Lucie Angel

Aging and self-reported internal and external memory strategy uses: The role of executive functioning

The aim of this study was to investigate the effect of advanced age on self-reported internal and external memory strategy uses, and whether this effect can be predicted by executive functioning. A sample of 194 participants aged 21 to 80 divided into three age groups (21-40, 41-60, 61-80) completed the two strategy scales of the Metamemory in Adulthood (MIA) questionnaire, differentiating between internal and external everyday memory strategy uses, and three tests of executive functioning. The results showed that: (1) the use of external memory strategies increased with age, whereas use of internal memory strategy decreased; (2) executive functioning appeared to be related only to internal strategies, the participants who reported the greatest use of internal strategies having the highest executive level; and (3) executive functioning accounted for a sizeable proportion of the age-related variance in internal strategy use. These findings suggest that older adults preferentially use external memory strategies to cope with everyday memory impairment due to aging. They also support the view that the age-related decrease in the implementation of internal memory strategies can be explained by the executive hypothesis of cognitive aging. This result parallels those observed using objective laboratory memory strategy measures and then supports the validity of self-reported memory strategy questionnaire.

Differential effects of aging on the neural correlates of recollection and familiarity.

The present experiment aimed to investigate age differences in the neural correlates of familiarity and recollection, while keeping performance similar across age groups by varying task difficulty. Twenty young and 20 older adults performed an episodic memory task in an event-related functional magnetic resonance imaging (fMRI) design. At encoding, participants were presented with pictures, either once or twice. Then, they performed a recognition task, with a Remember/Know paradigm. A similar performance was observed for the two groups in the Easy condition for recollection and in the Hard condition for familiarity. Imaging data revealed the classic recollection-related and familiarity-related networks, common to young and older groups. In addition, we observed that some activity related to recollection (left frontal, left temporal, left parietal cortices and left parahippocampus) and familiarity (bilateral anterior cingulate, right frontal gyrus and left superior temporal gyrus) was reduced in older compared to young adults. However, for recollection processes only, older adults additionally recruited the right precuneus, possibly to successfully compensate for their difficulties, as suggested by a positive correlation between recollection and precuneus activity.

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.

Two hemispheres for better memory in old age: Role of executive functioning

This experiment explored the functional significance of age-related hemispheric asymmetry reduction associated with episodic memory and the cognitive mechanisms that mediate this brain pattern. ERPs were recorded while young and older adults performed a word-stem cued-recall task. Results confirmed that the parietal old/new effect was of larger latency and reduced magnitude and less lateralized in the older group than the young group. Correlational and regression analyses indicated that the degree of laterality of brain activity determines the accuracy of memory performance and mediates age-related differences in memory performance among older participants. They also confirmed a cascade model in which the individual level of executive functioning of older adults mediates age-related differences in the degree of lateralization of brain activity, which in turn mediates age-related differences in memory performance.

Does the greater involvement of executive control in memory with age act as a compensatory mechanism

Recent behavioural and imaging data have shown that memory functioning seems to rely more on executive functions and on the prefrontal cortex (PFC) in older than in young adults. Using a behavioural approach, our objective was to confirm the hypothesis that young and older adults present different patterns of correlation between episodic memory performance and executive functioning. We report three studies comparing the correlations of young and older adults in a broad range of episodic memory and executive function tasks. The results indicated that memory and executive performance were consistently and significantly correlated in older but not in younger adults. Regression analyses confirmed that age-related differences in episodic memory performance could be explained by individual differences in executive functioning. The results are consistent with the view that memory functioning in aging is accompanied by a shift from automatic to controlled forms of processing. They also generalise the executive hypothesis of episodic memory aging and are in line with the idea that executive functions act as a compensatory mechanism against age-related memory decline.

Neural correlates of cued recall in young and older adults: an event-related potential study.

This experiment investigated age differences in electrophysiological correlates of retrieval success in a word-stem cued recall task. Young adults (M±SD: 21.4 years±1.9) performed this memory task more accurately than older participants (M±SD: 65.1 years±3.3). Robust event-related brain potential (ERP) old/new effects were identified in both age groups. The main age differences were observed in latency and lateralization of ERP effects. Young adults exhibited a parietal effect that became focused over left parietal electrodes, whereas no asymmetry was observed in older adults. Moreover, ERP effects were more delayed in the older group. Overall, these findings provide some evidence of the reduction of processing speed during aging and suggest that young and older adults may recruit distinct cerebral patterns during episodic cued recall.

The amount of retrieval support modulates age effects on episodic memory: Evidence from event-related potentials

This experiment was designed to explore the impact of age and amount of retrieval support on episodic memory and its electrophysiological correlates. Event-related potentials (ERPs) were recorded while young and older participants performed a word-stem cued-recall task in a low-support condition (LSC) in which the stem was composed of three letters, and a high-support condition (HSC) in which the cue consisted of four letters. Behavioral analyses showed that recall in the older group was less accurate than in the young group in the LSC, but no age differences were observed in the HSC. In the LSC, old/new ERP effects at frontal and parietal sites were later and less sustained for the older adults. Furthermore, the parietal old/new effect was symmetrically distributed for older adults, whereas it was predominant over the left hemisphere for their younger counterparts. In addition, young participants demonstrated early and long-lasting frontal and parietal effects in the HSC but with predominance over the right hemisphere, whereas the older adults exhibited a frontal effect and an early and long-lasting parietal effect becoming predominant over the left hemisphere. No age differences in the time course of the parietal old/new effect were observed in this more supportive condition. In addition, in the last period, the left parietal effect was greater for the older group. This study suggests that episodic memory performance and ERP correlates of recall processes are more similar between young and older adults when increased support is provided at retrieval.

Differential Involvement of Knowledge Representation and Executive Control in Episodic Memory Performance in Young and Older Adults

Craik and Bialystok (2006, 2008) postulated that examining the evolution of knowledge representation and control processes across the life span could help in understanding age-related cognitive changes. The present study explored the hypothesis that knowledge representation and control processes are differentially involved in the episodic memory performance of young and older adults. Young and older adults were administered a cued-recall task and tests of crystallized knowledge and executive functioning to measure representation and control processes, respectively. Results replicate the classic finding that executive and cued-recall performance decline with age, but crystallized-knowledge performance does not. Factor analysis confirmed the independence of representation and control. Correlation analyses showed that the memory performance of younger adults was correlated with representation but not with control measures, whereas the memory performance of older adults was correlated with both representation and control measures. Regression analyses indicated that the control factor was the main predictor of episodic-memory performance for older adults, with the representation factor adding an independent contribution, but the representation factor was the sole predictor for young adults. This finding supports the view that factors sustaining episodic memory vary from young adulthood to old age; representation was shown to be important throughout adulthood, and control was also important for older adults. The results also indicated that control and representation modulate age-group-related variance in episodic memory.

Neural correlates of successful memory retrieval in aging: Do executive functioning and task difficulty matter?

The current experiment aimed to explore age differences in brain activity associated with successful memory retrieval in older adults with different levels of executive functioning, at different levels of task demand. Memory performance and fMRI activity during a recognition task were compared between a young group and two older groups characterized by a low (old-low group) vs. high (old-high group) level of executive functioning. Participants first encoded pictures, presented once (Hard condition) or twice (Easy condition), and then completed a recognition memory task. Old-low adults had poorer memory performance than the two other groups, which did not differ, in both levels of task demands. In the Easy condition, even though older adults demonstrated reduced activity compared to young adults in several regions, they also showed additional activations in the right superior frontal gyrus and right parietal lobule (positively correlated to memory accuracy) for the old-high group and in the right precuneus (negatively correlated to memory accuracy), right anterior cingulate gyrus and right supramarginal gyrus for the old-low group. In the Hard condition, some regions were also more activated in the young group than in the older groups. Vice versa, old-high participants demonstrated more activity than either the young or the old-low group in the right frontal gyrus, associated with more accurate memory performance, and in the left frontal gyrus. In sum, the present study clearly showed that age differences in the neural correlates of retrieval success were modulated by task difficulty, as suggested by the CRUNCH model, but also by interindividual variability, in particular regarding executive functioning.

Neural correlates of encoding processes predicting subsequent cued recall and source memory.

In this experiment, event-related potentials were used to examine whether the neural correlates of encoding processes predicting subsequent successful recall differed from those predicting successful source memory retrieval. During encoding, participants studied lists of words and were instructed to memorize each word and the list in which it occurred. At test, they had to complete stems (the first four letters) with a studied word and then make a judgment of the initial temporal context (i.e. list). Event-related potentials recorded during encoding were segregated according to subsequent memory performance to examine subsequent memory effects (SMEs) reflecting successful cued recall (cued recall SME) and successful source retrieval (source memory SME). Data showed a cued recall SME on parietal electrode sites from 400 to 1200 ms and a late inversed cued recall SME on frontal sites in the 1200–1400 ms period. Moreover, a source memory SME was reported from 400 to 1400 ms on frontal areas. These findings indicate that patterns of encoding-related activity predicting successful recall and source memory are clearly dissociated.