In a recent study, researchers discovered the areas of the brain that motivate people to exercise.

Researchers from Seattle Children's Research Institute discovered a small area in the brain that controls the desire to exercise. This region is known as the dorsal medial habenula and its structure is similar in humans and rodents. These basic functions in mood regulation and motivation are likely to be the same across species.

"Changes in physical activity and the inability to enjoy rewarding or pleasurable experiences are two hallmarks of major depression," Dr. Eric Turner, a principal investigator in Seattle Children's Research Institute's Center for Integrative Brain Research, said. "But the brain pathways responsible for exercise motivation have not been well understood. Now, we can seek ways to manipulate activity within this specific area of the brain without impacting the rest of the brain's activity."

For the study, researchers used mouse models that were genetically engineered to block signals from the dorsal medial habenula. In the first part of the study, Dr. Turner's team collaborated with Dr. Horacio de la Iglesia, a professor in University of Washington's Department of Biology, to show that compared to typical mice - who enjoy running on exercise wheels - the genetically engineered mice were lethargic and ran far less. Turner's genetically engineered mice also lost their preference for sweetened drinking water.

"Without a functioning dorsal medial habenula, the mice became couch potatoes," Turner said. "They were physically capable of running but appeared unmotivated to do it."

For the second part of the study, researchers activated the dorsal medial habenula using optogenetics. The mice could choose to activate this area of the brain by turning one of two response wheels with their paws. The mice strongly preferred turning the wheel that stimulated the dorsal medial habenula, demonstrating that this area of the brain is tied to rewarding behavior.

"Traditional methods of stimulation could not isolate this part of the brain," Turner said. "But cutting-edge technology at Seattle Children's Research Institute makes discoveries like this possible.  Working in mental health can be frustrating. We have not made a lot of progress in developing new treatments. I hope the more we can learn about how the brain functions the more we can help people with all kinds of mental illness."

The study was funded by the National Institute of Mental Health and National Institute on Drug Abuse. Findings were published online in the Journal of Neuroscience.