Environmental enrichment, exercise and corticosterone affect endothelial cell proliferation in adult rat hippocampus and prefrontal cortex

Adolescent environmental enrichment induces social resilience and alters neural gene expression in a selectively bred rodent model with anxious phenotype

Stress is a major influence on mental health status; the ways that individuals respond to or copes with stressors determine whether they are negatively affected in the future. Stress responses are established by an interplay between genetics, environment, and life experiences. Psychosocial stress is particularly impactful during adolescence, a critical period for the development of mood disorders. In this study we compared two established, selectively-bred Sprague Dawley rat lines, the "internalizing" bred Low Responder (bLR) line versus the "externalizing" bred High Responder (bHR) line, to investigate how genetic temperament and adolescent environment impact future responses to social interactions and psychosocial stress, and how these determinants of stress response interact. Male bLR and bHR rats were exposed to social and environmental enrichment in adolescence prior to experiencing social defeat and were then assessed for social interaction and anxiety-like behavior. Adolescent enrichment caused rats to display more social interaction, as well as nominally less social avoidance, less submission during defeat, and resilience to the effects of social stress on corticosterone, in a manner that seemed more notable in bLRs. For bHRs, enrichment also caused greater aggression during a neutral social encounter and nominally during defeat, and decreased anxiety-like behavior. To explore the neurobiology underlying the development of social resilience in the anxious phenotype bLRs, RNA-seq was conducted on the hippocampus and nucleus accumbens, two brain regions that mediate stress regulation and social behavior. Gene sets previously associated with stress, social behavior, aggression and exploratory activity were enriched with differential expression in both regions, with a particularly large effect on gene sets that regulate social behaviors. Our findings provide further evidence that adolescent enrichment can serve as an inoculating experience against future stressors. The ability to induce social resilience in a usually anxious line of animals by manipulating their environment has translational implications, as it underscores the feasibility of intervention strategies targeted at genetically vulnerable adolescent populations.

Adolescent environmental enrichment induces social resilience and alters neural gene expression in a selectively bred rodent model with anxious phenotype

Stress is a major influence on mental health status; the ways that individuals respond to or copes with stressors determine whether they are negatively affected in the future. Stress responses are established by an interplay between genetics, environment, and life experiences. Psychosocial stress is particularly impactful during adolescence, a critical period for the development of mood disorders. In this study we compared two established, selectively-bred Sprague Dawley rat lines, the "internalizing" bred Low Responder (bLR) line versus the "externalizing" bred High Responder (bHR) line, to investigate how genetic temperament and adolescent environment impact future responses to social interactions and psychosocial stress, and how these determinants of stress response interact. Male bLR and bHR rats were exposed to social and environmental enrichment in adolescence prior to experiencing social defeat and were then assessed for social interaction and anxiety-like behavior. Adolescent enrichment caused rats to display more social interaction, as well as nominally less social avoidance, less submission during defeat, and resilience to the effects of social stress on corticosterone, in a manner that seemed more notable in bLRs. For bHRs, enrichment also caused greater aggression during a neutral social encounter and nominally during defeat, and decreased anxiety-like behavior. To explore the neurobiology underlying the development of social resilience in the anxious phenotype bLRs, RNA-seq was conducted on the hippocampus and nucleus accumbens, two brain regions that mediate stress regulation and social behavior. Gene sets previously associated with stress, social behavior, aggression and exploratory activity were enriched with differential expression in both regions, with a particularly large effect on gene sets that regulate social behaviors. Our findings provide further evidence that adolescent enrichment can serve as an inoculating experience against future stressors. The ability to induce social resilience in a usually anxious line of animals by manipulating their environment has translational implications, as it underscores the feasibility of intervention strategies targeted at genetically vulnerable adolescent populations.

Neonatal stress disrupts the glymphatic system development and increases the susceptibility to Parkinson's disease in later life

INTRODUCTION

Neonatal stress disrupts brain development and increases the risk of neurological disorders later in life. However, the impact of neonatal stress on the development of the glymphatic system and susceptibility to Parkinson's disease (PD) remains largely unknown.

METHODS

Neonatal maternal deprivation (NMD) was performed on mice for 14 consecutive days to model chronic neonatal stress. Adeno-associated virus expressing A53T-α-synuclein (α-syn) was injected into the substantia nigra to establish PD model mice. Glymphatic activity was determined using in vivo magnetic resonance imaging, ex vivo fluorescence imaging and microplate assay. The transcription and expression of aquaporin-4 (AQP4) and other molecules were evaluated by qPCR, western blotting, and immunofluorescence. Animal's responses to NMD and α-syn overexpression were observed using behavioral tests.

RESULTS

Glymphatic activity was impaired in adult NMD mice. AQP4 polarization and platelet-derived growth factor B (PDGF-B) signaling were reduced in the frontal cortex and hippocampus of both young and adult NMD mice. Furthermore, exogenous α-syn accumulation was increased and PD-like symptoms were aggravated in adult NMD mice.

CONCLUSION

The results demonstrated that NMD could disrupt the development of the glymphatic system through PDGF-B signaling and increase the risk of PD later in life, indicating that alleviating neonatal stress could be beneficial in protecting the glymphatic system and reducing susceptibility to neurodegeneration.

Environmental enrichment enhanced neurogenesis and behavioral recovery after stroke in aged rats

BACKGROUND AND PURPOSE

Age is identified as a significant prognostic factor for poorer outcome after stroke. However, environmental enrichment (EE) has been reported to promote functional recovery after ischemic stroke. The purpose of this study was to investigate whether environmental enrichment was beneficial to ischemic stroke in aged rats.

METHODS

Aged rats were randomly assigned as control rats, rats subjected to cerebral ischemia, and rats with cerebral ischemia treated with EE for 30 days. Focal cortical ischemia was induced by intracranial injection of endothelin-1 (ET-1). EE housing began one day after focal ischemia and was maintained for the whole experimental period. We used immunofluorescence staining to analyze the neurogenesis in the subventricular zone (SVZ) and TdT-mediated dUTP-biotin nick-end labeling (TUNEL) assay to evaluate apoptosis. The expression of neuronal nuclei, glial fibrillary acidic protein (GFAP) and Iba-1 around the infarcted area were also measured by double immunohistochemistry.

RESULTS

EE enhanced the proliferation of newborn neurons in the SVZ, as well as increased the long-term survival of newborn neurons. EE also exerted effects on inflammation after stroke. Furthermore, EE suppressed apoptosis and improved the motor functions after stroke in the aged rats.

CONCLUSIONS

EE improved post-stroke recovery on the basis of enhancing neurogenesis in aged rats.

NMDA receptors in the insular cortex modulate cardiovascular and autonomic but not neuroendocrine responses to restraint stress in rats

The insular cortex (IC) is a brain structure involved in physiological and behavioural responses during stressful events. However, the local neurochemical mechanisms involved in control of stress responses by the IC are poorly understood. Thus, this study aimed to investigate the involvement of glutamatergic neurotransmission within the IC in cardiovascular, autonomic and neuroendocrine responses to an acute session of restraint stress. For this, the selective NMDA glutamate receptor antagonist LY235959 (1 nmol/100 nL) or the selective non-NMDA glutamate receptor antagonist NBQX (1 nmol/100 nL) were microinjected into the IC 10 min before the onset of the 60 min session of restraint stress. We observed that the antagonism of NMDA receptors within the IC enhanced the restraint-evoked increase in arterial pressure and heart rate, while blockade of non-NMDA receptors did not affect these cardiovascular responses. Spontaneous baroreflex analysis demonstrated that microinjection of LY235959 into the IC decreased baroreflex activity during restraint stress. The decrease in tail skin temperature during restraint stress was shifted to an increase in animals treated with the NMDA receptor antagonist. Nevertheless, the blockade of either NMDA or non-NMDA glutamate receptors within the IC did not affect the increase in circulating corticosterone levels during restraint stress. Overall, our findings provide evidence that IC glutamatergic neurotransmission, acting via local NMDA receptors, plays a prominent role in the control of autonomic and cardiovascular responses to restraint stress, but without affecting neuroendocrine adjustments.

The Molecular Effects of Environmental Enrichment on Alzheimer's Disease

Environmental enrichment (EE) is an environmental paradigm encompassing sensory, cognitive, and physical stimulation at a heightened level. Previous studies have reported the beneficial effects of EE in the brain, particularly in the hippocampus. EE improves cognitive function as well as ameliorates depressive and anxiety-like behaviors, making it a potentially effective neuroprotective strategy against neurodegenerative diseases such as Alzheimer's disease (AD). Here, we summarize the current evidence for EE as a neuroprotective strategy as well as the potential molecular pathways that can explain the effects of EE from a biochemical perspective using animal models. The effectiveness of EE in enhancing brain activity against neurodegeneration is explored with a view to differences present in early and late life EE exposure, with its potential application in human being discussed. We discuss EE as one of the non pharmacological approaches in preventing or delaying the onset of AD for future research.

Thyroid hormone, cortisol, interleukin-2, and procalcitonin regulate postoperative delirium in acute type A aortic dissection patients

BACKGROUND

We assessed the relationships between levels of preoperative thyroid hormone (TH), cortisol, interleukin-2 (IL-2), and procalcitonin (PCT) and postoperative delirium (POD) in acute type A aortic dissection (ATAAD) patients receiving modified triple-branched stent-graft (MTBSG) implant surgeries.

METHODS

ATAAD patients received MTBSG implant surgeries in our hospital between February 2019 and December 2020 were recruited. We separated them into a POD and non-POD cohort and employed univariable and multivariable regression analysis to establish independent correlations between preoperative THs, cortisol, IL-2, and PCT and POD. In addition, we conducted stratification analyses to examine the link between pre-surgical THs and POD in normal TSH and lower TSH subgroups.

RESULTS

POD occurred in 78 of 224 patients (34.8%). POD patients exhibited markedly reduced preoperative free triiodothyronine (FT3) (P = 0.008) and free thyroxine (FT4) (P = 0.023) levels, while remarkably enhanced preoperative cortisol (P < 0.001), IL-2 (P < 0.001), and PCT (P < 0.001) levels. Based on multivariate regression analysis, reduced preoperative FT3 (P = 0.032), as well as augmented preoperative IL-2 (P = 0.001), cortisol (P < 0.001), and PCT (P = 0.016) were strong stand-alone risk factors for POD. Moreover, subgroup analysis found the association between FT3 (P = 0.029), FT4 (P = 0.042) and POD was both significant in patients with normal TSH levels.

CONCLUSIONS

Reduced preoperative FT3 and elevated preoperative cortisol, IL-2, and PCT were strong indicators of POD in ATAAD patients. Hence, we recommend that the thyroid function, cortisol, PCT, and IL-2 should be evaluated prior to surgery in ATAAD patients.

Horizons in Human Aging Neuroscience: From Normal Neural Aging to Mental (Fr)Agility

While aging is an important risk factor for neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease, age-related cognitive decline can also manifest without apparent neurodegenerative changes. In this review, we discuss molecular, cellular, and network changes that occur during normal aging in the absence of neurodegenerative disease. Emerging findings reveal that these changes include metabolic alterations, oxidative stress, DNA damage, inflammation, calcium dyshomeostasis, and several other hallmarks of age-related neural changes that do not act on their own, but are often interconnected and together may underlie age-related alterations in brain plasticity and cognitive function. Importantly, age-related cognitive decline may not be reduced to a single neurobiological cause, but should instead be considered in terms of a densely connected system that underlies age-related cognitive alterations. We speculate that a decline in one hallmark of neural aging may trigger a decline in other, otherwise thus far stable subsystems, thereby triggering a cascade that may at some point also incur a decline of cognitive functions and mental well-being. Beyond studying the effects of these factors in isolation, considerable insight may be gained by studying the larger picture that entails a representative collection of such factors and their interactions, ranging from molecules to neural networks. Finally, we discuss some potential interventions that may help to prevent these alterations, thereby reducing cognitive decline and mental fragility, and enhancing mental well-being, and healthy aging.

Prediction of Postoperative Delirium After Cardiac Surgery with A Quick Test of Cognitive Speed, Mini-Mental State Examination and Hospital Anxiety and Depression Scale

Purpose

To evaluate if preoperative assessment with A Quick Test of Cognitive Speed (AQT) could increase the accuracy of predicting delirium after cardiac surgery compared to Mini-Mental State Examination (MMSE), and examine if a composite of variables, including cognitive function and depressive symptoms, could be useful to predict delirium.

Patients and Methods

Cardiac surgery was performed in 218 patients (mean age 72 years). Preoperative evaluation involved AQT, MMSE and Hospital Anxiety And Depression Scale (HADS). Postoperative delirium was assessed using Nursing Delirium Screening Scale (Nu-DESC) and Confusion Assessment Method-ICU (CAM-ICU). Logistic regression was performed to detect predictors of postoperative delirium and receiver operator characteristic curves (ROC) with area under the curve (AUC) to determine the accuracy.

Results

Postoperative delirium occurred in 47 patients (22%) who had lower MMSE scores (median (range), 27 (19–30) vs 28 (20–30), p=0.009) and slower AQT (median (range), 76 (48–181) vs 70 (40–182) seconds, p=0.030) than patients without delirium. Predictive power measured as AUC (95% CI) was 0.605 (0.51–0.70) for AQT and 0.623 (0.53–0.72) for MMSE. Logistic regression (OR, 95% CI) showed MMSE <27 points (2.72, 1.27–5.86), AQT >70 sec (2.26, 1.03–4.95), HADS-D >4 points (2.60, 1.21–5.58) and longer cardiopulmonary bypass-time (1.007, 1.002–1.013) to be associated with postoperative delirium. Combining these parameters yielded an AUC of 0.736 (0.65–0.82).

Conclusion

The ability of predicting delirium using AQT was similar to MMSE, and only slightly higher by combining AQT and MMSE. Adding HADS-D and cardiopulmonary bypass-time to MMSE and AQT increased the predictive power to a borderline acceptable discriminatory value. Preoperative cognitive tests and screening for depressive symptoms may help identify patients at risk of postoperative delirium. Yet, there is still a need to establish useful preoperative tests.

Experience-dependent plasticity in early stations of sensory processing in mature brains: effects of environmental enrichment on dendrite measures in trigeminal nuclei

Nervous systems respond with structural changes to environmental changes even in adulthood. In recent years, experience-dependent structural plasticity was shown not to be restricted to the cerebral cortex, as it also occurs at subcortical and even peripheral levels. We have previously shown that two populations of trigeminal nuclei neurons, trigeminothalamic barrelette neurons of the principal nucleus (Pr5), and intersubnuclear neurons in the caudal division of the spinal trigeminal nucleus (Sp5C) that project to Pr5 underwent morphometric and topological changes in their dendritic trees after a prolonged total or partial loss of afferent input from the vibrissae. Here we examined whether and what structural alterations could be elicited in the dendritic trees of the same cell populations in young adult rats after being exposed for 2 months to an enriched environment (EE), and how these changes evolved when animals were returned to standard housing for an additional 2 months. Neurons were retrogradely labeled with BDA delivered to, respectively, the ventral posteromedial thalamic nucleus or Pr5. Fully labeled cells were digitally reconstructed with Neurolucida and analyzed with NeuroExplorer. EE gave rise to increases in dendritic length, number of trees and branching nodes, spatial expansion of the trees, and dendritic spines, which were less pronounced in Sp5C than in Pr5 and differed between sides. In Pr5, these parameters returned, but only partially, to control values after EE withdrawal. These results underscore a ubiquity of experience-dependent changes that should not be overlooked when interpreting neuroplasticity and developing plasticity-based therapeutic strategies.

Blood-Brain Barrier Dysfunction in the Pathogenesis of Major Depressive Disorder

Major depression represents a complex and prevalent psychological disease that is characterized by persistent depressed mood, impaired cognitive function and complicated pathophysiological and neuroendocrine alterations. Despite the multifactorial etiology of depression, one of the most recent factors to be identified as playing a critical role in the development of depression is blood-brain barrier (BBB) disruption. The occurrence of BBB integrity disruption contributes to the disturbance of brain homeostasis and leads to complications of neurological diseases, such as stroke, chronic neurodegenerative disorders, neuroinflammatory disorders. Recently, BBB associated tight junction disruption has been shown to implicate in the pathophysiology of depression and contribute to increased susceptibility to depression. However, the underlying mechanisms and importance of BBB damage in depression remains largely unknown. This review highlights how BBB disruption regulates the depression process and the possible molecular mechanisms involved in development of depression-induced BBB dysfunction. Moreover, insight on promising therapeutic targets for treatment of depression with associated BBB dysfunctions are also discussed.

The Cellular Senescence Stress Response in Post-Mitotic Brain Cells: Cell Survival at the Expense of Tissue Degeneration

In 1960, Rita Levi-Montalcini and Barbara Booker made an observation that transformed neuroscience: as neurons mature, they become apoptosis resistant. The following year Leonard Hayflick and Paul Moorhead described a stable replicative arrest of cells in vitro, termed "senescence". For nearly 60 years, the cell biology fields of neuroscience and senescence ran in parallel, each separately defining phenotypes and uncovering molecular mediators to explain the 1960s observations of their founding mothers and fathers, respectively. During this time neuroscientists have consistently observed the remarkable ability of neurons to survive. Despite residing in environments of chronic inflammation and degeneration, as occurs in numerous neurodegenerative diseases, often times the neurons with highest levels of pathology resist death. Similarly, cellular senescence (hereon referred to simply as "senescence") now is recognized as a complex stress response that culminates with a change in cell fate. Instead of reacting to cellular/DNA damage by proliferation or apoptosis, senescent cells survive in a stable cell cycle arrest. Senescent cells simultaneously contribute to chronic tissue degeneration by secreting deleterious molecules that negatively impact surrounding cells. These fields have finally collided. Neuroscientists have begun applying concepts of senescence to the brain, including post-mitotic cells. This initially presented conceptual challenges to senescence cell biologists. Nonetheless, efforts to understand senescence in the context of brain aging and neurodegenerative disease and injury emerged and are advancing the field. The present review uses pre-defined criteria to evaluate evidence for post-mitotic brain cell senescence. A closer interaction between neuro and senescent cell biologists has potential to advance both disciplines and explain fundamental questions that have plagued their fields for decades.

Hair glucocorticoids and resting-state frontal lobe oxygenation: Findings from The Irish Longitudinal Study on Ageing

Cerebral blood flow and oxygenation are crucial for maintaining healthy brain structure and function, with hypoperfusion and hypometabolism associated with neurodegenerative and neuropsychiatric conditions. Chronic stress and elevated cortisol have also been associated with cognitive decline, poor mental health and peripheral vascular and cerebrovascular changes. It is plausible that glucocorticoids could alter brain structure and function through increased vulnerability to hypoperfusion and reduced oxygenation. The aim of the current study was to investigate the association between hair glucocorticoids (GCs) and frontal lobe oxygenation using near-infra red spectroscopy (NIRS) in a population sample of 1078 older adults. Data from Wave 3 of The Irish Longitudinal Study of Ageing was analysed. Hair samples were taken for the analysis of glucocorticoids and NIRS was used to measure frontal lobe oxygenation. After both minimal and full adjustment for covariates, hair cortisol and the cortisol-to-cortisone ratio were associated with lower Tissue Saturation Index (TSI; cortisol: B = -0.37, CI -0.60 to -0.14, p = .002; ratio: B = -0.43, CI -0.70 to -0.16, p = .002). Cortisone was not significantly associated with TSI (B = -0.17, CI -0.55 to.21, p = .388). The finding of an inverse relationship between frontal lobe oxygenation and GCs as assessed over a period of months may indicate that reduced oxygenation is one pathway through which chronically elevated GCs affect brain health and function. However, no causality can be inferred from the current data and prospective studies are required to interrogate this.

Long-Term Running Exercise Delays Age-Related Changes in White Matter in Rats

Running exercise, one of the strategies to protect brain function, has positive effects on neurons and synapses in the cortex and hippocampus. However, white matter, as an important structure of the brain, is often overlooked, and the effects of long-term running exercise on white matter are unknown. Here, 14-month-old male Sprague–Dawley (SD) rats were divided into a middle-aged control group (18-month-old control group), an old control group (28-month-old control group), and a long-term runner group (28-month-old runner group). The rats in the runner group underwent a 14-month running exercise regime. Spatial learning ability was tested using the Morris water maze, and white matter volume, myelinated fiber parameters, total mature oligodendrocyte number, and white matter capillary parameters were investigated using stereological methods. The levels of growth factors related to nerve growth and vascular growth in peripheral blood and the level of neurite outgrowth inhibitor-A (Nogo-A) in white matter were measured using an enzyme-linked immunosorbent assay (ELISA). The present results indicated that long-term running exercise effectively delayed the age-related decline in spatial learning ability and the atrophy of white matter by protecting against age-related changes in myelinated fibers and oligodendrocytes in the white matter. Moreover, long-term running exercise prevented age-related changes in capillaries within white matter, which might be related to the protective effects of long-term exercise on aged white matter.

Physical activity and cognitive stimulation ameliorate learning and motor deficits in a transgenic mouse model of Alzheimer's disease

Epidemiological studies suggest that physical exercise or cognitive stimulation might contribute to lower the risk of developing dementia disorders such as Alzheimer's disease (AD). Here, we used the well-established enrichment environment (EE) paradigm to study the impact of prolonged physical activity and cognitive stimulation in a mouse model of AD overexpressing only Aβ_4-42 peptides. These mice display age-dependent memory and motor deficits, in the absence of human amyloid precursor protein (APP) overexpression. We demonstrate that housing under EE conditions leads to an entire preservation of recognition and spatial memory, as well as a rescue of motor deficits in this mouse model. Moreover, we find that Tg4-42^hom mice present a typical floating phenotype in the Morris water maze task that could be completely ameliorated upon long-term EE housing. Our findings are in line with epidemiological studies suggesting that physical activity and cognitive stimulation might represent efficient strategies to prevent age-related neurodegenerative disorders such as AD.

Differential impact of stress and environmental enrichment on corticolimbic circuits

Stress exposure can produce profound changes in physiology and behavior that can impair health and well-being. Of note, stress exposure is linked to anxiety disorders and depression in humans. The widespread impact of these disorders warrants investigation into treatments to mitigate the harmful effects of stress. Pharmacological treatments fail to help many with these disorders, so recent work has focused on non-pharmacological alternatives. One of the most promising of these alternatives is environmental enrichment (EE). In rodents, EE includes social, physical, and cognitive stimulation for the animal, in the form of larger cages, running wheels, and toys. EE successfully reduces the maladaptive effects of various stressors, both as treatment and prophylaxis. While we know that EE can have beneficial effects under stress conditions, the morphological and molecular mechanisms underlying these behavioral effects are still not well understood. EE is known to alter neurogenesis, dendrite development, and expression of neurotrophic growth factors, effects that vary by type of enrichment, age, and sex. To add to this complexity, EE has differential effects in different brain regions. Understanding how EE exerts its protective effects on morphological and molecular levels could hold the key to developing more targeted pharmacological treatments. In this review, we summarize the literature on the morphological and molecular consequences of EE and stress in key emotional regulatory pathways in the brain, the hippocampus, prefrontal cortex, and amygdala. The similarities and differences among these regions provide some insight into stress-EE interaction that may be exploited in future efforts toward prevention of, and intervention in, stress-related diseases.

The effects of environmental enrichment on skin barrier recovery in humans: a randomised trial

This study investigated whether environmental enrichment (EE) could reduce stress and improve wound healing in humans. 120 participants underwent a standardised tape-stripping procedure and were then randomised to interact for 30 minutes with one of three EE interventions (comfort blankets as tactile enrichment, music as auditory enrichment or a Paro robot as multi-sensory enrichment) or to a control group. Skin barrier recovery (SBR) was measured using transepidermal water loss at baseline, after tape-stripping and after the intervention. Psychological variables, cortisol and alpha-amylase were measured at the three time-points. SBR did not significantly differ between the EE conditions and the control condition. The music condition had higher stimulation levels than the control condition, and the comfort condition had significantly lower relaxation levels than the control condition after the intervention. The EE interventions tested were not beneficial for wound healing compared to a control group. Limitations were that the sample were not stressed and an active control condition was used.

Environmental enrichment enhances post-ischemic cerebral blood flow and functional hyperemia in the ipsilesional somatosensory cortex

Environmental enrichment has been reported to promote functional recovery in an ischemic stroke. However, the underlying mechanism remains unclear. This study aimed to investigate the effect of environmental enrichment treatment on post-ischemic cerebral blood flow and functional hyperemia in the ipsilesional primary somatosensory cortex of rats. With laser speckle imaging, we were able to monitor the resting cerebral blood flow alteration in the middle cerebral artery occlusion model. Both 3- and 28-day post-ischemic infarct volumes were then examined with triphenyltetrazolium chloride and cresyl violet staining, respectively. We found that an exposure to environmental enrichment was associated with higher post-ischemic cerebral blood flow and less brain tissue loss in the ipsilesional primary somatosensory cortex compared with the standard cage environment. Furthermore, environmental enrichment also enhanced the cerebral blood flow response to whisker stimulation in the ipsilesional barrel cortex when measured 28 days after the middle cerebral artery occlusion. Together, the data suggested that an exposure to environmental enrichment promoted the restoration of cerebral blood flow in the ipsilesional cortex and contributed to a better coupling between functional activation and cerebral blood flow change, which might be the possible mechanisms underlying the neuroprotective effects of EE after ischemia.

Environmental Enrichment: Disentangling the Influence of Novelty, Social, and Physical Activity on Cerebral Amyloid Angiopathy in a Transgenic Mouse Model

Cerebral amyloid angiopathy (CAA) is the deposition of amyloid protein in the cerebral vasculature, a common feature in both aging and Alzheimer's disease (AD). However, the effects of environmental factors, particularly cognitive stimulation, social stimulation, and physical activity, on CAA pathology are poorly understood. These factors, delivered in the form of the environmental enrichment (EE) paradigm in rodents, have been shown to have beneficial effects on the brain and behavior in healthy aging and AD models. However, the relative importance of these subcomponents on CAA pathology has not been investigated. Therefore, we assessed the effects of EE, social enrichment (SOC), and cognitive enrichment (COG) compared to a control group that was single housed without enrichment (SIN) from 4 to 8 months of age in wild-type mice (WT) and Tg-SwDI mice, a transgenic mouse model of CAA that exhibits cognitive/behavioral deficits. The results show that individual facets of enrichment can affect an animal model of CAA, though the SOC and combined EE conditions are generally the most effective at producing physiological, cognitive/behavioral, and neuropathological changes, adding to a growing literature supporting the benefits of lifestyle interventions.

Shaping the adult brain with exercise during development: Emerging evidence and knowledge gaps

Exercise is known to produce a myriad of positive effects on the brain, including increased glia, neurons, blood vessels, white matter and dendritic complexity. Such effects are associated with enhanced cognition and stress resilience in humans and animal models. As such, exercise represents a positive experience with tremendous potential to influence brain development and shape an adult brain capable of responding to life's challenges. Although substantial evidence attests to the benefits of exercise for cognition in children and adolescents, the vast majority of existing studies examine acute effects. Nonetheless, there is emerging evidence indicating that exercise during development has positive cognitive and neural effects that last to adulthood. There is, therefore, a compelling need for studies designed to determine the extent to which plasticity driven by developmental exercise translates into enhanced brain health and function in adulthood and the underlying mechanisms. Such studies are particularly important given that modern Western society is increasingly characterized by sedentary behavior, and we know little about how this impacts the brain's developmental trajectory. This review synthesizes current literature and outlines significant knowledge gaps that must be filled in order to elucidate what exercise (or lack of exercise) during development contributes to the health and function of the adult brain.

Education modulates brain maintenance in presymptomatic frontotemporal dementia

OBJECTIVE

Cognitively engaging lifestyles have been associated with reduced risk of conversion to dementia. Multiple mechanisms have been advocated, including increased brain volumes (ie, brain reserve) and reduced disease progression (ie, brain maintenance). In cross-sectional studies of presymptomatic frontotemporal dementia (FTD), higher education has been related to increased grey matter volume. Here, we examine the effect of education on grey matter loss over time.

METHODS

Two-hundred twenty-nine subjects at-risk of carrying a pathogenic mutation leading to FTD underwent longitudinal cognitive assessment and T1-weighted MRI at baseline and at 1 year follow-up. The first principal component score of the graph-Laplacian Principal Component Analysis on 112 grey matter region-of-interest volumes was used to summarise the grey matter volume (GMV). The effects of education on cognitive performances and GMV at baseline and on the change between 1 year follow-up and baseline (slope) were tested by Structural Equation Modelling.

RESULTS

Highly educated at-risk subjects had better cognition and higher grey matter volume at baseline; moreover, higher educational attainment was associated with slower loss of grey matter over time in mutation carriers.

CONCLUSIONS

This longitudinal study demonstrates that even in presence of ongoing pathological processes, education may facilitate both brain reserve and brain maintenance in the presymptomatic phase of genetic FTD.

Human Hippocampal Neurogenesis Persists throughout Aging

Adult hippocampal neurogenesis declines in aging rodents and primates. Aging humans are thought to exhibit waning neurogenesis and exercise-induced angiogenesis, with a resulting volumetric decrease in the neurogenic hippocampal dentate gyrus (DG) region, although concurrent changes in these parameters are not well studied. Here we assessed whole autopsy hippocampi from healthy human individuals ranging from 14 to 79 years of age. We found similar numbers of intermediate neural progenitors and thousands of immature neurons in the DG, comparable numbers of glia and mature granule neurons, and equivalent DG volume across ages. Nevertheless, older individuals have less angiogenesis and neuroplasticity and a smaller quiescent progenitor pool in anterior-mid DG, with no changes in posterior DG. Thus, healthy older subjects without cognitive impairment, neuropsychiatric disease, or treatment display preserved neurogenesis. It is possible that ongoing hippocampal neurogenesis sustains human-specific cognitive function throughout life and that declines may be linked to compromised cognitive-emotional resilience.

Environmental Enrichment Reverses Tyrosine Kinase Inhibitor-Mediated Impairment Through BDNF-TrkB Pathway

Exposure to an enriched environment (EE) has neuroprotective benefits and improves recovery from brain injury due to, among other, increased neurotrophic factor expression. Through these neurotrophins, important cortical and hippocampal changes occur. Vandetanib acts as a tyrosine kinase inhibitor of cell receptors, among others, the vascular endothelial growth factor receptor (VEGFR). Our aim was to investigate the effectiveness of EE counteracting cognitive and cellular effects after tyrosine kinase receptor blockade. Animals were reared under standard laboratory condition or EE; both groups received vandetanib or vehicle. Visuospatial learning was tested with Morris water maze. Neuronal, interneuronal, and vascular densities were measured by inmunohistochemistry and histochemistry techniques. Quantifications were performed in the hippocampus and in the visual cortex. Brain-derived neurotrophic factor (BDNF), tyrosine kinase B receptor (TrkB), Akt, and Erk were measured by Western blot technique. Vandetanib produces a significant decrease in vascular and neuronal densities and reduction in the expression of molecules involved in survival and proliferation processes such as phospho-Akt/Akt and phospho-Erk/Erk. These results correlated to a cognitive impairment in visuospatial test. On the other hand, animals reared in an EE are able to reverse the negative effects, activating PI3K-AKT and MAP kinase pathways mediated by BDNF-TrkB binding. Present results provide novel and consistent evidences about the usefulness of living in EE as a strategy to improve deleterious effects of blocking neurotrophic pathways by vandetanib and the notable role of the BDNF-TrkB pathway to balance the neurovascular unit and cognitive effects.

Exercising New Neurons to Vanquish Alzheimer Disease

Alzheimer disease (AD) is the most common type of dementia in individuals over 65 years of age. The neuropathological hallmarks of the condition are Tau neurofibrillary tangles and Amyloid-β senile plaques. Moreover, certain susceptible regions of the brain experience a generalized lack of neural plasticity and marked synaptic alterations during the progression of this as yet incurable disease. One of these regions, the hippocampus, is characterized by the continuous addition of new neurons throughout life. This phenomenon, named adult hippocampal neurogenesis (AHN), provides a potentially endless source of new synaptic elements that increase the complexity and plasticity of the hippocampal circuitry. Numerous lines of evidence show that physical activity and environmental enrichment (EE) are among the most potent positive regulators of AHN. Given that neural plasticity is markedly decreased in many neurodegenerative diseases, the therapeutic potential of making certain lifestyle changes, such as increasing physical activity, is being recognised in several non-pharmacologic strategies seeking to slow down or prevent the progression of these diseases. This review article summarizes current evidence supporting the putative therapeutic potential of EE and physical exercise to increase AHN and hippocampal plasticity both under physiological and pathological circumstances, with a special emphasis on neurodegenerative diseases and AD.

Environmentally enriched pigs have transcriptional profiles consistent with neuroprotective effects and reduced microglial activity

Environmental enrichment (EE) is widely used to study the effects of external factors on brain development, function and health in rodent models, but very little is known of the effects of EE on the brain in a large animal model such as the pig. Twenty-four young pigs (aged 5 weeks at start of study, 1:1 male: female ratio) were housed in environmentally enriched (EE) pens and provided with additional enrichment stimulation (a bag filled with straw) once daily. Litter, weight and sex matched controls n= (24) were housed in barren (B) conditions. Behaviour was recorded on alternate days from study day 10. After 21 days, RNA-sequencing of the frontal cortex of male piglets culled one hour after the enrichment stimulation, but not those at 4 h after stimulation, showed upregulation of genes involved in neuronal activity and synaptic plasticity in the EE compared to the B condition. This result is mirrored in the behavioural response to the stimulation which showed a peak in activity around the 1 h time-point. By contrast, EE piglets displayed a signature consistent with a relative decrease in microglial activity compared to those in the B condition. These results confirm those from rodents, suggesting that EE may also confer neuronal health benefits in large mammal models, through a potential relative reduction in neuroinflammatory process and increase in neuroprotection driven by an enrichment-induced increase in behavioural activity.

Relationships in Ongoing Structural Maintenances of the Two Cerebral Cortices of an Individual Brain

A human brain has separate left and right cerebral cortices, each of which must be continuously structurally maintained during adulthood. There is no understanding of how ongoing structural maintenances of separate parts of a mature individual brain, including the 2 cortices, are related. To explore this issue, this study used an unconventional N-of-1 magnetic resonance imaging time-series paradigm to identify relationships between maintenances of structural thicknesses of the 2 cortices in an adult human brain over week intervals for 6 months. The results suggest that maintenances of left and right cortical thicknesses were symmetrically related in some, but asymmetrically related in other, respects. For matched times, thickness magnitudes and variations on the 2 sides were positively correlated and appeared to reflect maintenance symmetry. Maintenance relationships also extended from earlier to later times with temporal continuity and apparent “if-then” contingencies which were reflected in symmetry and asymmetry dynamics spanning 1- to 2-week periods. The findings suggest concepts of individual brain cortical maintenance symmetry, asymmetry, and temporal continuity dynamics that have not been previously recognized. They have implications for defining cortical maintenance traits or states and for development of N-of-1 precision medicine paradigms that can contribute to understanding individual brain health.

Effects of Physical Exercise on Cognitive Functioning and Wellbeing: Biological and Psychological Benefits

Much evidence shows that physical exercise (PE) is a strong gene modulator that induces structural and functional changes in the brain, determining enormous benefit on both cognitive functioning and wellbeing. PE is also a protective factor for neurodegeneration. However, it is unclear if such protection is granted through modifications to the biological mechanisms underlying neurodegeneration or through better compensation against attacks. This concise review addresses the biological and psychological positive effects of PE describing the results obtained on brain plasticity and epigenetic mechanisms in animal and human studies, in order to clarify how to maximize the positive effects of PE while avoiding negative consequences, as in the case of exercise addiction.

Enriched Environment Elicits Proangiogenic Mechanisms After Focal Cerebral Ischemia

Brain has limited capacity for spontaneous recovery of lost function after stroke. Exposure to enriched environment (EE) can facilitate functional recovery, but mechanisms underlying this effect are poorly understood. Here, we used a middle cerebral artery occlusion (MCAO) model to investigate the impact of EE on angiogenesis in the post-ischemic brain in adult male Sprague Dawley rats, and examined whether blood-borne factors may contribute. Compared with standard cage (SC), exposure to EE was associated with greater improvement in neurological function, higher peri-infarct vascular density, and higher chronic post-ischemic cerebral blood flow assessed by laser speckle imaging. The effect persisted for at least 28 days. EE also enhanced the expression of hepatocyte growth factor in the peri-ischemic cortex when measured 15 days after MCAO. Interestingly, serum from rats exposed to EE after MCAO showed elevated levels of hepatocyte growth factor, and plasma or serum from rats exposed to EE after MCAO enhanced the survival and proliferation of cultured endothelial cells, in vitro, when compared with control plasma or serum from SC group after MCAO. Together, our data suggest that exposure to EE promotes angiogenesis in the ischemic brain that may in part be mediated by blood-borne factors.

Intermittent intense exercise protects against cognitive decline in a similar manner to moderate exercise in chronically stressed mice

It is well known that regular low or mild exercise helps to improve and maintain cognition. On the other hand, ever thought many people prefer high-intensity exercise (e.g., running, swimming, biking, soccer, basketball, etc.) to get rid of stress or improve their health, the previous studies reported that intense exercise either impairs cognition or has no effect on cognitive function. However, we previously showed that intermittent intense exercise prevents stress-induced depressive behavior in mice in a similar manner to moderate exercise. On the basis of this finding, we investigated the effect of intermittent intense exercise on cognitive deficit in chronically stressed mice. A total of forty mice were evenly divided into control, stressed, stressed with moderate exercise, and stressed with intense exercise groups. The stressed mice were chronically exposed a restraint stress (10 h/day, 6 days/week for 7 weeks). The exercised mice were subjected to intermittent intense or endurance moderate running on the treadmill three times a week. Cognition was evaluated using the Morris water maze test and the object recognition test. Chronic stress decreased cognition, and newborn cell survival and blood vessel density in the hippocampus. However, both regular intense and moderate exercise prevented decrease of cognition, improved newborn cell survival and blood vessel density. These findings suggest that intermittent intense exercise may protect against decrease of cognition in a similar manner to moderate exercise and that both exercise-induced protection of decrease of cognition is closely related to newborn cell survival and angiogenesis in the hippocampus.

An Exploration Into Short-Interval Maintenance of Adult Hemispheric Cortical Thickness at an Individual Brain Level

Adult cerebral cortical structure is thought to be statically maintained over short intervals. This view is based on group average findings but has never been studied at the individual level. This issue was examined with an unconventional longitudinal magnetic resonance imaging design which measured hemispheric mean cortical thickness of an adult man repeatedly at week intervals over 6 months. These measures were compared with measurement error estimates to test the current prediction that thickness measures would be statically maintained within measurement error variation. The results did not support this prediction. Thickness underwent incremental and decremental fluctuations which ranged up to 0.12 mm and 5.83% over week and multiweek intervals and which differed from measurement error variation. These exploratory analyses suggest a working hypothesis that short-interval cortical structural maintenance in an individual can involve fluctuations in thickness. If confirmed, this hypothesis has potential implications for cortical maintenance mechanisms and precision medicine approaches.

Enriched housing promotes post-stroke functional recovery through astrocytic HMGB1-IL-6-mediated angiogenesis

Enriched environment (EE) is shown to promote angiogenesis, neurogenesis and functional recovery after ischemic stroke. However, the underlying mechanisms remain unclear. C57BL/6 mice underwent middle cerebral artery occlusion (60 min) followed by reperfusion, after which mice were housed in either standard environment (SE) or EE. Here we found that post-ischemic EE exhibited decreased depression and anxiety-like behavior, and promoted angiogenesis and functional recovery compared to SE mice. EE mice treated with high-mobility group box-1 (HMGB1) inhibitor glycyrrhizin had an increased post-stroke depression and anxiety-like behavior, and the angiogenesis and functional recovery were decreased. HMGB1 and interleukin-6 (IL-6) expression in astrocyte were increased in EE mice. EE mice treated with glycyrrhizin decreased, whereas EE mice treated with recombinant HMGB1 (rHMGB1) increased the levels of IL-6 and p-AKT. Blockade of IL-6 with anti-IL-6-neutralizing antibody in EE mice attenuated EE-mediated angiogenesis and functional recovery. Furthermore, our in vitro data revealed that in primary astrocyte cultures rHMGB1 promoted the expression of IL-6 in activated astrocytes. PI₃K/AKT signaling pathway was involved in HMGB1-mediated expression of astrocytic IL-6. Thus, our results reveal a previously uncharacterized property of HMGB1/IL-6 signaling pathway in EE-mediated angiogenesis and functional recovery after ischemic stroke.

The Neuroprotective Effects of Experience on Cognitive Functions: Evidence from Animal Studies on the Neurobiological Bases of Brain Reserve

Brain plasticity is the ability of the nervous system to change structurally and functionally in response to experience. By shaping brain structure and function, experience leads to the creation of a protective reserve that accounts for differences among individuals in susceptibility to age-related brain modifications and pathology. This review is aimed to address the biological bases of the experience-dependent "brain reserve" by describing the results of animal studies that focused on the neuroanatomical and molecular effects of environmental enrichment. More specifically, the effects at the cellular level are considered in terms of changes in neurogenesis, gliogenesis, angiogenesis, and synaptogenesis. Moreover, the effects at the molecular level are described, highlighting gene- and protein-level changes in neurotransmitter and neurotrophin expression. The experimental evidence for the basic biological consequences of environmental enrichment is described for healthy animals. Subsequently, by discussing the findings for animal models that mimic age-related diseases, the involvement of such plastic changes in supporting an organism as it copes with normal and pathological age-related cognitive decline is considered. On the whole, studies of the structural and molecular effects of environmental enrichment strongly support the neuroprotective action of a particularly stimulating lifestyle on cognitive functions. Our current level of understanding of these effects and mechanisms is such that additional and novel studies, systematic reviews, and meta-analyses are necessary to investigate the specific effects of the different components of environmental enrichment in both healthy and pathological models. Only in this way can comprehensive recommendations for proper life habits be developed.

In Vivo Analysis of the Neurovascular Niche in the Developing Xenopus Brain

The neurovascular niche is a specialized microenvironment formed by the interactions between neural progenitor cells (NPCs) and the vasculature. While it is thought to regulate adult neurogenesis by signaling through vascular-derived soluble cues or contacted-mediated cues, less is known about the neurovascular niche during development. In Xenopus laevis tadpole brain, NPCs line the ventricle and extend radial processes tipped with endfeet to the vascularized pial surface. Using in vivo labeling and time-lapse imaging in tadpoles, we find that intracardial injection of fluorescent tracers rapidly labels Sox2/3-expressing NPCs and that vascular-circulating molecules are endocytosed by NPC endfeet. Confocal imaging indicates that about half of the endfeet appear to appose the vasculature, and time-lapse analysis of NPC proliferation and endfeet-vascular interactions suggest that proliferative activity does not correlate with stable vascular apposition. Together, these findings characterize the neurovascular niche in the developing brain and suggest that, while signaling to NPCs may occur through vascular-derived soluble cues, stable contact between NPC endfeet and the vasculature is not required for developmental neurogenesis.

Extinction of Contextual Fear with Timed Exposure to Enriched Environment: A Differential Effect

BACKGROUND

Extinction of fear memory depends on the environmental and emotional cues. Furthermore, consolidation of extinction is also dependent on the environmental exposure. But, the relationship of the time of the exposure to a variety of environmental cues is not well known. The important region involved in facilitation of extinction of fear memory is through diversion of the flow of information leaving the lateral nucleus of amygdala.

PURPOSE

The study aimed to address a question to explain how these brain regions react to environmental stimulation during the retention and extinction of fear memory.

METHODS

An enriched environment (EE) is assumed to mediate extinction of fear memory, we examined the apparent discrepancy between the effects of defensive response, the freezing behavior induced by Pavlovian classical fear conditioning by subjecting them to variance in the timing to EE. The different timing of EE exposure was 10 days of EE either before fear conditioning and/or after extinction training to the rats. The local field potentials was recorded from CA1 hippocampus, lateral nucleus of amygdala and infralimbic region of medial prefrontal cortex (mPFC) during the fear learning and extinction from the control rats and rats exposed to EE before and after fear conditioning.

RESULTS

Exposure to EE before the fear conditioning and after extinction training was more effective in the extinction fear memory. In addition, we also found switching from exploratory locomotion to freezing during retention of contextual fear memory which was associated with decreased theta power and reduced synchronized theta oscillations in CA1-hippocampus, lateral nucleus of amygdala, and infralimbic region of mPFC.

CONCLUSION

Thus, we propose that the timing of exposure to EE play a key role in the extinction of fear memory.

The effects of aging in the hippocampus and cognitive decline

Aging is a natural process that is associated with cognitive decline as well as functional and social impairments. One structure of particular interest when considering aging and cognitive decline is the hippocampus, a brain region known to play an important role in learning and memory consolidation as well as in affective behaviours and mood regulation, and where both functional and structural plasticity (e.g., neurogenesis) occur well into adulthood. Neurobiological alterations seen in the aging hippocampus including increased oxidative stress and neuroinflammation, altered intracellular signalling and gene expression, as well as reduced neurogenesis and synaptic plasticity, are thought to be associated with age-related cognitive decline. Non-invasive strategies such as caloric restriction, physical exercise, and environmental enrichment have been shown to counteract many of the age-induced alterations in hippocampal signalling, structure, and function. Thus, such approaches may have therapeutic value in counteracting the deleterious effects of aging and protecting the brain against age-associated neurodegenerative processes.

Neonatal alcohol exposure reduces number of parvalbumin-positive interneurons in the medial prefrontal cortex and impairs passive avoidance acquisition in mice deficits not rescued from exercise

Developmental alcohol exposure causes a host of cognitive and neuroanatomical abnormalities, one of which is impaired executive functioning resulting from medial prefrontal cortex (mPFC) damage. This study determined whether third-trimester equivalent alcohol exposure reduced the number of mPFC GABAergic parvalbumin-positive (PV+) interneurons, hypothesized to play an important role in local inhibition of the mPFC. The impact on passive avoidance learning and the therapeutic role of aerobic exercise in adulthood was also explored. Male C57BL/6J mice received either saline or 5g/kg ethanol (two doses, two hours apart) on PD 5, 7, and 9. On PD 35, animals received a running wheel or remained sedentary for 48days before behavioral testing and perfusion on PD 83. The number of PV+ interneurons was stereologically measured in three separate mPFC subregions: infralimbic, prelimbic and anterior cingulate cortices (ACC). Neonatal alcohol exposure decreased number of PV+ interneurons and volume of the ACC, but the other regions of the mPFC were spared. Alcohol impaired acquisition, but not retrieval of passive avoidance, and had no effect on motor performance on the rotarod. Exercise had no impact on PV+ cell number, mPFC volume, or acquisition of passive avoidance, but enhanced retrieval in both control and alcohol-exposed groups, and enhanced rotarod performance in the control mice. Results support the hypothesis that part of the behavioral deficits associated with developmental alcohol exposure are due to reduced PV+ interneurons in the ACC, but unfortunately exercise does not appear to be able to reverse any of these deficits.

Oral administration of corticosterone at stress-like levels drives microglial but not vascular disturbances post-stroke

Exposure to chronic stress following stroke has been shown, both clinically and pre-clinically, to impact negatively on the recovery process. While this phenomenon is well established, the specific mechanisms involved have remained largely unexplored. One obvious signaling pathway through which chronic stress may impact on the recovery process is via corticosterone, and its effects on microglial activity and vascular remodeling. In the current study, we were interested in examining how orally delivered corticosterone at a stress-like concentration impacted on microglial activity and vascular remodeling after stroke. We identified that corticosterone administration for two weeks following stroke significantly increased tissue loss and decreased the weight of the spleen and thymus. We also identified that corticosterone administration significantly altered the expression of the key microglial complement receptor, CD11b after stroke. Corticosterone administration did not alter the expression of the vessel basement membrane protein, Collagen IV after stroke. Together, these results suggest that corticosterone is likely to represent only one of the major stress signals responsible for driving the negative impacts of chronic stress on recovery.

Environmental Enrichment Induces Increased Cerebral Capillary Density and Improved Cognitive Function in Mice

Enrichment provides an environment that fosters increased physical activity and sensory stimulation as compared to standard housing. Promoting and sustaining stimulation increases neuronal activity and, consequently, brain oxygen demand. The mammalian brain modulates its microvascular network to accommodate tissue energy demand in a process referred to as angioplasticity. In this study we investigated the effect of an environmental enrichment on cerebral capillary density and cognitive performance in mice. Microvascular density (N/mm²) was determined by GLUT-1 immunohistochemistry in mice (3 months old) after 3 weeks of placement in a non-enriched or an enriched environment. The Y-maze test and a novel object recognition test were used to evaluate cognitive function in the aged mice (18 months old) after 4 weeks of environmental enrichment. Compared to the non-enriched control mice, the mice with environmental enrichment had significantly higher (~30%) capillary density in cortical brain. The enriched aged mice (n = 12) showed improved cognitive function, presented as a significantly higher alternation rate in the Y-Maze test compared to the non-enriched controls (n = 8). Our data suggest that environmental enrichment may result in increased brain capillary density and improved cognitive performance.

VEGF preconditioning leads to stem cell remodeling and attenuates age-related decay of adult hippocampal neurogenesis

Several factors are known to enhance adult hippocampal neurogenesis but a factor capable of inducing a long-lasting neurogenic enhancement that attenuates age-related neurogenic decay has not been described. Here, we studied hippocampal neurogenesis following conditional VEGF induction in the adult brain and showed that a short episode of VEGF exposure withdrawn shortly after the generation of durable new vessels (but not under conditions where newly made vessels failed to persist) is sufficient for neurogenesis to proceed at a markedly elevated level for many months later. Continual neurogenic increase over several months was not accompanied by accelerated exhaustion of the neuronal stem cell (NSC) reserve, thereby allowing neurogenesis to proceed at a markedly elevated rate also in old mice. Neurogenic enhancement by VEGF preconditioning was, in part, attributed to rescue of age-related NSC quiescence. Remarkably, VEGF caused extensive NSC remodelling manifested in transition of the enigmatic NSC terminal arbor onto long cytoplasmic processes engaging with and spreading over even remote blood vessels, a configuration reminiscent of early postnatal "juvenile" NSCs. Together, these findings suggest that VEGF preconditioning might be harnessed for long-term neurogenic enhancement despite continued exposure to an "aged" systemic milieu.

Restricted vs. unrestricted wheel running in mice: Effects on brain, behavior and endocannabinoids

Beneficial effects of voluntary wheel running on hippocampal neurogenesis, morphology and hippocampal-dependent behavior have widely been studied in rodents, but also serious side effects and similarities to stereotypy have been reported. Some mouse strains run excessively when equipped with running wheels, complicating the comparability to human exercise regimes. Here, we investigated how exercise restriction to 6h/day affects hippocampal morphology and metabolism, stereotypic and basal behaviors, as well as the endocannabinoid system in wheel running C57BL/6 mice; the strain most commonly used for behavioral analyses and psychiatric disease models. Restricted and unrestricted wheel running had similar effects on immature hippocampal neuron numbers, thermoregulatory nest building and basal home-cage behaviors. Surprisingly, hippocampal gray matter volume, assessed with magnetic resonance (MR) imaging at 9.4 Tesla, was only increased in unrestricted but not in restricted runners. Moreover, unrestricted runners showed less stereotypic behavior than restricted runners did. However, after blockage of running wheels for 24h stereotypic behavior also increased in unrestricted runners, arguing against a long-term effect of wheel running on stereotypic behavior. Stereotypic behaviors correlated with frontal glutamate and glucose levels assessed by ¹H-MR spectroscopy. While acute running increased plasma levels of the endocannabinoid anandamide in former studies in mice and humans, we found an inverse correlation of anandamide with the daily running distance after long-term running. In conclusion, although there are some diverging effects of restricted and unrestricted running on brain and behavior, restricted running does not per se seem to be a better animal model for aerobic exercise in mice.

More than one road leads to Rome: A narrative review and meta-analysis of physical activity intervention effects on cognition in youth

A growing body of research indicates that physical activity (PA) positively impacts cognitive function in youth. However, not all forms of PA benefit cognition equally. The purpose of this review was to determine the effect of different types of chronic PA interventions on cognition in children and adolescents. A systematic search of electronic databases and examination of the reference lists of relevant studies resulted in the identification of 28 studies. Seven categories of PA were identified, based on all possible combinations of three types of PA (aerobic, motor skill, cognitively engaging), and four comparison groups (no treatment, academic, traditional physical education, aerobic). Effect sizes were calculated based on means and SDs at the post-test using Hedge's g formula, which includes a correction for small sample bias. Each study was only entered once in each intervention-comparator category. Full data were provided from 21 studies (28 effect sizes; n=2042 intervention; n=2002 comparison group). Overall, chronic PA interventions had a significant small-to-moderate effect on cognition (0.46). Moderate significant positive effects were identified when PA interventions were compared to no treatment (0.86) or academic content (0.57). A non-significant effect was noted when PA interventions were compared to traditional physical education (0.09) or aerobic group (0.80). However, high heterogeneity in pooled effect sizes suggests that important differences in the qualitative characteristics of the PA intervention and comparison interventions may exist. Effect sizes based on comparisons between different types of PA interventions and comparison groups are discussed in order to identify possible directions for future investigations. We conclude that chronic PA interventions have a positive impact on cognitive function in youth, but more systematic research is needed in this area.

Exercise and Environmental Enrichment as Enablers of Task-Specific Neuroplasticity and Stroke Recovery

Improved stroke care has resulted in greater survival, but >50% of patients have chronic disabilities and 33% are institutionalized. While stroke rehabilitation is helpful, recovery is limited and the most significant gains occur in the first 2-3 months. Stroke triggers an early wave of gene and protein changes, many of which are potentially beneficial for recovery. It is likely that these molecular changes are what subserve spontaneous recovery. Two interventions, aerobic exercise and environmental enrichment, have pleiotropic actions that influence many of the same molecular changes associated with stroke injury and subsequent spontaneous recovery. Enrichment paradigms have been used for decades in adult and neonatal animal models of brain injury and are now being adapted for use in the clinic. Aerobic exercise enhances motor recovery and helps reduce depression after stroke. While exercise attenuates many of the signs associated with normal aging (e.g., hippocampal atrophy), its ability to reverse cognitive impairments subsequent to stroke is less evident. It may be that stroke, like other diseases such as cancer, needs to use multimodal treatments that augment complimentary neurorestorative processes.

Dancer perceptions of the cognitive, social, emotional, and physical benefits of modern styles of partnered dancing

OBJECTIVE

To study dancers' perceptions of the physical, cognitive, affective, and social benefits of partnered dancing.

METHOD

225 dancers (71% female) were recruited through a community ballroom dance center and completed an online survey designed to measure their perceptions of the physical, cognitive, affective, and social benefits of modern, partnered dance styles (swing, Lindy Hop, and ballroom dancing). Subgroups were formed for analyses. For one set of analyses, groups based on length of dance participation were formed: experienced (dancing for more than 2 years) or novice (dancing for less than a year) dancers. For another set of analyses, groups based on frequency of dance practice were formed: committed (dancing at least one or more times per week) or occasional (dancing two or fewer times per month).

RESULTS

The majority of participants reported perceived benefits in physical fitness, cognition, affect, and social functioning. Experienced dancers reported significantly greater self-perceived physical, social, and cognitive benefits than novice dancers. Committed dancers were more likely than occasional dancers to report improvements in physical fitness, U=6942, z=2.38, r=0.16, p<0.05. A Mann-Whitney test indicated that self-reported improvements in mood (i.e., feeling less depressed and more happy) were greater for women than for men, U=3945, z=-3.07, r=0.20, p<0.001. Length and frequency of dance participation significantly predicted perceived physical benefits [Χ(2) (1,6)=35.463, p <0.001, R(2)=0.16] and social benefits [Χ(2) (1,6)=15.776, p<0.05, R(2)=0.07], but not cognitive benefits.

CONCLUSIONS

Results suggest that participation in partnered dance styles is associated with perceived improvements in physical fitness, cognitive functioning, social functioning, mood, and self-confidence, and that perceived benefits may increase as individuals dance more frequently and over longer periods of time.

Behavioral experiences as drivers of oligodendrocyte lineage dynamics and myelin plasticity

Many behavioral experiences are known to promote hippocampal neurogenesis. In contrast, the ability of behavioral experiences to influence the production of oligodendrocytes and myelin sheath formation remains relatively unknown. However, several recent studies indicate that voluntary exercise and environmental enrichment can positively influence both oligodendrogenesis and myelination, and that, in contrast, social isolation can negatively influence myelination. In this review we summarize studies addressing the influence of behavioral experiences on oligodendrocyte lineage cells and myelin, and highlight potential mechanisms including experience-dependent neuronal activity, metabolites, and stress effectors, as well as both local and systemic secreted factors. Although more study is required to better understand the underlying mechanisms by which behavioral experiences regulate oligodendrocyte lineage cells, this exciting and newly emerging field has already revealed that oligodendrocytes and their progenitors are highly responsive to behavioral experiences and suggest the existence of a complex network of reciprocal interactions among oligodendrocyte lineage development, behavioral experiences, and brain function. Achieving a better understanding of these relationships may have profound implications for human health, and in particular, for our understanding of changes in brain function that occur in response to experiences. This article is part of the Special Issue entitled 'Oligodendrocytes in Health and Disease'.

Molecular Mechanisms for Exercise Training-Induced Changes in Vascular Structure and Function: Skeletal Muscle, Cardiac Muscle, and the Brain

Compared with resting conditions, during incremental exercise, cardiac output in humans is elevated from ~5 to 25 L min(-1). In conjunction with this increase, the proportion of cardiac output directed toward skeletal muscle increases from ~20% to 85%, while blood flow to cardiac muscle increases 500% and blood flow to specific brain structures increases nearly 200%. Based on existing evidence, researchers believe that blood flow in these tissues is matched to the increases in metabolic rate during exercise. This phenomenon, the matching of blood flow to metabolic requirement, is often referred to as functional hyperemia. This chapter summarizes mechanical and metabolic factors that regulate functional hyperemia as well as other exercise-induced signals, which are also potent stimuli for chronic adaptations in vascular biology. Repeated exposure to exercise-induced increases in shear stress and the induction of angiogenic factors alter vascular cell gene expression and mediate changes in vascular volume and blood flow control. The magnitude and regulation of this coordinated response appear to be tissue specific and coupled to other factors such as hypertrophy and hyperplasia. The cumulative effects of these adaptations contribute to increased exercise capacity, reduced relative challenge of a given submaximal exercise bout and ameliorated vascular outcomes in patient populations with pathological conditions. In the subsequent discussion, this chapter explores exercise as a regulator of vascular biology and summarizes the molecular mechanisms responsible for exercise training-induced changes in vascular structure and function in skeletal and cardiac muscle as well as the brain.