November 11, 1998

Slow-learning mice can improve learning speed when raised in enriched environment

Salk News

Slow-learning mice can improve learning speed when raised in enriched environment

La Jolla, CA – Like their human counterparts, all mice are not created equal when it comes to learning new tasks.

But if given the opportunity to live in a social, playful and otherwise stimulating environment, even slow mice can increase their capacity to learn, according to new research by scientists at The Salk Institute for Biological Studies.

What’s more, the production of new neurons in the hippocampus — a key area of the brain linked to memory and learning — also is stepped up in these mice after they’re moved into better housing.

“What this shows is that strains of mice which are considered poor learners are not poor learners under all conditions,” said Eugene Brandon, a postdoctoral fellow in the Salk Institute Laboratory of Genetics and co-investigator of the study.

Also participating in the study, presented this week to the 28th annual meeting of the Society for Neurosciences, are Gerd Kempermann, MD, and Fred H. Gage, director of the laboratory and the study’s senior author.

The study builds on earlier work which showed that a strain of fast-learning mice would learn to swim through a water “maze” even more rapidly if they were raised in an enriched environment. Here, their cages would contain far more living space, and be fitted with running wheels, tunnels, toys, treats and other mice for socialization.

In the current experiment, a strain of slower-learning mouse was given the same opportunity to live in this improved environment. The results were dramatic. After five weeks in their new surroundings, the slower-learning mice learned to negotiate the water maze in about 15 seconds, roughly three-quarters the time it takes other slow-learning mice living in a standard laboratory cage.

Further studies also revealed marked changes in the hippocampus of these mice, with mice raised in the enriched environment producing nearly twice as many brain cells as their litter mates raised in standard laboratory housing. “This research is important because it recapitulates in a new context what is now a classic tenet in biology: the effects of genes upon an organism are dependent upon the environment in which the organism is raised,” said Brandon.

Future work will focus on determining which specific genes are responsible for the differences in learning and neuronal production observed between the two strains of mice.

“If the same genes are found to be important for both learning abilities and adult neuronal production, that might suggest that the production of new cells in the adult hippocampus is relevant to learning,” said Brandon. “It will also be of great interest to determine the specific elements of the complex environment that are critical for increasing neuronal production and learning capabilities.”

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.

The Salk Institute for Biological Studies, located in La Jolla, Calif., is an independent nonprofit institution dedicated to fundamental discoveries in the life sciences, the improvement of human health and conditions, and the training of future generations of researchers. The Institute was founded in 1960 by Jonas Salk, MD, with a gift of land from the City of San Diego and the financial support of the March of Dimes Birth Defects Foundation.

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