Recollection, not familiarity, decreases in healthy ageing: Converging evidence from four estimation methods

Implicit auditory memory in older listeners: From encoding to 6-month retention

Any listening task, from sound recognition to sound-based communication, rests on auditory memory which is known to decline in healthy ageing. However, how this decline maps onto multiple components and stages of auditory memory remains poorly characterised. In an online unsupervised longitudinal study, we tested ageing effects on implicit auditory memory for rapid tone patterns. The test required participants (younger, aged 20-30, and older adults aged 60-70) to quickly respond to rapid regularly repeating patterns emerging from random sequences. Patterns were novel in most trials (REGn), but unbeknownst to the participants, a few distinct patterns reoccurred identically throughout the sessions (REGr). After correcting for processing speed, the response times (RT) to REGn should reflect the information held in echoic and short-term memory before detecting the pattern; long-term memory formation and retention should be reflected by the RT advantage (RTA) to REGr vs REGn which is expected to grow with exposure. Older participants were slower than younger adults in detecting REGn and exhibited a smaller RTA to REGr. Computational simulations using a model of auditory sequence memory indicated that these effects reflect age-related limitations both in early and long-term memory stages. In contrast to ageing-related accelerated forgetting of verbal material, here older adults maintained stable memory traces for REGr patterns up to 6 months after the first exposure. The results demonstrate that ageing is associated with reduced short-term memory and long-term memory formation for tone patterns, but not with forgetting, even over surprisingly long timescales.

Aging and Alzheimer's disease have dissociable effects on local and regional medial temporal lobe connectivity

Functional disruption of the medial temporal lobe-dependent networks is thought to underlie episodic memory deficits in aging and Alzheimer's disease. Previous studies revealed that the anterior medial temporal lobe is more vulnerable to pathological and neurodegenerative processes in Alzheimer's disease. In contrast, cognitive and structural imaging literature indicates posterior, as opposed to anterior, medial temporal lobe vulnerability in normal aging. However, the extent to which Alzheimer's and aging-related pathological processes relate to functional disruption of the medial temporal lobe-dependent brain networks is poorly understood. To address this knowledge gap, we examined functional connectivity alterations in the medial temporal lobe and its immediate functional neighbourhood-the Anterior-Temporal and Posterior-Medial brain networks-in normal agers, individuals with preclinical Alzheimer's disease and patients with Mild Cognitive Impairment or mild dementia due to Alzheimer's disease. In the Anterior-Temporal network and in the perirhinal cortex, in particular, we observed an inverted 'U-shaped' relationship between functional connectivity and Alzheimer's stage. According to our results, the preclinical phase of Alzheimer's disease is characterized by increased functional connectivity between the perirhinal cortex and other regions of the medial temporal lobe, as well as between the anterior medial temporal lobe and its one-hop neighbours in the Anterior-Temporal system. This effect is no longer present in symptomatic Alzheimer's disease. Instead, patients with symptomatic Alzheimer's disease displayed reduced hippocampal connectivity within the medial temporal lobe as well as hypoconnectivity within the Posterior-Medial system. For normal aging, our results led to three main conclusions: (i) intra-network connectivity of both the Anterior-Temporal and Posterior-Medial networks declines with age; (ii) the anterior and posterior segments of the medial temporal lobe become increasingly decoupled from each other with advancing age; and (iii) the posterior subregions of the medial temporal lobe, especially the parahippocampal cortex, are more vulnerable to age-associated loss of function than their anterior counterparts. Together, the current results highlight evolving medial temporal lobe dysfunction in Alzheimer's disease and indicate different neurobiological mechanisms of the medial temporal lobe network disruption in aging versus Alzheimer's disease.

The vertical position of visual information conditions spatial memory performance in healthy aging

Memory for objects and their location is a cornerstone of adequate cognitive functioning across the lifespan. Considering that human visual perception depends on the position of stimuli within the visual field, we posit that the position of objects in the environment may be a determinant aspect of mnemonic performance. In this study, a population of 25 young and 20 older adults completed a source-monitoring task with objects presented in the upper or lower visual field. Using standard Pr and multinomial processing tree analyses, we revealed that although familiarity-based item memory remained intact in older age, spatial memory was impaired for objects presented in the upper visual field. Spatial memory in aging is conditioned by the vertical position of information. These findings raise questions about the view that age-related spatial mnemonic deficits are attributable to associative dysfunctions and suggest that they could also originate from the altered encoding of object attributes.

Characterization of apathy-like behaviors in the 5xFAD mouse model of Alzheimer's disease

Most patients with Alzheimer's disease (AD) develop neuropsychiatric symptoms (NPS) alongside cognitive decline, and apathy is one of the most common symptoms. Few preclinical studies have investigated the biological substrates underlying NPS in AD. In this study, we used a cross-sectional design to characterize apathy-like behaviors and assess memory in 5xFAD and wildtype control mice at 6, 12, and 16 months of age. Nest building, burrowing, and marble burying were used to test representative behaviors of apathy, and a composite score of apathy-like behavior was generated from these assays. Soluble Aβ42 and plaques were quantified in the prefrontal cortex and hippocampus of the 5xFAD mice with the highest and lowest composite scores using ELISA and histology. Results suggest that 5xFAD mice develop significant apathy-like behaviors starting at 6 months of age that worsen with aging and are positively correlated with soluble Aβ42 and plaques in the prefrontal cortex and hippocampus. Our findings highlight the utility of studying NPS in mouse models of AD to uncover important relationships with underlying neuropathology.

Differential decay of gist and detail memory in older adults with amnestic mild cognitive impairment

Amnestic mild cognitive impairment (aMCI) has been identified as a risk factor for dementia due to Alzheimer's disease. The medial temporal structures, which are crucial for memory processing, are the earliest affected regions in the brains of patients with aMCI, and episodic memory performance has been identified as a reliable way to discriminate between patients with aMCI and cognitively normal older adults. However, whether the detail and gist memory of patients with aMCI and cognitively normal older adults decay differently remains unclear. In this study, we hypothesized that detail and gist memory would be retrieved differentially, with a larger group performance gap in detail memory than in gist memory. In addition, we explored whether an increasing group performance gap between detail memory and gist memory groups would be observed over a 14-day period. Furthermore, we hypothesized that unisensory (audio-only) and multisensory (audiovisual) encoding would lead to differences in retrievals, with the multisensory condition reducing between and within-group performance gaps observed under the unisensory condition. The analyses conducted were analyses of covariance controlling for age, sex, and education and correlational analyses to examine behavioral performance and the association between behavioral data and brain variables. Compared with cognitively normal older adults, the patients with aMCI performed poorly on both detail and gist memory tests, and this performance gap persisted over time. Moreover, the memory performance of the patients with aMCI was enhanced by the provision of multisensory information, and bimodal input was significantly associated with medial temporal structure variables. Overall, our findings suggest that detail and gist memory decay differently, with a longer lasting group gap in gist memory than in detail memory. Multisensory encoding effectively reduced or overcame the between- and within-group gaps between time intervals, especially for gist memory, compared with unisensory encoding.

Unfamiliar face matching ability predicts the slope of face learning

We provide the first examination of individual differences in the efficiency of face learning. Investigating individual differences in face learning can illuminate potential mechanisms and provide greater understanding of why certain individuals might be more efficient face learners. Participants completed two unfamiliar face matching tasks and a learning task in which learning was assessed after viewing 1, 3, 6, and 9 images of to-be-learned identities. Individual differences in the slope of face learning (i.e., increases in sensitivity to identity) were predicted by the ability to discriminate between matched (same-identity) vs. mismatched (different-identity) pairs of wholly unfamiliar faces. A Dual Process Signal Detection model showed that three parameters increased with learning: Familiarity (an unconscious type of memory that varies in strength), recollection-old (conscious recognition of a learned identity), and recollection-new (conscious/confident rejection of novel identities). Good (vs. poor) matchers had higher Recollection-Old scores throughout learning and showed a steeper increase in Recollection-New. We conclude that good matchers are better able to capitalize on exposure to within-person variability in appearance, an effect that is attributable to their conscious memory for both learned and novel faces. These results have applied implications and will inform contemporary and traditional models of face identification.

Adult age differences in subjective context retrieval in dual-list free recall

Age-related episodic memory deficits imply that older and younger adults differentially retrieve and monitor contextual features that indicate the source of studied information. Such differences have been shown in subjective reports during recognition and cued recall as well as process estimates derived from computational models of free recall organisation. The present study extends the subject report method to free recall to characterise age differences in context retrieval and monitoring, and to test assumptions from a context-based computational model. Older and younger adults studied two lists of semantically related words and then recalled from only the first or second list. After each recall, participants indicated their subjective context retrieval using remember/know judgments. Compared to younger adults, older adults showed lower recall accuracy and subjective reports of context retrieval (i.e., remember judgments) that were less specific to correct recalls. These differences appeared after first-recall attempts. Recall functions conditioned on serial positions were more continual across correct recalls from target lists and intrusions from non-target lists for older than younger adults. Together with other analyses of context retrieval and monitoring reported here, these findings suggest that older adults retrieved context less distinctively across the recall period, leading to greater perceived similarity for temporally contiguous lists.

Aging and Alzheimer's Disease Have Dissociable Effects on Medial Temporal Lobe Connectivity

Functional disruption of the medial temporal lobe-dependent networks is thought to underlie episodic memory deficits in aging and Alzheimer's disease. Previous studies revealed that the anterior medial temporal lobe is more vulnerable to pathological and neurodegenerative processes in Alzheimer's disease. In contrast, cognitive and structural imaging literature indicates posterior, as opposed to anterior, medial temporal lobe vulnerability in normal aging. However, the extent to which Alzheimer's and aging-related pathological processes relate to functional disruption of the medial temporal lobe-dependent brain networks is poorly understood. To address this knowledge gap, we examined functional connectivity alterations in the medial temporal lobe and its immediate functional neighborhood - the Anterior-Temporal and Posterior-Medial brain networks - in normal agers, individuals with preclinical Alzheimer's disease, and patients with Mild Cognitive Impairment or mild dementia due to Alzheimer's disease. In the Anterior-Temporal network and in the perirhinal cortex, in particular, we observed an inverted 'U-shaped' relationship between functional connectivity and Alzheimer's stage. According to our results, the preclinical phase of Alzheimer's disease is characterized by increased functional connectivity between the perirhinal cortex and other regions of the medial temporal lobe, as well as between the anterior medial temporal lobe and its one-hop neighbors in the Anterior-Temporal system. This effect is no longer present in symptomatic Alzheimer's disease. Instead, patients with symptomatic Alzheimer's disease displayed reduced hippocampal connectivity within the medial temporal lobe as well as hypoconnectivity within the Posterior-Medial system. For normal aging, our results led to three main conclusions: (1) intra-network connectivity of both the Anterior-Temporal and Posterior-Medial networks declines with age; (2) the anterior and posterior segments of the medial temporal lobe become increasingly decoupled from each other with advancing age; and, (3) the posterior subregions of the medial temporal lobe, especially the parahippocampal cortex, are more vulnerable to age-associated loss of function than their anterior counterparts. Together, the current results highlight evolving medial temporal lobe dysfunction in Alzheimer's disease and indicate different neurobiological mechanisms of the medial temporal lobe network disruption in aging vs. Alzheimer's disease.

Temporal and contextual binding in episodic memory in younger and older adults

Episodic memory (EM) is a subsystem responsible for storing and recalling information about the basic elements of an event in a binding manner. Some approaches consider the temporal element to be one of the basic components of EM (WWWhen paradigm), while others consider that the contextual component is able in practice to better represent this cognitive ability (WWWhich paradigm). The relationship of both paradigms simultaneously with other instruments for measuring EM has not been investigated in healthy older adults. Thus, the present study examined the performance of young and older adults on questions based on the WWWhen and WWWhich paradigms, investigating the relationship of these questions with episodic (Remember) and non-episodic (Know) strategies. The results showed that for the younger adults both the questions demonstrated to only be significantly related with the "remember" strategy. On the other hand, older adults presented a response pattern in which the "WWWhich" questions used only episodic strategies for their correct resolution. Aging appears to promote a substantial reduction in both "Remember" and "Know" strategies, mainly those associated with solving tasks based on the temporal element of EM.

Inflammation, depression, and anxiety related to recognition memory in young adults

Previous research suggests that common modifiable health risk factors (e.g., depression, anxiety, metabolic illness, inflammation) may have an impact on memory. In the present study, we sought to investigate relationships between a number of these health risk factors and two components of recognition memory (recollection and familiarity). Data were analyzed for 96 healthy young adults between 17 and 25 years old. Recollection and familiarity were measured using an associative recognition procedure involving unitized and unrelated word pairs, and regression analyses were used to relate recognition memory performance to physical health (inflammation via plasma IL-6 levels, central obesity via waste-to-hip ratio, and heart rate variability) and mental health (depression via CESD-R, stress via PSS, and state and personality trait anxiety via STAI) measures of modifiable risk factors. Together, these health variables predicted an additional 19% of the variance in recollection beyond what was accounted for by familiarity, and 15% of the variance in familiarity beyond what was accounted for by recollection. These effects were primarily driven by inflammation, depression, and trait anxiety, which were each significant (p < .05) independent predictors of recognition. Higher levels of depression and inflammation were related to worse recollection yet better familiarity. Higher levels of trait anxiety were related to better recollection but were not related to familiarity. These findings demonstrate complex relationships between these modifiable health risk factors and recognition memory. Future longitudinal and cross-sectional research is needed to further explore these relationships and determine whether or not poor health causes these changes in recognition.

Neural distinctiveness and reinstatement of hippocampal representations support unitization for associations

The medial temporal lobe (MTL) is critical to associative memory success, yet not all types of associations may be processed in a similar manner within MTL subregions. In particular, previous work suggests intra- and inter-item associations not only exhibit differences in overall rates of recollection, but also recruit different MTL subregions. Whereas intra-item associations, akin to unitization, take advantage of associations between within-item features, inter-item associations form links across discrete items. The current work examines the neural differences between these two types of associations using fMRI and multivoxel analyses. Specifically, the current study examines differences across face-occupation as a function of whether the pairing was viewed as a person performing the given job (intra-item binding) or a person saying they knew someone who had a particular job (inter-item binding). The results show that at encoding, successfully recollected neural patterns related to intra- and inter-item associations are distinct from one another in the hippocampus, parahippocampal and perirhinal cortex. Additionally, the two trial types are reinstated distinctly such that inter-item trials have higher neural reinstatement from encoding to retrieval compared to intra-item trials in the hippocampus. We conclude that intra- and inter- associative pairs may utilize similar neural regions that represent patterns of activation differentially at encoding. However, to reinstate information to the same degree (i.e., subsequently successfully recollected) inter-item associations, that are all encoded in the same manner, may be reinstated more similarly compared to intra-item associations that are encoded by imagining pairs differently and occupation specific. This may indicate that intra-item associations promote more efficient reinstatement.

Familiarity Deficits for Words and Objects in Amnestic Mild Cognitive Impairment in a Context Minimizing the Role of Recollection

OBJECTIVES

Amnestic mild cognitive impairment (aMCI) is associated with cortical thinning in perirhinal and entorhinal cortices, key regions of the brain supporting familiarity. Individuals with aMCI demonstrate familiarity deficits in their behavior, often repeating questions in the same conversation. While familiarity deficits in healthy aging are minimal, past studies measuring familiarity in aMCI have mixed results, perhaps due to the influence of recollection. We therefore used a paradigm that minimized the influence of recollection, and hypothesized that familiarity would be impaired in aMCI relative to age-matched controls, but not in healthy older adults relative to younger adults. We also hypothesized that familiarity deficits in aMCI would be greater for objects than words because the perirhinal cortex plays a significant role in visual discrimination.

METHODS

A sample of 36 younger adults, 38 cognitively intact older adults, and 30 older adults with aMCI made absolute frequency judgments for words and objects seen a variable number of times in an incidental encoding task. Estimates of familiarity were derived from correlating participants' frequency judgments with the actual frequency of presentation.

RESULTS

Familiarity was largely spared in healthy aging, with minor deficits in familiarity for words. Familiarity deficits were evident in aMCI comparably for words and objects.

DISCUSSION

The present research underscores the need to study familiarity in contexts minimizing recollection, particularly when comparing groups with different levels of recollection, and adds to our understanding of the phenomenology of aMCI. Familiarity deficits may provide an early biomarker of dementia risk.

Integrity of Neuronal Size in the Entorhinal Cortex Is a Biological Substrate of Exceptional Cognitive Aging

Average aging is associated with a gradual decline of memory capacity. SuperAgers are humans ≥80 years of age who show exceptional episodic memory at least as good as individuals 20-30 years their junior. This study investigated whether neuronal integrity in the entorhinal cortex (ERC), an area critical for memory and selectively vulnerable to neurofibrillary degeneration, differentiated SuperAgers from cognitively healthy younger individuals, cognitively average peers ("Normal Elderly"), and individuals with amnestic mild cognitive impairment. Postmortem sections of the ERC were stained with cresyl violet to visualize neurons and immunostained with mouse monoclonal antibody PHF-1 to visualize neurofibrillary tangles. The cross-sectional area (i.e., size) of layer II and layer III/V ERC neurons were quantified. Two-thirds of total participants were female. Unbiased stereology was used to quantitate tangles in a subgroup of SuperAgers and Normal Elderly. Linear mixed-effect models were used to determine differences across groups. Quantitative measurements found that the soma size of layer II ERC neurons in postmortem brain specimens were significantly larger in SuperAgers compared with all groups (p < 0.05)-including younger individuals 20-30 years their junior (p < 0.005). SuperAgers had significantly fewer stereologically quantified Alzheimer's disease-related neurofibrillary tangles in layer II ERC than Normal Elderly (p < 0.05). This difference in tangle burden in layer II between SuperAgers and Normal Elderly suggests that tangle-bearing neurons may be prone to shrinkage during aging. The finding that SuperAgers show ERC layer II neurons that are substantially larger even compared with individuals 20-30 years younger is remarkable, suggesting that layer II ERC integrity is a biological substrate of exceptional memory in old age.SIGNIFICANCE STATEMENT Average aging is associated with a gradual decline of memory. Previous research shows that an area critical for memory, the entorhinal cortex (ERC), is susceptible to the early formation of Alzheimer's disease neuropathology, even during average (or typical) trajectories of aging. The Northwestern University SuperAging Research Program studies unique individuals known as SuperAgers, individuals ≥80 years old who show exceptional memory that is at least as good as individuals 20-30 years their junior. In this study, we show that SuperAgers harbor larger, healthier neurons in the ERC compared with their cognitively average same-aged peers, those with amnestic mild cognitive impairment, and - remarkably - even compared with individuals 20-30 years younger. We conclude that larger ERC neurons are a biological signature of the SuperAging trajectory.

Forgetting rate for the familiarity and recollection components of recognition in amnestic mild cognitive impairment: A longitudinal study

Here we aimed to investigate the rate of forgetting of the familiarity and recollection components of recognition in patients at the onset of medial temporal lobe (MTL) pathology and destined to convert to Alzheimer's disease (AD). For this purpose, we conducted a longitudinal study of 13 patients who were diagnosed with amnestic mild cognitive impairment (a-MCI) at the first assessment and followed-up for 3 years. During this time, five patients converted to AD and eight remained in a stable condition of cognitive impairment. A group of 15 healthy subjects were enrolled as the control group (HC). In order to separately quantify the contribution of recollection and familiarity to recognition memory performance, the experimental sample was submitted to a modified version of Huppert and Piercy's procedure that included a Remember/Know paradigm. Data demonstrated that both stable and converter a-MCI patients forgot memory traces relative to the familiarity components of recognition at the same rate as HC. Conversely, converter a-MCI patients showed accelerated long-term forgetting specifically for the recollection component of recognition compared to stable a-MCI and HC. This is the first empirical demonstration that familiarity and recollection components of declarative memory are subject to different rates of forgetting in a-MCI patients as a function of their longitudinal clinical outcome. Our finding of accelerated long-term forgetting of the recollection component of recognition disclosed by converter a-MCI patients suggests that atrophy in the MTL not only interferes with the storage aspects but also disrupts the consolidation of memory traces.

The contribution of the left precuneus to emotion memory in migraine without aura patients

Background

The impact of migraine without aura (MWoA) on cognitive function remains controversial, especially given the sparse literature on emotional memory.

Methods

Twenty seven MWoA patients and 25 healthy controls (HCs) were enrolled in this cross-sectional study. Emotional memory behavior was evaluated by combining incidental encoding with intentional encoding of five emotional categories of visual stimulus [positive valence + high arousal (PH), negative valence + high arousal (NH), positive valence + low arousal (PL), negative valence + low arousal (NL), and neutral (N)]. The recollection performance (Pr) was measured and compared. Then, the neural relevance was explored by correlating the Pr with gray matter volume (GMV) and resting-state functional connectivity (rs-FC) based on structural and functional magnetic resonance imaging.

Results

No significant differences in recollection performance or emotional enhancement of memory effect were observed. However, MWoA patients were more sensitive to the valence and arousal of emotional stimuli under incidental encoding. Significantly, the Pr-PH under incidental encoding and Pr-PL under intentional encoding were negatively correlated with the GMV of the left precuneus, and the rs-FC between the left precuneus and putamen was positively correlated with Pr-PL under intentional encoding in MWoA patients.

Conclusion

Our study demonstrated the tendency for the influence of migraine on emotional memory and revealed the left precuneus as a critical contributor to recollection performance, providing novel insights for understanding emotional memory and its neural mechanisms in MWoA patients.

Episodic memory updating among older adults: moderating role of prior knowledge

Memory updating is an adaptive function that requires people's registry of changes of episodes. However, the research on the role of prior knowledge on memory updating among older adults is scant. We instructed young and older adults to learn two sets of pairs with overlapping scene (A) on Day 1 (A-B) and Day 2 (A-C) and tested the competing memories on Day 3. We further manipulated the schema-congruency between item (B/C) and scene (A). Young adults performed comparatively well in the A-B and A-C memory tests, and showed no difference under different congruency conditions. However, memory updating among older adults was moderated by prior knowledge, with better memory performance in A-C test relative to A-B test when the to-be-updated item C was schema-congruent, however, with poorer memory performance in the A-C test when the to-be-updated item is schema-incongruent. This study advances the understanding that prior knowledge significantly contributes to memory updating among older adults. They would experience retroactive interference when the to-be-updated memories were consistent with their prior knowledge, yet proactive interference when the to-be-updated memories were inconsistent with their prior knowledge. Meanwhile, prior knowledge among young adults does not affect memory updating, given that their memory patterns are consistent across congruency conditions.

Can the elderly take the action? - The influence of unitization induced by action relationships on the associative memory deficit

Healthy aging is associated with intact familiarity, whereas recollection, usually supporting associative memory, is attenuated. Accordingly, associative memory shows a stronger age-related decline than item memory. One approach to alleviate age-related associative memory deficits is to increase the contribution of familiarity to associative memory by creating encoding conditions that allow to integrate separate stimuli to an entity (unitization). The current study investigated whether bottom-up unitization can reduce age-related differences in associative memory. Younger (YA) and older adults (OA) studied associations between semantically unrelated objects, spatially arranged in a way that an action between these two objects is possible (unitized, e.g., emptying a bottle into a sneaker) or not (non-unitized). At test, participants distinguished intact from recombined and new object pairs. As expected, we found larger age differences for associative memory than for item memory. Additionally, the presence of action relationships supports memory performance in both age groups. In the event-related potentials (ERP) of the test phase, we observed an age-related attenuation of recollection and preserved familiarity independent of the action relationship condition. Considering comparisons including the recombined pairs, the ERP correlate of associative familiarity (i.e., intact vs. recombined) was present in OA for action-related pairs, whereas for YA, there was no evidence for enhanced familiarity for action-related pairs. In the late time window, ERP evidence for recollection for intact action-related object pairs was obtained independent of age group. In conclusion, both age groups benefited from unitization by action relationships but by different mechanisms. While YA show no associative familiarity for action-related object pairs but a general reliance on recollection for associations in action-related and -unrelated pairs, OA seem to rely more on familiarity for the specific arrangement of action-related pairs.

The dual-process perspective and the benefits of retrieval practice in younger and older adults

The testing effect is often considered a recollection-related phenomenon. However, recent work has observed a benefit of testing to both recollection and familiarity on immediate and delayed final tests. Further, although aging populations show marked declines in recollection, older and younger adults often benefit similarly from testing. This finding suggests that the testing effect in older adults may function via relatively preserved familiarity and lends further support to the hypothesis that the testing effect does not function solely via recollection-related processes. The current study builds on this work to better understand the mechanisms from the dual-process perspective that underlie the testing effect in both younger and older adults. To this end, younger (18-22 year old) and older (65-82 year old) adults studied words, took cued-recall tests on half of the words, and took a final Remember-Know recognition test on all words immediately or after a 1-day delay. At both delays, older and younger adults exhibited a testing effect in both recollection and familiarity, although the magnitude of the testing effect in recollection was reduced for older relative to younger adults. Implications for theories of the testing effect and its application in older adult populations are explored.

I remember it like it was yesterday: Age-related differences in the subjective experience of remembering

It has been frequently described that older adults subjectively report the vividness of their memories as being as high, or even higher, than young adults, despite poorer objective memory performance. Here, we review studies that examined age-related differences in the subjective experience of memory vividness. By examining vividness calibration and resolution, studies using different types of approaches converge to suggest that older adults overestimate the intensity of their vividness ratings relative to young adults, and that they rely on retrieved memory details to a lesser extent to judge vividness. We discuss potential mechanisms underlying these observations. Inflation of memory vividness with regard to the richness of memory content may stem from age-differences in vividness criterion or scale interpretation and psycho-social factors. The reduced reliance on episodic memory details in older adults may stem from age-related differences in how they monitor these details to make their vividness ratings. Considered together, these findings emphasize the importance of examining age-differences in memory vividness using different analytical methods and they provide valuable evidence that the subjective experience of remembering is more than the reactivation of memory content. In this vein, we recommend that future studies explore the links between memory vividness and other subjective memory scales (e.g., ratings of details or memory confidence) in healthy aging and/or other populations, as it could be used as a window to better characterize the cognitive processes that underpin the subjective assessment of the quality of recollected events.

A passive and objective measure of recognition memory in Alzheimer's disease using Fastball memory assessment

Earlier diagnosis of Alzheimer's disease requires biomarkers sensitive to associated structural and functional changes. While considerable progress has been made in the development of structural biomarkers, functional biomarkers of early cognitive change, unconfounded by effort, practice and level of education, are still needed. We present Fastball, a new EEG method for the passive and objective measurement of recognition memory, that requires no behavioural memory response or comprehension of the task . Younger adults, older adults and Alzheimer's disease patients (n = 20 per group) completed the Fastball task, lasting just under 3 min. Participants passively viewed rapidly presented images and EEG assessed their automatic ability to differentiate between images based on previous exposure, i.e. old/new. Participants were not instructed to attend to previously seen images and provided no behavioural response. Following the Fastball task, participants completed a two-alternative forced choice (2AFC) task to measure their explicit behavioural recognition of previously seen stimuli. Fastball EEG detected significantly impaired recognition memory in Alzheimer's disease compared to healthy older adults (P < 0.001, Cohen's d = 1.52), whereas behavioural recognition was not significantly different between Alzheimer's disease and healthy older adults. Alzheimer's disease patients could be discriminated with high accuracy from healthy older adult controls using the Fastball measure of recognition memory (AUC = 0.86, P < 0.001), whereas discrimination performance was poor using behavioural 2AFC accuracy (AUC = 0.63, P = 0.148). There were no significant effects of healthy ageing, with older and younger adult controls performing equivalently in both the Fastball task and behavioural 2AFC task. Early diagnosis of Alzheimer's disease offers potential for early treatment when quality of life and independence can be retained through disease modification and cognitive enhancement. Fastball provides an alternative way of testing recognition responses that holds promise as a functional marker of disease pathology in stages where behavioural performance deficits are not yet evident. It is passive, non-invasive, quick to administer and uses cheap, scalable EEG technology. Fastball provides a new powerful method for the assessment of cognition in dementia and opens a new door in the development of early diagnosis tools.

The effects of age on neural correlates of recognition memory: An fMRI study

Studies examining the effects of age on the neural correlates of recognition memory have yielded mixed results. In the present study, we employed a modified remember-know paradigm to compare the fMRI correlates of recollection and familiarity in samples of healthy young and older adults. After studying a series of words, participants underwent fMRI scanning during a test phase in which they responded "remember" to a test word if any qualitative information could be recollected about the study event. When recollection failed, participants signaled how confident they were that the test item had been studied. Young and older adults demonstrated statistically equivalent estimates of recollection and familiarity strength, while recognition memory accuracy was significantly lower in the older adults. Robust, age-invariant fMRI effects were evident in two sets of a priori defined brain regions consistently reported in prior studies to be sensitive to recollection and familiarity respectively. In addition, the magnitudes of 'familiarity-attenuation effects' in perirhinal cortex demonstrated age-invariant correlations with estimates of familiarity strength and memory accuracy, replicating prior findings. Together, the present findings add to the evidence that the neural correlates of recognition memory are largely stable across much of the healthy human adult lifespan.

Familiarity in Mild Cognitive Impairment as a Function of Patients' Clinical Outcome 4 Years Later

OBJECTIVES

The current study addresses the nature of memory difficulties in amnestic mild cognitive impairment (aMCI). Whereas recollection is consistently found to be impaired in aMCI, the results on familiarity are divergent. One potential factor that could explain this divergence in findings relates to the heterogeneity of aMCI patients, so that only those aMCI patients who develop Alzheimer disease (AD) may present with impaired familiarity. The present study aimed at testing this hypothesis.

METHODS

A group of 45 aMCI patients and a group of 26 healthy older adults performed a verbal recognition memory test with the Remember/Know paradigm to assess recollection and familiarity processes. All participants were followed for 4 years with clinical and neuropsychological testing. At the end of follow-up, 22 aMCI patients progressed to AD and 23 aMCI patients remained stable. Initial memory performance was compared between the 3 groups.

RESULTS

Whereas recollection was severely diminished in all aMCI patients, familiarity accuracy (and consequently global recognition accuracy) was found to be impaired only in aMCI patients who subsequently developed AD.

CONCLUSION

These findings suggest that the enrichment of the aMCI population with predementia stage patients may modulate the likelihood to observe familiarity deficits, and impaired global recognition accuracy may accompany incipient AD.

How Processing Fluency Contributes to the Old/New Effects of Familiarity and Recollection: Evidence From the Remember/Know Paradigm

Previous investigations have demonstrated FN400 and LPC, 2 event-related potential old/new effects that respectively reflect familiarity- and recollection-based processes in memory. However, it is unclear whether these effects are susceptible to processing fluency, particularly different types of processing fluency. To address this issue, applying a masked priming paradigm, we conducted an event-related potential experiment by manipulating semantic relations between the prime and the target as identical (reflecting perceptual fluency), thematically and taxonomically related (referring to conceptual fluency), and unrelated. A remember/know (R/K) judgment task in the test phase was used to distinguish familiarity- and recollection-based processes. Behaviorally, both task performance and response speed were modulated by the variables of priming condition, item type, and response type. All 4 priming conditions elicited significant FN400 and LPC. Compared with the K response, the R response was more relevant to the recollection-based processes reflected by LPC. Both FN400 and LPC were modulated by whether there was a response of R, K, or new. The former was susceptible only to conceptual fluency, and the latter was sensitive to both perceptual fluency and conceptual fluency, which offered telling evidence for the dual process model. Considerations for future investigations are proposed. See supplemental materials here: https://www.press.uillinois.edu/journals/ajp/media/evidence_in_remember_know_paradigm/

The effect of age on recollection is not moderated by differential estimation methods

Episodic memory performance declines with increasing age. It has sometimes been reported that this decline is more marked when episodic recollection is estimated by "objective" measures such as source memory performance than when it is estimated by "subjective" measures such as the "Remember/Know" procedure. Here, our main goal was to directly contrast recollection estimates derived from these procedures in the same samples of young and older participants (24 adults per age group, within-subjects manipulation of test procedure). Following identical study phases in which words were paired with either faces or scenes, participants' memories were assessed in separate test blocks using either Remember/Know or source memory procedures. Contrary to several prior reports, the deleterious effects of age on recollection estimates did not differ according to test type. Thus, we found no evidence that age differentially impacts subjective and objective recollection estimates. Additionally, and consistent with prior findings, effects of age on estimates of familiarity-driven recognition were small and non-significant.

Links between autobiographical memory richness and temporal discounting in older adults

When making choices between smaller, sooner rewards and larger, later ones, people tend to discount future outcomes. Individual differences in temporal discounting in older adults have been associated with episodic memory abilities and entorhinal cortical thickness. The cause of this association between better memory and more future-oriented choice remains unclear, however. One possibility is that people with perceptually richer recollections are more patient because they also imagine the future more vividly. Alternatively, perhaps people whose memories focus more on the meaning of events (i.e., are more "gist-based") show reduced temporal discounting, since imagining the future depends on interactions between semantic and episodic memory. We examined which categories of episodic details - perception-based or gist-based - are associated with temporal discounting in older adults. Older adults whose autobiographical memories were richer in perception-based details showed reduced temporal discounting. Furthermore, in an exploratory neuroanatomical analysis, both discount rates and perception-based details correlated with entorhinal cortical thickness. Retrieving autobiographical memories before choice did not affect temporal discounting, however, suggesting that activating episodic memory circuitry at the time of choice is insufficient to alter discounting in older adults. These findings elucidate the role of episodic memory in decision making, which will inform interventions to nudge intertemporal choices.

Mnemoscape: Supporting Older Adults' Event Memory Using Wearable Camera Photographs on an Immersive Interface

BACKGROUND

Wearable camera photographs have been shown to be an effective memory aid in people with and without memory impairment. Most studies using wearable cameras as a memory aid have presented photographs on a computer monitor and used a written diary or no review as a comparison. In this pioneering study, we took a new and innovative approach to wearable camera photograph review that embeds the photographs within a virtual landscape. This approach may enhance these benefits by reinstating the original environmental context to increase participants' sense of re-experiencing the event.

OBJECTIVE

We compare the traditional computer monitor presentation of wearable camera photographs and actively taken digital photographs with the presentation of wearable camera photographs in a new immersive interface that reinstates the spatiotemporal context.

METHODS

Healthy older adults wore wearable or took digital photographs during a staged event. The next day and 2 weeks later, they viewed wearable camera photographs on a computer monitor or in context on an immersive interface, or digital photographs.

RESULTS

Participants who viewed wearable camera photographs in either format recalled more details during photo viewing and subsequent free recall than participants who viewed digital photographs they had taken themselves.

CONCLUSION

Wearable camera photographs are an effective support for event memory, regardless of whether they are presented in context in an experience-near format.

Accelerated long-term forgetting is not evident in adults with genetic generalized epilepsy irrespective of the paradigm used

Accelerated long-term forgetting (ALF) is a recently discovered memory disorder characterized by intact acquisition and retention over short delays, followed by abnormally fast rates of forgetting. Accelerated long-term forgetting has been repeatedly found in children, but not in adults, with genetic generalized epilepsy (GGE). It is possible that this discrepancy is due to a difference in paradigms used in these studies. The current study aimed to determine whether adults with GGE displayed ALF using two paradigms, one that required complete learning and another one that did not. In addition, we explored the relationships with everyday memory difficulties, working memory, mood, and epilepsy variables. Fourteen adults with GGE were compared with 16 healthy controls on two verbal memory tests: a modified version of the California Verbal Learning Test learned to a criterion of 100% (complete learning) and Logical Memory from the Wechsler Memory Scale (Fourth Edition) presented only once (incomplete learning). Recall was tested at 2 min, 30 min, and 1 week, and recognition at 1 week only. Working memory, everyday memory, and mood were also assessed. We found no evidence of ALF on either of the two verbal memory paradigms on recall or recognition tests although patients displayed significantly poorer working memory. Moreover, patients with GGE reported significantly more memory difficulties in everyday life, and these were associated with greater mood disturbances but not with memory tests scores. Greater number of antiepileptic drugs and epilepsy severity also related to memory scores on some tests. Our study suggests that a difference in paradigms used to investigate ALF in children and adults with GGE is unlikely to explain the differences in findings. The study tentatively raises a hypothesis that developmental factors may play a role in ALF in patients with GGE; children with GGE may grow out of ALF. Nevertheless, this hypothesis would need to be tested in a longitudinal study that would follow patients from childhood to early adulthood.

Intact strategic retrieval processes in older adults: no evidence for age-related deficits in source-constrained retrieval

Aging is thought to involve impairments to cognitive control functions that support episodic memory, for example by enabling people to strategically constrain their retrieval search towards a specific context ("source") in order to facilitate retrieval of goal-relevant memories. The "memory-for-foils" paradigm investigates source-constrained retrieval by assessing whether incidental encoding of new foils during an old/new recognition test differs depending on the type of processing that was previously used during study of the old items in the test. If it does, it suggests that people process foils differently as a result of engaging in source-constrained retrieval attempts. Young adults typically show differences in incidental encoding foils, but such differences have not been found in older adults. Here, we compared source-constrained retrieval and reward effects on incidental foil encoding between younger and older adults, to assess if age-related reductions in strategic retrieval processing are accompanied by differences in responsiveness to external rewards. The results showed only minor effects of rewards on memory processing, in younger adults only. Contrary to prior findings, older adults had equivalent overall memory performance and spontaneously constrained retrieval to the same extent as the young group, showing that aging-related impairments to strategic retrieval processes are not inevitable.

Proactive interference in working memory is related to adult age and cognitive factors: cross-sectional and longitudinal evidence from the Betula study

In working memory (WM), successful maintenance of information is affected by interference. Older adults may be especially susceptible to the effects of interference, which may cause age-related cognitive impairments. A relative score of IC was derived from cross-sectional (n = 869) and longitudinal (n = 443) data to investigate (1) if IC is reduced in normal aging, (2) if individual differences in IC related to individual performance in other cognitive domains, and (3) if 5-year change in IC is related to change in general cognition. Older age was associated with reduced IC, but no decline in IC occurred over 5 years. Also, the ability to control interference in WM was related to performance in episodic memory, verbal fluency, and block design. We also found that IC mediates the relationship between age and cognition, suggesting that age-related cognitive decline is linked to IC. Finally, we demonstrate that change in IC was related to decline in episodic memory.

The importance of the ventromedial prefrontal cortex for associative memory in older adults: A latent structural equation analysis

Older adults show relatively minor age-related decline in memory for single items, while their memory for associations is markedly reduced. Inter-individual differences in memory function in older adults are substantial but the neurobiological underpinnings of such differences are not well understood. In particular, the relative importance of inter-individual differences in the medio-temporal lobe (MTL) and the lateral prefrontal cortex (PFC) for associative and item recognition in older adults is still ambiguous. We therefore aimed to first establish the distinction between inter-individual differences in associative memory (recollection-based) performance and item memory (familiarity-based) performance in older adults and subsequently link these two constructs to differences in cortical thickness in the MTL and lateral PFC regions, in a latent structural equation modelling framework. To this end, a sample of 160 older adults (65-75 years old) performed three intentional item-associative memory tasks, of which a subsample (n ​= ​72) additionally had cortical thickness measures in MTL and PFC regions of interest available. The results provided support for a distinction between familiarity-based item memory and recollection-based associative memory performance in older adults. Cortical thickness in the ventro-medial prefrontal cortex was positively correlated with associative recognition performance, above and beyond any relationship between item recognition performance and cortical thickness in the same region and between associative recognition performance and brain structure in the MTL (parahippocampus). The findings highlight the relative importance of the ventromedial prefrontal cortex in allowing for intentional recollection-based associative memory functioning in older adults.

A role for familiarity in supporting the testing effect over time

Endel Tulving (1985) drew a distinction between Remembering and Knowing, spurring a great deal of research on the memorial experiences of recollection and familiarity and their contribution to various phenomena in memory. More recently, studies have used this distinction to situate our understanding of the processes that contribute to the testing effect-or, the benefit of retrieval practice to later memory (see also Tulving, 1967). Using retention intervals of approximately 15 min or less between initial and final testing, several studies have found that initial testing magnifies estimates of recollection but not familiarity, regardless of whether a testing effect is revealed in overall recognition performance (Chan and McDermott, 2007). However, the efficacy of prior testing in enhancing memory has been shown to change over time, as have estimates of recollection and familiarity. Thus, the mechanisms that underlie the quintessential testing effect-one that occurs in overall recognition or recall over longer delays-are still uncertain. To investigate this issue, in two experiments, subjects studied word lists, took 3-letter stem cued-recall tests on half of the studied words, and completed a final recognition test in which estimates of recollection and familiarity were obtained via confidence (Experiment 1) or Remember-Know-New (Experiment 2) judgments. Critically, final recognition tests occurred either immediately, 1 day (Experiment 1 only), or 4 days after initial learning. At all retention intervals and in both methods of estimating recollection and familiarity on the final test (i.e. receiver-operating characteristic and remember-know analyses), initial testing magnified estimates of both recollection and familiarity. These findings suggest that the testing effect can result from changes in both processes and pose issues for theories of the testing effect that consider an exclusive role for recollection.

The Impact of Semantic Relatedness on Associative Memory in Aging Depending on the Semantic Relationships between the Memoranda

Background: Aging is characterized by a decline in associative memory. However, under some conditions, such as in the presence of semantic relatedness within the association, the age-related associative decline can be attenuated. In this study, we evaluated whether the nature of the semantic relationship between the memoranda (taxonomic versus thematic) could modulate the impact of semantic relatedness on older adults' associative memory. Methods: We assessed 40 young adults and 40 older adults' associative memory for associations that were either taxonomically-related, thematically-related, or unrelated. Results: While the main results showed age-related differences in all associative memory tasks without attenuation by semantic relatedness, the results after excluding 4 outlier older participants suggest that older adults' associative memory performance did not differ from that of young adults for thematically-related pairs, while there was an age-related difference in associative memory for taxonomically-related pairs as well as for unrelated pairs. Discussion: This could suggest that the nature of the semantic relationship between the memoranda can modulate the impact of semantic relatedness on older adults' associative memory performance, although the reason why this is not the case for all older participants still needs to be understood.

Neural evidence for age-related differences in representational quality and strategic retrieval processes

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.

Age doesn't matter much: hybrid visual and memory search is preserved in older adults

We tested younger and older observers' attention and long-term memory functions in a "hybrid search" task, in which observers look through visual displays for instances of any of several types of targets held in memory. Apart from a general slowing, search efficiency did not change with age. In both age groups, reaction times increased linearly with the visual set size and logarithmically with the memory set size, with similar relative costs of increasing load (Experiment 1). We replicated the finding and further showed that performance remained comparable between age groups when familiarity cues were made irrelevant (Experiment 2) and target-context associations were to be retrieved (Experiment 3). Our findings are at variance with theories of cognitive aging that propose age-specific deficits in attention and memory. As hybrid search resembles many real-world searches, our results might be relevant to improve the ecological validity of assessing age-related cognitive decline.

Age-Related Differences in the Impact of Prior Knowledge on Recognition Performance: A Face Recognition Study

Background/Study context: The dual-process hypothesis of memory and aging (DPHMA) postulates a decline of recollection with no decline in recognition. While the age-related recollection deficit is well-documented, any age-changes in the familiarity process remain unclear. Some studies have shown that familiar and meaningful material can enhance the recognition performance of older adults. The goal of the present study was to explore the impact of familiar material on age-related recognition-memory decline, using a dual-process approach.

METHODS

One hundred participants (50 young adults and 50 older adults) performed two recognition tasks using an unfamiliar and a famous face recognition task. A receiver operating characteristic (ROC) analysis was used to examine the memory processes underlying recognition memory.

RESULTS

The older adults showed lower performance on recognition accuracy and false alarms rate, only in the unfamiliar-face recognition task. A DPHMA-like pattern on unfamiliar-face recognition task was obtained. Prior knowledge in the famous-face recognition task improved recollection for older adults and no age-related deficit was found.

CONCLUSION

The present study suggests that episodic memory deficits in healthy aging are primarily driven by a recollection deficit while familiarity is relatively well spared. However, this age-related recollection deficit could be alleviated using knowledge-based material.

Phonological false recognition produced by bottom-up automatic activation in young and older people

Two experiments explored a new procedure to implicitly induce phonological false memories in young and older people. On the study tasks, half of the words were formed from half of the letters in the alphabet, whereas the remaining words were formed from all the letters in the alphabet. On the recognition tests, there were three types of non-studied new words: critical lures formed from the same half of the letters as the studied words; distractors formed from the other half of the letters not used, and distractors formed from all the letters in the alphabet. In both experiments, the results showed that, in both young and older people, critical lures produced more false recognitions than distractors composed of all the letters in the alphabet, which, in turn, produced more false alarms than distractors composed of the letters not used during the study. These results support the predictions of the activation/monitoring models, which assume that false memories are partly due to activation spreading from items (semantically or phonologically) related to the critical words.

Drawing as an Encoding Tool: Memorial Benefits in Younger and Older Adults

Background/Study Context. In a recent study, drawing pictures relative to writing words at encoding has been shown to benefit later memory performance in young adults. In the current study, we sought to test whether older adults' memory might also benefit from drawing as an encoding strategy. Our prediction was that drawing would serve as a particularly effective form of environmental support at encoding as it encourages a more detailed perceptual representation.

METHODS

Participants were presented 30 nouns, one at a time, and asked to either draw a picture or repeatedly write out the word, which was followed by a free recall test for all words (Experiment 1). In Experiment 2, we added an elaborative processing task in which we asked participants to list physical characteristics of the objects. In Experiment 3, we probed recognition memory for the words.

RESULTS

Of the words recalled in Experiment 1, a larger proportion had been drawn than written at encoding, and this effect was larger in older relative to younger adults. In Experiment 2, we demonstrated that drawing improves memory in both younger and older adults more than does an elaborative encoding task consisting of listing descriptive characteristics of the target nouns. In Experiment 3, older and younger adults drew or wrote out words at encoding, and subsequently provided Remember-Know-New recognition memory decisions. We showed that drawing reduced age-related differences in Remember responses.

CONCLUSIONS

We suggest that incorporating visuo-perceptual information into the memory trace, by drawing pictures at study, increases reliance of the memory trace on visual sensory regions, which are relatively intact in normal aging, relative to simply writing out or elaborately encoding words. Overall, results indicate that drawing is a highly valuable form of environmental support that can significantly enhance memory performance in older adults.

Distinguishing the precision of spatial recollection from its success: Evidence from healthy aging and unilateral mesial temporal lobe resection

Successful episodic recollection can vary in the precision of the information recalled. The hypothesis that recollection precision requires functional neuroanatomical contributions distinct from those required for recollection success remains controversial. Some findings in individuals with hippocampal lesions have indicated that precision is dependent on the hippocampus. However, other neuroimaging and lesion studies have implicated regions outside of the mesial temporal lobe (MTL) in precision, such as parietal cortex. To further elucidate distinctions of recollection precision versus success, we examined whether they were differentially sensitive to aging and to unilateral MTL lesions. Precision and success were measured using a novel task that required memory for item-location associations across different spatial contexts. We found impairments in recollection precision, but not success, in older adults (59-80 years) relative to younger adults (18-33 years). Recollection precision was also selectively impaired in individuals with unilateral MTL resections made to treat refractory epilepsy. Moreover, recollection precision was significantly worse when resections included the hippocampus compared to when only non-hippocampal MTL tissue was resected. These findings suggest that the MTL is critically involved in the high-resolution binding required to support spatial recollection precision, and thus provide evidence for functional neuroanatomical differences between recollection success and precision.

Hippocampal-targeted Theta-burst Stimulation Enhances Associative Memory Formation

The hippocampus plays a critical role in episodic memory, among other cognitive functions. However, few tools exist to causally manipulate hippocampal function in healthy human participants. Recent work has targeted hippocampal-cortical networks by performing TMS to a region interconnected with the hippocampus, posterior inferior parietal cortex (pIPC). Such hippocampal-targeted TMS enhances associative memory and influences hippocampal functional connectivity. However, it is currently unknown which stages of mnemonic processing (encoding or retrieval) are affected by hippocampal-targeted TMS. Here, we examined whether hippocampal-targeted TMS influences the initial encoding of associations (vs. items) into memory. To selectively influence encoding and not retrieval, we performed continuous theta-burst TMS before participants encoded object-location associations and assessed memory after the direct effect of stimulation dissipated. Relative to control TMS and baseline memory, pIPC TMS enhanced associative memory success and confidence. Item memory was unaffected, demonstrating a selective influence on associative versus item memory. The strength of hippocampal-pIPC functional connectivity predicted TMS-related memory benefits, which was mediated by parahippocampal and retrosplenial cortices. Our findings indicate that hippocampal-targeted TMS can specifically modulate the encoding of new associations into memory without directly influencing retrieval processes and suggest that the ability to influence associative memory may be related to the fidelity of hippocampal TMS targeting. These results support the notion that pIPC TMS may serve as a potential tool for manipulating hippocampal function in healthy participants. Nonetheless, future work combining hippocampal-targeted continuous theta-burst TMS with neuroimaging is needed to better understand the neural basis of TMS-induced memory changes.

Statistical learning for speech segmentation: Age-related changes and underlying mechanisms

Statistical learning (SL) is a powerful learning mechanism that supports word segmentation and language acquisition in infants and young adults. However, little is known about how this ability changes over the life span and interacts with age-related cognitive decline. The aims of this study were to: (a) examine the effect of aging on speech segmentation by SL, and (b) explore core mechanisms underlying SL. Across four testing sessions, young, middle-aged, and older adults were exposed to continuous speech streams at two different speech rates, both with and without cognitive load. Learning was assessed using a two-alterative forced-choice task in which words from the stream were pitted against either part-words, which occurred across word boundaries in the stream, or nonwords, which never appeared in the stream. Participants also completed a battery of cognitive tests assessing working memory and executive functions. The results showed that speech segmentation by SL was remarkably resilient to aging, although age effects were visible in the more challenging conditions, namely, when words had to be discriminated from part-words, which required the formation of detailed phonological representations, and when SL was performed under cognitive load. Moreover, an analysis of the cognitive test data indicated that performance against part-words was predicted mostly by memory updating, whereas performance against nonwords was predicted mostly by working memory storage capacity. Taken together, the data show that SL relies on a combination of implicit and explicit skills, and that age effects on SL are likely to be linked to an age-related selective decline in memory updating. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Impaired perceptual integration and memory for unitized representations are associated with perirhinal cortex atrophy in Alzheimer's disease

Unitization, the capacity to encode associations as one integrated entity, can enhance associative memory in populations with an associative memory deficit by promoting familiarity-based associative recognition. Patients with Alzheimer's disease (AD) are typically impaired in associative memory compared with healthy controls but do not benefit from unitization strategies. Using fragmented pictures of objects, this study aimed at assessing which of the cognitive processes that compose unitization is actually affected in AD: the retrieval of unitized representations itself, or some earlier stages of processing, such as the integration process at a perceptual or conceptual stage of representation. We also intended to relate patients' object unitization capacity to the integrity of their perirhinal cortex (PrC), as the PrC is thought to underlie unitization and is also one of the first affected regions in AD. We evaluated perceptual integration capacity and subsequent memory for those items that have supposedly been unitized in 23 mild AD patients and 20 controls. We systematically manipulated the level of perceptual integration during encoding by presenting object pictures that were either left intact, separated into 2 fragments, or separated into 4 fragments. Subjects were instructed to unitize the fragments into a single representation. Success of integration was assessed by a question requiring the identification of the object. Participants also underwent a structural magnetic resonance imaging examination, and measures of PrC, posterior cingulate cortex volume and thickness, and hippocampal volume, were extracted. The results showed that patients' perceptual integration performance decreased with the increased fragmentation level and that their memory for unitized representations was impaired whatever the demands in terms of perceptual integration at encoding. Both perceptual integration and memory for unitized representations were related to the integrity of the PrC, and memory for unitized representations was also related to the volume of the hippocampus. We argue that, globally, this supports representational theories of memory that hold that the role of the PrC is not only perceptual nor mnemonic but instead underlies complex object representation.

Shared Functions of Perirhinal and Parahippocampal Cortices: Implications for Cognitive Aging

A predominant view of perirhinal cortex (PRC) and postrhinal/parahippocampal cortex (POR/PHC) function contends that these structures are tuned to represent objects and spatial information, respectively. However, known anatomical connectivity, together with recent electrophysiological, neuroimaging, and lesion data, indicate that both brain areas participate in spatial and nonspatial processing. Instead of content-based organization, the PRC and PHC/POR may participate in two computationally distinct cortical-hippocampal networks: one network that is tuned to process coarse information quickly, forming gist-like representations of scenes/environments, and a second network tuned to process information about the specific sensory details that are necessary for discrimination across sensory modalities. The available data suggest that the latter network may be more vulnerable in advanced age.

Age-related Differences in Prestimulus Subsequent Memory Effects Assessed with Event-related Potentials

Prestimulus subsequent memory effects (preSMEs)-differences in neural activity elicited by a task cue at encoding that are predictive of later memory performance-are thought to reflect differential engagement of preparatory processes that benefit episodic memory encoding. We investigated age differences in preSMEs indexed by differences in ERP amplitude just before the onset of a study item. Young and older adults incidentally encoded words for a subsequent memory test. Each study word was preceded by a task cue that signaled a judgment to perform on the word. Words were presented for either a short (300 msec) or long (1000 msec) duration with the aim of placing differential benefits on engaging preparatory processes initiated by the task cue. ERPs associated with subsequent successful and unsuccessful recollection, operationalized here by source memory accuracy, were estimated time-locked to the onset of the task cue. In a late time window (1000-2000 msec after onset of the cue), young adults demonstrated frontally distributed preSMEs for both the short and long study durations, albeit with opposite polarities in the two conditions. This finding suggests that preSMEs in young adults are sensitive to perceived task demands. Although older adults showed no evidence of preSMEs in the same late time window, significant preSMEs were observed in an earlier time window (500-1000 msec) that was invariant with study duration. These results are broadly consistent with the proposal that older adults differ from their younger counterparts in how they engage preparatory processes during memory encoding.

Recollection-related increases in functional connectivity across the healthy adult lifespan

In young adults, recollection-sensitive brain regions exhibit enhanced connectivity with a widely distributed set of other regions during successful versus unsuccessful recollection, and the magnitude of connectivity change correlates with individual differences in recollection accuracy. Here, we examined whether recollection-related changes in connectivity and their relationship with performance varied across samples of young, middle-aged, and older adults. Psychophysiological interaction analyses identified recollection-related increases in connectivity both with recollection-sensitive seed regions and among regions distributed throughout the whole brain. The seed-based approach failed to identify age-related differences in recollection-related connectivity change. However, the whole-brain analysis revealed a number of age-related effects. Numerous pairs of regions exhibited a main effect of age on connectivity change, mostly due to decreased change with increasing age. After controlling for recollection accuracy, however, these effects of age were for the most part no longer significant, and those effects that were detected now reflected age-related increases in connectivity change. A subset of pairs of regions also exhibited an age by performance interaction, driven mostly by a weaker relationship between connectivity change and recollection accuracy with increasing age. We conjecture that these effects reflect age-related differences in neuromodulation.

Effects of Stimuli Repetition and Age in False Recognition

The aim of the current study is to examine the effects of stimuli repetition and age in false recognition using the Deese-Roediger-McDermott experimental paradigm. Two matched samples of 32 young adults and 32 healthy older adults studied 10 lists of six words associated with three non-presented critical words. On half of the lists, the words were presented once, and on the other five lists, the words were presented three times, always following a same sequential order. After each study list, participants performed a self-paced recognition test containing 12 words: the 6 studied words and 6 other non-studied words (the 3 critical words and 3 distractors). The results show that false recognition increases with age and declines in both samples with repetitions (although more in the young adults than in the older people). Results are discussed in relation to the dual-process theories of (false) memory.

Assumptions behind scoring source versus item memory: Effects of age, hippocampal lesions and mild memory problems

Source monitoring paradigms have been used to separate: 1) the probability of recognising an item (Item memory) and 2) the probability of remembering the context in which that item was previously encountered (Source memory), conditional on it being recognised. Multinomial Processing Tree (MPT) models are an effective way to estimate these conditional probabilities. Moreover, MPTs make explicit the assumptions behind different ways to parameterise Item and Source memory. Using data from six independent groups across two different paradigms, we show that one would draw different conclusions about the effects of age, age-related memory problems and hippocampal lesions on Item and Source memory, depending on the use of: 1) standard accuracy calculation vs MPT analysis, and 2) two different MPT models. The MPT results were more consistent than standard accuracy calculations, and furnished additional parameters that can be interpreted in terms of, for example, false recollection or missed encoding. Moreover, a new MPT structure that allowed for separate memory representations (one for item information and one for item-plus-source information; the Source-Item model) fit the data better, and provided a different pattern of significant differences in parameters, than the more conventional MPT structure in which source information is a subset of item information (the Item-Source model). Nonetheless, there is no theory-neutral way of scoring data, and thus proper examination of the assumptions underlying the scoring of source monitoring paradigms is necessary before theoretical conclusions can be drawn.

Declines in representational quality and strategic retrieval processes contribute to age-related increases in false recognition

In a Yes/No object recognition memory test with similar lures, older adults typically exhibit elevated rates of false recognition. However, the contributions of impaired retrieval, relative to reduced availability of target details, are difficult to disentangle using such a test. The present investigation sought to decouple these factors by comparing performance on a Yes/No (YN) test to that on a Forced Choice (FC) test, which minimizes demands on strategic retrieval processes, enabling a more direct measure of the availability of object details. Older adults exhibited increased lure false recognition across test formats (Experiment 1), suggesting a decline in the availability of object details contributes to deficits in performance. Manipulating interference by varying the number of objects studied selectively enhanced performance in the FC test, resulting in matched performance across groups, whereas age differences in YN performance persisted (Experiment 2), indicating an additional contribution of impaired strategic retrieval. Consistent with differential sensitivity of test format to strategic retrieval and the quality of stimulus representations among older adults, variability in the quality of object representations, measured using a perceptual discrimination task, was selectively related to FC performance. In contrast, variability in memory control processes, as measured with tests of recall and executive function, was related to performance across test formats. These results suggest that both declines in the availability of object details and impaired retrieval of object details contribute to elevated rates of lure false recognition with age, and highlight the utility of test format for dissociating these factors in memory-impaired populations.