Environmental enrichment: Effects on spatial memory and hippocampal CREB immunoreactivity

Environmental enrichment has been shown to improve performance in tests of spatial memory, induce neurogenesis in the hippocampus, enhance survival of newly formed granule cells, and inhibit spontaneous apoptosis. Although ne uroplasticity of the mammalian brain declines with age, recent evidence sug gests that the adult brain exhibits significant plasticity in response to e nvironmental stimulation. The present study was designed to evaluate the ef fect of environmental enrichment on spatial memory and on immunoreactivity to cAMP response element binding protein (CREB) from the hippocampus. C57/B L/6 mice were trained in a Morris water maze after exposure to an enriched environment, either from 35 to 94 days or from 100 to 159 days of age. Hipp ocampal tissue from representative animals was later analyzed by Western bl ot for CREB immunoreactivity. Results indicate that environmental enrichmen t (particularly during the earlier period) improved performance on the Morr is water maze and tended to increase immunoreactivity to CREB in the hippoc ampus. Social interaction by itself did not result in significant differenc es in navigational performance. Results with regard to social interaction a nd CREB immunoreactivity were mixed. Results are discussed in terms of eval uating the construct of enrichment, the correlation of CREB transcription a nd behavior change, and the importance of the developmental period for enri chment. (C) 2001 Elsevier Science Inc. All rights reserved.