Effects of Environmental Enrichment Exposure on Synaptic Transmission and Plasticity in the Hippocampus

Abstract

Exposure to an enriched environment (EE) is beneficial to the structure and function of the brain. The added sensory, social, and spatial complexity of the EE also improves cognitive functions such as memory in both healthy brains and damaged or diseased brains, yet the underlying neural mechanisms of these cognitive improvements are poorly understood. In particular, studies that have examined the effects of EE on cellular function in the hippocampus, a structure critical for memory storage, have produced somewhat confusing results. Experiments performed in ex vivo hippocampal slices have reported a variety of EE effects on synaptic transmission and plasticity in both CA1 and the dentate gyrus. However, together with data from in vivo recordings made during and after the EE treatment, the overall results suggest an evolution of changes in neuronal function in the hippocampus, whereby there is an early transient increase in cell activity and plasticity that gives rise to more subtle long-term enhancements in cellular and network function that may contribute to enhanced hippocampus-dependent cognition.

Environmental enrichment modulates intrinsic cellular excitability of hippocampal CA1 pyramidal cells in a housing duration and anatomical location-dependent manner

“…In addition, Amaral et al [2] reported that reduced locomotion behavior in an open field persisted after a prolonged (8 weeks), but not after a shorter (4 weeks), housing duration. This discrepancy between the effect of EE on the physiological properties and on the behavioral measures has recently been pointed out by Eckert and Abraham [10]. They suggest that initially heightened excitability and synaptic plasticity might return to baseline levels through a homeostatic mechanism, while other more subtle mechanisms underlie long lasting behavioral effects.…”

“…While increased intrinsic excitability was observed after a relatively short duration of enrichment (<35 days; [35]), this was not the case in another study which used a longer duration (8 weeks; [9]). Interestingly, it has recently been pointed out in a review article, that enhanced synaptic properties and population spike induction by environmental enrichment, were mostly observed in studies with a relatively short housing duration (<4 weeks; [10]). However, a systematic study of the effect of housing duration on intrinsic cellular excitability has not been reported.…”

Does physical activity protect against drug abuse vulnerability?

“…For example, exercise reduces the incidence of obesity-related diseases, at least in part, by altered lipoprotein levels (Ainslie et al, 2005;Craig et al, 1996). In contrast, the ability of physical activity to enhance learning during development may be mediated by the proliferation of glial and endothelial cells, as well as an increases in neurogenesis and neuronal connectivity, in brain regions critical for learning and memory (Eckert and Abraham, 2013;Gelfo et al, 2009;Mandyam et al, 2007;Viola et al, 2009).…”

Phonologic errors in the logopenic variant of primary progressive aphasia

“…Recent studies suggest that enriching life experiences, such as higher education, increase memory and learning formation (Bennett, McRae, Levy, & Frick, 2006;Bousiges et al, 2010;Eckert & Abraham, 2012;Leal-Galicia, Castañeda-Bueno, Quiroz-Baez, & Arias, 2008;Patel, 2012) and that higher education and occupational attainment may decrease the risk of Alzheimer's dementia, possibly because of greater cognitive reserve that may delay clinical manifestations (e.g., Stern, 2012;Stern et al, 1994;Valenzuela & Sachdev, 2006). Education/literacy may, to some degree, strengthen neural redundancy and perhaps play a role in delaying clinical manifestations, such as phonologic errors, or rate of progression in LPA.…”