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.