episodes. Remote memories were recalled more often than recent ones. These findings suggest that more frequently retrieved autobiographical memories generally become more independent of the hippocampal complex and might thus be better protected against early hippocampal damage related to AD. Hence, the extent of retrograde amnesia in AD appears mainly mediated by the frequency of memory retrieval, which could plausibly explain why cognitive activity can effectively delay the onset of memory decline in AD.

The Petrified Self 10 Years After: Current Evidence for Mnemonic anosognosia

“…Furthermore, recent evidence supports multiple trace theory (MTT), according to which semantic memory retrieval is independent from the hippocampus and mediated by the neocortex after a certain consolidation period (Moscovitch et al, 2005a), while episodic retrieval is subserved by medial temporal lobe/hippocampus regardless of the lifetime period of acquisition (Moscovitch et al, 2005b). For example, the presence of a temporal gradient is more consistent for episodic memory (Philippi et al, 2012), including vividness and details specificity (Donix et al, 2010;Irish et al, 2011b;Seidl et al, 2011;Müller et al, 2016), while personal semantics can be relatively preserved in AD (Martinelli et al, 2013). Moreover, it has been suggested that the degree of impairment of semantic ABM may depend on the stage of the disease.…”

“…Interestingly, it has been reported that remote memories are proportionally more frequently retrieved by people with AD (De Simone et al, 2016;Müller et al, 2016) and that detail specificity is positively associated to retrieval frequency of memories (Müller et al, 2016). Hence, retrieval frequency may modulate vividness and temporal gradient effects, as a result of the semanticisation process of more frequently retrieved memories, which would gradually acquire independence from medial temporal structures.…”

The life span distribution of autobiographical memory in Alzheimer’s disease.

“…32(8), 906-919. DOI: 10.1037/neu0000486 6 1989; Leyhe, Müller, Milian, Eschweiler & Saur, 2009;Müller, Mychajliw, Reichert, Melcher & Leyhe, 2016). A few studies using the AMI have failed to find statistically significant effects, but report numerical differences in the same directions (Addis & Tippet, 2004;Gilboa et al, 2005;Meeter, Eijsackers & Mulder, 2006;Nestor, Graham, Bozeat, Simons & Hodges, 2002).…”

A Longitudinal Study of Episodic and Semantic Autobiographical Memory in aMCI and Alzheimer’s Disease Patients

“…It can be argued that representations of personally relevant knowledge that became part of semantic memories earlier in life are more strongly integrated in the brain, better consolidated, and therefore, less degraded by AD [ 19 ]. The episodic memory findings suggest that the more frequently retrieved autobiographical memories generally become more independent from the hippocampal complex, and might thus be better protected from early hippocampal damage related to AD [ 20 ].…”