[Episodic memory and Alzheimer's disease: evolution of theories and clinical assessment tools]. / Mémoire épisodique et maladie d'Alzheimer : évolution des théories et des outils d'évaluation clinique.

Alzheimer's disease is characterized by an impairment of episodic memory in the early stages of the disease. Neuropsychological evaluation is performed for diagnostic purposes and to personalize follow-up. However, although many tests have been developed over the last few decades, not all of them seem to be able to meet this dual challenge. Through a review of the evolution of the concept of episodic memory and of knowledge about the disease, we discuss how neuropsychological tools have adapted. We question the interests and limits of existing tools for patients with Alzheimer's disease. At the end of this review, we suggest the criteria to be taken into account in order to propose a more integrative evaluation, able to describe the difficulties encountered as close as possible to the lived experience.

Music as a mnemonic strategy to mitigate verbal episodic memory in Alzheimer's disease: Does musical valence matter?

Introduction: Music is increasingly used to improve cognition in clinical settings. However, it remains unclear whether its use as a mnemonic strategy is effective in Alzheimer's disease (AD). The present study aimed at determining whether a musical mnemonic might mitigate patients' learning of new verbal information and at exploring the effect of factors such as retention delay and emotional valence of the musical excerpt used. Method: 13 patients with AD and 26 healthy comparisons (HC) with a low musical expertise were included. They learned texts about everyday life themes that were either set to familiar instrumental music, which was positively- or negatively-valenced, or spoken only. Immediate and delayed recalls (after 10 min and 24 hours) were measured. Results: Main results showed that (i) HC demonstrated better verbal episodic memory performance than participants with AD; (ii) participants with AD encoded texts paired with positively-valenced music better than texts paired with negatively-valenced music; (iii) participants with AD recalled sung texts better than spoken texts (after 10 min and 24 hours), regardless of musical valence while HC displayed better recall for texts paired with positively-valenced music. Conclusions: Musical mnemonics may help people with AD learn verbal information that relates to their daily life, regardless the musical expertise of the patients. This result gives promising clinical insights showing that music processing is robust to brain damage in AD. Possible hypotheses explaining the effectiveness of musical mnemonics in AD regardless the musical valence are discussed (e.g., different processing between musical and spoken conditions; disappearance of the positivity bias and implications with respect to the underlying socio-emotional selectivity theory).

Executive functioning and processing speed in age-related differences in time estimation: a comparison of young, old, and very old adults.

Age-related differences in time estimation were examined by comparing the temporal performance of young, young-old, and old-old adults, in relation to two major theories of cognitive aging: executive decline and cognitive slowing. We tested the hypothesis that processing speed and executive function are differentially involved in timing depending on the temporal task used. We also tested the assumption of greater age-related effects in time estimation in old-old participants. Participants performed two standard temporal tasks: duration production and duration reproduction. They also completed tests measuring executive function and processing speed. Findings supported the view that executive function is the best mediator of reproduction performance and inversely that processing speed is the best mediator of production performance. They also showed that young-old participants provide relatively accurate temporal judgments compared to old-old participants. These findings are discussed in terms of compensation mechanisms in aging.

Is music a memory booster in normal aging? The influence of emotion.

Age-related differences in episodic memory have been explained by a decrement in strategic encoding implementation. It has been shown in clinical populations that music can be used during the encoding stage as a mnemonic strategy to learn verbal information. The effectiveness of this strategy remains equivocal in older adults (OA). Furthermore, the impact of the emotional valence of the music used has never been investigated in this context. Thirty OA and 24 young adults (YA) learned texts that were either set to music that was positively or negatively valenced, or spoken only. Immediate and delayed recalls were measured. Results showed that: (i) OA perform worse than YA in immediate and delayed recall; (ii) sung lyrics are better remembered than spoken ones in OA, but only when the associated music is positively-valenced; (iii) this pattern is observed regardless the retention delay. These findings support the benefit of a musical encoding on verbal learning in healthy OA and are consistent with the positivity effect classically reported in normal aging. Added to the potential applications in daily life, the results are discussed with respect to the theoretical hypotheses of the mechanisms underlying the advantage of musical encoding.

Age-related differences in time-based prospective memory: The role of time estimation in the clock monitoring strategy.

Time-based prospective memory (TBPM) is required when it is necessary to remember to perform an action at a specific future point in time. This type of memory has been found to be particularly sensitive to ageing, probably because it requires a self-initiated response at a specific time. In this study, we sought to examine the involvement of temporal processes in the time monitoring strategy, which has been demonstrated to be a decisive factor in TBPM efficiency. We compared the performance of young and older adults in a TBPM task in which they had to press a response button every minute while categorising words. The design allowed participants to monitor time by checking a clock whenever they decided. Participants also completed a classic time-production task and several executive tasks assessing inhibition, updating and shifting processes. Our results confirm an age-related lack of accuracy in prospective memory performance, which seems to be related to a deficient strategic use of time monitoring. This could in turn be partially explained by age-related temporal deficits, as evidenced in the duration production task. These findings suggest that studies designed to investigate the age effect in TBPM tasks should consider the contribution of temporal mechanisms.

Protective role of educational level on episodic memory aging: an event-related potential study.

The aim of the present experiment was to investigate whether educational level could modulate the effect of aging on episodic memory and on the electrophysiological correlates of retrieval success. Participants were divided into four groups based on age (young vs. older) and educational level (high vs. low), with 14 participants in each group. Event-related potentials (ERP) were recorded while participants performed a word-stem cued-recall task. Age-related memory deficits were greater for the less educated individuals. Age differences in the ERP old/new effects were also modulated by the level of education. This study demonstrated that the effects of age on episodic memory and ERP correlates of retrieval success are smaller in participants with high educational levels than those with lower levels. These findings provide support for the reserve hypothesis and highlight the need to consider individual differences when studying cognitive and cerebral changes in aging.

Episodic memory and organizational strategy in free recall in unipolar depression: the role of cognitive support and executive functions.

Executive functioning and memory impairment have been demonstrated in adults with depression. Executive functions and memory are related, mainly when the memory tasks require controlled processes (attentional resource demanding processes)--that is, when a low cognitive support (external aid) is provided. A cross-sectional study was carried out on 45 participants: 21 with depression, and 24 healthy controls matched for age, verbal ability, education level, and anxiety score. Cognitive support was manipulated by providing a categorized word list at encoding, presented either clustered (high cognitive support) or randomized (low cognitive support) to both depressed and healthy adults. The number of words recalled was calculated, and an index of clustering was computed to assess organizational strategies. Participants were also administered cognitive tests (executive functions, cognitive speed, and categorical fluency) to explore the mediators of organizational strategies. Depressed participants had greater difficulty recalling and organizing the words, but the differences between the two groups were reduced for both measures when high cognitive support was provided at encoding. Healthy adults performed better on all cognitive tests. Statistical analyses revealed that in the depressed group, executive functions were the only variable associated with clustering and only when low cognitive support was provided. These findings support the view that the decrement in executive function due to depression may lead to impairment in organization when this mnemonic strategy has to be self-initiated.

Executive functioning and processing speed in age-related differences in memory: contribution of a coding task.

The aim of the present study was to examine executive dysfunctioning and decreased processing speed as potential mediators of age-related differences in episodic memory. We compared the performances of young and elderly adults in a free-recall task. Participants were also given tests to measure executive functions and perceptual processing speed and a coding task (the Digit Symbol Substitution Test, DSST). More precisely, we tested the hypothesis that executive functions would mediate the age-related differences observed in the free-recall task better than perceptual speed. We also tested the assumption that a coding task, assumed to involve both executive processes and perceptual speed, would be the best mediator of age-related differences in memory. Findings first confirmed that the DSST combines executive processes and perceptual speed. Secondly, they showed that executive functions are a significant mediator of age-related differences in memory, and that DSST performance is the best predictor.

Ageing, remembering, and executive function.

This study was designed to investigate the relationship between executive functions and the age-related decline in episodic memory through the states-of-awareness approach. Following the presentation of a word list, a group of younger adults and a group of older adults undertook a recognition test in which they classified their responses according to the Remember-Know-Guess procedure (Gardiner & Richardson-Klavehn, 2000). In order to operationalise the executive function hypothesis, we investigated three specific executive functions (updating, shifting, and inhibition of a prepotent response) described in Miyake et al.'s (2000) theoretical model, and a complex executive task. The results revealed that fewer "R" responses were made during the recognition test by the older than the younger group, whereas there was no difference between the groups in the number of "K" responses. In addition, correlations indicated that remembering depended on executive function measures, whereas knowing did not. The hierarchical regression analyses showed that controlling for executive function, and particularly for the 2-back test, largely removed the age-related variance in remembering. These findings support the notion that executive dysfunction, and specifically updating decline, plays a central role in age-related memory loss.

Aging and implementation of encoding strategies in the generation of rhymes: the role of executive functions.

This experiment examines whether the age-related decrease in the generation effect of rhymes is mediated by executive functioning. Young and elderly adults read and generated pairs of rhyming words for subsequent recall. Participants were also administered neuropsychological tests (executive and mnemonic functions). Results showed that elderly adults performed less well on the neuropsychological tests and benefited less than the younger participants from the generation effect. Hierarchical regression analyses revealed that the executive functions composite score was correlated with the generation effect and that it accounted for a large proportion of the age-related variance of the size of this measure. This finding supports the view that the age-related decrement in strategic encoding implementation is due to a decrease of executive functioning.

Age-related changes in duration reproduction: involvement of working memory processes.

The aim of the present research was to study age-related changes in duration reproduction by differentiating the working memory processes underlying this time estimation task. We compared performances of young and elderly adults in a duration reproduction task performed in simple and concurrent task conditions. Participants were also administered working memory tests to measure storage and central executive functions. Findings indicated a differential involvement of working memory storage and central executive functions in age-related differences in temporal tasks. The limited storage capacities explained age-related changes in the simple task of duration reproduction, and the dysfunctioning of central executive functions accounted for age-related changes in duration reproduction performed in a concurrent task condition, which involves greater attentional resources.

Differential involvement of internal clock and working memory in the production and reproduction of duration: a study on older adults.

The present study uses the inter-individual variability in time perception of a group of elderly participants to differentiate the processes underlying time production and time reproduction. Participants performed duration production and reproduction tasks. They were also administered working memory tests and a spontaneous motor tempo task. The findings suggest that duration production and duration reproduction involve different mechanisms. Correlational analyses revealed a double dissociation: production was only correlated with spontaneous motor tempo and reproduction only with working memory measures. These findings suggest that the internal clock rate modulates the production of duration and that reproduced duration varies according to working memory capacities.

Age-related cognitive slowing: the role of spontaneous tempo and processing speed.

This research studied the relationships between two types of slowing observed in aging-loss of general processing speed and slowing of spontaneous tempo-in an attempt to test the assumption that there is an internal timing mechanism responsible for cognitive age-related decrease. Processing speed has been evaluated as a mediator of the relationship between age and working memory, concurrently with spontaneous tempo measures. The authors compared the performance of young and older adults on tasks involving spontaneous motor tempo, processing speed, and working memory. The findings confirmed the agerelated slowing of spontaneous motor tempo but did not indicate superiority of tempo mediation in the decline in working memory. Processing speed appeared to be a major mediator of working memory, but also of spontaneous tempo slowing.