Successful Memory Aging Nyberg, Lars; Pudas, Sara
Annual review of psychology,
01/2019, Letnik:
70, Številka:
1
Journal Article
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For more than 50 years, psychologists, gerontologists, and, more recently, neuroscientists have considered the possibility of successful aging. How to define successful aging remains debated, but ...well-preserved age-sensitive cognitive functions, like episodic memory, is an often-suggested criterion. Evidence for successful memory aging comes from cross-sectional and longitudinal studies showing that some older individuals display high and stable levels of performance. Successful memory aging may be accomplished via multiple paths. One path is through brain maintenance, or relative lack of age-related brain pathology. Through another path, successful memory aging can be accomplished despite brain pathology by means of efficient compensatory and strategic processes. Genetic, epigenetic, and lifestyle factors influence memory aging via both paths. Some of these factors can be promoted throughout the life course, which, at the individual as well as the societal level, can positively impact successful memory aging.
Cognitive control is the foundation for attaining goals by flexible adaptation of action to changing environmental demands. It has been hypothesized to be critically dependent upon the prefrontal ...cortex (PFC). In this mini‐review, evidence for domain‐general versus domain‐specific cognitive control is examined, with a particular focus on attention and memory. The reviewed studies examined different levels of cognitive control in relation to performance and patterns of brain activity, and a few included direct comparisons of cognitive‐control modulations across cognitive domains. Within domains, increased demands on cognitive control consistently translated into increased PFC activity, but limited overlap in recruited PFC regions was observed between domains. It is concluded that the PFC supports multiple cognitive‐control systems that collectively may be conceived of as a distributed executive.
The brain is not idle during rest. Functional MRI (fMRI) studies have identified several resting-state networks, including the default mode network (DMN), which contains a set of cortical regions ...that interact with a hippocampus (HC) subsystem. Age-related alterations in the functional architecture of the DMN and HC may influence memory functions and possibly constitute a sensitive biomarker of forthcoming memory deficits. However, the exact form of DMN–HC alterations in aging and concomitant memory deficits is largely unknown. Here, using both task and resting data from 339 participants (25–80 y old), we have demonstrated age-related decrements in resting-state functional connectivity across most parts of the DMN, except for the HC network for which age-related elevation of connectivity between left and right HC was found along with attenuated HC–cortical connectivity. Elevated HC connectivity at rest, which was partly accounted for by age-related decline in white matter integrity of the fornix, was associated with lower cross-sectional episodic memory performance and declining longitudinal memory performance over 20 y. Additionally, elevated HC connectivity at rest was associated with reduced HC neural recruitment and HC–cortical connectivity during active memory encoding, which suggests that strong HC connectivity restricts the degree to which the HC interacts with other brain regions during active memory processing revealed by task fMRI. Collectively, our findings suggest a model in which age-related disruption in cortico–hippocampal functional connectivity leads to a more functionally isolated HC at rest, which translates into aberrant hippocampal decoupling and deficits during mnemonic processing.
Significance Aging is accompanied by disruptive alterations in large-scale brain systems, such as the default mode network (DMN) and the associated hippocampus (HC) subsystem, which support higher cognitive functions. However, the exact form of DMN–HC alterations and concomitant memory deficits is largely unknown. We identified age-related decrements in resting-state functional connectivity of the cortical DMN, whereas elevated connectivity between the bilateral HC was found along with attenuated HC–cortical connectivity. Critically, elevated HC at rest restricts the degree to which HC interacts with other brain regions during memory tasks, and thus results in memory deficits. This study provides empirical evidence of how the relationship between the DMN and HC breaks down in aging and how such alterations underlie deficient mnemonic processing.
•We performed the first meta-analysis of fMRI studies on working memory (WM) training.•We demonstrated that WM training modulates only the canonical WM network.•This general-purpose brain network was ...also modulated by perceptual-motor learning.•Only DLPFC/VLPFC was highlighted in WM training studies.
The present meta-analytic study examined brain activation changes following working memory (WM) training, a form of cognitive training that has attracted considerable interest. Comparisons with perceptual-motor (PM) learning revealed that WM training engages domain-general large-scale networks for learning encompassing the dorsal attention and salience networks, sensory areas, and striatum. Also the dynamics of the training-induced brain activation changes within these networks showed a high overlap between WM and PM training. The distinguishing feature for WM training was the consistent modulation of the dorso- and ventrolateral prefrontal cortex (DLPFC/VLPFC) activity. The strongest candidate for mediating transfer to similar untrained WM tasks was the frontostriatal system, showing higher striatal and VLPFC activations, and lower DLPFC activations after training. Modulation of transfer-related areas occurred mostly with longer training periods. Overall, our findings place WM training effects into a general perception-action cycle, where some modulations may depend on the specific cognitive demands of a training task.
Molecular-imaging studies of dopaminergic neurotransmission measure biomarkers of dopamine (DA), such as the DA transporter and D
1 and D
2 receptor densities in the living brain. These studies ...indicate that individual differences in DA functions are linked to cognitive performance irrespective of age, and serve as powerful mediators of age-related decline in executive functioning, episodic memory, and perceptual speed. This focused review targets several recent findings pertaining to these relationships. Specifically, we discuss novel evidence concerning (a) the role of DA in within-person cognitive variability; (b) age-related differences in DA release during cognitive processing; (c) DA release following cognitive training in younger and older adults; and (d) the relationship between DA and task-induced functional brain activity. Based on these lines of empirical inquiry, we outline a series of avenues for future research on aging, DA, and cognition.
Studies have shown that aerobic exercise has the potential to improve cognition and reduce brain atrophy in older adults. However, the literature is equivocal with regards to the specificity or ...generality of these effects. To this end, we report results on cognitive function and brain structure from a 6-month training intervention with 60 sedentary adults (64-78 years) randomized to either aerobic training or stretching and toning control training. Cognitive functions were assessed with a neuropsychological test battery in which cognitive constructs were measured using several different tests. Freesurfer was used to estimate cortical thickness in frontal regions and hippocampus volume. Results showed that aerobic exercisers, compared to controls, exhibited a broad, rather than specific, improvement in cognition as indexed by a higher "Cognitive score," a composite including episodic memory, processing speed, updating, and executive function tasks (
= 0.01). There were no group differences in cortical thickness, but additional analyses revealed that aerobic fitness at baseline was specifically related to larger thickness in dorsolateral prefrontal cortex (dlPFC), and hippocampus volume was positively associated with increased aerobic fitness over time. Moreover, "Cognitive score" was related to dlPFC thickness at baseline, but changes in "Cognitive score" and dlPFC thickness were associated over time in the aerobic group only. However, aerobic fitness did not predict dlPFC change, despite the improvement in "Cognitive score" in aerobic exercisers. Our interpretation of these observations is that potential exercise-induced changes in thickness are slow, and may be undetectable within 6-months, in contrast to change in hippocampus volume which in fact was predicted by the change in aerobic fitness. To conclude, our results add to a growing literature suggesting that aerobic exercise has a broad influence on cognitive functioning, which may aid in explaining why studies focusing on a narrower range of functions have sometimes reported mixed results.
Process-specific training can improve performance on untrained tasks, but the magnitude of gain is variable and often there is no transfer at all. We demonstrate transfer to a 3-back test of working ...memory after 5 weeks of training in updating. The transfer effect was based on a joint training-related activity increase for the criterion (letter memory) and transfer tasks in a striatal region that also was recruited pretraining. No transfer was observed to a task that did not engage updating and striatal regions, and age-related striatal changes imposed constraints on transfer. These findings indicate that transfer can occur if the criterion and transfer tasks engage specific overlapping processing components and brain regions.
Neuroimaging studies of the aging brain provide support that the strongest predictor of preserved memory and cognition in older age is brain maintenance, or relative lack of brain pathology. Evidence ...for brain maintenance comes from different levels of examination, but up to now relatively few studies have used a longitudinal design. Examining factors that promote brain maintenance in aging is a critical task for the future and may be combined with the use of new techniques for multimodal imaging.
Abstract There is marked variability in both onset and rate of episodic-memory decline in aging. Structural magnetic-resonance imaging (MRI) studies have revealed that the extent of age-related brain ...changes varies markedly across individuals. Past studies of whether regional atrophy accounts for episodic-memory decline in aging have yielded inconclusive findings. Here we related 15-year changes in episodic memory to 4-year changes in cortical and subcortical gray matter volume and in white-matter connectivity and lesions. In addition, changes in word fluency, fluid IQ (Block Design), and processing speed were estimated and related to structural brain changes. Significant negative change over time was observed for all cognitive and brain measures. A robust brain-cognition change-change association was observed for episodic-memory decline and atrophy in the hippocampus. This association was significant for older (65-80 years) but not middle-aged (55-60 years) participants and not sensitive to the assumption of ignorable attrition. Thus, these longitudinal findings highlight medial-temporal lobe system integrity as particularly crucial for maintaining episodic-memory functioning in older age.
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