Environmental enrichment is the stimulation of the
brain by its physical and social surroundings. Brains in richer, more stimulating environments have higher rates of
synaptogenesis and more complex
dendrite arbors, leading to increased brain activity. This effect takes place primarily during
neurodevelopment, but also during adulthood to a lesser degree. With extra
synapses there is also increased synapse activity, leading to an increased size and number of
glial energy-support cells. Environmental enrichment also enhances
capillary vasculation, providing the neurons and glial cells with extra energy. The
neuropil (neurons, glial cells, capillaries, combined together) expands, thickening the cortex. Research on rodent brains suggests that environmental enrichment may also lead to an increased rate of
neurogenesis.