Age Differences In Retrieval-Related Reinstatement Reflect Age-Related Dedifferentiation At Encoding.
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ABSTRACT:
SUBMITTER: Hill PF
PROVIDER: S-EPMC7727391 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:When sentence processing taxes verbal working memory, comprehension difficulties arise. This is specifically the case when processing resources decline with advancing adult age. Such decline likely affects the encoding of sentences into working memory, which constitutes the basis for successful comprehension. To assess age differences in encoding-related electrophysiological activity, we recorded the electroencephalogram from three age groups (24, 43, and 65 years). Using an auditory sentence comprehension task, age differences in encoding-related oscillatory power were examined with respect to the accuracy of the given response. That is, the difference in oscillatory power between correctly and incorrectly encoded sentences, yielding subsequent memory effects (SME), was compared across age groups. Across age groups, we observed an age-related SME inversion in the alpha band from a power decrease in younger adults to a power increase in older adults. We suggest that this SME inversion underlies age-related comprehension difficulties. With alpha being commonly linked to inhibitory processes, this shift may reflect a change in the cortical inhibition-disinhibition balance. A cortical disinhibition may imply enriched sentence encoding in younger adults. In contrast, resource limitations in older adults may necessitate an increase in cortical inhibition during sentence encoding to avoid an information overload. Overall, our findings tentatively suggest that age-related comprehension difficulties are associated with alterations to the electrophysiological dynamics subserving general higher cognitive functions.
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Project description:The goal of the present study was to investigate whether hippocampal contribution to episodic memory retrieval varies as a function of age (8-9 versus 10-11 versus adults), performance levels (high versus low) and hippocampal sub-region (head, body, tail). We examined fMRI data collected during episodic retrieval from a large sample (N=126). Participants judged whether a stimulus had been encoded previously, and, if so, which of three scenes it had been paired with (i.e., source judgment). For 8- to 9-years-olds as well as low-performing 10- to 11-year-olds, hippocampal activations did not reliably differentiate between trials on which item-scene associations were correctly recalled (correct source), incorrectly recalled (incorrect source), or trials on which the item was forgotten (miss trials). For high-performing 10-11-year olds and low-performing adults, selective hippocampal activation was observed for correct source relative to incorrect source and miss trials; this effect was observed across the entire hippocampus. For high-performing adults, hippocampal activation also distinguished between correct and incorrect source trialsl, but only in the hippocampal head, suggesting that good performance in adults is associated with more focal hippocampal recruitment. Thus, both age and performance are important factors for understanding the development of memory and hippocampal function.
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Project description:Although memory recall is known to be reduced with normal aging, little is known about the patterns of brain activity that accompany these recall failures. By assessing faulty memory, we can identify the brain regions engaged during retrieval attempts in the absence of successful memory and determine the impact of aging on this functional activity. We used functional magnetic resonance imaging to examine age differences in brain activity associated with memory failure in three memory retrieval tasks: autobiographical (AM), episodic (EM) and semantic (SM). Compared to successful memory retrieval, both age groups showed more activity when they failed to recall a memory in regions consistent with the salience network (SLN), a brain network also associated with non-memory errors. Both groups also showed strong functional coupling among SLN regions during incorrect trials and in intrinsic patterns of functional connectivity. In comparison to young adults, older adults demonstrated (1) less activity within the SLN during unsuccessful AM trials; (2) weaker intrinsic functional connectivity between SLN nodes and dorsolateral prefrontal cortex; and (3) less differentiation of SLN functional connectivity during incorrect trials across memory conditions. These results suggest that the SLN is engaged during recall failures, as it is for non-memory errors, which may be because errors in general have particular salience for adapting behavior. In older adults, the dedifferentiation of functional connectivity within the SLN across memory conditions and the reduction of functional coupling between it and prefrontal cortex may indicate poorer inter-network communication and less flexible use of cognitive control processes, either while retrieval is attempted or when monitoring takes place after retrieval has failed. This article is part of a Special Issue entitled SI: Memory & Aging.
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Project description:According to current models of episodic memory, the hippocampus binds together the neural representation of an experience during encoding such that it can be reinstated in cortex during subsequent retrieval. However, direct evidence linking hippocampal engagement during encoding with subsequent cortical reinstatement during retrieval is lacking. In this study, we aim to directly test the relationship between hippocampal activation during encoding and cortical reinstatement during retrieval. During a scanned encoding session, human participants studied Noun-Sound and Noun-Picture pairs. One day later, during a scanned retrieval session, participants retrieved the sounds and pictures when given the nouns as cues. First, we found that trial-by-trial hippocampal encoding activation was related to trial-by-trial reactivation during retrieval as measured by the univariate BOLD response in several modality-specific cortical regions. Second, using multivariate measures, we found a correlation between encoding-retrieval pattern similarity computed for each trial and hippocampal encoding activation on the corresponding encoding event, suggesting that the magnitude of hippocampal activation during an experience is related to the fidelity of subsequent reinstatement of cortical activity patterns during retrieval. Consistent with current theories of episodic memory, our findings demonstrate a critical link between initial hippocampal activation during an experience and subsequent cortical reinstatement.
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Project description:Functional magnetic resonance imaging (fMRI) was used to investigate whether age-related differences in episodic memory performance are accompanied by a reduction in the specificity of recollected information. We addressed this question by comparing recollection-related cortical reinstatement in young and older adults. At study, subjects viewed objects and concrete words, making 1 of 2 different semantic judgments depending on the study material. Test items were words that corresponded to studied words or the names of studied objects. Subjects indicated whether each test item was recollected, familiar, or novel. Reinstatement of information differentiating the encoding tasks was quantified both with a univariate analysis of the fMRI signal and with a multivoxel pattern analysis, using a classifier that had been trained to discriminate between the 2 classes of study episode. The results of these analyses converged to suggest that reinstatement did not differ according to age. Thus, there was no evidence that specificity of recollected information was reduced in older individuals. Additionally, there were no age effects in the magnitude of recollection-related modulations in regional activity or in the neural correlates of post-retrieval monitoring. Taken together, the findings suggest that the neural mechanisms engaged during successful episodic retrieval can remain stable with advancing age.
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Project description:Mounting behavioral evidence suggests that declines in both representational quality and controlled retrieval processes contribute to episodic memory decline with age. The present study sought neural evidence for age-related change in these factors by measuring neural differentiation during encoding of paired associates and changes in regional blood oxygenation level-dependent activity and functional connectivity during retrieval conditions that placed low (intact pairs) and high (recombined pairs) demands on controlled retrieval processes. Pattern similarity analysis revealed age-related declines in the differentiation of stimulus representations at encoding, manifesting as both reduced pattern similarity between closely related events and increased pattern similarity between distinct events. During retrieval, both groups increased recruitment of areas within the core recollection network when endorsing studied pairs, including the hippocampus and angular gyrus. In contrast, only younger adults increased recruitment of, and hippocampal connectivity with, lateral prefrontal regions during correct rejections of recombined pairs. These results provide evidence for age-related changes in representational quality and in the neural mechanisms supporting memory retrieval under conditions of high, but not low, control demand.
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Project description:Older adults often demonstrate a monitoring deficit by producing more high-confidence memory errors on recognition memory tests. To eliminate lower memory performance by older adults (OA) as a candidate explanation, we studied how distinctive encoding enhances the retrieval-monitoring accuracy in older adults and younger adults (YA) under different delays (2-day delay for OA, 7-day delay for YA). Individuals viewed items consisting of four randomly selected exemplars (e.g., SALMON, BASS, PERCH, and SHARK) from a taxonomic category (e.g., FISH), one being designated as the to-be-remembered target. Participants were randomly assigned to two encoding conditions: Shared (generate a shared feature of all exemplars, e.g., GILLS) or Distinctive (generate a distinctive feature of the designated target). We collected retrospective confidence judgments (RCJs) after a five-alternative forced-choice (5AFC) recognition test, with the lures being either previously presented (old) exemplars or new category exemplars. Recall and recognition memory were better with distinctive encoding, with shared feature generation producing more high-confidence false alarms (HCFAs). Distinctive encoding dramatically reduced HCFAs and improved RCJ resolution. Comparison of OA with 2-day delay YA revealed age differences in HCFA consistent with previous studies. As important, age differences in memory for OA and 7-day delay YA were minimized, eliminating age deficits in HCFAs. Matching OAs to a subset of 7-day delay YAs on recognition memory produced additional evidence favoring the null hypothesis of age-equivalence in HCFAs. The results therefore indicated that age differences in recognition-based retrieval monitoring in a forced-choice recognition test are an epiphenomenon of age differences in memory. (PsycInfo Database Record (c) 2021 APA, all rights reserved).
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