30th August 2014 Scientists discover area of brain responsible for exercise motivation Scientists have discovered an area of the brain that could control a person’s motivation to exercise and participate in other rewarding activities – potentially leading to improved treatments for depression.
Professor Eric Turner at Seattle Children’s Research Institute’s Center for Integrative Brain Research, together with lead author Dr. Yun-Wei (Toni) Hsu, have discovered that a tiny region of the brain – the dorsal medial habenula – controls the desire to exercise in mice. The structure of the habenula is similar in humans and rodents and these basic functions in mood regulation and motivation are likely to be the same across species. Exercise is one of the most effective non-pharmacological therapies for depression. Determining that such a specific area of the brain may be responsible for motivation to exercise could help researchers develop more targeted, effective treatments for depression. “Changes in physical activity and the inability to enjoy rewarding or pleasurable experiences are two hallmarks of major depression,” Prof. Turner 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.” Turner’s study – “Role of the Dorsal Medial Habenula in the Regulation of Voluntary Activity, Motor Function, Hedonic State, and Primary Reinforcement” – used mouse models that were genetically engineered to block signals from the dorsal medial habenula. Compared to typical mice, who love to run in exercise wheels, the genetically engineered mice were lethargic and ran far less. These 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.” In a second group of mice, Dr. Turner’s team activated the dorsal medial habenula using optogenetics – a new and rapidly emerging laser technology – developed in collaboration with the Allen Institute for Brain Science. 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 behaviour.
Past studies have attributed many different functions to the habenula, but technology was not advanced enough to determine roles of the various subsections of this brain region, including the dorsal medial habenula. “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.” As a professor in the University of Washington Department of Psychiatry and Behavioral Sciences, Dr. Turner treats depression and hopes this research will make a difference in the lives of future patients. Depression is expected to be the number one global disease burden by 2030. “Working in mental health can be frustrating,” Turner said. “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.”
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