Factors that positively or negatively mediate the effects of age on working memory across the adult life span

Eight brain structures mediate the age-related alterations of the working memory: forward and backward digit span tasks

Introduction

Working memory (WM) as one of the executive functions is an essential neurocognitive ability for daily life. Findings have suggested that aging is often associated with working memory and neural decline, but the brain structures and resting-state brain networks that mediate age-related differences in WM remain unclear.

Methods

A sample consisting of 252 healthy participants in the age range of 20 to 70years was used. Several cognitive tasks, including the n-back task and the forward and backward digit span tests were used. Also, resting-state functional imaging, as well as structural imaging using a 3T MRI scanner, were performed, resulting in 85 gray matter volumes and five resting-state networks, namely the anterior and posterior default mode, the right and left executive control, and the salience networks. Also, mediation analyses were used to investigate the role of gray matter volumes and resting-state networks in the relationship between age and WM.

Results

Behaviorally, aging was associated with decreased performance in the digit span task. Also, aging was associated with a decreased gray matter volume in 80 brain regions, and with a decreased activity in the anterior default mode network, executive control, and salience networks. Importantly, the path analysis showed that the GMV of the medial orbitofrontal, precentral, parieto-occipital, amygdala, middle occipital, posterior cingulate, and thalamus areas mediated the age-related differences in the forward digit span task, and the GMV of superior temporal gyrus mediated the age-related differences in the backward digit span task.

Discussion

This study identified the brain structures mediating the relationship between age and working memory, and we hope that our research provides an opportunity for early detection of individuals at risk of age-related memory decline.

Diet May Moderate the Relationship Between Arterial Stiffness and Cognitive Performance in Older Adults

BACKGROUND

Cognitive decline is influenced by various factors including diet, cardiovascular disease, and glucose control. However, the combined effect of these risk factors on cognitive performance is yet to be fully understood.

OBJECTIVE

The current study aimed to explore the inter-relationship between these risk factors and cognitive performance in older adults at risk of future cognitive decline.

METHODS

The sample comprised 163 (Age: M = 65.23 years, SD = 6.50) participants. Food Frequency Questionnaire data was used to score diet quality and adherence to the Western Style Diet (WSD) and Prudent Style Diet (PSD). Glucose control was gauged by serum levels of glycated hemoglobin (HbA1c) and arterial stiffness was measured using carotid to femoral pulse wave velocity. Cognitive performance was assessed using two subtests of the Swinburne University Computerized Cognitive Assessment Battery (SUCCAB) and Rey's Verbal Learning Test (RVLT).

RESULTS

Diet quality, adherence to the WSD or PSD, and glucose control were not significantly related to cognitive outcomes. However, a significant negative association was found between arterial stiffness and the spatial working memory subtest of SUCCAB (β= -0.21, p <  0.05). Arterial stiffness also significantly interacted with the PSD to impact total recall (F change (1,134) = 5.37, p <  0.05) and the composite score of RVLT (F change (1,134) = 4.03, p <  0.05).

CONCLUSION

In this sample of older adults at risk of cognitive decline, diet alone was not found to predict cognitive performance; however, it was found to moderate the relationship between arterial stiffness and cognition.

The role of cognitive reserve as mediator for addition and multiplication skills in late adulthood

BACKGROUND

The role played by cognitive reserve for the maintenance of numeracy skills in late adulthood is still not sufficiently explored.

AIMS

This study mainly investigated whether cognitive reserve (i.e., vocabulary) mediates on the relationship between non-verbal reasoning and addition and multiplication skills of older individuals. Moreover, the impact of schooling and gender on written calculation was examined, controlling for the effect of cognitive decline.

METHODS

One hundred and six 68-94-year-old participants completed a battery of tests assessing numeracy, executive functions, and cognitive reserve skills.

RESULTS

Significant correlations were found between age, cognitive reserve, numeracy, and executive functions measures. Besides, mediation analyses indicated that cognitive reserve and non-verbal reasoning explain 23% and 29% of the variance in written addition and multiplication conditions, respectively. Finally, more educated individuals performed better numeracy tasks, whereas the solution of additions and multiplications was not impact by gender.

CONCLUSIONS

Cognitive reserve impacts numeracy in late adulthood.

Interleukin 6 reduces allopregnanolone synthesis in the brain and contributes to age-related cognitive decline in mice

Cognitive decline with age is a harmful process that can reduce quality of life. Multiple factors have been established to contribute to cognitive decline, but the overall etiology remains unknown. Here, we hypothesized that cognitive dysfunction is mediated, in part, by increased levels of inflammatory cytokines that alter allopregnanolone (AlloP) levels, an important neurosteroid in the brain. We assessed the levels and regulation of AlloP and the effects of AlloP supplementation on cognitive function in 4-month-old and 24-month-old male C57BL/6 mice. With age, the expression of enzymes involved in the AlloP synthetic pathway was decreased and corticosterone (CORT) synthesis increased. Supplementation of AlloP improved cognitive function. Interestingly, interleukin 6 (IL-6) infusion in young animals significantly reduced the production of AlloP compared with controls. It is notable that inhibition of IL-6 with its natural inhibitor, soluble membrane glycoprotein 130, significantly improved spatial memory in aged mice. These findings were supported by in vitro experiments in primary murine astrocyte cultures, indicating that IL-6 decreases production of AlloP and increases CORT levels. Our results indicate that age-related increases in IL-6 levels reduce progesterone substrate availability, resulting in a decline in AlloP levels and an increase in CORT. Furthermore, our results indicate that AlloP is a critical link between inflammatory cytokines and the age-related decline in cognitive function.

Executive Function and Diabetes: A Clinical Neuropsychology Perspective

Objective

Diabetes is a global public health concern. Management of diabetes depends on successful implementation of strategies to alleviate decline in executive functions (EFs), a characteristic of diabetes progression. In this review, we describe recent research on the relationship between diabetes and EF, summarize the existing evidence, and put forward future research directions and applications.

Methods

Herein, we provide an overview of recent studies, to elucidate the relationship between DM and EF. We identified new screening objectives, management tools, and intervention targets for diabetes management. We also discuss the implications for clinical practice.

Results

In both types 1 and 2 diabetes mellitus (DM), hyperglycemia substantially impairs EF in people of all age groups and ethnicities. Hypoglycemia can similarly impair EF. Interestingly, a decline in EF contributes to DM progression. Glucose dysregulation and EF decline exacerbate each other in a vicious cycle: poor blood glucose control, impaired EF, diabetes management task failure, then back to poor blood glucose control. Many pathophysiological indexes (e.g., obesity, metabolic index, inflammatory and immune factors), neuropsychological indexes (e.g., compliance, eating habits, physical exercise, sleep, and depression), and genetic factors are changed by this pathological interaction between DM and EF. These changes can provide insight into the pathophysiological mechanisms of diabetes-related EF decline.

Conclusion

Further studies, including large-scale prospective and randomized controlled trials, are needed to elucidate the mechanism of the interaction between diabetes and EF and to develop novel strategies for breaking this cycle.

Predictors of Working Memory Maintenance and Decline in Older Adults

The aging process is associated with the gradual decline of several cognitive functions, and working memory is particularly affected. Although the majority of older adults experience a deterioration of their working memory, some individuals maintain their working memory in older age, and some suffer an extreme deterioration of their working memory. The purpose of the present study was to identify, among a total of 120 potential predictors, those that significantly contributed to these two extreme outcomes in working memory. A sample of 588 healthy adults was examined with the n-back task in the spatial and verbal domains using a 2-back level of difficulty. Individuals were classified as working memory maintainers or decliners if their discrimination level in the two domains was superior to the 80th percentile or inferior to the 20th percentile, respectively. Logistic regression identified eight and six significant predictors of working memory maintenance and decline, respectively. High vocabulary scores and smoking more were significant predictors of working memory maintenance; however, in the opposite direction, these same variables predicted working memory decline. Several consumption habits that influenced cerebrovascular function were found in both models. Psychological traits and everyday activities were present in both models. We identified specific predictors that contribute to extremely high or low working memory performance in older age.

Effect of ageing on verbal and visuo-spatial working memory: Evidence from 880 individuals

It is well-known that ageing is associated with a decrease in working memory abilities. It is not so clear at what age the decline begins and if there are differences in the decline of verbal and visuo-spatial working memory. This study investigates the effect of ageing on verbal and visuo-spatial working memory by comparing the performance of 880 subjects aged between 15- and 80-year old who were subdivided into five groups. The results show that age is negatively correlated with performance on both verbal and visuo-spatial working memory tasks. Specifically, we observed a gradual deterioration in performance with increasing age starting at 36-year old. Comparing the performance of the five groups, it is possible to observe a clear decline in both verbal and visuo-spatial working memory domains in subjects over 66-year old. However, in the next youngest age group, it is possible to notice differences in performance depending on the type of material being processed and the cognitive load required. This variability is discussed by analyzing the factors that may have influenced test performance.

Important regulatory function of transient receptor potential ankyrin 1 receptors in age-related learning and memory alterations of mice

Expression of the transient receptor potential ankyrin 1 (TRPA1) receptor has been demonstrated not only in the dorsal root and trigeminal ganglia but also in different brain regions (e.g., hippocampus, hypothalamus, and cortex). However, data concerning their role in neurodegenerative and age-related diseases of the CNS is still indistinct. The aim of our study was to investigate the potential role of TRPA1 in a mouse model of senile dementia. For the investigation of changes during aging, we used male young (3-4-month-old) and old (18-month-old) wild-type (TRPA1+/+;WT) and TRPA1 receptor gene-deleted (TRPA1-/-) mice. Novel object recognition (NOR) test as well as Y maze (YM), radial arm maze (RAM), and Morris water maze (MWM) tests were used to assess the decline of memory and learning skills. In the behavioral studies, significant memory loss was detected in aged TRPA1+/+ mice with the NOR and RAM, but there was no difference measured by YM and MWM tests regarding the age and gene. TRPA1-/- showed significantly reduced memory loss, which could be seen as higher discrimination index in the NOR and less exploration time in the RAM. Furthermore, young TRPA1-/- animals showed significantly less reference memory error in the RAM and notably higher mobility in NOR, RAM, and YM compared with the age-matched WTs. Our present work has provided the first evidence that TRPA1 receptors mediate deteriorating effects in the old age memory decline. Understanding the underlying mechanisms could open new perspectives in the pharmacotherapy of dementia.

Predictors of Source Memory Success and Failure in Older Adults

Source memory decline has been identified as one of the types of memory most seriously affected during older age. It refers to our capacity to recollect the contextual information in which our experiences take place. Although most elderly adults will be affected by progressive source memory decline, a subset of individuals will not follow this average pattern; instead, their source memory capabilities will remain functional. Likewise, a minority of individuals will manifest an extreme decay of their source memory abilities. The objective of the present study was to identify among 120 potential predictors that significantly contributed to these two extreme source memory outcomes. Spatial source memory was measured in a sample of 519 healthy individuals between 61 and 80 years old. Individuals who performed below the 20th and above the 80th percentiles in the source memory task were defined as individuals whose episodic memory failed and succeeded, respectively. Logistic models identified five and six significant predictors of source memory success and failure in older age, respectively. High source memory performance was mainly predicted by healthy cardiovascular markers and psychological traits, whereas low source memory performance was primarily predicted by consumption habits and by less engagement in mental activities. The models identified relevant biological and life experiences that underlie these unusual source memory outcomes in older age.