Memory Trajectories Before and After First and Recurrent Strokes

Background and objectivesThe evidence on timing of memory change after first and recurrent strokes is limited and inconsistent. We investigated memory trajectories before and after first and recurrent strokes in eighteen European countries, and tested whether the country-level acute stroke care was associated with memory change after stroke.MethodsData were from the Survey of Health, Ageing and Retirement in Europe (2004–2019). Incident first and recurrent strokes were identified among baseline stroke-free individuals. Within each country, each participant with incident stroke (case group) was matched with a stroke-free individual (control group) using the Propensity Score Matching. We applied multilevel segmented linear regression to quantify acute and accelerated memory changes (measured by the sum score of immediate and delayed word recall tests; 0–20 words) before and after first and recurrent strokes in both groups. Associations between stroke and memory were compared between countries with different levels of acute stroke care indicators.ResultsThe final analytical sample included 35,164 participants who were stroke-free at baseline (≥50 years). 2,362 incident first and 341 recurrent strokes between 2004 and 2019 were identified. In case group, mean acute decreases in memory scores were 0.48 (95% confidence interval: 0.31, 0.65) and 1.14 (95% confidence interval: 0.80, 1.48) words after first and recurrent stroke, respectively, independent of a range of confounders. No such acute decreases were observed in control group after a hypothetical non-stroke onset date. In both groups, memory declined over time but decline rates were similar (-0.07 [95% confidence interval: -0.10, -0.05] versus -0.06 [95% confidence interval: -0.08, -0.05] words per year). The mean acute decreases in memory scores after first and recurrent strokes were smaller in countries with better access to endovascular treatment.DiscussionWe found acute decreases but not accelerated declines in memory after first and recurrent strokes. Improved endovascular therapy might be associated with smaller memory loss after stroke but more evidence based on individual-level data is needed. More effort should be made in early assessment and intensive prevention of stroke among the ageing population, and promoting access to and delivery of acute stroke care among patients with stroke.

Episodic memory enhancement versus impairment is determined by contextual similarity across events

For over a century, stability of spatial context across related episodes has been considered a source of memory interference, impairing memory retrieval. However, contemporary memory integration theory generates a diametrically opposite prediction. Here, we aimed to resolve this discrepancy by manipulating local context similarity across temporally disparate but related episodes and testing the direction and underlying mechanisms of memory change. A series of experiments show that contextual stability produces memory integration and marked reciprocal strengthening. Variable context, conversely, seemed to result in competition such that new memories become enhanced at the expense of original memories. Interestingly, these patterns were virtually inverted in an additional experiment where context was reinstated during recall. These observations 1) identify contextual similarity across original and new memories as an important determinant in the volatility of memory, 2) present a challenge to classic and modern theories on episodic memory change, and 3) indicate that the sensitivity of context-induced memory changes to retrieval conditions may reconcile paradoxical predictions of interference and integration theory.

Mechanisms of Memory Updating: State Dependency vs. Reconsolidation

Reactivating a memory trace has been argued to put it in a fragile state where it must undergo a stabilization process known as reconsolidation. During this process, memories are thought to be susceptible to interference and can be updated with new information. In the spatial context paradigm, memory updating has been shown to occur when new information is presented in the same spatial context as old information, an effect attributed to a reconsolidation process. However, the integration concept holds that memory change can only occur when reactivation and test states are the same, similar to a state-dependent effect. Thus, in human episodic memory, memory updating should only be found when state is the same across the study, reactivation, and test sessions. We investigated whether memory updating can be attributed to state dependency in two experiments using mood as a state. We found evidence of memory updating only when mood was the same across all sessions of the experiments, lending support to the integration concept and posing a challenge to a reconsolidation explanation.

Systems consolidation, transformation and reorganization: Multiple Trace Theory, Trace Transformation Theory and their Competitors

We review the literature on systems consolidation by providing a brief history of the field to place the current research in proper perspective. We cover the literature on both humans and non-humans, which are highly related despite the differences in techniques and tasks that are used. We argue that understanding the interactions between hippocampus and neocortex (and other structures) that underlie systems consolidation, depend on appreciating the close correspondence between psychological and neural representations of memory, as postulated by Multiple Trace Theory and Trace Transformation Theory. We end by evaluating different theories of systems consolidation in light of the evidence we reviewed and suggest that the concept of systems consolidation, with its central concern with the time-limited role the hippocampus plays in memory, may have outlived its usefulness. We suggest replacing it with a program of research on the psychological processes and neural mechanisms that underlie changes in memory across the lifetime – a natural history of memory change.

Temporal Trends in Stroke-Related Memory Change

Background and Purpose: Findings from the Framingham Heart Study suggest that declines in dementia incidence rates over recent decades are partially due to decreases in stroke incidence and mortality; however, whether trends of declining dementia rates extend to survivors of incident stroke remains unclear. We investigated evidence for temporal trends in memory change related to incident stroke in a nationally representative cohort. Methods: Adults age 50+ in the HRS (Health and Retirement Study) were followed across three successive 6-year epochs (epoch 1: 1998–2004, n=16 781; epoch 2: 2004–2010, n=15 345; and epoch 3: 2010–2016; n=15 949). Participants were included in an epoch if they were stroke-free at the start of that epoch. Annual rates of change in a composite z-standardized memory score were compared using demographic-adjusted linear regression models for stroke-free participants, those who survived after stroke, and those who died after stroke, considering memory change before stroke, at the time of stroke, and for years following stroke. Results: Crude stroke incidence rates decreased from 8.5 per 1000 person-years in epoch 1 to 6.8 per 1000 person-years in epoch 3. Rates of memory change before and following stroke onset were similar across epochs. Memory decrement immediately after stroke onset attenuated from −0.37 points (95% CI, −0.44 to −0.29) in epoch 1 to −0.26 (95% CI, −0.33 to −0.18) points in epoch 2 and −0.25 (95% CI, −0.33 to −0.17) points in epoch 3 ( P value for linear trend=0.02). Conclusions: Decreases in stroke-related dementia in recent years may be partially attributable to smaller memory decrements immediately after stroke onset. Findings suggest reductions in stroke incidence and improvements in stroke care may also reduce population burden of dementia. Further investigations into whether temporal trends are attributable to improvements in stroke care are needed.

Episodic memory enhancement versus impairment is determined by contextual similarity across events

For over a century, stability of environmental context across related episodes has been considered a source of memory interference. However, contemporary memory integration theory generates a diametrically opposite prediction. Here, we aimed to resolve this discrepancy by manipulating local context similarity across temporally disparate but related episodes, and testing the direction and underlying mechanisms of memory change. A series of experiments show that contextual stability produces memory integration and marked reciprocal strengthening, whereas variable context results in one memory to dominate at a related memory’s expense. Intriguingly, however, retrieval patterns reversed when the original encoding contexts were reintroduced during memory recall. These observations (i) identify environmental context during new learning and subsequent recall as opposing determinants in the volatility of memory, (ii) present a challenge to several classic and modern theories on episodic memory change, and (iii) reconcile paradoxical predictions of memory interference and integration.

The Impact of Memory Change on Everyday Life Among Older Adults: Association with Cognition and Self-Reported Memory

Objectives: Many older adults experience memory changes that can have a meaningful impact on their everyday lives, such as restrictions to lifestyle activities and negative emotions. Older adults also report a variety of positive coping responses that help them manage these changes. The purpose of this study was to determine how objective cognitive performance and self-reported memory are related to the everyday impact of memory change. Methods: We examined these associations in a sample of 94 older adults (age 60–89, 52% female) along a cognitive ability continuum from normal cognition to mild cognitive impairment. Results: Correlational analyses revealed that greater restrictions to lifestyle activities (|rs| = .36–.66), more negative emotion associated with memory change (|rs| = .27–.76), and an overall greater burden of memory change on everyday living (|rs| = .28–.61) were associated with poorer objective memory performance and lower self-reported memory ability and satisfaction. Performance on objective measures of executive attention was unrelated to the impact of memory change. Self-reported strategy use was positively related to positive coping with memory change (|r| = .26), but self-reported strategy use was associated with more negative emotions regarding memory change (|r| = .23). Conclusions: Given the prevalence of memory complaints among older adults, it is important to understand the experience of memory change and its impact on everyday functioning in order to develop services that target the specific needs of this population.

Religiosity, Cognition, and Engagement in Advance Care Planning Among Older Adults

Advance care planning (ACP) is an important process of discussion and documentation that may help older adults receive the end-of-life care they prefer. Although existing literature predominantly finds greater self-reported religiosity to decrease the rates of ACP, a clear consensus is not yet evident. Data from 3,182 adults aged 55 and older participating in the 2012 wave of the Health and Retirement Study were used to investigate this association and examine the moderating role of cognition. Participants reporting at least one of two ACP behaviors (written instructions and assigning a health care proxy) were categorized as formal planning only, engaging in only informal discussions was categorized as informal planning, and those who completed both or none were categorized accordingly. Cognition was measured using self-reported memory change over the last two years and with objective cognitive testing scores. Using multinomial logistic regression, three forms of ACP behaviors were regressed on a religiosity/spirituality scale, the two cognition measures, and demographic and psychosocial covariates. Greater religiosity was associated with a lower likelihood of engaging in both plans compared to none (OR=0.91, 95%CI=0.84-0.97), however this effect was no longer significant with the inclusion of race. Higher cognitive scores were associated with greater odds of engaging in informal-only (OR=1.07, 95%CI=1.04-1.10) and both plans (OR=1.04, 95%CI=1.01-1.06); subjective memory change was not associated with ACP. Neither cognitive measure significantly moderated the negative association of religiosity on ACP, suggesting that the awareness of worsening memory does not undermine the tendency to avoid planning among the highly religious.