Effects of differential environments on plasticity of dendrites of cortical pyramidal neurons in adult rats

Abstract

Thickening of the frontal cortex and especially the occipital cortex was observed in adult rats after exposure to the “enriched” condition. An increase in branching and in length of terminal segments was found in the dendritic tree of pyramidal cells in layers II and III of the visual cortex of the adult rat after exposure to “standard” and enriched conditions. These exposures began at day 112 and continued 30 days. The increase observed in the basal dendritic tree of pyramidal cells in the superficial layers was significantly greater in the enriched conditions than in the standard condition. It appeared, furthermore, that branching occurred predominantly on basal terminal segments of all orders at a considerable distance from the tip. This mode of growth is similar to that observed in the cortex of normal immature rats. The differential conditions did not influence the bifurcation angles. The dendritic and cortical changes and changes reported in the literature indicate that the effects of differential experience are not limited to a short, “critical” period.