Effects of enriched environment on animal models of neurodegenerative diseases and psychiatric disorders

Prolonged exposure to a music-enriched environment mitigates acute noise-induced inflammation and apoptosis in the chicken spleen by modulating the Keap-1/Nrf2 and NF-κB pathways

The rise of operational noise as an environmental pollutant for farm animals is an emerging concern. The mechanisms through which music can alleviate oxidative stress, inflammation, and apoptosis induced by noise exposure remain underexplored. This study aims to investigate the alleviating effects and underlying mechanisms of long-term music exposure on noise-induced damage to the chicken spleen. Male Arbor Acres (AA) broilers were divided into four groups: control (C), acute noise stimulation (NS), noise stimulation with music mitigation (NSM), and music only (M). NS and NSM groups were exposed to noise (simulating sudden intensity noise, 115 to 120dB) for 10 minutes daily for a week, starting at 14-days-old. NSM and M groups then received 28 days of 6-hour daily music (Mozart K.448, 60-65 dB). The results showed that noise stimulation significantly activated the Keap-1/Nrf2 and NF-κB signaling pathways. Long-term music intervention has also been demonstrated to successfully mitigate oxidative stress and abnormal apoptosis induced by acute noise stimulation. Microscopic examination of the spleen revealed that acute noise stimulation resulted in an increase in splenic cells, a decrease in lymphocytes, and blurred boundaries between the red and white pulps in the NS group. However, these pathological changes were alleviated in the NSM group following music intervention. Compared with the control group, the NS group exhibited significantly elevated oxidative stress parameters. In contrast, music intervention in the NSM group notably improved antioxidant capacity and partially alleviated morphological abnormalities in the spleen. Additionally, noise stimulation activated the NF-κB pathway, upregulating the downstream genes of the inflammatory factors IL-1β, IL-6, and TNF-α. Noise-induced mitochondrial damage led to apoptosis, as observed by TUNEL staining, along with increased gene and protein expression of Bcl-2, Bax, Cyt-C, Casp-3, Casp-8, and Casp-9. These findings indicate that acute noise exposure can induce splenic damage via oxidative stress, inflammation, and apoptosis by modulating the Keap-1/Nrf2 and NF-κB pathways. Prolonged music stimulation effectively mitigates noise-induced damage, offering a vital experimental foundation for further research on noise pollution's impact on organisms and music's alleviating role.

Virtual Reality Environmental Enrichment Effects on Craving for Cigarette in Smokers

Background: Preclinical studies suggested the exposure to environmental enrichment (EE) as an intervention able to prevent or reduce nicotine-taking and nicotine-seeking behaviors. Virtual reality (VR) may help to test the effects of EE in smokers in a reproducible and feasible manner. Materials and Methods: In the present study, 31 smokers (14 women) were divided into two groups: (1) exposure to a virtual EE (VR-EE) and (2) exposure to a virtual neutral environment (VR-NoEE). Cigarette craving was assessed as basal and evoked, at different timepoints during the session. Behavior activity during VR exposure, mood, and subjective measures were also collected. Results: EE exposure in VR significantly reduced craving scores from basal timepoint. This was not observed in the VR-NoEE group, which significantly increased craving compared with values at neutral scenario. When both groups were exposed to smoking-related VR scenario, the VR-EE group showed an increased craving compared with previous timepoint up to score values not different from those in the VR-NoEE group. A significant positive correlation between basal craving scores and interactive behavior with virtual smoking cues was observed in the VR-NoEE but not in the VR-EE group. Conclusion: These findings suggest that virtual EE might have an inhibitory effect in smokers on basal, but not on evoked cigarette craving. Noteworthily, the interactive activity correlation to craving scores in the VR-NoEE participants was not observed in the VR-EE group, adding further evidence that the enrichment simulation was nonetheless able to modify behavior in the smoking-related scenario.

An epigenetic mechanism of social isolation stress in adolescent female mice

Social isolation during adolescence can increase the risk of mental disorders. Epigenetic changes induced by chronic social isolation may serve as a mechanism underlying emotional disturbances. To test this, we exposed female mice to a post-weaning 6-week social isolation (SI) stress. We found the significantly increased methylation of histone H3 at lysine 9 (H3K9), a histone mark linked to gene repression, as well as the increased H3K9 methyltransferases SUV39H1 and SETDB1, in prefrontal cortex (PFC) of SI females. To find out potential downstream genes affected by this epigenetic alteration, we examined genes linked to neuronal and synaptic functions. Activity-dependent genes, including Arc, c-Fos and Npas4, were significantly reduced in PFC of SI females, correlated with the increased H3K9me2 occupancy around Arc enhancer. Treatment of SI females with UNC0642, a selective inhibitor of H3K9 methylation, significantly attenuated the anxiety-like behavior and elevated Arc expression. These results have revealed an epigenetic mechanism and intervention avenue for anxiety induced by chronic social isolation.

Environmental enrichment promotes adaptive responding during tests of behavioral regulation in male heterogeneous stock rats

Organisms must regulate their behavior flexibly in the face of environmental challenges. Failure can lead to a host of maladaptive behavioral traits associated with a range of neuropsychiatric disorders, including attention deficit hyperactivity disorder, autism, and substance use disorders. This maladaptive dysregulation of behavior is influenced by genetic and environmental factors. For example, environmental enrichment produces beneficial neurobehavioral effects in animal models of such disorders. The present study determined the effects of environmental enrichment on a range of measures related to behavioral regulation using a large cohort of male, outbred heterogeneous stock (HS) rats as subjects. Subjects were reared from late adolescence onwards either in pairs in standard housing with minimal enrichment (n = 200) or in groups of 16 in a highly enriched environment consisting of a large multi-level cage filled with toys, running wheels, and shelters (n = 64). Rats were subjected to a battery of tests, including: (i) locomotor response to novelty, (ii) light reinforcement, (iii) social reinforcement, (iv) reaction time, (v) a patch-depletion foraging test, (vi) Pavlovian conditioned approach, (vii) conditioned reinforcement, and (viii) cocaine conditioned cue preference. Results indicated that rats housed in the enriched environment were able to filter out irrelevant stimuli more effectively and thereby regulate their behavior more efficiently than standard-housing rats. The dramatic impact of environmental enrichment suggests that behavioral studies using standard housing conditions may not generalize to more complex environments that may be more ethologically relevant.

[The psychosocial rehabilitation in addiction medicine]

OBJECTIVES

Addictive behaviors constitute complex behaviors that are usually related to social habits, such as substance use, gambling or gaming activities, or sexual or physical activity. They progressively overrun and stifle the routine habits of the concerned individuals, for example within their occupational or family spheres of life, as well as in their hobbies or in their main physiological functions, such as sleep or eating cycles. The rehabilitation approach of care integrates the objective of restoring the altered habits and functional rhythms, to optimize the clinical outcomes and improve quality of life of the concerned persons.

METHODS

Using a focused and narrative literature review, we aimed to explain what psychosocial rehabilitation consists in, and why this approach is particularly relevant for the addiction care, although to date it has remained insufficiently developed in the routine practice of many facilities.

RESULTS

The "rehab" approach, is first based on a structured and comprehensive assessment of the clinical and functional aspects of the patient, which secondarily allows to frame an individualized project of care that is closely built together with the patient. This project of care can integrate classical pharmacotherapeutic and psychotherapeutic tools, but it also emphasizes wider approaches for restoring some basic social and physiological functions of the concerned person, such as sleep, eating, social functioning, physical activity, or spiritual needs. Priorities among these different dimensions have to be defined by the concerned person.

CONCLUSIONS

The "rehab" approach is particularly relevant in addiction medicine. It represents a more global conception of care that conceives the recovery of social and physiological functioning as a core treatment objective for the concerned persons. The consequences for care organization are that many additional professionals should be integrated into the treatment schemes for addiction, including peer counselors, occupational therapists, physical activity coaches, or dieticians.

Social environment enrichment alleviates anxiety-like behavior in mice: Involvement of the dopamine system

Rearing environment plays a vital role in maintaining physical and mental health of both animals and humans. Plenty of studies have proved that physical environment enrichment in adolescence has protective effects on emotion, social behavior, learning and memory deficits. However, the following effects of social environment enrichment in adolescence remain largely elusive. Using the paradigm of companion rotation (CR), the present study found that social environment enrichment reduced anxiety-like behaviors of early adult male C57BL/6J mice. CR group also showed significantly higher expression of tyrosine hydroxylase in the ventral tegmental area and dopamine 1 receptor mRNA in the nucleus accumbens shell than control group. Taken together, these findings demonstrate that CR from adolescence to early adulthood can suppress the level of anxiety and upregulate dopaminergic neuron activity in early adult male C57BL/6J mice.

Environmental Enrichment Cage for Laboratory Mice: A Downloadable Alternative

Environmentally enriched housing (EE) provides a stimulating and species-typical environment that enhances brain plasticity and cognition, while reducing disease severity in laboratory animals. However, standardizing EE protocols has been challenging due to issues such as variability, high pricing, or limited laboratory space. To address these challenges, we present a replicable and cost-efficient cage protocol that is accessible to researchers with limited resources and space constraints. The protocol is designed to provide a stimulating and species-typical environment for the animals. It incorporates elements such as social interaction, physical exercise, cognitive stimulation, manipulable objects, environmental variability, and sensory stimulation. As evidenced in our previous studies using our protocol, users can expect to observe similar neuroplastic and health-wise benefits that accompany EE experimental paradigms. These included straightforward step-by-step guide, which allows for construction of functional EE cages in under 8 hr. Basic knowledge of 3D printing and laser cutting is required, but no advanced skills are necessary. The protocol enables researchers to create stimulating and replicable environments that promote animal welfare, enhance brain plasticity, and yield valuable experimental results for low cost. © 2024 Wiley Periodicals LLC. Basic Protocol: An effective and cost-efficient environmental enrichment cage designed to encourage standardization amongst laboratory protocols.

Therapeutic Viewpoint on Rat Models of Locomotion Abnormalities and Neurobiological Indicators in Parkinson's Disease

BACKGROUND

Locomotion problems in Parkinson's syndrome are still a research and treatment difficulty. With the recent introduction of brain stimulation or neuromodulation equipment that is sufficient to monitor activity in the brain using electrodes placed on the scalp, new locomotion investigations in patients having the capacity to move freely have sprung up.

OBJECTIVE

This study aimed to find rat models and locomotion-connected neuronal indicators and use them all over a closed-loop system to enhance the future and present treatment options available for Parkinson's disease.

METHODS

Various publications on locomotor abnormalities, Parkinson's disease, animal models, and other topics have been searched using several search engines, such as Google Scholar, Web of Science, Research Gate, and PubMed.

RESULTS

Based on the literature, we can conclude that animal models are used for further investigating the locomotion connectivity deficiencies of many biological measuring devices and attempting to address unanswered concerns from clinical and non-clinical research. However, translational validity is required for rat models to contribute to the improvement of upcoming neurostimulation-based medicines. This review discusses the most successful methods for modelling Parkinson's locomotion in rats.

CONCLUSION

This review article has examined how scientific clinical experiments lead to localised central nervous system injuries in rats, as well as how the associated motor deficits and connection oscillations reflect this. This evolutionary process of therapeutic interventions may help to improve locomotion- based treatment and management of Parkinson's syndrome in the upcoming years.

The effects of virtual reality environmental enrichments on craving to food in healthy volunteers

RATIONALE

Environmental enrichment (EE) is a non-pharmacological approach that has been shown to be effective in reducing food-taking in rats. Studies in human volunteers are still in their infancy, given the difficulty to translate the complexity of EE in clinical practice. Virtual reality (VR) is a promising methodological approach, but no study has yet applied it to model and test EE in humans.

OBJECTIVES

The present study is the first to assess the effects of virtual EE on craving for palatable food.

METHODS

Eighty-one healthy volunteers (43 women) were divided into three groups: (i) exposure to a virtual EE (VR-EE), (ii) exposure to a virtual neutral environment (VR-NoEE), and (iii) without exposure to VR (No VR). Craving for palatable food at basal level and evoked by neutral and palatable food images was assessed before and after the VR simulation. Behavior during VR exposure and subjective measures related to the experience were also collected.

RESULTS

VR-EE group showed a significantly greater decrease in pre-post craving difference compared to No VR for all assessments and at basal level compared to VR-NoEE. Interestingly, an inverse correlation between craving and deambulation in the VR simulation emerged in VR-EE group only.

CONCLUSIONS

The study highlighted the feasibility of exposing human subjects to an EE as a virtual simulation. Virtual EE induced effects on basal craving for food that suggest the potential for further improvements of the protocol to extend its efficacy to palatable food cues.

Melamine Exacerbates Neurotoxicity in D-Galactose-Induced Neuronal SH-SY5Y Cells

Numerous studies have depicted the role of diet and environmental toxins in aging. Melamine (Mel) is a globally known notorious food adulterant, and its toxicity has been shown in several organs including the brain. However, till now, there are no reports regarding Mel neurotoxicity in aging neurons. So, this study examined the in vitro neurotoxicity caused by Mel in the D-galactose (DG)-induced aging model of neuronal SH-SY5Y cells. In the present study, the neuronal SH-SY5Y cells were treated with DG and Mel separately and in combination to assess the neurotoxicity potential using MTT assay and neurite length measurement. Further, the superoxide dismutase (SOD), catalase (CAT), and total antioxidant activities were evaluated followed by the determination of the intracellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and caspase3 (Casp3) activity. The cotreatment of Mel and DG in neuronal SH-SY5Y cells showed maximum cell death than the cells treated with DG or Mel individually and untreated control cells. The neurite length shrinkage and ROS production were maximum in the DG and Mel cotreated cells showing exacerbated toxicity of Mel. The activity of SOD, CAT, and total antioxidants was also found to be lowered in the cotreatment group (Mel + DG) than in Mel- or DG-treated and untreated cells. Further, the combined toxicity of Mel and DG also elevated the Casp3 activity more than any other group. This is the first study showing the increased neurotoxic potential of Mel in an aging model of neuronal SH-SY5Y cells which implicates that Mel consumption by the elderly may lead to increased incidences of neurodegeneration like Alzheimer's disease and Parkinson's disease.

Environmental enrichment initiated in adolescence restores the reduced expression of synaptophysin and GFAP in the hippocampus of chronically stressed rats in a sex-specific manner

This study aims at investigating whether environmental enrichment (EE) initiated in adolescence can alter chronic unpredictable stress (CUS)-associated changes in astroglial and synaptic plasticity markers in male and female rats. To this end, we studied possible alterations in hippocampal glial fibrillary acidic protein (GFAP) and synaptophysin (SYN) in CUS rats previously housed in EE. Wistar rats on postnatal day (PND) 23 were housed for 10 weeks in standard housing (SH) or enriched conditions. On PND 66, animals were exposed to CUS for 4 weeks. SYN and GFAP expressions were evaluated in CA1 and CA3 subfields and dentate gyrus (DG). CUS reduced the expression of SYN in all hippocampal areas, whereas lower GFAP expression was evident only in CA1 and CA3. The reduced expression of SYN in DG and CA3 was evident to male SH/CUS rats, whereas the reduced GFAP expression in CA1 and CA3 was limited to SH/CUS females. EE housing increased the hippocampal expression of both markers and protected against CUS-associated decreases. Our findings indicate that the decreases in the expression of SYN and GFAP following CUS are region and sex-specific and underline the neuroprotective role of EE against these CUS-associated changes.

Which form of environmental enrichment is most effective in rodent models of autism?

Environmental enrichment (EE) is known to produce experience-dependent changes in the brains and behaviors of rodents, and it has therefore been widely used to study neurodevelopmental disorders, including autism. Current studies show significant protocol variation, such as the presence of running wheels, number of cagemates, duration of enrichment, and the age of the animals at the beginning and end of the enrichment interventions. EE has been shown to have prominent positive effects in animal models of idiopathic and syndromic autism, but little is known about the ideal type of EE and the most efficient protocols for reversing autism spectrum disorder (ASD) behaviors modeled in rodents. This review presents evidence that social enrichment is the most effective way to rescue typical behaviors, and that variables such as onset, duration, and type of induction in the ASD model are important for EE success. Understanding which EE protocols are most beneficial for reversing ASD behaviors modeled in rodents opens up possibilities for the potential treatment of neuropsychiatric disorders characterized by behavioral deficits, such as autism.

The systemic effects of the enriched environment on the conditioned fear reaction

In this review, a hypothesis is proposed to explain the beneficial effect of an enriched environment (EE) on the conditioned fear reaction (CFR) from the perspective of a functional system of behavioral control. According to the hypothesis, the EE affects all behavioral act components, including the processing of sensory information, memory, motivational and reinforcing systems, and motor activities, which weakens the CFR. Animals raised in the EE have effects that are comparable to those of context (CTX) and CS pre-exposures at latent inhibition. An abundance of stimuli in the EE and constant contact with them provide the formation of CS-noUS and CTX-noUS connections that later, during CFR learning, slow down and diminish fear. The EE also contributes to faster processing of information and habituation to it. As a result, many stimuli in the context lose their significance, and subjects simply ignore them. And finally, the EE affects the motivational and reinforcing brain mechanisms, induces an impairment of search activity, and worsens memory consolidation, which leads to a reduction of CFR.

Environmental enrichment promotes adaptive responding during tests of behavioral regulation in male heterogeneous stock rats

Organisms must regulate their behavior flexibly in the face of environmental challenges. Failure can lead to a host of maladaptive behavioral traits associated with a range of neuropsychiatric disorders, including attention deficit hyperactivity disorder, autism, and substance use disorders. This maladaptive dysregulation of behavior is influenced by genetic and environmental factors. For example, environmental enrichment produces beneficial neurobehavioral effects in animal models of such disorders. The present study determined the effects of environmental enrichment on a range of measures related to behavioral regulation using a large cohort of male, outbred heterogeneous stock (HS) rats as subjects to mimic the genetic variability found in the human population. Subjects were reared from late adolescence onwards either in pairs in standard housing with minimal enrichment (n=200) or in groups of 16 in a highly enriched environment consisting of a large multi-level cage filled with toys, running wheels, and shelters (n=64). Rats were subjected to a battery of tests, including: (i) locomotor response to novelty, (iI) light reinforcement, (iii) social reinforcement, (iv) reaction time, (v) a patch-depletion foraging test, (vi) Pavlovian conditioned approach, (vii) conditioned reinforcement, and (viii) cocaine conditioned cue preference. Results indicated that rats housed in the enriched environment were able to filter out irrelevant stimuli more effectively and thereby regulate their behavior more efficiently than standard-housing rats. The dramatic impact of environmental enrichment suggests that behavioral studies using standard housing conditions may not generalize to more complex environments that may be more ethologically relevant.

Environmental eustress promotes liver regeneration through the sympathetic regulation of type 1 innate lymphoid cells to increase IL-22 in mice

BACKGROUND AND AIMS

The liver has the unique ability of regeneration, which is extremely important for restoring homeostasis after liver injury. Although clinical observations have revealed an association between psychological stress and the liver, whether stress has a causal influence on the liver regeneration remains markedly less defined.

APPROACH AND RESULTS

Rearing rodents in an enriched environment (EE) can induce eustress or positive psychological stress. Herein, EE-induced eustress was found to significantly enhance the ability of liver regeneration after partial hepatectomy or carbon tetrachloride-induced liver injury based on the more rapid restoration of liver/body weight ratio and the significantly increased number of proliferating hepatocytes in EE mice. Mechanistically, the cytokine array revealed that IL-22 was markedly increased in the regenerating liver in response to EE. Blockade of IL-22 signaling abrogated the enhanced liver regeneration induced by EE. Group 1 innate lymphoid cells (ILCs), including type 1 ILCs (ILC1s), have been identified as the major sources of IL-22 in the regenerating liver. EE housing led to a rapid accumulation of hepatic ILC1s after partial hepatectomy and the EE-induced enhancement of liver regeneration and elevation of IL-22 was nearly eliminated in ILC1-deficient Tbx21-/- mice. Chemical sympathectomy or blockade of β-adrenergic signaling also abolished the effect of EE on ILC1s and attenuated the enhanced liver regeneration of EE-housed mice.

CONCLUSION

The study findings support the brain-liver axis and suggest that environment-induced eustress promotes liver regeneration through the sympathetic nerve/ILC1/IL-22 axis.

Comparison of the effect of postweaning social isolation, enriched environment, and exercise training on learning and memory functions in rats

Background/aim

To assess the effects of postweaning social isolation, an enriched environment, and exercise training on learning and memory functions in rats, as well as their relation with the brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) concentrations in the hippocampus.

Materials and methods

Randomly assigned into 4 groups were 35 female postweaning rats (25 day old), as the control (C), social isolation (SI), enriched environment (EE), and exercise training (E) groups. The SI and the EE groups were housed under their specific conditions and the E and the C groups were housed under standard conditions for 6 weeks. The rats in the E group swam for 60 min/day, 5 days a week, for 6 weeks. After 6 weeks, the rats were evaluated in the Morris water maze (MWM). Following MWM assessment, hippocampal tissue and blood samples were taken to measure the BDNF and NGF.

Results

According to the results of the MWM probe trial session, the thigmotaxis behavior was higher in the SI group compared to the C group (p < 0,05). Furthermore, the time spent in the target quadrant (quadrant with an escape platform) was lower in the SI group compared to the EE group (p < 0.05). The BDNF and NGF levels in the hippocampus and plasma were not different between the groups (p < 0.05).

Conclusion

Postweaning social isolation may increase thigmotaxis behaviors. Postweaning social isolation, enriched environment, and exercise training did not affect the spatial learning, memory function, hippocampal BDNF or NGF levels in female rats.

Enriched environment remodels the central immune environment and improves the prognosis of acute ischemic stroke in elderly mice with chronic ischemia

With the aging of many populations, cognitive and motor dysfunction caused by ischemic stroke (IS) secondary to long-term chronic cerebral ischemia presents a global problem. Enriched environment (EE), a classic paradigm of environment response and genetic interaction, has shown tremendous influence on the brain. This research aimed to investigate the potential effect of EE on cognitive and motor function in mice with chronic cerebral ischemia and secondary IS. In the chronic cerebral hypoperfusion (CCH) phase, EE treatment improved behavior performance by alleviating neuronal loss and white matter myelin damage, promoting the expression of brain-derived neurotrophic factor (BDNF) and phosphor-cAMP response element binding protein (p-CREB). Furthermore, infiltration of microglia/macrophages and astrocytes was inhibited, and the levels of IL-1β and TNFα were decreased. In the IS phase, EE altered the neuronal outcome on day 21 but not on day one after IS. In addition, EE inhibited IS-induced infiltration of microglia/macrophages and astrocytes, mediated the polarization of microglia/macrophages, and reduced pro-inflammatory factors. Importantly, EE improved IS-induced cognitive and motor deficits on day 21. Collectively, our work demonstrates that EE protects mice from cognitive and motor dysfunction and inhibits neuroinflammation caused by CCH and IS.

miR-101a-3p Impairs Synaptic Plasticity and Contributes to Synucleinopathy

BACKGROUND

Synucleinopathies are disorders characterized by the abnormal accumulation of α-synuclein (aSyn). Synaptic compromise is observed in synucleinopathies parallel to aSyn aggregation and is accompanied by transcript deregulation.

OBJECTIVE

We sought to identify microRNAs associated with synaptic processes that may contribute to synaptic dysfunction and degeneration in synucleinopathies.

METHODS

We performed small RNA-sequencing of midbrain from 6-month-old transgenic mice expressing A30P mutant aSyn, followed by comparative expression analysis. We then used real-time quantitative polymerase chain reaction (qPCR) for validation. Functional analysis was performed in primary neurons by biochemical assays and imaging.

RESULTS

We found several deregulated biological processes linked to the synapse. miR-101a-3p was validated as a synaptic miRNA upregulated in aSyn Tg mice and in the cortex of dementia with Lewy bodies patients. Mice and primary cultured neurons overexpressing miR-101a-3p showed downregulation of postsynaptic proteins GABA Ab2 and SAPAP3 and altered dendritic morphology resembling synaptic plasticity impairments and/or synaptic damage. Interestingly, primary cultured neuron exposure to recombinant wild-type aSyn species efficiently increased miR-101a-3p levels. Finally, a dynamic role of miR-101a-3p in synapse plasticity was shown by identifying downregulation of miR-101a-3p in a condition of enhanced synaptic plasticity modelled in Wt animals housed in enriched environment.

CONCLUSION

To conclude, we correlated pathologic aSyn with high levels of miR-101a-3p and a novel dynamic role of the miRNA in synaptic plasticity.

A rodent obstacle course procedure controls delivery of enrichment and enhances complex cognitive functions

Enrichment in rodents affects brain structure, improves behavioral performance, and is neuroprotective. Similarly, in humans, according to the cognitive reserve concept, enriched experience is functionally protective against neuropathology. Despite this parallel, the ability to translate rodent studies to human clinical situations is limited. This limitation is likely due to the simple cognitive processes probed in rodent studies and the inability to control, with existing methods, the degree of rodent engagement with enrichment material. We overcome these two difficulties with behavioral tasks that probe, in a fine-grained manner, aspects of higher-order cognition associated with deterioration with aging and dementia, and a new enrichment protocol, the 'Obstacle Course' (OC), which enables controlled enrichment delivery, respectively. Together, these two advancements will enable better specification (and comparisons) of the nature of impairments in animal models of complex mental disorders and the potential for remediation from various types of intervention (e.g., enrichment, drugs). We found that two months of OC enrichment produced substantial and sustained enhancements in categorization memory, perceptual object invariance, and cross-modal sensory integration in mice. We also tested mice on behavioral tasks previously shown to benefit from traditional enrichment: spontaneous object recognition, object location memory, and pairwise visual discrimination. OC enrichment improved performance relative to standard housing on all six tasks and was in most cases superior to conventional home-cage enrichment and exercise track groups.

“Mens Sana in Corpore Sano”: The Emerging Link of Motor Reserve with Motor and Cognitive Abilities and Compensatory Brain Networks in SCA2 Patients

The ability to resiliently cope with neuropathological lesions is a key scientific concern. Accordingly, this study aims to investigate whether motor reserve (MR), likely to be boosted by exercise engagement in a lifetime, affects motor symptom severity, cognitive functioning, and functional brain networks in spinocerebellar ataxia type 2 (SCA2)—a cerebellar neurodegenerative disease. The MR of 12 SCA2 patients was assessed using the Motor Reserve Index Questionnaire (MRIq), developed ad hoc for estimating lifespan MR. The International Cooperative Ataxia Rating Scale was used to assess clinical motor features, and neuropsychological tests were used to evaluate cognitive functioning. Patients underwent an MRI examination, and network-based statistics (NBS) analysis was carried out to detect patterns of functional connectivity (FC). Significant correlations were found between MRIq measures and the severity of motor symptoms, educational and intellectual levels, executive function, and processing speed. NBS analysis revealed a higher FC within subnetworks consisting of specific cerebellar and cerebral areas. FC patterns were positively correlated with MRIq measures, likely indicating the identification of an MR network. The identified network might reflect a biomarker likely to underlie MR, influenced by education and cognitive functioning, and impacting the severity of motor symptoms.

The differential effects of brief environmental enrichment following social isolation in rats

Environmental enrichment (EE) in rodents is associated with a wide range of physiological, affective, and cognitive benefits. A seemingly opposite housing condition, social isolation (SI), is used as a rodent model of stress, negatively affecting several neurobiological mechanisms and hampering cognitive performance. Experimental designs that involve switching between these housing conditions produced mixed results. We evaluated different behavioral and cognitive effects of brief EE following long-term, SI-induced stress. We revealed the influence of enrichment after 30 days of isolation on behavioral despair, anxiety-like behavior, and spatial working memory in adult male Wistar rats and found a substantial anxiolytic effect in the experimental (SI to EE) group. Interestingly, rats exposed to EE also showed increased behavioral despair compared with the control (continuous SI) group. There was no difference in spatial working memory performance at the end of a 5-day water Y-maze (WYM) test. However, the SI to EE animals displayed better memory performance in the first 2 days of the WYM, indicating faster learning. In line with this difference, we recorded significantly more c-Fos-immunopositive (c-Fos+) cells in the retrosplenial and perirhinal cortices of the SI to EE animals. The lateral and basolateral nuclei of the amygdala showed no such difference. These results suggest that brief enrichment following isolation stress leads to differential results in affective and cognitive systems.

Enriched environment ameliorates propagation of tau pathology and improves cognition in rat model of tauopathy

Introduction

The typical symptoms of Alzheimer's disease (AD) are cognitive impairment, disrupted spatial orientation, behavioral and psychiatric abnormalities, and later motor deficits. Neuropathologically, AD is characterized by deposits of pathological forms of endogenous proteins - amyloid-β, and neurofibrillary tau protein pathology. The latter closely correlates with brain atrophy and clinical impairment. Pharmacological therapies for these pathologies are largely absent, raising the question whether non-pharmacological interventions could be efficacious. Environmental factors can play a role in the manifestation of AD. It is unknown whether enriched environment (EE) can ameliorate the propagation of protein aggregates or their toxic components.

Methods

We injected insoluble tau extracts from human brains with AD (600 or 900 ng per animal) into hippocampi of SHR72 transgenic rats that express non-mutated truncated human tau 151-391/4R, but usually do not develop hippocampal tangles. The rats had either standard housing, or could access an EE 5×/week for 3 months. Behavioral analysis included the Morris Water Maze (MWM). Histological analysis was used to assess the propagation of tau pathology.

Results

Animals exposed to EE performed better in the MWM (spatial acquisition duration and total distance, probe test); unexposed animals improved over the course of acquisition trials, but their mean performance remained below that of the EE group. Enriched environment abrogated tau propagation and hippocampal tangle formation in the 600 ng group; in the 900 ng group, tangle formation was ∼10-fold of the 600 ng group, and unaffected by EE.

Conclusion

Even a small difference in the amount of injected human AD tau can cause a pronounced difference in the number of resulting tangles. EE leads to a noticeably better spatial navigation performance of tau-injected animals. Furthermore, EE seems to be able to slow down tau pathology progression, indicating the possible utility of similar interventions in early stages of AD where tangle loads are still low.

Scoping review on environmental enrichment: Are critical periods and sex differences adequately studied?

BACKGROUND

Decades of research have shown the robust behavioral, structural, and molecular effects of environmental enrichment (EE) which predominantly improves neuropathological conditions. However, systematic examination of age and sex influences in response to EE is limited.

OBJECTIVE

Examine the use of EE and evaluate where sex differences (or similarities) are described and whether critical developmental periods are addressed. A critical examination of review articles about EE will establish a framework for the context of the findings of EE-induced effects, improve the impact of future EE studies and improve translatability.

ELIGIBILITY CRITERIA

Narrative, systematic reviews (not original reports) and meta-analyses of any animal species published during 2011 to 2021. Clinical and farming studies were excluded.

SOURCES OF EVIDENCE

Indexed review articles in Pubmed and Psychinfo.

RESULTS

Most studies examine EE during adulthood such as following an injury or following repeated addictive drug exposure. However, in various genetic models of disease states, little attention is paid to effects of EE at different ages. Only some reviews acknowledge that sex differences exist even when the disease state under study is known to be sexually dimorphic. Identified issues include lack of systematic reporting; status of the "control group" (i.e., isolation or pair housing); the use and reporting of proper statistical analyses.

CONCLUSION

Reviews have concluded that EE is most effective when administered early in life but that EE during adulthood is certainly effective. Too few review studies have compared sexes for the effects of EE to make a statement about sex differences. Overall, articles reflect a lack of integration of information on age and sex differences in response to EE. Future studies of EE should examine both sexes and consider critical periods of the lifespan in the experimental models to facilitate the adequate translation of EE as a non-pharmaceutical intervention.

Nicotine-conditioned place preference, reversal learning, and social interaction in MK-801-induced schizophrenia model: Effects of post-weaning enriched environment

Based on the clinical observations of severe cognitive deficits in schizophrenia patients and the relationship between environmental parameters and the severity of schizophrenia symptoms, the present study investigated these parameters in an MK-801-induced schizophrenia model in rats. In addition to, it evaluated whether a post-weaning enriched environment (EE) would affect the nicotine-induced conditioned place preference (CPP) and the motor and cognitive deficits caused by MK-801 treatment. Male Wistar rat pups were injected peritoneally with MK-801 (1 mg/kg) on a daily basis between the 6th and the 10th postnatal days (P) and were exposed to either an enriched or a standard cage from P21 until the end of the experiments. The rats were evaluated in open-field and three-chamber social interaction tests. Moreover, spatial and reversal learning was assessed by the Morris water maze (MWM). Also, the animals were conditioned with 0.6 mg/kg nicotine and tested for CPP. Increased self-grooming, exploratory behavior, potentiated nicotine-CPP, and decreased social behaviors, delayed spatial learning and memory, and impaired reversal learning in the water maze were observed in the MK-801 treatment group. Housing in an EE improved cognitive and behavioral deficits associated with postnatal MK-801 treatment. The results suggested that neonatal N-methyl-D-aspartate (NMDA) receptor hypofunction may cause susceptibility to these behaviors and indicated the importance of environmental conditions in the development of schizophrenia and probably other neuropsychiatric disorders.

Genomic modules and intramodular network concordance in susceptible and resilient male mice across models of stress

The multifactorial etiology of stress-related disorders necessitates a constant interrogation of the molecular convergences in preclinical models of stress that use disparate paradigms as stressors spanning from environmental challenges to genetic predisposition to hormonal signaling. Using RNA-sequencing, we investigated the genomic signatures in the ventral hippocampus common to mouse models of stress. Chronic oral corticosterone (CORT) induced increased anxiety- and depression-like behavior in wild-type male mice and male mice heterozygous for the gene coding for brain-derived neurotrophic factor Val66Met, a variant associated with genetic susceptibility to stress. In a separate set of male mice, chronic social defeat stress (CSDS) led to a susceptible or a resilient population, whose proportion was dependent on housing conditions, namely standard housing or enriched environment. Rank-rank-hypergeometric overlap (RRHO), a threshold-free approach that ranks genes by their p value and effect size direction, was used to identify genes from a continuous gradient of significancy that were concordant across groups. In mice treated with CORT and in standard-housed susceptible mice, differentially expressed genes (DEGs) were concordant for gene networks involved in neurotransmission, cytoskeleton function, and vascularization. Weighted gene co-expression analysis generated 54 gene hub modules and revealed two modules in which both CORT and CSDS-induced enrichment in DEGs, whose function was concordant with the RRHO predictions, and correlated with behavioral resilience or susceptibility. These data showed transcriptional concordance across models in which the stress coping depends upon hormonal, environmental, or genetic factors revealing common genomic drivers that embody the multifaceted nature of stress-related disorders.

Environmental Enrichment for Rats and Mice Housed in Laboratories: A Metareview

Simple Summary

Environmental enrichment has been widely studied with laboratory rodents, but there is no consensus regarding what counts as enrichment or what it should achieve. Inconsistent use of the term “enrichment” creates challenges in drawing conclusions about the quality of an environment. We conducted a metareview to better understand the definitions and goals of enrichment, perceived risks or requirements of enrichment, and what forms of enrichment have previously been endorsed for use with rodents housed in laboratories. This may help researchers and animal care staff to better define their chosen approach and intended outcomes when providing environmental enrichment.

Abstract

Environmental enrichment has been widely studied in rodents, but there is no consensus on what enrichment should look like or what it should achieve. Inconsistent use of the term “enrichment” creates challenges in drawing conclusions about the quality of an environment, which may slow housing improvements for laboratory animals. Many review articles have addressed environmental enrichment for laboratory rats and mice (Rattus norvegicus and Mus musculus). We conducted a metareview of 29 review articles to assess how enrichment has been defined and what are commonly described as its goals or requirements. Recommendations from each article were summarised to illustrate the conditions generally considered suitable for laboratory rodents. While there is no consensus on alternative terminology, many articles acknowledged that the blanket use of the terms “enriched” and “enrichment” should be avoided. Environmental enrichment was most often conceptualised as a method to increase natural behaviour and improve animal welfare. Authors also commonly outlined perceived risks and requirements of environmental enrichment. We discuss these perceptions, make suggestions for future research, and advocate for the adoption of more specific and value-neutral terminology.

An enriched environment reestablishes metabolic homeostasis by reducing obesity-induced inflammation

Obesity can lead to chronic inflammation in different tissues, generating insulin and leptin resistance and alterations in glucose and lipid metabolism, favoring the development of degenerative diseases, including type II diabetes. Congruently, the inflammatory signaling inhibition prevents the development of obesity and restores insulin sensitivity. Via the enhancement of central nervous system activity, an enriched environment (EE) has beneficial effects on learning and memory as well as on immune cell functions and inflammation in different disease models. Here, we explored whether an EE can restore energy balance in obese mice that previously presented metabolic alterations. We discovered that an EE improved glucose metabolism, increased insulin signaling in liver, and reduced hepatic steatosis and inflammation, and increased lipolysis and browning in the white adipose tissue of high-fat diet (HFD)-fed mice. Finally, we found reduced inflammatory signaling and increased anorexigenic signaling in the hypothalamus of HFD-fed mice exposed to an EE. These data indicate that an EE is able to restore the metabolic imbalance caused by HFD feeding. Thus, we propose EE as a novel therapeutic approach for treating obesity-related metabolic alterations.

This article has an associated First Person interview with the first author of the paper.

Summary: A series of physiological, histochemical and molecular analyses reveal that enriched environment decreases inflammation in adipose tissue and in hypothalamus, re-establishing glucose metabolism in metabolically compromised mice.

Early environmental enrichment prevents cognitive impairments and developing addictive behaviours in a mouse model of prenatal psychological and physical stress

Environmental enrichment (EE) has shown remarkable effects in improving cognition and addictive behaviour. We tested whether EE could help recover from prenatal stress exposure. Mature Swiss Webster male and virgin female mice were placed together until vaginal plugs were detectable. Next, pregnant rodents were randomized into the control, physically and psychologically stressed groups. The application of stress was initiated on the 10th day of pregnancy and persisted for a week to induce stress in the mice. Open field and elevated plus-maze (EPM) tests were utilized as explorative and anxiety assays, respectively. A passive avoidance shuttle-box test was carried out to check anxiety-modulated behaviour. Morris water maze (MWM) test was undertaken to evaluate spatial learning and memory. Conditioned place preference (CPP) test was selected for evaluation of tendency to morphine consumption. Our results showed that prenatal stress elevated anxiety-like behaviour in the offspring which EE could significantly alleviate after weaning. We also found a higher preference for morphine use in the physical stress and psychological stress offspring group. However, no difference was observed among the genders. Application of EE for the stress group improved several parameters of the cognitive behaviour significantly. Although prenatal stress can lead to detrimental behavioural and cognitive outcomes, it can in part be relieved by early exposure to EE. However, some outcomes linked to prenatal stress exposure may not be diminished by EE therapy. In light of such irreversible effects, large-scale preventive actions promoting avoidance from stress during pregnancy should be advised.

Brief Environmental Enrichment exposure enhances contextual-induced sucrose-seeking with and without memory reactivation in rats

Chronic Environmental Enrichment (EE) has been shown to prevent the relapse to addictive behaviours, such as drug-taking and -seeking. Recently, acute EE was shown to reduce cue-induced sucrose-seeking, but its effects on contextual (Cx)-induced sucrose-seeking is still unknown. Here we report the effects of brief EE exposure on Cx-induced sucrose-seeking with and without prior Cx-memory reactivation. Adult male Sprague-Dawley rats were trained to sucrose self-administration associated to a specific conditioning Cx (CxA), followed by a 7-day extinction in a different Cx (CxB). Afterwards, rats were exposed for 22 h to EE, and 1 h later to either i) Cx-induced sucrose-seeking (1 h, renewal without Cx-memory reactivation), ii) or two different Cx-memory reactivations: short (2-min) and long (15-min) CxA-retrieval session (Cx-Ret). In Cx-Ret experiments, CxA-induced sucrose-seeking test (1 h) was done after a subsequent 3-day extinction phase. The assessment of molecular markers of memory reactivation/reconsolidation, Zif-268 and rpS6P, was performed 2 h after Cx-Ret. Brief EE exposure enhanced Cx-induced sucrose-seeking without and with short but not long Cx-retrieval. Moreover, EE impaired discriminative responding at test prior to long, whereas improved it with or without short Cx-retrieval. Different changes in Zif-268 and rpS6P expression induced by short vs. long Cx-Ret were correlated to behavioural data, suggesting the occurrence of different memory processes affected by EE. Our data show that brief EE exposure may differently affect subsequent appetitive relapse depending on the modality of re-exposure to conditioned context. This finding suggests caution and further studies to understand the proper conditions for the use of EE against appetitive and addiction disorders.

Exploring Effects of the HEP (Homeostasis-Enrichment-Plasticity) Approach as a Comprehensive Therapy Intervention for an Infant with Cerebral Palsy: A Case Report

Cerebral palsy (CP) is a common non-progressive neurodevelopmental disorder which causes developmental disabilities in children. Varied interventions for CP exist to address medical and physical needs but with limited effectiveness evidence. Environmental enrichment (EE) is an animal model intervention for many neurodevelopmental disorders, including CP, with considerable positive effects. This case report defines the Homeostasis-Enrichment-Plasticity (HEP) approach, which is based upon principles of EE and ecological theories of development and describes its use to promote the developmental and functional skills of an infant with CP. Parent interviews and assessment data were completed before and after intervention. For the interested parameters data was gathered by developmental history, systematic observation of behaviors in the clinical setting and at home, Beck Anxiety Inventory (BAI), Infant-Toddler Symptom Checklist, the Sensory Profile Infant/Toddler, Peabody Developmental Motor Scales-2, Gross Motor Function Measurement-88 (GMFM-88), the Gross Motor Function Classification System (GMFCS), and Pediatric Evaluation of Disability Inventory (PEDI). The HEP approach intervention was implemented one time per week for 12 months. Following the HEP approach intervention, self-regulation and sensory processing scores improved. GMFM-88 total score improved from 45/264 to 123/264. The Peabody found all gross motor (54–110), fine motor (65–117), and total motor quotient (119–227) scores improved after intervention. Post-intervention observations showed obvious gross motor progress with movement from GMFCS Level IV to Level I. Performance on the Functional Skills Scales and Caregiver Assistance Scales of PEDI also demonstrated notable improvements. BAI scores revealed low anxiety scores for both the mother (13/63 points) and father (14/63) before intervention. These scores did not change after intervention. A definition and detailed description of the HEP approach intervention is presented here for the first time. The case report demonstrated preliminary evidence for the effectiveness of the HEP approach on self-regulation, sensory processing, motor development, functional skills, and caregiver assistance with an infant with CP. Additional studies are needed to validate the findings.

Factors modulating the incubation of drug and non-drug craving and their clinical implications

It was suggested in 1986 that cue-induced cocaine craving increases progressively during early abstinence and remains high during extended periods of time. Clinical evidence now supports this hypothesis and that this increase is not specific to cocaine but rather generalize across several drugs of abuse. Investigators have identified an analogous incubation phenomenon in rodents, in which time-dependent increases in cue-induced drug seeking are observed after abstinence from intravenous drug or palatable food self-administration. Incubation of craving is susceptible to variation in magnitude as a function of biological and/or the environmental circumstances surrounding the individual. During the last decade, the neurobiological correlates of the modulatory role of biological (sex, age, genetic factors) and environmental factors (environmental enrichment and physical exercise, sleep architecture, acute and chronic stress, abstinence reinforcement procedures) on incubation of drug craving has been investigated. In this review, we summarized the behavioral procedures adopted, the key underlying neurobiological correlates and clinical implications of these studies.

Environmental enrichment for stroke and other non-progressive brain injury

BACKGROUND

Rehabilitation is effective for recovery after stroke and other non-progressive brain injuries but it is unclear if the rehabilitation environment itself, outside of limited therapy hours, is maximally conducive to recovery. Environmental enrichment is a relatively new concept within rehabilitation for humans. In this review, this is defined as an intervention designed to facilitate physical (motor and sensory), cognitive and social activity by the provision of equipment and organisation of a structured, stimulating environment. The environment should be designed to encourage (but not force) activities without additional specialised rehabilitation input.

OBJECTIVES

To assess the effects of environmental enrichment on well-being, functional recovery, activity levels and quality of life in people who have stroke or non-progressive brain injury.

SEARCH METHODS

We conducted the search on 26 October 2020. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library; MEDLINE (from 1950); Embase (from 1980); the Cumulative Index to Nursing and Allied Health Literature (CINAHL; from 1982); the Allied and Complementary Medicine Database (AMED; from 1985); PsycINFO (from 1806); the Physiotherapy Evidence Database (PEDro; from 1999); and 10 additional bibliographic databases and ongoing trial registers.

SELECTION CRITERIA

We planned to include randomised controlled trials (RCTs) that compared environmental enrichment with standard services.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligible studies, extracted data, and assessed study quality. Any disagreements were resolved through discussion with a third review author. We determined the risk of bias for the included study and performed a 'best evidence' synthesis using the GRADE approach.

MAIN RESULTS

We identified one RCT, involving 53 participants with stroke, comparing environmental enrichment (which included physical, cognitive and social activities such as reading material, board and card games, gaming technology, music, artwork, and computer with Internet) with standard services in an inpatient rehabilitation setting. We excluded five studies, found two studies awaiting classification and one ongoing study which described environmental enrichment in their interventions. Of the excluded studies, three were non-RCTs and two described co-interventions with a significant component of rehabilitation. Based on the single small included RCT at high risk of bias, data are insufficient to provide any reliable indication of benefit or risk to guide clinical practice in terms of the provision of environmental enrichment.

AUTHORS' CONCLUSIONS

The gap in current research should not, however, be interpreted as proof that environmental enrichment is ineffective. Further research is needed with robust study designs, such as cluster RCTs, and consistent outcome measurement evaluating the effectiveness of environmental enrichment in different settings (inpatient versus outpatient), the relative effectiveness of various components of environmental enrichment, cost-effectiveness, and safety of the intervention in people following stroke or other non-progressive brain injuries. It should be noted, however, that it is challenging to randomise or double-blind trials of environmental enrichment given the nature of the intervention.

Animal models of developmental dyslexia: Where we are and what we are missing

Developmental dyslexia (DD) is a complex neurodevelopmental disorder and the most common learning disability among both school-aged children and across languages. Recently, sensory and cognitive mechanisms have been reported to be potential endophenotypes (EPs) for DD, and nine DD-candidate genes have been identified. Animal models have been used to investigate the etiopathological pathways that underlie the development of complex traits, as they enable the effects of genetic and/or environmental manipulations to be evaluated. Animal research designs have also been linked to cutting-edge clinical research questions by capitalizing on the use of EPs. For the present scoping review, we reviewed previous studies of murine models investigating the effects of DD-candidate genes. Moreover, we highlighted the use of animal models as an innovative way to unravel new insights behind the pathophysiology of reading (dis)ability and to assess cutting-edge preclinical models.

Effects of early noise exposure on hippocampal-dependent behaviors during adolescence in male rats: influence of different housing conditions

Central nervous system (CNS) development is a very complex process that can be altered by environmental stimuli such as noise, which can generate long-term auditory and/or extra-auditory impairments. We have previously reported that early noise exposure can induce hippocampus-related behavioral alterations in postnatal day (PND) 28 adolescent rats. Furthermore, we recently found biochemical modifications in the hippocampus (HC) of these animals that seemed to endure even in more mature animals (i.e. PND35) and that have not been studied along with behavioral correlates. Thus, the aim of this work was to reveal novel data about the effects of early noise exposure on hippocampal-dependent behaviors in more mature animals. Additionally, extended enriched environment (EE) housing was evaluated to determine its capacity to induce behavioral modifications, either by its neuroprotective ability or the greater stimulation that it generates. Male Wistar rats were exposed to different noise schemes at PND7 or PND15. Upon weaning, some animals were transferred to EE whereas others were kept in standard cages. At PND35, different hippocampal-dependent behavioral assessments were performed. Results showed noise-induced behavioral changes that differed according to the scheme and age of exposure used. In addition, housing in an EE was effective either in preventing some of these changes or in inducing the appearance of new behavioral modifications. These findings suggest that CNS development would be sensitive to the effects of different type of environmental stimuli such as noise or enriched housing, leading to maladaptive behavioral changes that last even until adolescence.

Is It Possible to Shift from Down to Top Rank? A Focus on the Mesolimbic Dopaminergic System and Cocaine Abuse

Impaired social behavior is a common feature of many psychiatric disorders, in particular with substance abuse disorders. Switching the preference of the substance-dependent individual toward social interaction activities remains one of the major challenges in drug dependence therapy. However, social interactions yield to the emergence of social ranking. In this review, we provide an overview of the studies that examined how social status can influence the dopaminergic mesolimbic system and how drug-seeking behavior is affected. Generally, social dominance is associated with an increase in dopamine D_2/3 receptor binding in the striatum and a reduced behavioral response to drugs of abuse. However, it is not clear whether higher D₂ receptor availability is a result of increased D₂ receptor density and/or reduced dopamine release in the striatum. Here, we discuss the possibility of a potential shift from down to top rank via manipulation of the mesolimbic system. Identifying the neurobiology underlying a potential rank switch to a resilient phenotype is of particular interest in order to promote a positive coping behavior toward long-term abstinence from drugs of abuse and a protection against relapse to drugs. Such a shift may contribute to a more successful therapeutic approach to cocaine addiction.

miR-128 as a Regulator of Synaptic Properties in 5xFAD Mice Hippocampal Neurons

Alzheimer's disease (AD) is characterized by progressive synaptic dysfunction, deterioration of neuronal transmission, and consequently neuronal death. Although there is no treatment for AD, exposure to enriched environment (EE) in mice, as well as physical and mental activity in human subjects have been shown to have a protective effect by slowing the disease's progression and reducing AD-like cognitive impairment. However, the molecular mechanism of this mitigating effect is still not understood. One of the mechanisms that has recently been shown to be involved in neuronal degeneration is microRNAs (miRNAs) regulation, which act as a post-transcriptional regulators of gene expression. miR-128 has been shown to be significantly altered in individuals with AD and in mice following exposure to EE. Here, we focused on elucidating the possible role of miR-128 in AD pathology and found that miR-128 regulates the expression of two proteins essential for synaptic transmission, SNAP-25, and synaptotagmin1 (Syt1). Clinically relevant, in 5xFAD mouse model for AD, this miRNA's expression was found as downregulated, resembling the alteration found in the hippocampi of individuals with AD. Interestingly, exposing WT mice to EE also resulted in downregulation of miR-128 expression levels, although EE and AD conditions demonstrate opposing effects on neuronal functioning and synaptic plasticity. We also found that miR-128 expression downregulation in primary hippocampal cultures from 5xFAD mice results in increased neuronal network activity and neuronal excitability. Altogether, our findings place miR-128 as a synaptic player that may contribute to synaptic functioning and plasticity through regulation of synaptic protein expression and function.

Postoperative Cognitive Dysfunction and the Protective Effects of Enriched Environment: A Systematic Review

BACKGROUND

Currently, the number of individuals who undergo surgery is greatly increased. As a consequence, postoperative cognitive dysfunction (POCD) has gradually gained more attention.

SUMMARY

POCD is a perioperative complication requiring sensitive preoperative and postoperative neuropsychiatric tests, and its incidence in both cardiac and noncardiac surgery is high, especially in elderly individuals. Surgical, patient, and anesthetic factors may all lead to the occurrence and development of POCD. The key mechanism of POCD may be the inflammatory response of the central nervous system during surgery, which is similar to that of Alzheimer's disease (AD). Enriched environment (EE), a factor that can significantly improve and prevent neurodegenerative diseases, may have a beneficial effect on POCD. Key Messages: This review aims to elucidate the mechanism of the occurrence and development of POCD, analyze the possible influence of EE on POCD at the molecular level, and provide a direction for its treatment.

Effects of handling on the behavioural phenotype of the neuregulin 1 type III transgenic mouse model for schizophrenia

Handling of laboratory mice affects animal wellbeing and behavioural test outcomes. However, present research has focused on handling effects in common strains of laboratory mice despite the knowledge that environmental factors can modify established phenotypes of genetic mouse models. Thus, we examined the impact of handling on the face validity of a transgenic mouse model for the schizophrenia risk gene neuregulin 1 (i.e. Nrg1 type III overexpression). Nrg1 III tg and wild type-like (WT) control mice of both sexes underwent tail or tunnel handling before being assessed in the open field (OF), elevated plus maze (EPM), social preference/novelty, prepulse inhibition, and fear conditioning tests. Tunnel-handling reduced the startle response in all mice, increased OF locomotion and exploration in males and reduced anxiety in males (OF) and females (EPM) compared to tail-handling. Importantly, tunnel handling induced a more pronounced startle response to increasing startle stimuli in Nrg1 III tg females compared to respective controls, a phenomenon absent in tail-handled females. Finally, Nrg1 III tg males displayed reduced OF exploration and centre locomotion and Nrg1 III tg females displayed increased cue freezing over time compared to controls. In conclusion, handling methods have a significant impact on a variety of behavioural domains thus the impact of routine handling procedures need be considered when testing behavioural phenotypes. Handling did not change the main schizophrenia-relevant characteristics of Nrg1 III tg mice but affected the acoustic startle-response in a genotype- and sex-specific manner. Future research should evaluate the effect of handling on other genetic models.

Childhood trauma and post-trauma environment affect fear memory and alcohol use differently in male and female mice

BACKGROUND

Childhood trauma is associated with the development of adult mental health and substance use disorders, with females generally being more at risk. Alcohol is commonly used for coping with trauma, and alcohol use disorder (AUD) affects ∼14.4 million adult Americans annually. Research investigating sex differences in the environmental modification of anxiety and alcohol use following childhood trauma will extend our understanding of the etiology of AUD. Here, we sought to model the interacting effects of a single-episode late childhood trauma with post-trauma environment on adult alcohol use using male and female mice.

METHODS

C57Bl6/J mice (d22) exposed to predator odor (TMT) or water were reared in standard environments (SE) or environmental enrichment (EE). Mice were assessed for adolescent anxiety and conditioned fear, and for adult alcohol use in a limited access, response non-contingent, alcohol exposure paradigm.

RESULTS

A single exposure to predator odor was an effective stressor, inducing long-term sex-dependent changes in conditioned fear and alcohol behaviors that interacted with post-trauma environment. Adolescent EE females showed more conditioned freezing to the trauma-associated context. Adult EE mice consumed less total alcohol than SE mice. However, alcohol use across time differed for males and females. Exposure to a childhood stressor increased alcohol use significantly in females, but not males. EE males, but not EE females, drank less than SE counterparts.

CONCLUSIONS

Findings from this model recapitulate greater vulnerability to childhood trauma in females and support sex differences in post-trauma development of conditioned fear and alcohol use that are modified by environment.

Noise-induced hippocampal oxidative imbalance and aminoacidergic neurotransmitters alterations in developing male rats: Influence of enriched environment during adolescence

Living in big cities might involuntarily expose people to high levels of noise causing auditory and/or extra-auditory impairments, including adverse effects on central nervous system (CNS) areas such as the hippocampus. In particular, CNS development is a very complex process that can be altered by environmental stimuli. We have previously shown that noise exposure of developing rats can induce hippocampal-related behavioral alterations. However, noise-induced biochemical alterations had not been studied yet. Thus, the aim of this work was to assess whether early noise exposure can affect rat hippocampal oxidative state and aminoacidergic neurotransmission tone. Additionally, the effectiveness of an enriched environment (EE) as a neuroprotective strategy was evaluated. Male Wistar rats were exposed to different noise schemes at 7 or 15 days after birth. Upon weaning, some animals were transferred to an EE whereas others were kept in standard cages. Short- and long-term measurements were performed to evaluate reactive oxygen species, thioredoxins levels and catalase activity as indicators of hippocampal oxidative status as well as glutamic acid decarboxylase and a subtype of glutamate transporter to evaluate aminoacidergic neurotransmission tone. Results showed noise-induced changes in hippocampal oxidative state and aminoacidergic neurotransmission markers that lasted until adolescence and differed according to the scheme and the age of exposure. Finally, EE housing was effective in preventing some of these changes. These findings suggest that CNS development seems to be sensitive to the effects of stressors such as noise, as well as those of an environmental stimulation, favoring prompt and lasting molecular changes.

A three-dimensional habitat for C. elegans environmental enrichment

As we learn more about the importance of gene-environment interactions and the effects of environmental enrichment, it becomes evident that minimalistic laboratory conditions can affect gene expression patterns and behaviors of model organisms. In the laboratory, Caenorhabditis elegans is generally cultured on two-dimensional, homogeneous agar plates abundantly covered with axenic bacteria culture as a food source. However, in the wild, this nematode thrives in rotting fruits and plant stems feeding on bacteria and small eukaryotes. This contrast in habitat complexity suggests that studying C. elegans in enriched laboratory conditions can deepen our understanding of its fundamental traits and behaviors. Here, we developed a protocol to create three-dimensional habitable scaffolds for trans-generational culture of C. elegans in the laboratory. Using decellularization and sterilization of fruit tissue, we created an axenic environment that can be navigated throughout and where the microbial environment can be strictly controlled. C. elegans were maintained over generations on this habitat, and showed a clear behavioral bias for the enriched environment. As an initial assessment of behavioral variations, we found that dauer populations in scaffolds exhibit high-frequency, complex nictation behavior including group towering and jumping behavior.

Environment-dependent behavioral traits and experiential factors shape addiction vulnerability

The transition from controlled drug use to drug addiction depends on an interaction between a vulnerable individual, their environment and a drug. Here we tested the hypothesis that conditions under which individuals live influence behavioral vulnerability traits and experiential factors operating in the drug taking environment to determine the vulnerability to addiction. The role of behavioral vulnerability traits in mediating the influence of housing conditions on the tendency to acquire cocaine self-administration was characterized in 48 rats housed in either an enriched (EE) or a standard (SE) environment. Then, the influence of these housing conditions on the individual vulnerability to develop addiction-like behavior for cocaine or alcohol was measured in 72 EE or SE rats after several months of cocaine self-administration or intermittent alcohol drinking, respectively. The determining role of negative experiential factors in the drug taking context was further investigated in 48 SE rats that acquired alcohol drinking to self-medicate distress in a schedule-induced polydipsia procedure. The environment influenced the acquisition of drug intake through its effect on behavioral markers of resilience to addiction. In contrast, the initiation of drug taking as a coping strategy or in a negative state occasioned by the contrast between enriched housing conditions and a relatively impoverished drug taking setting, facilitated the development of compulsive cocaine and alcohol intake. These data indicate that addiction vulnerability depends on environmentally determined experiential factors, and suggest that initiating drug use through negative reinforcement-based self-medication facilitates the development of addiction in vulnerable individuals. SIGNIFICANCE STATEMENT: The factors that underlie an individual's vulnerability to switch from controlled, recreational drug use to addiction are not well understood. We showed that in individuals housed in enriched conditions, the experience of drugs in the relative social and sensory impoverishment of the drug taking context, and the associated change in behavioral traits of resilience to addiction, exacerbate the vulnerability to develop compulsive drug intake. We further demonstrated that the acquisition of alcohol drinking as a mechanism to cope with distress increases the vulnerability to develop compulsive alcohol intake. Together these results demonstrate that experiential factors in the drug taking context shape the vulnerability to addiction.

Environmental enrichment-inspired pharmacological tools for the treatment of addiction

Environmental enrichment (EE) has been shown to produce powerful beneficial effects in animal models of addiction. In particular, the ability of EE to promote abstinence and prevent relapse may allow for the identification of brain mechanisms responsible for the recovery from addiction. Indeed, the effects of EE on specific brain mechanisms could be mimicked by old or new molecules, which may become novel medications, called enviromimetics. Here, we review the best known enviromimetics for the treatment of addiction and suggest that, whereas these compounds may be relatively ineffective by themselves, they may be useful complements for existing therapeutic approaches to manage addiction which includes behavioural, environmental and pharmacological interventions.

The Relevance of Operant Behavior in Conceptualizing the Psychological Well-Being of Captive Animals

The term "psychological well-being" is used in reference to husbandry with animals in human care settings such as research, agriculture, and zoos. This article seeks to clarify and conceptualize the term based upon two approaches that draw from several bodies of literature: the experimental analysis of behavior, experimental psychology, animal welfare and husbandry, farm animal behavior, zoo husbandry, and ethology. One approach focuses on the presence of problem behavior such as stereotypies, depressive-like behavior, and aggression, and emphasizes the conditions under which aberrant behavior in animals under human care occurs. The second approach examines what might be considered wellness by emphasizing opportunities to engage with its environment, or the absence of such opportunities, even if problematic behavior is not exhibited. Here, access to an interactive environment is relatively limited so opportunities for operant (voluntary) behavior could be considered. Designing for operant behavior provides opportunities for variability in both behavior and outcomes. Operant behavior also provides control over the environment, a characteristic that has been a core assumption of well-being. The importance of interactions with one's environment is especially evident in observations that animals prefer opportunities to work for items necessary for sustenance, such as food, over having them delivered freely. These considerations raise the importance of operant behavior to psychological well-being, especially as benefits to animals under human care.

Enriched Environment Rearing from Birth Reduced Anxiety, Improved Learning and Memory, and Promoted Social Interactions in Adult Male Mice

Rearing rodents in an enriched environment (EE), with increased sensory stimulations and social interactions, is a well-established model for naturally increasing neural activity. It is well-known that EE-rearing of rodents from adolescence or during adulthood leads to extensive biochemical, morphological, electrophysiological and behavioral changes. Here, we examine the effects of EE-rearing from birth on adult behavior. Through a battery of assays, we found that mice EE-reared from birth had better acquisition and consolidation of memory, in both aversive-based fear conditioning and reward-based contextual association tasks. Moreover, EE-reared mice showed reduced anxiety in novel environments and enhanced social interactions. Together, these results demonstrated that EE-rearing from birth significantly improved motor ability, learning and memory and sociability, while reducing anxiety. A better understanding of how early environmental influences affect behavior is not only important for understanding neural circuit wiring, but also provides insight into developing more effective intervention programs for neurodevelopmental disorders.

Improvements to Healthspan Through Environmental Enrichment and Lifestyle Interventions: Where Are We Now?

Environmental enrichment (EE) is an experimental paradigm that is used to explore how a complex, stimulating environment can impact overall health. In laboratory animal experiments, EE housing conditions typically include larger-than-standard cages, abundant bedding, running wheels, mazes, toys, and shelters which are rearranged regularly to further increase stimulation. EE has been shown to improve multiple aspects of health, including but not limited to metabolism, learning and cognition, anxiety and depression, and immunocompetence. Recent advances in lifespan have led some researchers to consider aging as a risk factor for disease. As such, there is a pressing need to understand the processes by which healthspan can be increased. The natural and predictable changes during aging can be reversed or decreased through EE and its underlying mechanisms. Here, we review the use of EE in laboratory animals to understand mechanisms involved in aging, and comment on relative areas of strength and weakness in the current literature. We additionally address current efforts toward applying EE-like lifestyle interventions to human health to extend healthspan. Although increasing lifespan is a clear goal of medical research, improving the quality of this added time also deserves significant attention. Despite hurdles in translating experimental results toward clinical application, we argue there is great potential in using features of EE toward improving human healthy life expectancy or healthspan, especially in the context of increased global longevity.

The social life of Norway rats (Rattus norvegicus)

The Norway rat has important impacts on our life. They are amongst the most used research subjects, resulting in ground-breaking advances. At the same time, wild rats live in close association with us, leading to various adverse interactions. In face of this relevance, it is surprising how little is known about their natural behaviour. While recent laboratory studies revealed their complex social skills, little is known about their social behaviour in the wild. An integration of these different scientific approaches is crucial to understand their social life, which will enable us to design more valid research paradigms, develop more effective management strategies, and to provide better welfare standards. Hence, I first summarise the literature on their natural social behaviour. Second, I provide an overview of recent developments concerning their social cognition. Third, I illustrate why an integration of these areas would be beneficial to optimise our interactions with them.

Duration of Environmental Enrichment Determines Astrocyte Number and Cervical Lymph Node T Lymphocyte Proportions but Not the Microglial Number in Middle-Aged C57BL/6 Mice

Environmental enrichment (EE) has been shown to modulate behavior and immunity. We recently reported that both short and long-term EE enhance baseline locomotion and alleviate depressive-like behavior, but only long-term EE affects locomotion adversely in a threatening environment and enhances anxiety-like behavior in middle-age mice. We have now investigated whether the observed changes in behavior after short- and long-term EE were associated with underlying immune changes. Hence, at the end of behavioral testing, mice were sacrificed, and brains and cervical lymph nodes were collected to investigate the differential effects of the duration of EE (short- and long-term) on the number of immunopositive glial cells in the dentate gyrus, CA1, CA2, and CA3 regions of the hippocampus and proportions of T cell subsets in the cervical lymph nodes using immunohistochemistry and flow cytometry, respectively. EE, regardless of duration, caused an increase in microglia number within the dentate gyrus, CA1 and CA3 hippocampal regions, but only long-term EE increased astrocytes number within the dentate gyrus and CA3 hippocampal regions. A significantly higher proportion of CD8⁺ naive T cells was observed after long-term EE vs. short-term EE. No significant differences were observed in the proportion of central memory and effector memory T cells or early activated CD25⁺ cells between any of the test groups. Our results suggest that EE, irrespective of duration, enhances the numbers of microglia, but long-term EE is required to modify astrocyte number and peripheral T cell proportions in middle-aged mice. Our findings provide new insights into the therapeutic effects of EE on various brain disorders, which may be at least partly mediated by glial and neuroimmune modulation.