AREA OF BRAIN RESPONSIBLE FOR EXERCISE MOTIVATION DISCOVERED
Scientists at Seattle Children's Research
Institute 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.
Dr. Eric Turner, a
principal investigator in 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," 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."
Dr. Turner's study,
titled "Role of the Dorsal Medial Habenula in the Regulation of Voluntary
Activity, Motor Function, Hedonic State, and Primary Reinforcement," was
published by the Journal of Neuroscience and funded by the
National Institute of Mental Health and National Institute on Drug Abuse. The
study 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
love to run in their 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." In a second group of mice, Dr. Turner's team
activated the dorsal medial habenula using optogenetics -- a precise 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 behavior.
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 area of
the brain, 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.
"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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