ENVIRONMENTAL COMPLEXITY MODULATES GROWTH OF GRANULE CELL DENDRITES IN DEVELOPING BUT NOT ADULT HIPPOCAMPUS OF RATS

The dendritic fields of hippocampal dentate gyrus granule cells were studied in Golgi-stained brains of rats placed in complex or isolated environments for 4 weeks after weaning or for 12 weeks in adulthood (beginning at 145 days of age). Rats placed in the complex environment at weaning had more lower-order dendritic branching by two measures and wider dendritic fields compared to rats reared in isolation. Rats reared socially and placed as adults in complex or isolated environments did not differ on any granule cell measures. The results are compatible with reports of the behavioral effects of environmental complexity, with prior studies of rearing complexity effects upon subcortical anatomy and chemistry, and with studies of hippocampal development, and they suggest a possible sensitive period for the effects of rearing complexity upon hippocampal dentrate gyrus organization. © 1978.