Standardized Environmental Enrichment Supports Enhanced Brain Plasticity in Healthy Rats and Prevents Cognitive Impairment in Epileptic Rats

Abstract

Environmental enrichment of laboratory animals influences brain plasticity, stimulates neurogenesis, increases neurotrophic factor expression, and protects against the effects of brain insult. However, these positive effects are not constantly observed, probably because standardized procedures of environmental enrichment are lacking. Therefore, we engineered an enriched cage (the Marlau™ cage), which offers: (1) minimally stressful social interactions; (2) increased voluntary exercise; (3) multiple entertaining activities; (4) cognitive stimulation (maze exploration), and (5) novelty (maze configuration changed three times a week). The maze, which separates food pellet and water bottle compartments, guarantees cognitive stimulation for all animals. Compared to rats raised in groups in conventional cages, rats housed in Marlau™ cages exhibited increased cortical thickness, hippocampal neurogenesis and hippocampal levels of transcripts encoding various genes involved in tissue plasticity and remodeling. In addition, rats housed in Marlau™ cages exhibited better performances in learning and memory, decreased anxiety-associated behaviors, and better recovery of basal plasma corticosterone level after acute restraint stress. Marlau™ cages also insure inter-experiment reproducibility in spatial learning and brain gene expression assays. Finally, housing rats in Marlau™ cages after severe status epilepticus at weaning prevents the cognitive impairment observed in rats subjected to the same insult and then housed in conventional cages. By providing a standardized enriched environment for rodents during housing, the Marlau™ cage should facilitate the uniformity of environmental enrichment across laboratories.

Environmental enrichment restores cognitive deficits induced by experimental childhood meningitis

“…In several animal models of neurological disorders, EE and exercise have been found to have advantageous effects, including beneficial effects on learning and memory, improved cellular plasticity, BDNF expression, adult neurogenesis, and associated molecular processes. 12,14,[28][29][30] Our study showed that animals subjected to pneumococcal meningitis during infancy presented memory impairment in adulthood. In the animals that were subjected to EE (promoting cognitive stimulation through motor activity, visual stimuli, object recognition, novelty, and the modulation of attention), these impairments of habituation and aversive memories were reversed.…”

“…EE rats also perform better on learning and memory tasks. 12 During the early postnatal period, EE increases cell proliferation in the dentate gyrus of guinea pigs. 15 The stimulation provided by EE fosters recovery from spatial memory deficits, 16 improves memory impairment on object recognition tests, and preserves hippocampal dendritic spine density following neonatal hypoxia-ischemia injury in rats.…”

“…11 In addition, when utilized in an attempt to minimize cognitive damage, environmental enrichment (EE) is a novel and promising non-pharmacological approach and has been shown to stimulate brain plasticity, neurogenesis, and increased neurotrophic factor expression, as well as protect against the effects of brain insults. 12 EE refers to housing conditions in which the animals are kept in spacious cages containing toys, running wheels, climbing ropes, and objects with different shapes and textures. 13 This environment promotes visual and sensory stimulation, minimizes stressful social interactions, increases voluntary exercise, and may have an effect on cognitive functions compromised in disorders of the central nervous system (CNS).…”

“…13 This environment promotes visual and sensory stimulation, minimizes stressful social interactions, increases voluntary exercise, and may have an effect on cognitive functions compromised in disorders of the central nervous system (CNS). [12][13][14] Compared with rats reared in groups in conventional cages, rats housed in an enriched environment exhibit increased cortical thickness, hippocampal neurogenesis, and hippocampal levels of transcripts that encode various genes involved in tissue plasticity and remodeling. EE rats also perform better on learning and memory tasks.…”

Effects of enriched environment on maximal lactate steady state of wistar rats

“…The animals housed in standardized cage (Malau Cage) since the fourth week of life during six weeks led to an increase in body weight (FARES et al, 2013). Tsai et al (2002) also found no changes promoted by enriched environment in body and heart mass.…”