The mammalian brain has a high degree of plasticity, with dentate granule
cell neurogenesis1 and glial2,
3 proliferation
stimulated by an enriched environment combining both complex inanimate and
social stimulation. Moreover, rodents exposed to an enriched environment both
before and after a cerebral insult show improved cognitive performance1,
4. One of the most robust associations of environmental enrichment
is improved learning and memory in the Morris water maze, a spatial task that
mainly involves the hippocampus5. Furthermore, clinical evidence
showing an association between higher educational attainment and reduced risk
of Alzheimer6 and Parkinson-related dementia7
indicates that a stimulating environment has positive effects on cerebral
health that may provide some resilience to cerebral insults. Here we show
that in addition to its effects on neurogenesis, an enriched environment reduces
spontaneous apoptotic cell death in the rat hippocampus by 45%. Moreover,
these environmental conditions protect against kainate-induced seizures and
excitotoxic injury. The enriched environment induces expression of glial-derived
neurotrophic factor and brain-derived neurotrophic factor and increases phosphorylation
of the transcription factor cyclic-AMP response element binding protein, indicating
that the influence of the environment on spontaneous apoptosis and cerebral
resistance to insults may be mediated through transcription factor activation
and induction of growth factor expression.
