Memory aging and brain maintenance

Episodic memory and working memory decline with advancing age. Nevertheless, large-scale population-based studies document well-preserved memory functioning in some older individuals. The influential ‘reserve’ notion holds that individual differences in brain characteristics or in the manner people process tasks allow some individuals to cope better than others with brain pathology and hence show preserved memory performance. Here, we discuss a complementary concept, that of brain maintenance (or relative lack of brain pathology), and argue that it constitutes the primary determinant of successful memory aging. We discuss evidence for brain maintenance at different levels: cellular, neurochemical, gray- and white-matter integrity, and systems-level activation patterns. Various genetic and lifestyle factors support brain maintenance in aging and interventions may be designed to promote maintenance of brain structure and function in late life.     

Memory search and the neural representation of context

A challenge for theories of episodic memory is to determine how we focus memory search on a set of recently learned items. Cognitive theories suggest that the recall of an item representation is driven by an internally maintained context representation that integrates incoming information with a long time-scale. Neural investigations have shown that recalling an item revives the pattern of brain activity present during its study. To link these neural and cognitive approaches, we propose a framework in which context is maintained and updated in prefrontal cortex, and is associated with item information through hippocampal projections. The proposed framework is broadly consistent with neurobiological studies of temporal integration and with studies of memory deficits in individuals with prefrontal damage.     

Memory for context becomes less specific with time

Context memories initially require the hippocampus, but over time become independent of this structure. This shift reflects a consolidation process whereby memories are gradually stored in distributed regions of the cortex. The function of this process is thought to be the extraction of statistical regularities and general knowledge from specific experiences. The current study examined this idea in mice by measuring the specificity of context memories during consolidation. In the first experiment, separate groups of animals were trained with a single shock and tested in the training context or a novel environment 1, 14, 28, or 36 d later. We found a systematic increase in generalization over this period. Initially, mice froze more in the training context, but fear of the novel environment grew over time until animals eventually froze an equivalent amount in both contexts. The second experiment demonstrated that the increase in generalization was due to a loss of detailed information about the context and not fear incubation. In this experiment, mice were exposed to the context and then trained with an immediate shock 1 or 36 d later. Animals trained 1 d after exposure acquired robust context fear that did not generalize across environments. In contrast, mice trained 36 d after exposure froze an equivalent amount in the training context and the novel environment. The same profile was observed in H-ras mutants that exhibit enhanced hippocampal plasticity and learning. These results suggest that context memories are specific early after training when they require the hippocampus, and become more general as they are permanently stored in the cortex.     

Memory for contextual details: effects of emotion and aging

When individuals are confronted with a complex visual scene that includes some emotional element, memory for the emotional component often is enhanced, whereas memory for peripheral (nonemotional) details is reduced. The present study examined the effects of age and encoding instructions on this effect. With incidental encoding instructions, young and older adults showed this pattern of results, indicating that both groups focused attention on the emotional aspects of the scene. With intentional encoding instructions, young adults no longer showed the effect: They were just as likely to remember peripheral details of negative images as of neutral images. The older adults, in contrast, did not overcome the attentional bias: They continued to show reduced memory for the peripheral elements of the emotional compared with the neutral scenes, even with the intentional encoding instructions.     

Memory performance and beliefs as a function of goal setting and aging

This research examined the impact of goals on memory and memory beliefs. Older and younger adults completed memory beliefs questionnaires and list recall at baseline. After additional recall trials, the questionnaires were repeated. In Experiment 1, participants were assigned to low challenge or high challenge goals. In Experiment 2, moderate challenge goals were compared to control. In both studies, participants were given a specific goal based on their own performance and received positive feedback for memory gains. Both older and younger adults responded to the goals, showing improved performance across trials, with little change in the control condition. Memory beliefs changed in the moderate and low challenge goal conditions, showing more striking changes for the older groups. These results confirmed that self-regulatory processes related to goal setting can have considerable impact on memory across the adult life span.     

中国人口老龄化和社会转型背景下的社会代际关系

与以血缘及婚姻为基准的家庭代际关系不同,社会代际关系是一种社会秩序,也是一种社会结构,直接反映了社会利益在代际之间的分配状况.在人口老龄化和社会转型背景下,我国的社会代际关系呈现出新的特点,并将对社会经济发展产生重大影响.本文在探究社会代际关系的实质、内容和特征基础上,从法律规则、行政规制和社会规范等方面,探讨了如何构建我国社会代际关系调节机制.     

Memory and aging: Implications for theories of memory development during childhood

Research is reviewed suggesting that early school age children and older adults demonstrate a similar pattern of performance deficits (relative to the performance of young adults) on memory tasks, raising the possibility that age-related changes in some common factor might account for both memory development and memory decline. It is argued here that whereas “metamemory” theory of memory development does not provide a viable theory of memory decline, Craik's (F. I. M. Craik & M. Byrd, 1982, in F. I. M. Craik & S. E. Trehub (Eds.), Aging and cognitive processes, New York: Plenum; F. I. M. Craik & E. Simon, 1980, in L. W. Poon, J. L. Fozard, L. S. Cermak, D. Arenberg, & L. W. Thompson (Eds.), New directions in memory and aging, Hillsdale, NJ: Erlbaum) attentional deficit theory of memory decline provides a viable theory of memory development as well. Evidence supporting this position is reviewed, and directions for future research are discussed.     

Tests of the DRYAD theory of the age-related deficit in memory for context: not about context, and not about aging

Older adults exhibit a disproportionate deficit in their ability to recover contextual elements or source information about prior encounters with stimuli. A recent theoretical account, DRYAD, attributes this selective deficit to a global decrease in memory fidelity with age, moderated by weak representation of contextual information. The predictions of DRYAD are tested here in three experiments. We show that an age-related deficit obtains for whichever aspect of the stimulus subjects' attention is directed away from during encoding (Experiment 1), suggesting a central role for attention in producing the age-related deficit in context. We also show that an analogous deficit can be elicited within young subjects with a manipulation of study time (Experiment 2), suggesting that any means of reducing memory fidelity yields an interaction of the same form as the age-related effect. Experiment 3 evaluates the critical prediction of DRYAD that endorsement probability in an exclusion task should vary nonmonotonically with memory strength. This prediction was confirmed by assessing the shape of the forgetting function in a continuous exclusion task. The results are consistent with the DRYAD account of aging and memory judgments and do not support the widely held view that aging entails the selective disruption of processes involved in encoding, storing, or retrieving contextual information.     

Context processing and context maintenance in healthy aging and early stage dementia of the Alzheimer's type

Declines in the ability to process context information may represent a fundamental mechanism of age-related cognitive changes. Two components of context processing--activation/updating and maintenance--were examined in a sample of healthy younger and older adults, along with individuals suffering from early stage dementia of the Alzheimer's type (DAT). All older adult groups showed context activation/updating impairments, whereas context maintenance was only impaired in the oldest adults (age>75 years) and was further exacerbated in DAT individuals. The results suggest that context processing may be composed of functionally dissociable components and point to the utility of this construct in understanding the timecourse of cognitive decline in healthy and pathological aging.     

Memory for temporal context: effects of ageing, encoding instructions, and retrieval strategies

Young and older adults were compared on a list discrimination task. In Experiment 1, performance declined with ageing after incidental and intentional encoding of the temporal context. Moreover, there was no benefit for intentional encoding in either group. In Experiment 2, each list was associated with a different encoding context. There were age differences in performance when participants tried to retrieve the encoding context of the items as a cue for their list of occurrence, but not when participants evaluated temporal distance from the strength of the memory trace. This suggests that the age-related decrease in list discrimination could be at least partly due to a difficulty in inferring strategically the temporal context of the items from information encoded in the same time.     

Repeated study of items with and without repeated context: aging effects on memory discriminability

Presenting items multiple times during encoding is a common way to enhance recognition accuracy. Under such conditions, older adults often show an increase in false recognition that counteracts benefits of repeated study. Using a false-memory paradigm with related study items and related lures, we tested whether repetition within the same encoding task or repetition across two different encoding tasks would be more beneficial to older adults’ memory discriminability. Results showed that, compared to items not repeated at study, items repeated in the same context and items repeated across different contexts showed improvements in memory discriminability in both young and older adults. This improvement was primarily reflected in improved recollection responses for both age groups across both repeat study conditions, as compared to no repetition. Importantly, the results demonstrated that repetition can be used to successfully mitigate age-related deficits by increasing memory discriminability and without incurring a cost of false recognition specific to any one age group.     

Memory for in-group and out-group information in a minimal group context: the self as an informational base

The authors argue that persons derive in-group expectancies from self-knowledge. This implies that perceivers process information about novel in-groups on the basis of the self-congruency of this information and not simply its valence. In Experiment 1, participants recalled more negative self-discrepant behaviors about an in-group than about an out-group. Experiment 2 replicated this effect under low cognitive load but not under high load. Experiment 3 replicated the effect using an idiographic procedure. These findings suggest that perceivers engage in elaborative inconsistency processing when they encounter negative self-discrepant information about an in-group but not when they encounter negative self-congruent information. Participants were also more likely to attribute self-congruent information to the in-group than to the out-group, regardless of information valence. Implications for models of social memory and self-categorization theory are discussed.     

The production of false recognition and the associated state of consciousness following encoding in a naturalistic context in aging

Using virtual reality, we implemented a naturalistic variant of the DRM paradigm in young and older adults to evaluate false recall and false recognition. We distinguished false recognition related to the highest semantic association (the critical lures), semantic similarity (i.e. items that belong to the same semantic category), and perceptual similarity (i.e. items that are similar, but not identical in terms of shape or color). The data revealed that younger adults recalled and recognized more correct elements than older adults did while the older adults intruded more critical items than younger adults. Both age groups produced false recognition related to the critical items, followed by perceptually and then semantically related items. False recognitions were highly recollective as they were mainly associated with a sense of remembering, even more so in older adults than in young adults. The decline of executive functions and working memory predicted age-related increases in false memories.     

A benefit of context reinstatement to recognition memory in aging: the role of familiarity processes

Reinstatement of encoding context facilitates memory for targets in young and older individuals (e.g., a word studied on a particular background scene is more likely to be remembered later if it is presented on the same rather than a different scene or no scene), yet older adults are typically inferior at recalling and recognizing target–context pairings. This study examined the mechanisms of the context effect in normal aging. Age differences in word recognition by context condition (original, switched, none, new), and the ability to explicitly remember target–context pairings were investigated using word–scene pairs (Experiment 1) and word–word pairs (Experiment 2). Both age groups benefited from context reinstatement in item recognition, although older adults were significantly worse than young adults at identifying original pairings and at discriminating between original and switched pairings. In Experiment 3, participants were given a three-alternative forced-choice recognition task that allowed older individuals to draw upon intact familiarity processes in selecting original pairings. Performance was age equivalent. Findings suggest that heightened familiarity associated with context reinstatement is useful for boosting recognition memory in aging.     

Effect of aging differs for memory of object identity and object position within a spatial context

There has been considerable focus on investigating age-related memory changes in cognitively healthy older adults, in the absence of neurodegenerative disorders. Previous studies have reported age-related domain-specific changes in older adults, showing increased difficulty encoding and processing object information but minimal to no impairment in processing spatial information compared with younger adults. However, few of these studies have examined age-related changes in the encoding of concurrently presented object and spatial stimuli, specifically the integration of both spatial and nonspatial (object) information. To more closely resemble real-life memory encoding and the integration of both spatial and nonspatial information, the current study developed a new experimental paradigm with novel environments that allowed for the placement of different objects in different positions within the environment. The results show that older adults have decreased performance in recognizing changes of the object position within the spatial context but no significant differences in recognizing changes in the identity of the object within the spatial context compared with younger adults. These findings suggest there may be potential age-related differences in the mechanisms underlying the representations of complex environments and furthermore, the integration of spatial and nonspatial information may be differentially processed relative to independent and isolated representations of object and spatial information.

Advancing age is associated with changes in a number of cognitive domains (Erickson and Barnes 2003; Salthouse 2004; Craik and Bialystok 2006). Particularly age-related changes in episodic memory function have been frequently reported (Grady and Craik 2000; Craik and Bialystok 2006). In addition to a general decline in long-term retention, older adults show a reduced ability to differentiate between highly similar object representations (Yassa et al. 2011; Stark et al. 2013, 2015; Reagh et al. 2016; Berron et al. 2018) and object features (Yeung et al. 2017) compared with young adults. In contrast, spatial representations appear to be relatively spared (Fidalgo et al. 2016; Stark and Stark 2017) with older adults showing performance similar to young adults recognizing subtle changes in a spatial environment (Berron et al. 2018) and changes in the location of an object when presented on a blank screen (Reagh et al. 2016, 2018).The dissociation and integration of object and spatial information has been a key question in memory research. Older adults show significant impairments in memory binding and maintaining associations despite having intact memory for the individual items (Chalfonte and Johnson 1996; Naveh-Benjamin 2000; Old and Naveh-Benjamin 2008). This is also observed in object-location binding with impairments in recalling the specific location of objects (Kessels et al. 2007; Berger-Mandelbaum and Magen 2019; Muffato et al. 2019) as well as recalling the identity of an object within an environment (Schiavetto et al. 2002; Kessels et al. 2007; Mazurek et al. 2015). The binding of object-location information has been hypothesized to involve the medial temporal lobes, including the hippocampus (Postma et al. 2008), although age-related changes in the prefrontal cortex, posterior neocortex and other regions have also been implicated in object location and object identity tasks (Schiavetto et al. 2002; Meulenbroek et al. 2010). In the medial temporal lobes, the integration of object and spatial information is thought to arise from two parallel information processing streams (Eichenbaum 1999; Eichenbaum et al. 1999; Davachi 2006; Ranganath and Ritchey 2012; Knierim et al. 2013). One pathway, commonly referred to as the “what” pathway involves the perirhinal cortex and the lateral entorhinal cortex, and is thought to predominately process information about objects, items and events, while the “where” pathway involving the parahippocampal cortex and the medial entorhinal cortex is thought to process contextual and spatial information. Information from both pathways is projected to the hippocampus, which is then thought to integrate the spatial and nonspatial information into a cohesive “memory space” through a mechanism that is common to both object or episodic and spatial information (Eichenbaum et al. 1999).However, emerging evidence suggests the processing of object and spatial information may be more integrated than previously thought with the lateral entorhinal cortex processing multimodal information, receiving both object and spatial information (Witter et al. 2017; Doan et al. 2019; Nilssen et al. 2019). In rodent studies, the lateral entorhinal cortex has been reported to be involved in the encoding of features from both the object and the environment (Deshmukh and Knierim 2011; Yoganarasimha et al. 2011; Deshmukh et al. 2012; Knierim et al. 2013). Rodent studies using single cell recordings in the lateral entorhinal cortex show that neurons in this region encode object-related information as well as spatial information about the object (e.g., position in relationship to the environment). These studies also show cells in the lateral entorhinal cortex that track the position of an object in the environment and do not fire when that object is no longer present (Deshmukh and Knierim 2011). A different subset of cells (“object trace cells”) have been reported to fire in previously experienced positions of an object within an environment (Deshmukh and Knierim 2011; Tsao et al. 2013). Lateral entorhinal cortex lesioned rodents show no impairment in performing an object-recognition task, but are impaired at recognizing spatial changes and object changes within a set of objects in an environment including position changes of the objects (Van Cauter et al. 2013) and previously learned object-place and object-context associations (Wilson et al. 2013a; Chao et al. 2016). Together, these findings suggest that, beyond encoding information about objects, the lateral entorhinal cortex encodes contextual information and may be binding nonspatial and spatial information, specifically encoding information about objects and certain spatial properties, including information about the object''s position within environment.Few studies have examined the role of the lateral entorhinal cortex in encoding object identity, object position or changes to the spatial context in humans. Reagh and Yassa (2014) report that subtle perceptual differences between similar objects (e.g., two slightly different apples) elicits activity observed with functional magnetic resonance imaging (fMRI) in both the lateral entorhinal cortex and perirhinal cortex, while changes to an object''s position on a blank screen elicited activity in both the parahippocampal cortex and medial entorhinal cortex. Subsequent studies in older adults show impaired performance recalling the identity of object (Reagh and Yassa 2014; Stark and Stark 2017; Yeung et al. 2017; Berron et al. 2018; Reagh et al. 2018) but similar performance recalling position of the object on a screen compared with young adults (Reagh et al. 2016, 2018). However, these studies examined memory for object identity and object position on a blank screen, devoid of any spatial or contextual information. Given the findings from rodent studies, it appears that object identity and object position information are represented in relationship to the spatial environment in which they occur.To examine the integration of nonspatial and spatial information, novel stimuli were developed to mimic real-life environments where objects could occur within the environment, more closely resembling animal studies in which rodents experience objects within an environment. A series of scenes were designed to have the same perspective, spatial dimensions and outdoor scenery (Fig. 1A). Scenes were classified into five general categories: living room, dining room, kitchen, bedroom, and office rooms to allow for the placement of categorically congruent furniture (Fig. 1B). Critically, within each scene, two to five different positions were defined that an object could logically occupy (Fig. 1C). The scene stimuli were first validated using mnemonic ratings and subsequently used in a novel object-in-context task to assess memory for object identity and object position in context and examine age-related changes in performance on this task in cognitively normal older adults compared with young adults.Open in a separate windowFigure 1.Task stimuli. (A) Scenes were designed to have identical dimensions and a similar perspective. (B) Scenes were designed to have two to five different positions where an object could be reasonably placed. Across all scenes, the same general positions were available for object placement. (C) Example of a scene with an object as seen by the participant. No object was present in the scenes for the stimulus validation study.     

Memory systems in the rat: effects of reward probability,context, and congruency between working and reference memory

The interaction of working and reference memory was studied in rats on an eight-arm radial maze. In two experiments, rats were trained to perform working memory and reference memory tasks. On working memory trials, they were allowed to enter four randomly chosen arms for reward in a study phase and then had to choose the unentered arms for reward in a test phase. On reference memory trials, they had to learn to visit the same four arms on the maze on every trial for reward. Retention was tested on working memory trials in which the interval between the study and test phase was 15 s, 15 min, or 30 min. At each retention interval, tests were performed in which the correct WM arms were either congruent or incongruent with the correct RM arms. Both experiments showed that congruency interacted with retention interval, yielding more forgetting at 30 min on incongruent trials than on congruent trials. The effect of reference memory strength on the congruency effect was examined in Experiment 1, and the effect of associating different contexts with working and reference memory on the congruency effect was studied in Experiment 2.     

Studying individual aging in an interindividual context: typical paths of age-related, dementia-related, and mortality-related cognitive development in old age

This study has 2 objectives: (a) to explore typical paths of cognitive development associated with aging, terminal decline, and dementia and (b) to promote and illustrate an individual-oriented approach to the study of cognitive aging based on longitudinal panel data from a population-based sample (N = 500; age range-sub(T1)= 60-80, where T refers to time) tested at 3 occasions 5 years apart. Results document interindividual differences in multivariate patterns of change. Although cognitive changes generally covary, the present study indicates that subgroups of individuals develop along different paths characterized by selective changes in subsets of cognitive functions. Typical progression of dementia followed a developmental cascade from low declarative memory, via low functioning across all observed cognitive measures, to dementia diagnosis, and finally, death.