Diversity of daily activities is associated with greater hippocampal volume

Environmental enrichment: a systematic review on the effect of a changing spatial complexity on hippocampal neurogenesis and plasticity in rodents, with considerations for translation to urban and built environments for humans

Introduction

Hippocampal neurogenesis is critical for improving learning, memory, and spatial navigation. Inhabiting and navigating spatial complexity is key to stimulating adult hippocampal neurogenesis (AHN) in rodents because they share similar hippocampal neuroplasticity characteristics with humans. AHN in humans has recently been found to persist until the tenth decade of life, but it declines with aging and is influenced by environmental enrichment. This systematic review investigated the impact of spatial complexity on neurogenesis and hippocampal plasticity in rodents, and discussed the translatability of these findings to human interventions.

Methods

Comprehensive searches were conducted on three databases in English: PubMed, Web of Science, and Scopus. All literature published until December 2023 was screened and assessed for eligibility. A total of 32 studies with original data were included, and the process is reported in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement and checklist.

Results

The studies evaluated various models of spatial complexity in rodents, including environmental enrichment, changes to in-cage elements, complex layouts, and navigational mazes featuring novelty and intermittent complexity. A regression equation was formulated to synthesize key factors influencing neurogenesis, such as duration, physical activity, frequency of changes, diversity of complexity, age, living space size, and temperature.

Conclusion

Findings underscore the cognitive benefits of spatial complexity interventions and inform future translational research from rodents to humans. Home-cage enrichment and models like the Hamlet complex maze and the Marlau cage offer insight into how architectural design and urban navigational complexity can impact neurogenesis in humans. In-space changing complexity, with and without physical activity, is effective for stimulating neurogenesis. While evidence on intermittent spatial complexity in humans is limited, data from the COVID-19 pandemic lockdowns provide preliminary evidence. Existing equations relating rodent and human ages may allow for the translation of enrichment protocol durations from rodents to humans.

The bidirectional relationship between brain structure and physical activity: A longitudinal analysis in the UK Biobank

Physical activity is a protective factor against brain atrophy, while loss of brain volume could also be a determinant of physical activity. Therefore, we aimed to explore the bidirectional association of physical activity with brain structures in middle-aged and older adults from the UK Biobank. Overall, 3027 participants (62.45 ± 7.27 years old, 51.3% females) had data at two time points. Hippocampal volume was associated with total (β=0.048, pFDR=0.016) and household (β=0.075, pFDR<0.001) physical activity. Global fractional anisotropy (β=0.042, pFDR=0.028) was also associated with household physical activity. In the opposite direction, walking was negatively associated with white matter volume (β=-0.026, pFDR=0.008). All these associations were confirmed by the linear mixed models. Interestingly, sports at baseline were linked to hippocampal and frontal cortex volumes at follow-up but these associations disappeared after adjusting for multiple comparisons (pall>0.104). In conclusion, we found more consistent evidence that a healthier brain structure predicted higher physical activity levels than for the inverse, more established relationship.

The bi-directional relationships between diversified leisure activity participation and cognitive function in older adults in China: separating between-person effects from within-person effects

OBJECTIVE

To examine the bi-directorial association between diversified leisure activity participation and cognitive function over a 7-year period.

METHODS

Data analyzed was from the Chinese Longitudinal Healthy Longevity Survey (CLHLS), a large-scale longitudinal national study. The baseline survey was conducted in 2011 with follow-up every three years. We traced a total of 2718 participants over a period of 7 years. We used adjusted random intercept cross-lagged panel models (RI-CLPMs) to examine the bi-directorial associations between diversified leisure activity participation and cognitive function.

RESULTS

We observed bi-directorial associations between diversity of leisure activity and cognitive function across waves at the between-person and within-person levels. The adjusted random intercept cross-lagged panel models fitted the data appropriately, and the 3-year cross-lagged effects of prior diversified leisure activity participation on cognitive function (β = 0.058, p < 0.01) and cognitive function on subsequent diversified leisure activity participation (β = 0.047, p < 0.05) were significant. The results remained after adjusting the model for baseline sex, age, educational level, marital status and current residence, the number of chronic diseases, ADL, depressive symptoms, sleep quality, smoking, and drinking.

CONCLUSION

This study suggests that a reciprocal causality relationship between diversified leisure activity participation and cognitive function, indicating a "positive circle" that further promotes cognition over time.

Diversity of network communication mode and interpersonal interactions: Relationship with social support and well-being

Social interactions today expand beyond in-person interactions. Therefore, it is important to recognize that social interactions can occur with social network members across multiple communication modes (in-person, phone, and online). The current study explored the role that social support plays in the relationship between mode frequency (in-person, phone, and online), network communication mode diversity (breadth and evenness of communicating with network members via different communication modes), and well-being (positive affect, stress, and loneliness) from the 3-year UCNET (UC Berkley Social Networks Study, N = 1159) dataset. The study contained samples for two age groups (cohorts) - 21-31 year-olds and 50-70 year-olds, which also allowed for an exploration of age differences in these relationships. Longitudinal random-intercept cross-lagged panel models (RI-CLPM) showed a high degree of stability over the 3 years for all variables. Cross-sectional structural equation mediation models showed that social support mediated the relationships of mode frequency (in-person, phone, and online) and network communication mode diversity with well-being (more positive affect and less loneliness and stress). Age differences were found in the relationship between frequency of communication modes and social support, in that the frequency of communication mode was positively related to social support for younger adults, but not for middle-aged/older adults. Current findings provided future research directions geared toward further understanding of the mode frequency and network communication mode diversity constructs and how they relate to various psychosocial outcomes.

Rewarded Maze Training Increases Approach Behavior in Rats Through Neurogenesis-Dependent Growth of Ventral Hippocampus-Prelimbic Circuits

Background

Learning complex navigation routes increases hippocampal volume in humans, but it is not clear whether this growth impacts behaviors outside the learning situation or what cellular mechanisms are involved.

Methods

We trained rats with pharmacogenetic suppression of adult neurogenesis and littermate controls in 3 mazes over 3 weeks and tested novelty approach behavior several days after maze exposure. We then measured hippocampus and prelimbic cortex volumes using magnetic resonance imaging and assessed neuronal and astrocyte morphology. Finally, we investigated the activation and behavioral role of the ventral CA1 (vCA1)-to-prelimbic pathway using immediate-early genes and DREADDs (designer receptors exclusively activated by designer drugs).

Results

Maze training led to volume increase of both the vCA1 region of the hippocampus and the prelimbic region of the neocortex compared with rats that followed fixed paths. Growth was also apparent in individual neurons and astrocytes in these 2 regions, and behavioral testing showed increased novelty approach in maze-trained rats in 2 different tests. Suppressing adult neurogenesis prevented the effects on structure and approach behavior after maze training without affecting maze learning itself. The vCA1 neurons projecting to the prelimbic area were more activated by novelty in maze-trained animals, and suppression of this pathway decreased approach behavior.

Conclusions

Rewarded navigational learning experiences induce volumetric and morphologic growth in the vCA1 and prelimbic cortex and enhance activation of the circuit connecting these 2 regions. Both the structural and behavioral effects of maze training require ongoing adult neurogenesis, suggesting a role for new neurons in experience-driven increases in novelty exploration.

Social activity diversity as a lifestyle factor to alleviate loneliness and chronic pain

OBJECTIVE

This study examined whether social activity diversity, a novel concept indicating an active social lifestyle, is associated with lower subsequent loneliness, and decreased loneliness is further associated with less chronic pain over time.

METHODS

2528 adults from the Midlife in the United States Study (Mage = 54 yrs) provided data at baseline (2004-2009) and 9 years later. Social activity diversity was operationalized by Shannon's entropy that captures the variety and evenness of engagement across 13 social activities (0-1). Participants reported feelings of loneliness (1-5), presence of any chronic pain (yes/no), the degree of chronic pain-related interference (0-10), and the number of chronic pain locations. Indirect associations of social activity diversity with chronic pain through loneliness were evaluated, adjusting for sociodemographics, living alone, and chronic conditions.

RESULTS

Higher social activity diversity at baseline (B = -0.21, 95%CI = [-0.41, -0.02]) and an increase in social activity diversity over time (B = -0.24, 95%CI = [-0.42, -0.06]) were associated with lower loneliness 9 years later. An increase in loneliness was associated with 24% higher risk of any chronic pain (95%CI = [1.11, 1.38]), greater chronic pain-related interference (B = 0.36, 95%CI = [0.14, 0.58]), and 17% increase in the number of chronic pain locations (95%CI = [1.10, 1.25]) at the follow-up, after controlling for corresponding chronic pain at baseline and covariates. Social activity diversity was not directly was associated with chronic pain, but there were indirect associations through its association with loneliness.

CONCLUSION

Diversity in social life may be associated with decreased loneliness, which in turn, may be associated with less chronic pain, two of the prevalent concerns in adulthood.

Adults Older Than Age 55 Engage in Less Diverse Activities Than Those 18 Years Ago

OBJECTIVES

Life-span perspectives have long acknowledged that individual functioning is shaped by historical and sociocultural contexts. Secular increases favoring recent cohorts are widely documented. However, little is known about secular trends in day-to-day activities and whether historical changes have occurred in younger and older adults alike.

METHODS

We compared data from 2 independent cohort samples of the daily diary portion of the Midlife in the United States Study obtained 18 years apart (1995/1996 cohort: n = 1,499 vs 2013/2014 cohort: n = 782) and identified case-matched cohorts (n = 757 per cohort) based on age, gender, education, and race. An activity diversity score was calculated based on 7 common daily activities, using Shannon's entropy method. We additionally examined the roles of age and other sociodemographic and health characteristics in cohort differences in activity diversity.

RESULTS

Results revealed that the 2013/2014 cohort experienced lower daily activity diversity than the 1995/1996 cohort. Age was positively associated with activity diversity in the 1995/1996 cohort, whereas age was negatively associated with activity diversity in the 2013/2014 cohort. These associations were significant for those who were older than age 55. Cohorts also differed in the types of most dominant activities and average time spent on those activities.

DISCUSSION

Findings show changes in the lifestyles and daily activities of U.S. adults across 2 decades. Contrasting to the common belief that today's adults may be healthier and more active, they seem engaging in less diverse daily activities, which can be a risk for future health outcomes.

Altered Grey Matter-Brain Healthcare Quotient: Interventions of Olfactory Training and Learning of Neuroplasticity

Recent studies revealed that grey matter (GM) changes due to various training and learning experiences, using magnetic resonance imaging. In this study, we investigate the effect of psychological characteristics and attitudes toward training and learning on GM changes. Ninety participants were recruited and distributed into three groups: an olfactory training group that underwent 40 olfactory training sessions designed for odour classification tasks, a group classified for learning of neuroplasticity and brain healthcare using a TED Talk video and 28 daily brain healthcare messages, and a control group. Further, we assessed psychological characteristics, such as curiosity and personal growth initiatives. In the olfactory training group, we conducted a questionnaire survey on olfactory training regarding their interests and sense of accomplishment. In the olfactory training group, the GM change was significantly correlated with the sense of achievement and interest in training. The learning of neuroplasticity and brain healthcare group showed a significantly smaller 2-month GM decline than did the control group. The Curiosity and Exploration Inventory-II scores were significantly correlated with GM changes in both intervention groups only. In conclusion, our result suggested that training or learning with a sense of accomplishment, interest, and curiosity would lead to greater GM changes.