Impaired retention is responsible for temporal order memory deficits in mild cognitive impairment

Effect of physio-cognitive dual-task training on cognition in pre-ageing and older adults with neurocognitive disorders: A meta-analysis and meta-regression of randomized controlled trial

Declines in cognitive performance, such as those seen in neurocognitive disorders (NCDs) are often associated with ageing. Both physical activity and cognitive training are common interventional strategies that can mitigate the decline in cognitive and physical performance. This review aims to (1) to evaluate the effects of Physio-Cognitive Dual-task Training (PCDT) intervention on cognition, physical performance, activities of daily living (ADL) and health-related quality of life (HRQoL) in pre-ageing and older adults with neurocognitive disorders, (2) explore the effects of covariates on intervention outcomes. A systematic search was conducted in eight databases. Cochrane's Risk of Bias Tool version 1 and GRADE criteria were used to assess risk of bias and certainty of evidence, respectively. Meta-analysis and meta-regression analyses were conducted using R software. Twenty-six randomized controlled trials involving 1,949 pre-ageing and older adults with NCDs were included in the meta-analysis. PCDT interventions had small-to-medium effect size on all cognition outcomes (g = 0.40-0.52) and instrumental ADL (g == 0.42), and a large effect size on HRQoL (g = 0.72). The quality of evidence was rated moderate to low for the outcome measures in pre-ageing and older adults with NCDs. These findings highlight the importance of PCDT interventions in preventing and slowing down cognitive impairment in pre-ageing and older adults. Registration: PROSPERO Number (CRD42020213962).

Time perspective and amnestic mild cognitive impairment

OBJECTIVE

We examined time perspective in patients with amnesic mild cognitive impairment (aMCI). Prior research has shown that aMCI is associated with difficulties in experiencing time duration and succession. However, this line of inquiry has not been extended to time perspective. We examined associations between aMCI and multiple dimensions of time perspective including perceived orientations and relationships among the past, present, and future.

METHOD

Thirty aMCI patients and thirty-three healthy controls participated. Measures were the Time Orientation Scale (TOS), the Time Relation Scale (TRS), and the Zimbardo Time Perspective Inventory (ZTPI), as well as a comprehensive neuropsychological evaluation.

RESULTS

The TRS was associated with aMCI. Patients with aMCI were more likely to perceive that time was unrelated than the healthy older adults. Among patients with aMCI, an unrelated time perspective was associated with poorer performance in executive function measures. However, aMCI was not associated with the TOS or the ZTPI.

CONCLUSIONS

Patients with aMCI have difficulty in perceiving relationships among the past, present, and future. This could be the consequence of deficits in executive functions. This research suggests that patients with aMCI may have limited understanding for how their current behaviours are related to both their past and future.

Relevance of a Novel Circuit-Level Model of Episodic Memories to Alzheimer's Disease

The medial temporal lobe memory system has long been identified as the brain region showing the first histopathological changes in early Alzheimer's disease (AD), and the functional decline observed in patients also points to a loss of function in this brain area. Nonetheless, the exact identity of the neurons and networks that undergo deterioration has not been determined so far. A recent study has identified the entorhinal and hippocampal neural circuits responsible for encoding new episodic memories. Using this novel model we describe the elements of the episodic memory network that are especially vulnerable in early AD. We provide a hypothesis of how reduced reelin signaling within such a network can promote AD-related changes. Establishing novel associations and creating a temporal structure for new episodic memories are both affected in AD. Here, we furnish a reasonable explanation for both of these previous observations.

EEG Alpha and Beta Band Functional Connectivity and Network Structure Mark Hub Overload in Mild Cognitive Impairment During Memory Maintenance

Background: While decreased alpha and beta-band functional connectivity (FC) and changes in network topology have been reported in Alzheimer’s disease, it is not yet entirely known whether these differences can mark cognitive decline in the early stages of the disease. Our study aimed to analyze electroencephalography (EEG) FC and network differences in the alpha and beta frequency band during visuospatial memory maintenance between Mild Cognitive Impairment (MCI) patients and healthy elderly with subjective memory complaints.

Methods: Functional connectivity and network structure of 17 MCI patients and 20 control participants were studied with 128-channel EEG during a visuospatial memory task with varying memory load. FC between EEG channels was measured by amplitude envelope correlation with leakage correction (AEC-c), while network analysis was performed by applying the Minimum Spanning Tree (MST) approach, which reconstructs the critical backbone of the original network.

Results: Memory load (increasing number of to-be-learned items) enhanced the mean AEC-c in the control group in both frequency bands. In contrast to that, after an initial increase, the MCI group showed significantly (p < 0.05) diminished FC in the alpha band in the highest memory load condition, while in the beta band this modulation was absent. Moreover, mean alpha and beta AEC-c correlated significantly with the size of medial temporal lobe structures in the entire sample. The network analysis revealed increased maximum degree, betweenness centrality, and degree divergence, and decreased diameter and eccentricity in the MCI group compared to the control group in both frequency bands independently of the memory load. This suggests a rerouted network in the MCI group with a more centralized topology and a more unequal traffic load distribution.

Conclusion: Alpha- and beta-band FC measured by AEC-c correlates with cognitive load-related modulation, with subtle medial temporal lobe atrophy, and with the disruption of hippocampal fiber integrity in the earliest stages of cognitive decline. The more integrated network topology of the MCI group is in line with the “hub overload and failure” framework and might be part of a compensatory mechanism or a consequence of neural disinhibition.

Serial position effects in the Logical Memory Test: Loss of primacy predicts amyloid positivity

BACKGROUND

Story recall is a frequently used neuropsychological test of episodic memory with clinical populations and for screening participants in drug trials for Alzheimer's disease. However, it is unclear at this stage which underlying mechanisms confer the test its sensitivity. In this paper, we examined serial position effects, that is, better recall for items learned early and late on a list, in story recall, and their usefulness to predict early changes associated with neurodegenerative markers.

METHODS

We analysed data from the Wisconsin Registry for Alzheimer's Prevention. First, we tested whether serial position effects were present in story recall (measured with the Wechsler Memory Scale Logical Memory Task; LMT) across individuals who were classified as cognitively unimpaired - stable, cognitively unimpaired - declining, or as having mild cognitive impairment (MCI).

RESULTS

Our results showed clear serial position effects for all groups, except for delayed recall among individuals with MCI, where no primacy effect was observed. Second, we tested whether loss of primacy from immediate to delayed recall was associated with amyloid burden (as measured with PiB PET) in individuals who were cognitively unimpaired at baseline. We found that more primacy loss predicted amyloid positivity, above and beyond the LMT total score.

CONCLUSIONS

This report is the first to show that loss of primacy between immediate and delayed story recall is associated with amyloid burden.

Temporal contiguity and ageing: The role of memory organization in cognitive decline

The temporal contiguity effect is the tendency to form associations between items presented in nearby study positions. In the present study, we explored whether temporal contiguity predicted conversion to cognitively unimpaired-declining (CUD) status from a baseline of unimpaired older adults. Data from 419 participants were drawn from the Wisconsin Registry of Alzheimer's Prevention (WRAP) data set and analysed with binary logistic regressions. Temporal contiguity was calculated using the Rey Auditory Verbal Learning Test. Other predictors included age, years of education, sex, APOE-ε4 status, and other measures of memory recall. Lower temporal contiguity predicted conversion to CUD after accounting for covariates. These findings support the hypothesis that temporal organization in memory is related to cognitive decline and suggest that temporal contiguity may be used for studies of early detection.

Age Differences in the Subcomponents of Executive Functioning

OBJECTIVES

Across the life span, deficits in executive functioning (EF) are associated with poor behavioral control and failure to achieve goals. Though EF is often discussed as one broad construct, a prominent model of EF suggests that it is composed of three subdomains: inhibition, set shifting, and updating. These subdomains are seen in both younger (YA) and older adults (OA), with performance deficits across subdomains in OA. Therefore, our goal was to investigate whether subdomains of EF might be differentially affected by age, and how these differences may relate to broader global age differences in EF.

METHODS

To assess these age differences, we conducted a meta-analysis at multiple levels, including task level, subdomain level, and of global EF. Based on previous work, we hypothesized that there would be overall differences in EF in OA.

RESULTS

Using 1,268 effect sizes from 401 articles, we found overall differences in EF with age. Results suggested that differences in performance are not uniform, such that variability in age effects emerged at the task level, and updating was not as affected by age as other subdomains.

DISCUSSION

These findings advance our understanding of age differences in EF, and stand to inform early detection of EF decline.

Age-related prefrontal cortex activation in associative memory: An fNIRS pilot study

Older adults typically perform more poorly than younger adults in free recall memory tests. This age-related deficit has been linked to decline of brain activation and brain prefrontal lateralization, which may be the result of compensatory mechanisms. In the present pilot study, we investigated the effect of age on prefrontal cortex (PFC) activation during performance of a task that requires memory associations (temporal vs. spatial clustering), using functional Near-Infrared Spectroscopy (fNIRS). Ten younger adults, ten cognitively high-performing older individuals, and ten low-performing older individuals completed a free recall task, where either a temporal or spatial strategy (but not both simultaneously) could be employed to retrieve groups of same-category stimuli, whilst changes in PFC hemodynamics were recorded by means of a 12-channel fNIRS system. The results suggest PFC activation, and right lateralization specific to younger adults. Moreover, age did not affect use of memory organization, given that temporal clustering was preferred over spatial clustering in all groups. These findings are in line with previous literature on the aging brain and on temporal organization of memory. Our results also suggest that the PFC may be specifically involved in memory for temporal associations. Future research may consider whether age-related deficits in temporal organization may be an early sign of PFC pathology and possible neurodegeneration.

Effects of functional tasks exercise on cognitive functions of older adults with mild cognitive impairment: a randomized controlled pilot trial

Background

Dementia has been presenting an imminent public health challenge worldwide. Studies have shown a combination of cognitive and physical trainings may have synergistic value for improving cognitive functions. Daily functional tasks are innately cognitive demanding and involve components found in common exercise. Individuals with mild cognitive impairment may demonstrate difficulties with complex activities of daily living. Functional tasks could possibly be used as a means of combined cognitive and exercise training for improving cognitive functions. This pilot aims to validate the effects of functional tasks exercise on cognitive functions and functional status in older adults with mild cognitive impairment.

Methods

A four-arm, rater-blinded randomized controlled trial. Participants (N = 59) were randomized to either a functional task exercise group, a cognitive training group, an exercise training group, or a waitlist control group for 8 weeks. All outcome measures were undertaken at baseline and post-intervention using Neurobehavioral Cognitive Status Examination, Trail Making Test A and B, Chinese Version Verbal Learning Test, Lawton Instrumental Activities of Daily Living Scale, and Zarit Burden Interview.

Results

Results of the Kruskal-Wallis one-way ANOVA showed higher improvement in the functional task exercise group with significant between-group differences in memory (p = 0.009) compared to the exercise group and cognitive training group, functional status (p = 0.005) compared to the cognitive training group and waitlist control group, and caregiver burden (p = 0.037) compared to the exercise group and cognitive training group.

Conclusion

This pilot study showed that functional tasks exercise using simulated functional tasks as a means of combined cognitive and exercise program is feasible and beneficial in improving the memory and functional status of older adults with mild cognitive impairment as well as reducing the care-related burdens of their caregivers. The present findings warrant further well-designed longitudinal studies to examine the sustainability of effects and draw more definitive conclusions.

Trial registration

Australian New Zealand Clinical Trials Registry, ACTRN 12616001635459. Registered on 25 November 2016.

Validation of the Chinese version of the memory binding test for distinguishing amnestic mild cognitive impairment from cognitively normal elderly individuals

BACKGROUND

Episodic memory starts to decline very early in the development of Alzheimer's disease (AD). Subtle impairments in memory binding may be detected in mild cognitive impairment (MCI). This study aims to examine the psychometric properties of the Chinese version of the memory binding test (MBT).

METHODS

One hundred and sixty-four subjects (26 individuals with AD, 67 individuals with amnestic MCI (aMCI), 30 individuals with subjective cognitive impairment (SCI), and 41 cognitively normal elderly individuals (NC)) participated in the study. Twenty-two subjects repeated the assessment of the MBT within 6 weeks (± 2 weeks). Pearson correlation was used to calculate the convergent validity. The test--retest reliability was determined by the calculation of the intraclass correlation coefficient (ICC). Discriminative validity was calculated to evaluate the receiver-operating characteristic curves. The optimal index was chosen by comparing the area under the curve for specificity and sensitivity ≥ 0.80. The optimal cutoff score of the index was chosen to maximize the sum of sensitivity and specificity.

RESULTS

The absolute value of the convergent validity of the direct indexes of MBT ranged from 0.443 to 0.684. The ICC for each of direct indexes was 0.887-0.958. Total delayed paired recall (TDPR) was the optimal index for discriminating aMCI from NC. The cutoff score for TDPR was ≤25 to distinguish aMCI from NC (sensitivity = 0.896, specificity = 0.707).

CONCLUSION

The Chinese version of MBT is a valid and reliable instrument to detect MCI.

Decreased Event-Related Beta Synchronization During Memory Maintenance Marks Early Cognitive Decline in Mild Cognitive Impairment

Mild cognitive impairment (MCI) refers to a measurable deficit in cognition in the absence of dementia or impairment in activities of daily living. Working memory impairment is among the earliest signs of MCI. Oscillatory analysis of working memory might be a potential tool for identifying patients at increased risk of developing dementia. Our study aimed to assess the temporospatial pattern of spectral differences during working memory maintenance between MCI patients and healthy controls and to compare the sources of oscillatory activity between the two groups. Event-related spectral perturbation of 17 MCI patients and 21 healthy control participants was studied with 128-channel EEG during the Sternberg working memory task. Source localization was performed by using the eLORETA software. Among the participants, 13 MCI and 15 control participants underwent a structural brain MRI examination. Event-related synchronization (ERS) in the alpha and beta frequency band was significantly lower in MCI patients compared to healthy control participants during retention. Both study groups showed significant memory load-related enhancement in both frequency band. In the MCI group, source localization revealed significantly attenuated beta oscillatory activity in the inferior and middle temporal gyrus, in the fusiform gyrus, and in the cuneus. Beta ERS correlated significantly with the size of the hippocampus, entorhinal cortex, and parahippocampal gyrus. During the retention period, MCI is characterized by decreased alpha and beta ERS compared to controls indicating early impairment in neural networks serving working memory maintenance. The assessment of electrophysiological changes in the beta frequency range may provide a useful diagnostic tool for the early detection of cognitive impairment.

Age-related differences on a new test of temporal order memory for everyday events

We developed a new test to examine incidental temporal order memory for a self-generated sequence of tasks one might complete in everyday life. Young and older adults were given 10 cards, each listing a task one might accomplish in a typical day. Participants were asked to self-generate a "to do" list by placing the 10 cards in a sequence representing the order in which they would accomplish the tasks, but were not informed of a subsequent memory test. We assessed immediate free recall, delayed free recall, and delayed cued recall for the order of the tasks in the sequence. Older adults were significantly impaired relative to young adults on immediate free recall, delayed free recall, and delayed cued recall. Correlation analyses with standardized neuropsychological tests provide preliminary evidence for construct validity for our test, which is portable and can be rapidly administered in clinical or laboratory settings.

The effect of interference on temporal order memory in individuals with Parkinson's disease

Memory for the temporal order of items or events in a sequence has been shown to be impaired in older adults and individuals with Parkinson's disease (PD). The present study examined the effects of high and low interference on temporal order memory in individuals diagnosed with PD (n=20) and demographically similar healthy older adults (n=20) utilizing a computerized task used in previously published studies. During the sample phase of each trial, a series of eight circles were randomly presented one at a time in eight different spatial locations. Participants were instructed to remember the sequence in which the circles appeared in the locations. During the choice phase, participants were presented with two circles in two different locations and were asked to indicate which circle appeared earliest in the sample phase sequence. The two circles were separated by one of four possible temporal separation lags (0, 2, 4, and 6), defined as the number of circles occurring in the sample phase sequence between the two choice phase circles. Shorter temporal lags (e.g., 0 and 2 lags) were hypothesized to result in higher interference compared to longer temporal lags (e.g., 4 and 6 lags). The results demonstrated that on trials involving high interference, no differences were found between the two groups. However, healthy older adults significantly outperformed individuals with PD (p<0.05) on trials involving low interference. Although differences were found between the PD and healthy older adult groups, both groups significantly improved on low interference trials compared to high interference trials (p<0.001). The findings indicate that temporal order memory improves in healthy older adults and individuals with PD when interference is reduced. However, individuals with PD demonstrated poorer temporal order memory even with less interference. Therefore, temporal order memory is differentially affected by interference in healthy older adults and individuals with PD. Given that both groups did improve with lessened interference, behavioral interventions that minimize temporal interference potentially could improve memory function in older adults and to a lesser extent in individuals with PD.

Differences in temporal order memory among young, middle-aged, and older adults may depend on the level of interference

Age-related changes in temporal order memory have been well documented in older adults; however, little is known about this ability during middle age. We tested healthy young, middle-aged, and older adults on a previously published visuospatial temporal order memory test involving high and low interference conditions. When interference was low, young and middle-aged adults did not differ, but both groups significantly outperformed older adults. However, when interference was high, significant differences were found among all three age groups. The data provide evidence that temporal order memory may begin to decline in middle age, particularly when temporal interference is high.

Absolute and relative temporal order memory for performed activities following stroke

Reconstructing the temporal order of events is a crucial part of episodic memory. The temporal dimension, however, is often discarded in clinical settings, and measurements of true temporal aspects of episodic memory are scarce. The present study assessed temporal memory in stroke patients and in age- and education-matched healthy controls. Both groups underwent a standardized neuropsychological examination. We asked participants afterwards to reconstruct the order of tests they had performed, measured in absolute temporal order (event placed on correct moment in sequence) and relative temporal order (event placed correctly relative to directly preceding and following events). The aim of the study was to examine how serial-position curve effects (measuring absolute temporal order anchored in exact time) and how relative temporal order memory (anchored to other events) may differ in a group of cerebral stroke patients. Another aim was to link temporal order memory deficits with established neuropsychological measures of cognitive functioning. Although item identification was comparable in both groups, absolute temporal order memory was impaired in patients: A total of 43% of the patients lacked the expected primacy and recency effects (serial position effect). In addition, relative temporal order memory was affected in this group as well, F(1, 70) = 4.08, p < .05; 25% of the patients were impaired in reconstructing the relative temporal order (p = .019, Fisher's Exact Test). Both absolute and relative temporal order memory performance related to the domains of executive functioning and memory. Our results suggest that it is important to test both absolute and relative temporal order memory, especially because these types of memory depend on different anchors, either on time or on adjacent events.

RBANS memory indices are related to medial temporal lobe volumetrics in healthy older adults and those with mild cognitive impairment

The current study (i) determined whether NeuroQuant(®) volumetrics are reflective of differences in medial temporal lobe (MTL) volumes between healthy older adults and those with mild cognitive impairment (MCI) and (ii) examined the relationship between RBANS indices and MTL volumes. Forty-three healthy older adults and 57 MCI patients completed the RBANS and underwent structural MRI. Hippocampal and inferior lateral ventricle (ILV) volumes were obtained using NeuroQuant(®). Results revealed significantly smaller hippocampal and larger ILV volumes in MCI patients. MTL volumes were significantly related to the RBANS Immediate and Delayed Memory and Language indices but not the Attention or Visuoconstruction indices; findings that demonstrate anatomical specificity. Following discriminant function analysis, we calculated a cutpoint that may prove clinically useful for integrating MTL volumes into the diagnosis of MCI. These findings demonstrate the potential clinical utility of NeuroQuant(®) and are the first to document the relationship between RBANS indices and MTL volumes.

Cognitive rehabilitation of memory for mild cognitive impairment: a methodological review and model for future research

Several recent reviews have suggested that cognitive rehabilitation may hold promise in the treatment of memory deficits experienced by patients with mild cognitive impairment. In contrast to the previous reviews that mainly focused on outcome, the current review examines key methodological challenges that are critical for designing and interpreting research studies and translating results into clinical practice. Using methodological details from 36 studies, we first examine diagnostic variability and how the use of cutoffs may bias samples toward more severely impaired patients. Second, the strengths and limitations of several common rehabilitative techniques are discussed. Half of the reviewed studies used a multi-technique approach that precludes the causal attribution between any specific technique and subsequent improvement. Third, there is a clear need to examine the dose-response relationship since this information was strikingly absent from most studies. Fourth, outcome measures varied widely and frequently depended on neuropsychological tests with little theoretical justification or ecological relevance. Fifth, we discuss how the variability in each of these other four areas complicates efforts to examine training generalization. Overall, future studies should place greater emphasis on ecologically relevant treatment approaches and outcome measures and we propose a hierarchical model that may aid in this pursuit.