Environmental enrichment may protect against hippocampal atrophy in the chronic stages of traumatic brain injury

Cognitive reserve in the recovery and rehabilitation of stroke and traumatic brain injury: A systematic review

Objective: Cognitive reserve (CR) is the brain's ability to cope with changes related to aging and/or disease. Originally introduced to explain individual differences in the clinical manifestations of dementia, CR has recently emerged as a relevant construct in stroke and traumatic brain injury (TBI). This systematic review aims to investigate whether CR could predict post-stroke and TBI clinical recovery and rehabilitation outcomes, and how different variables used to estimate CR (i.e., proxies) are related to the prognosis and effectiveness of rehabilitation in these clinical populations. Method: A search was made in Pubmed, Embase, and PsycInfo for articles published until 12 January 2023, following the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) protocol guidelines. Results: 31 studies were included after completing all screening stages. Overall, results show that a higher CR was associated with a better prognosis and a more effective rehabilitation in most of the clinical aspects considered: cognitive functioning, functional, occupational, and socio-emotional abilities, as well as psychiatric and neurological scales. Conclusions: A higher CR seems to be associated with a more favorable prognosis and a better rehabilitation outcome after stroke and TBI. Results suggest that CR should be taken into account in clinical practice to make more accurate predictions about recovery and effectiveness of rehabilitation. However, some inconsistencies suggest the need for further investigations, possibly using multiple proxies for CR.

Environmental factors and their impact on chronic pain development and maintenance

It is more than recognized and accepted that the environment affects the physiological responses of all living things, from bacteria to superior vertebrates, constituting an important factor in the evolution of all species. Environmental influences range from natural processes such as sunlight, seasons of the year, and rest to complex processes like stress and other mood disorders, infections, and air pollution, being all of them influenced by how each creature deals with them. In this chapter, it will be discussed how some of the environmental elements affect directly or indirectly neuropathic pain, a type of chronic pain caused by a lesion or disease of the somatosensory nervous system. For that, it was considered the edge of knowledge in translational research, thus including data from human and experimental animals as well as the applicability of such findings.

The role of cognitive reserve in traumatic brain injury: a systematic review of observational studies

OBJECTIVE

Evaluate the role of cognitive reserve (CR) on cognitive and physical sequelae in traumatic brain injury (TBI).

METHODS

A comprehensive search strategy was conducted in four databases in English and Spanish in the last 12 years (2011-2023). Inclusion criteria: original cross-sectional and longitudinal studies whose main or secondary objective was to evaluate the effect of CR in adult patients with TBI. PRISMA guidelines were used to report the search and selection method and STROBE checklist was used to evaluate the quality of studies.

RESULTS

Eighteen observational studies were included in this review. Multiple sources of variability were observed: number of patients, time of evolution, severity of the TBI, type of CR proxy, cognitive assessment instrument, etc. However, the most commonly used indicators of CR were premorbid IQ and educational attainment. A positive and consistent association between CR and performance on cognitive tests after injury was found.

CONCLUSIONS

CR has a consistent positive effect on cognition and on some other aspects of recovery in traumatic brain injury. In future studies, it will be necessary to promote the use of CR indices based on various indicators and explore the effects of CR on other aspects related to the recovery of brain trauma.

Environmental Enrichment for Stroke and Traumatic Brain Injury: Mechanisms and Translational Implications

Acquired brain injuries, such as ischemic stroke, intracerebral hemorrhage (ICH), and traumatic brain injury (TBI), can cause severe neurologic damage and even death. Unfortunately, currently, there are no effective and safe treatments to reduce the high disability and mortality rates associated with these brain injuries. However, environmental enrichment (EE) is an emerging approach to treating and rehabilitating acquired brain injuries by promoting motor, sensory, and social stimulation. Multiple preclinical studies have shown that EE benefits functional recovery, including improved motor and cognitive function and psychological benefits mediated by complex protective signaling pathways. This article provides an overview of the enriched environment protocols used in animal models of ischemic stroke, ICH, and TBI, as well as relevant clinical studies, with a particular focus on ischemic stroke. Additionally, we explored studies of animals with stroke and TBI exposed to EE alone or in combination with multiple drugs and other rehabilitation modalities. Finally, we discuss the potential clinical applications of EE in future brain rehabilitation therapy and the molecular and cellular changes caused by EE in rodents with stroke or TBI. This article aims to advance preclinical and clinical research on EE rehabilitation therapy for acquired brain injury. © 2024 American Physiological Society. Compr Physiol 14:5291-5323, 2024.

Moderate-Severe TBI as a Progressive Disorder: Patterns and Predictors of Cognitive Declines in the Chronic Stages of Injury

BACKGROUND

Moderate-severe traumatic brain injury (TBI) has been associated with progressive cognitive decline in the chronic injury stages in a small number of studies.

OBJECTIVE

This study aimed to (i) replicate our previous findings of decline from 1 to 3+ years post-injury in a larger, non-overlapping sample and (ii) extend these findings by examining the proportion of decliners in 2 earlier time windows, and by investigating novel predictors of decline.

METHODS

N = 48 patients with moderate-severe TBI underwent neuropsychological assessment at 2, 5, 12 months, and 30+ months post-injury. We employed the Reliable Change Index (RCI) to evaluate decline, stability and improvement across time and logistic regression to identify predictors of decline (demographic/cognitive reserve; injury-related).

RESULTS

The proportions of patients showing decline were: 12.5% (2-5 months post-injury), 17% (5-12 months post-injury), and 27% (12-30+ months post-injury). Measures of verbal retrieval were most sensitive to decline. Of the predictors, only left progressive hippocampal volume loss from 5 to 12 months post-injury significantly predicted cognitive decline from 12 to 30+ months post-injury.

CONCLUSIONS

Identical to our previous study, 27% of patients declined from 12 to 30+ months post-injury. Additionally, we found that the further from injury, the greater the proportion of patients declining. Importantly, earlier progressive hippocampal volume loss predicted later cognitive decline. Taken together, the findings highlight the need for ongoing research and treatment that target these deleterious mechanisms affecting patients in the chronic stages of moderate-severe TBI.

Modulation of neurotrophic factors in the treatment of dementia, stroke and TBI: Effects of Cerebrolysin

Neurotrophic factors (NTFs) are involved in the pathophysiology of neurological disorders such as dementia, stroke and traumatic brain injury (TBI), and constitute molecular targets of high interest for the therapy of these pathologies. In this review we provide an overview of current knowledge of the definition, discovery and mode of action of five NTFs, nerve growth factor, insulin-like growth factor 1, brain derived NTF, vascular endothelial growth factor and tumor necrosis factor alpha; as well as on their contribution to brain pathology and potential therapeutic use in dementia, stroke and TBI. Within the concept of NTFs in the treatment of these pathologies, we also review the neuropeptide preparation Cerebrolysin, which has been shown to resemble the activities of NTFs and to modulate the expression level of endogenous NTFs. Cerebrolysin has demonstrated beneficial treatment capabilities in vitro and in clinical studies, which are discussed within the context of the biochemistry of NTFs. The review focuses on the interactions of different NTFs, rather than addressing a single NTF, by outlining their signaling network and by reviewing their effect on clinical outcome in prevalent brain pathologies. The effects of the interactions of these NTFs and Cerebrolysin on neuroplasticity, neurogenesis, angiogenesis and inflammation, and their relevance for the treatment of dementia, stroke and TBI are summarized.

Modulating chronic outcomes after pediatric traumatic brain injury: Distinct effects of social and environmental enrichment

Impairments in social and cognitive function are a common consequence of pediatric traumatic brain injury (TBI). Rehabilitation has the potential to promote optimal behavioral recovery. Here, we evaluated whether an enhanced social and/or cognitive environment could improve long-term outcomes in a preclinical model of pediatric TBI. Male C57Bl/6 J mice received a moderately-severe TBI or sham procedure at postnatal day 21. After one week, mice were randomized to different social conditions (minimal socialization, n = 2/cage; or social grouping, n = 6/cage), and housing conditions (standard cage, or environmental enrichment (EE), incorporating sensory, motor, and cognitive stimuli). After 8 weeks, neurobehavioral outcomes were assessed, followed by post-mortem neuropathology. We found that TBI mice exhibited hyperactivity, spatial memory deficits, reduced anxiety-like behavior, and reduced sensorimotor performance compared to age-matched sham controls. Pro-social and sociosexual behaviors were also reduced in TBI mice. EE increased sensorimotor performance, and the duration of sociosexual interactions. Conversely, social housing reduced hyperactivity and altered anxiety-like behavior in TBI mice, and reduced same-sex social investigation. TBI mice showed impaired spatial memory retention, except for TBI mice exposed to both EE and group housing. In the brain, while TBI led to significant regional tissue atrophy, social housing had modest neuroprotective effects on hippocampal volumes, neurogenesis, and oligodendrocyte progenitor numbers. In conclusion, manipulation of the post-injury environment has benefit for chronic behavioral outcomes, but the benefits are specific to the type of enrichment available. This study improves understanding of modifiable factors that may be harnessed to optimize long-term outcomes for survivors of early-life TBI.

Beneficial effects of enriched environment on behavior, cognitive functions, and hippocampal brain-derived neurotrophic factor level following postnatal serotonin depletion in male rats

The neurotransmitter serotonin (5-HT) is one of the most important modulators of neural circuitry and has a critical role in neural development and functions. Previous studies indicated that changes in serotonergic system signaling in early life critically impact mental health, behavior, the morphology of hippocampal neurons, and cognitive functions across the lifespan. The enriched environment (EE) has indicated beneficial effects on behavior and cognitive functions in the developmental period of life, but its impacts on cognitive impairments and behavioral changes following postnatal serotonin depletion are unknown. Therefore, the present study aimed to evaluate the influences of the EE housing (postnatal days [PNDs] 21-60) following postnatal serotonin depletion (by para-chlorophenylalanine [PCPA], 100 mg/kg, s.c, in PNDs 10-20) on anxiety-related behaviors, cognitive functions, and brain-derived neurotrophic factor (BDNF) mRNA expression in the hippocampus of male rats. Memory and behavioral parameters were examined in early adulthood and after that, the hippocampi of rats were removed to determine the BDNF mRNA expression by PCR (PNDs 60-70). The findings of the present work indicated that adolescent EE exposure alleviated memory impairment, decreased BDNF levels, and anxiety disorders induced by experimental depletion of serotonin. Overall, these results indicate that serotonergic system dysregulation during the developmental periods can be alleviated by adolescent EE exposure.

Implementation of active injury management (AIM) in youth with acute concussion: A randomized controlled trial

BACKGROUND

Nearly 2 million youth seek acute medical care following concussion in the U.S. each year. Current standard of care recommends rest for the first 48 h after a concussion. However, research suggests that prolonged rest may lengthen recovery time especially for patients with certain risk profiles. Research indicates that physical activity and behavioral management interventions (sleep, stress management) may enhance recovery. To date, there is limited empirical evidence to inform acute (<72 h) concussion recommendations for physical activity and behavioral management in adolescents.

OBJECTIVE

To determine the effectiveness of physical activity and behavioral management for acute concussion in adolescents and young adults, and to evaluate the role of patient characteristics on treatment response.

METHODS

This multicenter prospective randomized controlled trial will determine which combination of physical activity and behavioral management is most effective for patients 11-24 years old who present to the emergency department or concussion clinic within 72 h of injury. Participants are randomized into: 1) rest, 2) physical activity, 3) mobile health application (mHealth) behavioral management, or 4) physical activity and mHealth app conditions. Assessments at enrollment, 3-5 days, 14 days, 1 month, and 2 months include: concussion symptoms, balance, vestibular-ocular and cognitive assessments, quality of life, and recovery time. Somatic symptoms and other risk factors are evaluated at enrollment. Compliance with treatment and symptoms are assessed daily using actigraph and daily self-report. The primary study outcome is symptoms at 14 days.

CONCLUSION

Prescribed physical activity and behavioral management may improve outcomes in youth following acute concussion.

Sex-dependent effects of postweaning exposure to an enriched environment on visceral pain and anxiety- and depression-like behaviors induced by neonatal maternal separation

BACKGROUND

Neonatal maternal separation (NMS) can lead to visceral pain and anxiety- and depression-like behaviors. An enriched environment (EE) can alleviate NMS-induced pain and mental disorders, but previous studies have mostly been performed in male animals. Therefore, the aim of this study was to investigate whether the effects of EE were sex dependent at different stages of development.

METHODS

Female and Male C57BL/6 J mice that had been subjected to NMS alone and those subjected to both NMS and exposed to EE were used in this study. The visceral pain threshold test (PTT), open field test (OFT), sucrose preference test (SPT), and forced swimming test (FST) were conducted to evaluate visceral pain, anxiety-like behavior, and depression-like behavior in mice, respectively.

RESULTS

Compared with the male mice in the NMS group without EE exposure, those exposed to EE from postnatal day (P)21 to 41 showed an increase of the visceral pain threshold in the PTT, an increase of the central time and central distance in the OFT, an increase of the sucrose preference rate in the SPT, and a decrease of the time of immobility in the FST. Compared with both female and male mice in the NMS group without EE exposure, those exposed to EE from P21 to P61 had an increase of the visceral pain threshold in the PTT, an increase of the central time and central distance in the OFT, an increase in the sucrose preference rate in the SPT, and a decrease of the time of immobility in the FST.

CONCLUSIONS

EE is more effective in male NMS mice, while longer EE is required in female NMS mice for positive effects.

Cognitive efficacy and neural mechanisms of music-based neurological rehabilitation for traumatic brain injury

Traumatic brain injury (TBI) causes lifelong cognitive deficits, most often in executive function (EF). Both musical training and music-based rehabilitation have been shown to enhance EF and neuroplasticity. Thus far, however, there is little evidence for the potential rehabilitative effects of music for TBI. Here, we review the core findings from our recent cross-over randomized controlled trial in which a 10-week music-based neurological rehabilitation (MBNR) protocol was administered to 40 patients with moderate-to-severe TBI. Neuropsychological testing and structural/functional magnetic resonance imaging were collected at three time points (baseline, 3 months, and 6 months); one group received the MBNR between time points 1 and 2, while a second group received it between time points 2 and 3. We found that both general EF and set shifting improved after the intervention, and this effect was maintained long term. Morphometric analyses revealed therapy-induced gray matter volume changes most consistently in the right inferior frontal gyrus, changes that correlated with better outcomes in set shifting. Finally, we found changes in the between- and within-network functional connectivity of large-scale resting-state networks after MBNR, which also correlated with measures of EF. Taken together, the data provide evidence for concluding that MBNR improves EF in TBI; also, the data show that morphometric and resting-state functional connectivity are sensitive markers with which to monitor the neuroplasticity induced by the MBNR intervention.

Patterns of change in cortical morphometry following traumatic brain injury in adults

Progressive cortical volumetric loss following moderate–severe traumatic brain injury (TBI) has been observed; however, regionally specific changes in the structural determinants of cortical volume, namely, cortical thickness (CT) and cortical surface area (CSA), are unknown and may inform the patterns and neural substrates of neurodegeneration and plasticity following injury. We aimed to (a) assess differences in CT and CSA between TBI participants and controls in the early chronic stage post‐injury, (b) describe longitudinal changes in cortical morphometry following TBI, and (c) examine how regional changes in CT and CSA are associated. We acquired magnetic resonance images for 67 participants with TBI at up to 4 time‐points spanning 5 months to 7 years post‐injury, and 18 controls at 2 time‐points. In the early chronic stage, TBI participants displayed thinner cortices than controls, predominantly in frontal regions, but no CSA differences. Throughout the chronic period, TBI participants showed widespread CT reductions in posterior cingulate/precuneus regions and moderate CT increase in frontal regions. Additionally, CSA showed a significant decrease in the orbitofrontal cortex and circumscribed increase in posterior regions. No changes were identified in controls. Relationships between regional cortical changes in the same morphological measure revealed coordinated patterns within participants, whereas correlations between regions with CT and CSA change yielded bi‐directional relationships. This suggests that these measures may be differentially affected by neurodegenerative mechanisms such as transneuronal degeneration following TBI and that degeneration may be localized to the depths of cortical sulci. These findings emphasize the importance of dissecting morphometric contributions to cortical volume change.

Environmental enrichment ameliorates high-fat diet induced olfactory deficit and decrease of parvalbumin neurons in the olfactory bulb in mice

Overweight induced by high-fat diet (HFD) represents one of the major health concerns in modern societies, which can cause lasting peripheral and central metabolic disorders in all age groups. Specifically, childhood obesity could lead to life-long impact on brain development and functioning. On the other hand, environmental enrichment (EE) has been demonstrated to be beneficial for learning and memory. Here, we explored the impact of high-fat diet on olfaction and organization of olfactory bulb cells in adolescent mice, and the effect of EE intervention thereon. Puberty mice (3-week-old) fed with HFD for 10 weeks exhibited poorer odor sensitivity and olfactory memory relative to controls consuming standard chows. The behavioral deficits were rescued in the HFD group with EE intervention. Neuroanatomically, parvalbumin (PV) interneurons in the olfactory bulb (OB) were reduced in the HFD-fed animals relative to control, while EE intervention also normalized this alteration. In contrast, cells expressing calbindin (CB), doublecortin (DCX) in the OB were not altered. Our findings suggest that PV interneurons may play a crucial role in mediating the HFD-induced olfactory deficit in adolescent mice, and can also serve a protective effect of EE against the functional deficit.

Environmental enrichment: A concept analysis

OBJECTIVES

The concept analysis of environmental enrichment aims to clarify the meaning of the term contributing to a shared understanding of its use in healthcare and future research studies. Environmental enrichment has implications in health promotion in children's development and healthy aging in the general population.

METHODS

A literature search using PubMed and CINAHL databases on environmental enrichment was conducted to identify the uses of the term from various disciplines. The keywords are "environmental enrichment", "socialization", "physical activity", "cognitive stimulation", and "experience-dependent". Human studies from 2000 to 2020 were included in the search.

RESULTS

Availability of green spaces, neighborhood safety, walkability to community centers, and accessibility of community resources are antecedents of environmental enrichment. Defining attributes are positive stimulation, interpersonal interaction, and physical engagement. The consequences of environmental enrichment are improved cognitive functioning in children, decline in memory impairment, and reduced risk of developing dementia in the elderly.

CONCLUSION

Engaging and counseling patients, family members, and the community in adverse effects of a deprived environment and the benefits of an enriched environment is a vital tenet of the nursing discipline. Understanding the optimum amount of positive stimulation, interpersonal interaction duration, and frequency are needed in future research.

Progressive Neurodegeneration Across Chronic Stages of Severe Traumatic Brain Injury

OBJECTIVE

To examine the trajectory of structural gray matter changes across 2 chronic periods of recovery in individuals who have sustained severe traumatic brain injury (TBI), adding to the growing literature indicating that neurodegenerative processes occur in the months to years postinjury.

PARTICIPANTS

Patients who experienced posttraumatic amnesia of 1 hour or more, and/or scored 12 or less on the Glasgow Coma Scale at the emergency department or the scene of the accident, and/or had positive brain imaging findings were recruited while receiving inpatient care, resulting in 51 patients with severe TBI.

METHODS

Secondary analyses of gray matter changes across approximately 5 months, 1 year, and 2.5 years postinjury were undertaken, using an automated segmentation protocol with improved accuracy in populations with morphological anomalies. We compared patients and matched controls on regions implicated in poorer long-term clinical outcome (accumbens, amygdala, brainstem, hippocampus, thalamus). To model brain-wide patterns of change, we then conducted an exploratory principal component analysis (PCA) on the linear slopes of all regional volumes across the 3 time points. Finally, we assessed nonlinear trends across earlier (5 months-1 year) versus later (1-2.5 years) time-windows with PCA to compare degeneration rates across time. Chronic degeneration was predicted cortically and subcortically brain-wide, and within specific regions of interest.

RESULTS

(1) From 5 months to 1 year, patients showed significant degeneration in the accumbens, and marginal degeneration in the amygdala, brainstem, thalamus, and the left hippocampus when examined unilaterally, compared with controls. (2) PCA components representing subcortical and temporal regions, and regions from the basal ganglia, significantly differed from controls in the first time-window. (3) Progression occurred at the same rate across both time-windows, suggesting neither escalation nor attenuation of degeneration across time.

CONCLUSION

Localized yet progressive decline emphasizes the necessity of developing interventions to offset degeneration and improve long-term functioning.

How environmental enrichment balances out neuroinflammation in chronic pain and comorbid depression and anxiety disorders

Depression and anxiety commonly occur in chronic pain states and the coexistence of these diseases worsens outcomes for both disorders and may reduce treatment adherence and response. Despite the advances in the knowledge of chronic pain mechanisms, pharmacological treatment is still unsatisfactory. Research based on exposure to environmental enrichment is currently under investigation and seems to offer a promising low-cost strategy with no side effects. In this review, we discuss the role of inflammation as a major biological substrate and aetiological factor of chronic pain and depression/anxiety and report a collection of preclinical evidence of the effects and mechanisms of environmental enrichment. As microglia participates in the development of both conditions, we also discuss microglia as a potential target underlying the beneficial actions of environmental enrichment in chronic pain and comorbid depression/anxiety. We also discuss how alternative interventions under clinical guidelines, such as environmental enrichment, may improve treatment compliance and patient outcomes.

Differential paraventricular nucleus activation and behavioral responses to social isolation in prairie voles following environmental enrichment with and without physical exercise

Social stressors produce neurobiological and emotional consequences in social species. Environmental interventions, such as environmental enrichment and exercise, may modulate physiological and behavioral stress responses. The present study investigated the benefits of environmental enrichment and exercise against social stress in the socially monogamous prairie vole. Female prairie voles remained paired with a sibling (control) or were isolated from a sibling for 4 weeks. The isolated groups were assigned to isolated sedentary, isolated with environmental enrichment, or isolated with both enrichment and exercise conditions. Behaviors related to depression, anxiety, and sociality were investigated using the forced swim test (FST), elevated plus maze (EPM), and a social crowding stressor (SCS), respectively. cFos expression was evaluated in stress-related circuitry following the SCS. Both enrichment and enrichment with exercise protected against depression-relevant behaviors in the FST and social behavioral disruptions in the SCS, but only enrichment with exercise protected against anxiety-related behaviors in the EPM and altered cFos expression in the hypothalamic paraventricular nucleus in isolated prairie voles. Enrichment may improve emotion-related and social behaviors, however physical exercise may be an important component of environmental strategies for protecting against anxiety-related behaviors and reducing neural activation as a function of social stress.

Resting-State Network Plasticity Induced by Music Therapy after Traumatic Brain Injury

Traumatic brain injury (TBI) is characterized by a complex pattern of abnormalities in resting-state functional connectivity (rsFC) and network dysfunction, which can potentially be ameliorated by rehabilitation. In our previous randomized controlled trial, we found that a 3-month neurological music therapy intervention enhanced executive function (EF) and increased grey matter volume in the right inferior frontal gyrus (IFG) in patients with moderate-to-severe TBI (N = 40). Extending this study, we performed longitudinal rsFC analyses of resting-state fMRI data using a ROI-to-ROI approach assessing within-network and between-network rsFC in the frontoparietal (FPN), dorsal attention (DAN), default mode (DMN), and salience (SAL) networks, which all have been associated with cognitive impairment after TBI. We also performed a seed-based connectivity analysis between the right IFG and whole-brain rsFC. The results showed that neurological music therapy increased the coupling between the FPN and DAN as well as between these networks and primary sensory networks. By contrast, the DMN was less connected with sensory networks after the intervention. Similarly, there was a shift towards a less connected state within the FPN and SAL networks, which are typically hyperconnected following TBI. Improvements in EF were correlated with rsFC within the FPN and between the DMN and sensorimotor networks. Finally, in the seed-based connectivity analysis, the right IFG showed increased rsFC with the right inferior parietal and left frontoparietal (Rolandic operculum) regions. Together, these results indicate that the rehabilitative effects of neurological music therapy after TBI are underpinned by a pattern of within- and between-network connectivity changes in cognitive networks as well as increased connectivity between frontal and parietal regions associated with music processing.

Envisioning the crosstalk between environmental enrichment and epilepsy: A novel perspective

Epilepsies are a diverse group of neurological disorders characterized by an unprovoked seizure and a brain that has an enduring predisposition to seizures. The lack of disease-modifying treatment strategies against the same has led to the exploration of novel treatment strategies that could halt epileptic seizures. In this regard, environmental enrichment (EE) has gained increased attention in recent days. EE modulates the effects of interactions between the genes and the environment on the structure and function of the brain. EE therapy can improve seizure-related symptoms in neurological diseases such as epilepsy. EE therapy can have a significant effect on cognitive disorders such as learning and memory impairments associated with seizures. EE therapy in epileptic hippocampus tissue can improve seizure-related symptoms by inducing enhanced neurogenesis and neuroprotective mechanisms. In this context, the efficiency of EE is regulated in the epilepsy by the brain-derived neurotrophic factor (BDNF)/extracellular signal-regulated kinase (ERK) signaling pathway regulated by extracellular signaling. Herein, we provide experimental evidence supporting the beneficial effects of EE in epileptic seizures and its underlying mechanism.

Sex-dependent effects of postweaning exposure to an enriched environment on novel objective recognition memory and anxiety-like behaviors: The role of hippocampal BDNF level

Exposure to enriched environment (EE) has been indicated to enhance cognitive functions, hippocampal neural plasticity, neurogenesis, long-term potentiation, and levels of the brain-derived neurotrophic factor (BDNF) in laboratory animals. Also, studies on the sex-dependent effects of exposure to EE during adolescence on adult cognitive functions are less. This is important because the beneficial effects of EE may be predominant in the adolescence stage. Therefore, the present study was designed to compare the effects of EE during adolescence (PND21-PND60) on novel objective recognition memory (NORM), anxiety-like behaviors, and hippocampal BDNF mRNA level in the adult male and female rats. Assessment of NORM and anxiety-like behaviors has been done by novel objective recognition task, open field (OF), and elevated plus maze (EPM), respectively. The expression of BDNF mRNA level was also evaluated by quantitative RT-PCR. Our findings demonstrated that housing in the EE during adolescence improves NORM in adult male rats. Also, exposure to EE during adolescence had a different effect on anxiety-like behaviors in both sexes. Additionally, our results indicated an augmented BDNF level in the hippocampus of male and female rats. In conclusion, adolescent exposure to EE has sex-dependent effects on cognitive functions and anxiety-like behaviors and increases BDNF mRNA expression in the hippocampus of both male and female rats; thus, BDNF is an important factor that can mediate the beneficial effects of EE and running exercise on cognitive functions and psychiatric traits.

Trajectory of 10-Year Neurocognitive Functioning After Moderate-Severe Traumatic Brain Injury: Early Associations and Clinical Application

OBJECTIVE

This study aimed to explore the 10-year trajectories of neurocognitive domains after moderate-severe traumatic brain injury (TBI), to identify factors related to long-term neurocognitive functioning, and to investigate whether performance remained stable or changed over time.

METHOD

Seventy-nine patients with moderate-severe TBI between the ages of 16 and 55 years were assessed at 3 months, 1, 5, and 10 years postinjury using neuropsychological tests and functional outcomes. Three hierarchical linear models were used to investigate the relationships of domain-specific neurocognitive trajectories (Memory, Executive function, and Reasoning) with injury severity, demographics, functional outcome at 3 months (Glasgow Outcome Scale-Extended) and emotional distress at 1 year (Symptom Checklist 90-Revised).

RESULTS

Education, injury severity measures, functional outcome, and emotional distress were significantly associated with both Memory and Executive function. Education and emotional distress were related to Reasoning. The interaction effects between time and these predictors in predicting neurocognitive trajectories were nonsignificant. Among patients with data at 1 and 10 year follow-ups (n = 47), 94-96% exhibited stable scores on Executive function and Reasoning tasks, and 83% demonstrated stable scores on Memory tasks. Significant memory decline was presented in 11% of patients.

CONCLUSIONS

The findings highlight the differential contribution of variables in their relationships with long-term neurocognitive functioning after moderate-severe TBI. Injury severity was important for Memory outcomes, whereas emotional distress influenced all neurocognitive domains. Reasoning (intellectual) abilities were relatively robust after TBI. While the majority of patients appeared to be cognitively stable beyond the first year, a small subset demonstrated a significant memory decline over time.

The scale of neurodegeneration in moderate-to-severe traumatic brain injury: a systematic review protocol

BACKGROUND

Our understanding of recovery after moderate-to-severe traumatic brain injury (TBI) has shifted. Until recently, it was presumed that following a period of acute neurological vulnerability, the brain remained stable in the chronic stages of injury. However, recent research has shown neurodegeneration in the chronic stages of moderate-to-severe TBI, challenging the assumption of neurological stability. While there is extensive evidence that neurodegeneration occurs, debate remains regarding the scale and timing. This systematic review will evaluate the scale and timelines of neurodegeneration in adult patients with moderate-to-severe TBI.

METHODS

Literature searches will be conducted in six electronic databases (from inception onwards), including MEDLINE, EMBASE, PsycINFO, CINAHL, SportDiscus, and Cochrane Central Register of Controlled Trials. We will include observational studies that examine neurodegenerative changes within a single sample of TBI patients or studies that compare neuroimaging outcomes between TBI patients and healthy controls. Our primary outcome is structural neuroimaging, and our secondary outcome is diffusion tensor imaging for detection of post-injury white matter changes. All screening, data extraction, and study quality appraisal will be performed independently by the same two study members. It is expected that a narrative summary of the literature will be produced. If feasible, we will conduct a random-effects meta-analysis. However, given the expected heterogeneity between studies (with respect to, for example, timing of imaging, regions imaged) we do not expect to perform a meta-analysis; rather, a narrative synthesis of our findings is expected to be performed.

DISCUSSION

Understanding the scale and timelines of neurodegeneration in moderate-to-severe TBI (as well as which brain areas are most vulnerable to chronic declines) can inform intervention research designed to offset such changes. This may help improve patient outcome following moderate-to-severe TBI and, in turn, reduce the burden of the injury.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019117548.

Enriched Environment and Effects on Neuropathic Pain: Experimental Findings and Mechanisms

Neuropathic pain inflicts tremendous biopsychosocial suffering for patients worldwide. However, safe and effective treatment of neuropathic pain is a prominent unmet clinical need. Environmental enrichment (EE) is an emerging cost-effective nonpharmacological approach to alleviate neuropathic pain and complement rehabilitation care. We present here a review of preclinical studies in ascertaining the efficacy of EE for neuropathic pain. Their proposed mechanisms, including the suppression of ascending nociceptive signaling to the brain, enhancement of the descending inhibitory system, and neuroprotection of the peripheral and central nervous systems, may collectively reduce pain perception and improve somatic and emotional functioning in neuropathic pain. The current evidence offers critical insights for future preclinical research and the translational application of EE in clinical pain management.

Role of early environmental enrichment on the social dominance tube test at adulthood in the rat

RATIONALE

Environmental enrichment (EE) could influence brain plasticity and behavior in rodents. Whether the early EE may predispose individuals to a particular social hierarchy in the social dominance tube test (SDTT) at adulthood is still unknown.

OBJECTIVE

The present study directly investigated the influence of EE on competitive success in the SDTT among adult rats.

METHODS

Male rats were maintained in EE from postnatal days 21 to 35. Social dominance behavior was determined by SDTT, competitive food foraging test, and mate preference test at adulthood. IBA-1 expression in the hypothalamus was examined using immunohistochemistry and western blot.

RESULTS

EE rats were prone to become submissive during a social encounter with standard environment (SE) rats in the SDTT. No difference was found in food foraging in the competitive food foraging test between SE and EE rats. Male EE rats were more attractive than the SE to the female rats in the mate preference test. IBA-1 expression was found to be decreased in the hypothalamus of EE rats compared to SE group. Infusion of a microglia inhibitor reduced percentage of forward in SE rats in the SDTT. Infusion of DNA methyltransferase inhibitor prevented the development of subordinate status in EE rats and restored the expression of IBA-1 in the hypothalamus.

CONCLUSIONS

The results suggest that early EE did not lead to reduced social hierarchy in the male rat. However, EE caused a reduction in the percentage of forward in the SDTT, which might be associated with reduced number of microglia in the hypothalamus.

Mild cognitive impairment and structural brain abnormalities in a sexagenarian with a history of childhood traumatic brain injury

In this report, we present a case study involving an older, female patient with a history of pediatric traumatic brain injury (TBI). Magnetic resonance imaging and diffusion tensor imaging volumes were acquired from the volunteer in question, her brain volumetrics and morphometrics were extracted, and these were then systematically compared against corresponding metrics obtained from a large sample of older healthy control (HC) subjects as well as from subjects in various stages of mild cognitive impairment (MCI) and Alzheimer disease (AD). Our analyses find the patient's brain morphometry and connectivity most similar to those of patients classified as having early-onset MCI, in contrast to HC, late MCI, and AD samples. Our examination will be of particular interest to those interested in assessing the clinical course in older patients having suffered TBI earlier in life, in contradistinction to those who experience incidents of head injury during aging.

Socioeconomic status and hippocampal volume in children and young adults

An individual's socioeconomic status (SES) is often viewed as a proxy for a host of environmental influences. SES disparities have been linked to variance in brain structures particularly the hippocampus, a neural substrate of learning and memory. However, it is unclear whether the association between SES and hippocampal volume is similar in children and adults. We investigated the relationship between hippocampal volume and SES in a group of children (n = 31, age 8-12 years) and a group of young adults (n = 32, age 18-25 years). SES was assessed with four indicators that loaded on a single factor, therefore a composite SES scores was used in the main analyses. Hippocampal volume was measured using manual demarcation on high resolution structural images. SES was associated with hippocampal volume in the children, but not in adults, suggesting that in childhood, but not adulthood, SES-related environmental factors influence hippocampal volume. In addition, hippocampal volume, but not SES, was associated with scores on a memory task, suggesting that net effects of postnatal environmental factors, captured by SES, are more distal determinants of memory performance than hippocampal volume. Longitudinal investigation of the association between SES, hippocampal volume and cognitive functioning may further our understanding of the putative neural mechanisms underlying SES-related environmental effects on cognitive development.

Environmental enrichment facilitates cocaine-cue extinction, deters reacquisition of cocaine self-administration and alters AMPAR GluA1 expression and phosphorylation

This study investigated the combination of environmental enrichment (EE) with cocaine-cue extinction training on reacquisition of cocaine self-administration. Rats were trained under a second-order schedule for which responses were maintained by cocaine injections and cocaine-paired stimuli. During three weekly extinction sessions, saline was substituted for cocaine but cocaine-paired stimuli were presented. Rats received 4-h periods of EE at strategic time points during extinction training, or received NoEE. Additional control rats received EE or NoEE without extinction training. One week later, reacquisition of cocaine self-administration was evaluated for 15 sessions, and then GluA1 expression, a cellular substrate for learning and memory, was measured in selected brain regions. EE provided both 24 h before and immediately after extinction training facilitated extinction learning and deterred reacquisition of cocaine self-administration for up to 13 sessions. Each intervention by itself (EE alone or extinction alone) was ineffective, as was EE scheduled at individual time points (EE 4 h or 24 h before, or EE immediately or 6 h after, each extinction training session). Under these conditions, rats rapidly reacquired baseline rates of cocaine self-administration. Cocaine self-administration alone decreased total GluA1 and/or pSer845GluA1 expression in basolateral amygdala and nucleus accumbens. Extinction training, with or without EE, opposed these changes and also increased total GluA1 in ventromedial prefrontal cortex and dorsal hippocampus. EE alone increased pSer845GluA1 and EE combined with extinction training decreased pSer845GluA1 in ventromedial prefrontal cortex. EE might be a useful adjunct to extinction therapy by enabling neuroplasticity that deters relapse to cocaine self-administration.

Feasibility of online self-administered cognitive training in moderate-severe brain injury

PURPOSE

Cognitive environmental enrichment (C-EE) offers promise for offsetting neural decline that is observed in chronic moderate-severe traumatic brain injury (TBI). Brain games are a delivery modality for C-EE that can be self-administered over the Internet without therapist oversight. To date, only one study has examined the feasibility of self-administered brain games in TBI, and the study focused predominantly on mild TBI. Therefore, the primary purpose of the current study was to examine the feasibility of self-administered brain games in moderate-severe TBI. A secondary and related purpose was to examine the feasibility of remote monitoring of any C-EE-induced adverse symptoms with a self-administered evaluation tool.

METHOD

Ten patients with moderate-severe TBI were asked to complete 12 weeks (60 min/day, five days/week) of online brain games with bi-weekly self-evaluation, intended to measure any adverse consequences of cognitive training (e.g., fatigue, eye strain).

RESULTS

There was modest weekly adherence (42.6% ± 4.4%, averaged across patients and weeks) and 70% patient retention; of the seven retained patients, six completed the self-evaluation questionnaire at least once/week for each week of the study.

CONCLUSIONS

Even patients with moderate-severe TBI can complete a demanding, online C-EE intervention and a self-administered symptom evaluation tool with limited therapist oversight, though at daily rate closer to 30 than 60 min per day. Further self-administered C-EE research is underway in our lab, with more extensive environmental support. Implications for Rehabilitation Online brain games (which may serve as a rehabilitation paradigm that can help offset the neurodegeneration observed in chronic TBI) can be feasibly self-administered by moderate-to-severe TBI patients. Brain games are a promising therapy modality, as they can be accessed by all moderate-to-severe TBI patients irrespective of geographic location, clinic and/or therapist availability, or impairments that limit mobility and access to rehabilitation services. Future efficacy trials that examine the effect of brain games for offsetting neurodegeneration in moderate-to-severe TBI patients are warranted.

Suitability of the Quality of Life after Brain Injury Instrument for Older People with Traumatic Brain Injury

We prospectively investigated the psychometric properties of the Quality of Life after Brain Injury (QOLIBRI) instrument among older patients with traumatic brain injury (TBI). The 37-item QOLIBRI comprises six domains (cognition, self, daily life and autonomy, social relationships, emotions, and physical problems). We recruited 333 patients ≥60 years of age with TBI from the neurosurgery clinics and emergency departments of three hospitals in Taipei, Taiwan. The ceiling and floor values for most QOLIBRI domains were <5%, and the internal consistency and test-retest reliability ranged from 0.84 to 0.97 and 0.83 to 0.96, respectively. For the known-groups validity, patients with TBI attained lower scores for all QOLIBRI domains, except physical problems, compared with those with soft-tissue injuries. Patients with intact cognition who had higher levels on the Glasgow Outcome Scale Extended (GOSE) and the Glasgow Coma Scale, fewer limitations in activities of daily living, and fewer chronic conditions obtained higher scores for almost all the QOLIBRI domains, compared with their counterparts. For convergent validity, the correlation coefficients for the QOLIBRI domains and the selected functional measures conceptually related to that domain were all ≥0.4. A confirmatory factor analysis revealed that the original six-domain structure fit the data with a comparative fit index of ≥0.9. Effect sizes for changes in the GOSE over a 6-month follow-up period were clinically meaningful (≥ 0.2) for all the QOLIBRI domains except emotions. For older people with TBI, the use of the QOLIBRI is generally appropriate, and adding the domain of environment to the scale would be beneficial.

Environmental enrichment and abstinence attenuate ketamine-induced cardiac and renal toxicity

The current study was designed to investigate the effect of abstinence in combination with environmental enrichment (EE) on cardiac and renal toxicity induced by 2 weeks of ketamine self-administration (SA) in rodents. In Experiment 1, one group of rats underwent ketamine SA for 14 days. In Experiment 2, the animals completed 2 weeks of ketamine SA followed by 2 and 4 weeks of abstinence. In Experiment 3, animals underwent 14 days of ketamine SA and 4 weeks of abstinence in which isolated environment (IE) and EE was introduced. The corresponding control groups were included for each experiment. Two weeks of ketamine SA caused significant increases in organ weight, Apoptosis Stimulating Fragment/Kidney Injury Molecule-1, and apoptotic level of heart and kidney. The extended length of withdrawal from ketamine SA partially reduced toxicity on the heart and kidney. Finally, introduction of EE during the period of abstinence greatly promoted the effect of abstinence on ketamine-induced cardiac and renal toxicity. The interactive effect of EE and abstinence was promising to promote the recovery of cardiac and renal toxicity of ketamine.

Environmental enrichment: evidence for an unexpected therapeutic influence

Environmental enrichment produces wide-ranging effects in the brain at molecular, cellular, network, and behavioral levels. The changes in neuronal plasticity are driven by changes in neurotransmitters, neurotrophic factors, neuronal morphology, neurogenesis, network properties of the brain, and behavioral correlates of learning and memory. Exposure to an enriched environment has also demonstrated intriguing possibilities for treatment of a variety of neurodegenerative diseases including Huntington's disease, Alzheimer's disease, and Parkinson's disease. The effect of environmental enrichment in epilepsy, a neurodegenerative disorder with pathological neuronal plasticity, is of considerable interest. Recent reports of the effect of environmental enrichment in the Bassoon mutant mouse, a genetic model of early onset epilepsy, provides a significant addition to the literature in this area.

Negative neuroplasticity in chronic traumatic brain injury and implications for neurorehabilitation

Based on growing findings of brain volume loss and deleterious white matter alterations during the chronic stages of injury, researchers posit that moderate-severe traumatic brain injury (TBI) may act to “age” the brain by reducing reserve capacity and inducing neurodegeneration. Evidence that these changes correlate with poorer cognitive and functional outcomes corroborates this progressive characterization of chronic TBI. Borrowing from a framework developed to explain cognitive aging (Mahncke et al., Progress in Brain Research, 157, 81–109, 2006a; Mahncke et al., Proceedings of the National Academy of Sciences of the United States of America, 103(33), 12523–12528, 2006b), we suggest here that environmental factors (specifically environmental impoverishment and cognitive disuse) contribute to a downward spiral of negative neuroplastic change that may modulate the brain changes described above. In this context, we review new literature supporting the original aging framework, and its extrapolation to chronic TBI. We conclude that negative neuroplasticity may be one of the mechanisms underlying cognitive and neural decline in chronic TBI, but that there are a number of points of intervention that would permit mitigation of this decline and better long-term clinical outcomes.

Environmental enrichment and the sensory brain: the role of enrichment in remediating brain injury

The brain's life-long capacity for experience-dependent plasticity allows adaptation to new environments or to changes in the environment, and to changes in internal brain states such as occurs in brain damage. Since the initial discovery by Hebb (1947) that environmental enrichment (EE) was able to confer improvements in cognitive behavior, EE has been investigated as a powerful form of experience-dependent plasticity. Animal studies have shown that exposure to EE results in a number of molecular and morphological alterations, which are thought to underpin changes in neuronal function and ultimately, behavior. These consequences of EE make it ideally suited for investigation into its use as a potential therapy after neurological disorders, such as traumatic brain injury (TBI). In this review, we aim to first briefly discuss the effects of EE on behavior and neuronal function, followed by a review of the underlying molecular and structural changes that account for EE-dependent plasticity in the normal (uninjured) adult brain. We then extend this review to specifically address the role of EE in the treatment of experimental TBI, where we will discuss the demonstrated sensorimotor and cognitive benefits associated with exposure to EE, and their possible mechanisms. Finally, we will explore the use of EE-based rehabilitation in the treatment of human TBI patients, highlighting the remaining questions regarding the effects of EE.

Scale and pattern of atrophy in the chronic stages of moderate-severe TBI

BACKGROUND

Moderate-severe traumatic brain injury (TBI) is increasingly being understood as a progressive disorder, with growing evidence of reduced brain volume and white matter (WM) integrity as well as lesion expansion in the chronic phases of injury. The scale of these losses has yet to be investigated, and pattern of change across structures has received limited attention.

OBJECTIVES

(1) To measure the percentage of patients in our TBI sample showing atrophy from 5 to 20 months post-injury in the whole brain and in structures with known vulnerability to acute TBI, and (2) To examine relative vulnerability and patterns of volume loss across structures.

METHODS

Fifty-six TBI patients [complicated mild to severe, with mean Glasgow Coma Scale (GCS) in severe range] underwent MRI at, on average, 5 and 20 months post-injury; 12 healthy controls underwent MRI twice, with a mean gap between scans of 25.4 months. Mean monthly percent volume change was computed for whole brain (ventricle-to-brain ratio; VBR), corpus callosum (CC), and right and left hippocampi (HPC).

RESULTS

(1) Using a threshold of 2 z-scores below controls, 96% of patients showed atrophy across time points in at least one region; 75% showed atrophy in at least 3 of the 4 regions measured. (2) There were no significant differences in the proportion of patients who showed atrophy across structures. For those showing decline in VBR, there was a significant association with both the CC and the right HPC (P < 0.05 for both comparisons). There were also significant associations between those showing decline in (i) right and left HPC (P < 0.05); (ii) all combinations of genu, body and splenium of the CC (P < 0.05), and (iii) head and tail of the right HPC (P < 0.05 all sub-structure comparisons).

CONCLUSIONS

Atrophy in chronic TBI is robust, and the CC, right HPC and left HPC appear equally vulnerable. Significant associations between the right and left HPC, and within substructures of the CC and right HPC, raise the possibility of common mechanisms for these regions, including transneuronal degeneration. Given the 96% incidence rate of atrophy, a genetic explanation is unlikely to explain all findings. Multiple and possibly synergistic mechanisms may explain findings. Atrophy has been associated with poorer functional outcomes, but recent findings suggest there is potential to offset this. A better, understanding of the underlying mechanisms could permit targeted therapy enabling better long-term outcomes.