delay in treatment after the injury when exposed to environmental enrichment. social interactions, exercise, and novelty all play major roles in aiding the recovery of an injured subject. this has led to some suggestions that the spinal cord has a continued plasticity and all efforts must be made for enriched environments to stimulate this plasticity in order to aid recovery. maternal deprivation stress maternal deprivation can be caused by the abandonment by a nurturing parent at a young age. in rodents or nonhuman primates, this leads to a higher vulnerability for stress-related illness. research suggests that environmental enrichment can reverse the effects of maternal separation on stress reactivity, possibly by affecting the hippocampus, the amygdala and the prefrontal cortex. child neglect in all children, maternal care is one of the significant influences for hippocampal development, providing the foundation for stable and individualized learning and memory. however, this is not the case for those who have experienced child neglect. researchers determined that through environmental enrichment, a neglected child can partially receive the same hippocampal development and stability, albeit not at the same level as that of the presence of a parent or guardian. the results were comparable to those of child intervention programs, rendering environmental enrichment a useful method for dealing with child neglect. aging decreased hippocampal neurogenesis is a characteristic of aging. environmental enrichment increases neurogenesis in aged rodents by potentiating neuronal differentiation and new cell survival. as a result, subjects exposed to environmental enrichment aged better due to superior ability in retaining their levels of spatial and learning memory. prenatal and perinatal cocaine exposure research has shown that mice exposed to environmental enrichment are less affected by the consequences of cocaine exposure in comparison with those in standard environments. although the levels of dopamine in the brains of both sets of mice were relatively similar, when both subjects were exposed to the cocaine injection, mice in enriched environment were significantly less responsive than those in standard environments. it was thus concluded that both the activating and rewarding effects are suppressed by environmental enrichment and early exposure to environmental enrichment can help prevent drug addiction. humans though environmental enrichment research has been mostly done upon rodents, similar effects occur in primates, and are likely to affect the human brain. however, direct research upon human synapses and their numbers is limited since this requires histological study of the brain. a link, however, has been found between educational level and greater dendritic branch complexity following autopsy removal of the brain. localized cerebral cortex changes mri detects localized cerebral cortex expansion after people learn complex tasks such as mirror reading (in this case in the right occipital cortex), three-ball juggling (bilateral mid-temporal area and left posterior intraparietal sulcus), and when medical students intensively revise for exams (bilaterally in the posterior and lateral parietal cortex). such changes in gray matter volume can be expected to link to changes in synapse numbers due to the increased numbers of glial cells and the expanded capillary vascularization needed to support their increased energy consumption. institutional deprivation children that receive impoverished stimulation due to being confined to cots without social interaction or reliable caretakers in low quality orphanages show severe delays in cognitive and social development. 12% of them if adopted after 6 months of age show autistic or mildly autistic traits later at four years of age. some children in such impoverished orphanages at two and half years of age still fail to produce intelligible words, though a year of foster care enabled such children to catch up in their language in most respects. catch-up in other cognitive functioning also occurs after adoption, though problems continue in many children if this happens after the age of 6 months such children show marked differences in their brains, consistent with research upon experiment animals, compared to children from normally stimulating environments. they have reduced brain activity in the orbital prefrontal cortex, amygdala, hippocampus, temporal cortex, and brain stem. they also showed less developed white matter connections between different areas in their cerebral cortices, particularly the uncinate fasciculus. conversely, enriching the experience of preterm infants with massage quickens the maturation of their electroencephalographic activity and their visual acuity. moreover, as with enrichment in experimental animals, this associates with an increase in igf-1. cognitive reserve and resilience another source of evidence for the effect of environment stimulation upon the human brain is cognitive reserve (a measure of the brain's resilience to cognitive impairment) and the level of a person's education. not only is higher education linked to a more cognitively demanding educational experience, but it also correlates with a person's general engagement in cognitively demanding activities. the more education a person has received, the less the effects of aging, dementia, white matter hyperintensities, mri-defined brain infarcts, alzheimer's disease, and traumatic brain injury. also, aging and dementia are less in those that engage in complex cognitive tasks. the cognitive decline of those with epilepsy could also be affected by the level of a person's education.