Habits are behaviors wired so deeply in our brains that we perform them automatically. This allows you to follow the same route to work every day without thinking about it, liberating your brain to ponder（考虑，沉思） other things, such as what to make for dinner. However, the brain's executive command center does not completely relinquish（放弃） control of habitual behavior. A new study from MIT neuroscientists has found that a small region of the brain's prefrontal cortex, where most thought and planning occurs, is responsible for moment-by-moment control of which habits are switched on at a given time.

"We've always thought -- and I still do -- that the value of a habit is you don't have to think about it. It frees up your brain to do other things," says Institute Professor Ann Graybiel, a member of the McGovern Institute for Brain Research at MIT. "However, it doesn't free up all of it. There's some piece of your cortex that's still devoted to that control."

The new study offers hope for those trying to kick bad habits, says Graybiel, senior author of the new study, which appears this week in the Proceedings of the National Academy of Sciences. It shows that though habits may be deeply ingrained, the brain's planning centers can shut them off. It also raises the possibility of intervening in that brain region to treat people who suffer from disorders involving overly habitual behavior, such as obsessive-compulsive disorder.

Lead author of the paper is Kyle Smith, a McGovern Institute research scientist. Other authors are recent MIT graduate Arti Virkud and Karl Deisseroth, a professor of psychiatry and behavioral sciences at Stanford University.