November 1, 2012 2:49 pm
Habits die hard, but researchers may have the first clue towards neurologically shutting down bad ones. Neuroscientists at MIT identified the region of the brain responsible for switching between old and new habits. Eventually, the discovery could lead to new treatments for turning off different cell types responsible for repetitive or addictive behaviors, the researchers write in a statement.
To arrive at these conclusions, the scientists trained rats to run in a T-shaped maze. When the rats turned left, they received a chocolate milk reward, while a right turn delivered a sugar water reward. The researchers cued the rats in on which way to turn by using a particular bell sound, with a preference towards turning left. When the researchers removed the bell, and then later the rewards, the left-turn trained rats continued to always head left, even though no incentive existed for doing so. They had formed a habit.
Taking this a step further, the researchers gave the caged rats chocolate milk laced with lithium chloride, a substance that causes nausea. Still, the rats continued to turn left when they entered the maze, even though they now associated the chocolate milk with feeling ill.
To see if they could break this deeply ingrained habit, the researchers used optogenetics—a technique that inhibits specific cells with light—to turn off parts of the region believed to control habits, in the infralimbic cortex. Just as the rats entered the maze’s branching T, the researchers zapped the infralimbic cortex with light. The rats began turning right in order to avoid the poison-laced chocolate milk, setting the stage for a new habit formation.
The old left-turn habit was not gone for good, however, just switched off. When the researchers again exposed the rats to the cell-inhibiting light, they stopped turning right, and switched back to their habitual preference for turning left, instead.
Optogenetics is probably too invasive a procedure to ever use on humans, but the scientists think their findings may eventually benefit humans by shedding further light on the process of habit formation and breakage.
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