Effects of Environmental Complexity and Deprivation on Brain Anatomy and Histology: A Review

Abstract

During the last 20 years the anatomical plasticity of the brain in response to sensory stimulation has been clearly demonstrated. This paper reviews the effects of environments rich in sensory stimulation versus those which are stimulus poor. Effects have been noted at all levels from the gross anatomical to the electromicroscopic.As compared to their stimulus-deprived counterparts, animals reared in complex environments tend to display greater cerebral height and length and cortical depth. The greatest effects occur in the occipital cortex where histological studies have revealed expanded neuron perikaryonal and nuclear size and dendritic branching, more dendritic spines, alterations in synaptic numbers and morphology, and greater numbers of neuroglia. Different cortical areas and layers respond to different degrees. Some responses have also been noted in the underlying hippocampus, particularly in the dentate gyrus. The emerging data present a picture of a dynamic, plastic brain adapting hoineostatically to the demands of its environment.

Neonatal serotonin depletion alters behavioral responses to spatial change and novelty

“…In conjunction, these findings suggest that changes in cortical plasticity continue to occur in adulthood in mice depleted of serotonin. It is well known that young adult mice at the ages used in our previous study are likely still susceptible to substantial environmentally mediated morphological plasticity, including pruning (Walsh, 1981;Rosenzweig and Bennett, 1996;Kolb and Whishaw, 1998). Consistent with this, neonatal depletion of serotonin in the cortex of kittens increased the number of callosal projection neurons (Djavadian et al, 2003).…”

MRI and X-ray scanning images of the brain of 3-, 6- and 9-month-old rats with bilateral neonatal ventral hippocampus lesions

“…Impairing the possibility to get information from the environment in the neonatal period even appears as a common feature of several different animal models of schizophrenia (Wong, 1995;Bloomfield et al, 2008). Similar behavioral modifications as in the NVHL model were obtained after impoverishment of the dam-pup interactions (Kuhn and Schanberg, 1998) or by disrupting proprioception in the first days of life (Walsh, 1981;Newson et al, 2005).…”

Effects of Preweaning Sensorimotor Stimulation on Behavioral and Neuronal Development in Motor and Visual Cortex of the Rat

“…So far, relatively few studies have been designed in order to evaluate if neocorti cal tissue presents a different degree of plastic ity in response to environmental complexity according to an anteroposterior (fronto-occipital) gradient of cytodifferentiation [7,13,14], Most studies have been performed in pri mary sensory areas, mainly in visual cortex. Results of some studies carried out in rat's frontal versus temporal or visual neocortical areas [4,15] have been compared in order to evaluate morphological brain responses pro duced by enriched milieu, although these re ports did not demonstrate plastic changes in the frontal cortex; such lack of effect was attributed to a localized influence of enriched environment.…”