An enriched environment stimulates an increase in the number of nerve cells in brains of older mice

April 24, 1997

An enriched environment stimulates an increase in the number of nerve cells in brains of older mice

April 24, 1997

La Jolla, CA – Salk investigators have discovered that aging mice living in a stimulating environment display three times the number of new brain cells as mice who live in a non-stimulating environment. The age of the mice in the study was 18 months – the human equivalent of 65 years.

The findings are reported in the May 1 issue of the Journal of Neuroscience; senior author is Fred Gage, PhD.

The current study builds on research reported a year ago by The Salk Institute in which it was shown, for the first time, that young adult mice can receive a boost in brain cells when exposed to an enriched environment (April 3, 1997, Nature).

“The results are even more pronounced in ‘senior citizen’ mice,” said Gerd Kempermann, MD, of The Salk Institute Laboratory of Genetics.

In the current study, Kempermann and H. Georg Kuhn, PhD, separated 18-month-old “senior citizen” mice into two groups: one group housed in “standard” conditions (cage containing only food and water) and the other group placed in a large cage “enriched” with tunnels, toys and an exercise wheel. After sixty-eight days, the brains from both groups were compared for the number of new nerve cells.

The mice living in enriched conditions were found to have generated three times as many new nerve cells in the hippocampus, a part of the brain important for learning and memory, when compared to the control group. The earlier experiments on younger animals from both enriched and standard groups displayed a difference of 60% between the groups.

“The benefit of the enriched environment appears to be in fostering the survival of new brain cells,” said Kempermann.

Scientists have known since the 1960s that laboratory animals raised in a complex environment out performed their litter mates on standard learning tests, such as navigating mazes. The biological mechanisms responsible for performance improvements were unknown but believed to lie in increased numbers of connections between existing cells. The 1997 study on young adult mice revealed that the number of new nerve cells in the brain actually increased.

The research was supported by the National Institute of Neurological Disorders and Stroke, the National Institute on Aging, the American Paralysis Association and the International Spinal Research Trust. In addition, Kempermann is supported by the Deutsche Forschungsgemeinschaft and Kuhn receives funding from the Hereditary Disease Foundation.

The Salk Institute for Biological Studies, located in La Jolla, Calif., is an independent nonprofit institution conducting basic science research dedicated to the improvement of human health and improving the quantity and quality of the world’s food supply.

Its two main fields of concentration are neuroscience and molecular-cellular biology and genetics; The Salk Institute was recently ranked the top research institution worldwide in both of these areas by the Philadelphia-based Institute for Scientific Information.

The Salk Institute was founded in 1960 by polio vaccine pioneer Jonas Salk, MD, with a gift of land from the City of San Diego and the finanancial support of the March of Dimes Birth Defects Foundation. Thomas D. Pollard, MD, is President and Chief Executive Officer.