Semantic relatedness corrects the age-related binding deficit in working memory and episodic memory

Objectives: It is well-known that age differentially impacts aspects of long-term episodic memory (EM): Whereas a binding deficit indicates that older adults are less capable than younger adults to encode or retrieve associations between information (e.g., the pairing between two memoranda, such as lock –race), item memory is relatively intact (e.g., recognizing lock without its original pairing). Method: We tested whether this deficit could be corrected by facilitating establishment of the bindings in working memory (WM) through adapting the semantic relatedness of studied pairs according to participants’ ongoing performance(Experiments 1 and 2).We also examined whether this was evident for the long-term retention of pairs that were not tested in WM (Experiment 2). Results: The results revealed matched binding and item memory in WM and EM between age groups. Most importantly, older adults required increased semantic strength between word pairs to achieve similar performance to that of younger adults, regardless of whether pairs were immediately tested during the WM task. Discussion: These findings indicate that relying on their superior semantic memory can correct the commonly exhibited profound deficit in binding memory in older age

Neural differentiation is moderated by age in scene- but not face-selective cortical regions

The aging brain is characterized by neural dedifferentiation, an apparent decrease in the functional selectivity of category-selective cortical regions. Age-related reductions in neural differentiation have been proposed to play a causal role in cognitive aging. Recent findings suggest, however, that age-related dedifferentiation is not equally evident for all stimulus categories and, additionally, that the relationship between neural differentiation and cognitive performance is not moderated by age. In light of these findings, in the present experiment, younger and older human adults (males and females) underwent fMRI as they studied words paired with images of scenes or faces before a subsequent memory task. Neural selectivity was measured in two scene-selective (parahippocampal place area (PPA) and retrosplenial cortex (RSC)] and two face-selective [fusiform face area (FFA) and occipital face area (OFA)] regions using both a univariate differentiation index and multivoxel pattern similarity analysis. Both methods provided highly convergent results, which revealed evidence of age-related reductions in neural dedifferentiation in scene-selective but not face-selective cortical regions. Additionally, neural differentiation in the PPA demonstrated a positive, age-invariant relationship with subsequent source memory performance (recall of the image category paired with each recognized test word). These findings extend prior findings suggesting that age-related neural dedifferentiation is not a ubiquitous phenomenon, and that the specificity of neural responses to scenes is predictive of subsequent memory performance independently of age

The retrieval-related anterior shift is moderated by age and correlates with memory performance

Recent research suggests that episodic memory is associated with systematic differences in the localization of neural activity observed during memory encoding and retrieval. The retrieval-related anterior shift is a phenomenon whereby the retrieval of a stimulus event (e.g., a scene image) is associated with a peak neural response which is localized more anteriorly than the response elicited when the stimulus is experienced directly. Here, we examine whether the magnitude of the anterior shift (i.e., the distance between encoding- and retrieval-related response peaks) is moderated by age, and also whether the shift is associated with memory performance. Younger and older human subjects of both sexes underwent fMRI as they completed encoding and retrieval tasks on word-face and word-scene pairs. We localized peak scene and face selectivity for each individual participant within the face-selective precuneus and in three scene-selective (parahippocampal place area [PPA], medial place area, occipital place area) ROIs. In line with recent findings, we identified an anterior shift in the PPA and occipital place area in both age groups and, in older adults only, in the medial place area and precuneus also. Of importance, the magnitude of the anterior shift was larger in older than in younger adults. The shift within the PPA exhibited an age-invariant across-participant negative correlation with source memory performance, such that a smaller displacement between encoding- and retrieval-related neural activity was associated with better performance. These findings provide novel insights into the functional significance of the anterior shift, especially in relation to memory decline in older age

Semantic Relatedness Corrects the Age-Related Binding Deficit in Working Memory and Episodic Memory

It is well-known that age differentially impacts aspects of long-term episodic memory (EM): Whereas a binding deficit indicates that older adults are less capable than younger adults to encode or retrieve associations between information (e.g., the pairing between two memoranda, such as lock – race), item memory is relatively intact (e.g., recognizing lock without its original pairing). We tested whether this deficit could be corrected by facilitating establishment of the bindings in working memory (WM) through adapting the semantic relatedness of studied pairs according to participants’ ongoing performance (Experiments 1 and 2). We also examined whether this was evident for the long-term retention of pairs that were not tested in WM (Experiment 2). The results revealed matched binding and item memory in WM and EM between age groups. Most importantly, older adults required increased semantic strength between word pairs to achieve similar performance to that of younger adults, regardless of whether pairs were immediately tested during the WM task. These findings indicate that relying on their superior semantic memory can correct the commonly exhibited profound deficit in binding memory in older age

Effects of age on neural reinstatement during memory retrieval

Here, we review studies examining the effects of age on neural reinstatement – retrieval-related reactivation of the patterns of neural activity which were elicited when the remembered event was first experienced. Although the findings are mixed, the balance of the evidence suggests that age-related reductions in reinstatement are largely attributable to reductions in the selectivity with which later remembered events were neurally represented as they were encoded. The implications of these findings for the understanding of age-related memory decline are discussed, as are other findings indicating that reinstatement is accompanied by a representational transformation of the encoded information

Age-Related Neural Dedifferentiation and Cognition

This review focuses on possible contributions of neural dedifferentiation to age-related cognitive decline. Neural dedifferentiation is held to reflect a breakdown in the functional specificity of brain regions and networks that compromises the fidelity of neural representations supporting episodic memory and related cognitive functions. The evidence for age-related dedifferentiation is robust when it is operationalized as neural selectivity for different categories of perceptual stimuli or as decreased segregation or modularity of resting-state functional brain networks. Neural dedifferentiation for perceptual categories appears to demonstrate a negative, age-invariant relationship with performance on tests of memory and fluid processing. Whether this pattern extends to network-level measures of dedifferentiation cannot currently be determined due to insufficient evidence. The existing data highlight the importance of further examination of neural dedifferentiation as a factor contributing to episodic memory and to cognitive performance more generally