Over half a century ago Mark R. Rosenzweig at UC Berkeley was asking if experience could produce observable changes in the brain. The question wasn’t new but in conjunction with work from his laboratory it was a harbinger of many of the developments in psychology and the neurosciences that we see today. We’ll address the ways in which current research on experience (e.g., exercise, socialization, cognitive activity, etc.) induced alterations in the brain in future blog postings, but in this report, we will describe some of the early work from Rosenzweig’s laboratory. We are summarizing the findings described in a February 1972 article in Scientific American by Rosenzweig and colleagues.
In the Rosenzweig laboratory three male rat littermates were assigned to either a baseline standard cage condition (typically 2-3 rats to a cage with bedding and a water bottle), an enriched condition (typically 12 rats in a large cage containing an assortment of ‘rat toys’ that were regularly changed), or an impoverished condition (a single rat in a cage with a view of a blank wall in a dimly lit quite room). Rats were assigned to differential environmental conditions shortly after weaning and remained in these conditions from a few days to months. After a predetermined duration of differential environments, effects on neurochemistry, neuroanatomy, and behavior of the rats were assessed. This early popularized report (1972) on brain changes associated with different environments is somewhat qualified. Rats in the enriched environment showed a thicker cortex and greater total acetylcholinesterase activity than rats in the impoverished condition. Similarly, studies of learning showed consistently superior learning by the enriched rats relatively to the rats reared in an impoverished environment. The most consistent finding was the ratio of cortex weight to subcortex weight being greater in the enriched rats.
One question that arose from these studies was what happens if the animal’s natural environment serves as the baseline condition. Rats that were placed in a large outdoor enclosure in the Berkeley Field station for 30 days showed greater brain development changes than littermates maintained in a laboratory enriched condition. Similar findings have been obtained in deer mice and Belding Ground Squirrels
These early studies may have you thinking about the possibility of different environments on the human brain and behavior. Specifically, what are the effects of poverty on brain and behavior. Perhaps you recall the reports on Genie Wiley who was isolated by her father until 13 years of age. She could not walk, speak, or socialize when found and remains profoundly impaired. Similar but lesser impairment is reported for Romanian children placed in orphanages (see the following YouTube video: https://www.youtube.com/watch?v=VCeWr8OFuEs)
Ana Levy and Hasker Davis 08/23/2017