Application of optogenetics to control habitual behavior

Application of optogenetics to control habitual behavior

In an article entitled, “Reversible online control of habitual behavior by optogenetics perturbation of medial prefrontal cortex”, published in November 13, 2012, issue of PNAS 109:46; 18932–18937, the lead author Kyle S. Smith with three other associates from two research groups  (McGovern Institute for Brain Research and Dept of Brain and Cognitive Science, MIT, MA and Dept of Bioengineering, Stanford University of Medicine, CA.), conducted a study in the field of optogenetics aimed

at finding the master switch in the brain that controls habits.  Researchers 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. In the study, researchers trained rats to run in a T-shaped maze. They would receive chocolate milk for turning left or sugar water for turning right. When the researchers took away the rewards, the rats who had learned to turn left continued to do so, even though they weren’t benefitting in any way. Even when the researchers added nausea-inducing lithium chloride to the chocolate milk, the rats still turned to the left. This is how the researchers knew that the habit was pretty deeply ingrained. The next step was to use optogenetics (a technique that allows researchers to inhibit specific cells with light) to inhibit cells in the infralimbic cortex–a region inside the pre-frontal cortex that is believed to control habits. For several seconds at a time, they turned off activity in the infralimbic cortex just as the rats were making the decision of which way to turn. Immediately, the rats learned the new habit of turning right. Still, the old habit wasn’t erased from the rat’s brain, but merely switched off. The process reversed when the researchers shined light into the infralimbic cortex. The rats that broke their old habit regained it instantly. Though this optogenetics process is too invasive to use in humans, it has implications about the flexibility of destructive habits. As technology advances and with further research, scientists may soon be able to intervene in disorders and addictions involving overly repetitive or addictive behavior. [Summarized by a graduate student, Samsad Razzaque]

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