Continuous enriched environment improves learning and memory in adult NMRI mice through theta burst-related-LTP independent mechanisms but is not efficient in advanced aged animals

Introduction: Effects of 3-month continuous environmental enrichment (EE) on cognitive abilities and on theta burst-related synaptic plasticity of CA1 hippocampal neuronal networks have been assessed in 6-and 20-month old NMRI female mice. Results: EE decreased anxiety-like behavior and improved learning and memory performances in adult but not in aged mice. Electrophysiological results in CA1 hippocampal slices showed that basal synaptic transmission was not affected by EE in adult mice whereas it was partially improved in aged animals, even though not sufficient to rescue the decrease related to aging. Besides, no effect of EE on N-methyl-D-aspartate receptor activation and theta-burst-induced long-term potentiation was found in adult or aged animals. Discussion: These results indicate that continuous EE is able to improve cognitive abilities in adult NMRI female mice, that does not correlate with changes in theta burst-related synaptic plasticity within neuronal networks. In addition, the lack of effects in aged animals suggests the existence of a critical delay for the beneficial effects of EE on cognitive aging. (C) 2011 Elsevier Ireland Ltd. All rights reserved.