There is a good and bad side to having habits, both of which affect the kind of behavior people exhibit. To better understand how these behaviors come about, researchers carried out a study to show what occurs in the brain when habits control behavior.
Published in the journal Neuron, the study offers the strongest evidence so far showing that brain circuits responsible for deliberate and habitual actions actually compete for control in the brain's decision-making area, the orbitofrontral cortex.
Additionally, neurochemicals known as endocannabinoids let habitual actions take over by restricting the functions of brain circuits associated with deliberate action.
According to Christina Gremel, who led the study, endocannabinoids are naturally produced by humans and other animals. They have receptors all over the brain and body and have been implicated in various psychological processes like memory, mood, pain sensation and appetite. The endocannabinoid system is also the one that mediates cannabis' psychoactive effectives.
Past research has shown that the orbitofrontal cortex is a key area in the brain for processing information related to deliberate action. Specifically, an increase in neurons in the brain area, which can be facilitated through a technique known as optogenetics (turning neurons on and off with light flashes), leads to an increase in deliberate action. Alternatively, when neuron activity is decreased, deliberate action decreases.
"Habit takes over when the [orbitofrontal cortex] is quieted," said Gremel.
To test the role that endocannabinoids play, the researchers removed a receptor known as cannabinoid type 1, or CB1, in a mice model. Mice missing CB1 weren't able to form habits, highlighting the importance of the neurochemical in controlling habitual and deliberate actions.
According to the researchers, their findings may be used to further study treatments for obsessive-compulsive disorder or addiction, restoring ability to use deliberate action and stop overreliance on habitual ones through pharmaceutical and/or behavioral therapy.
Other authors of the study include Rui Costa, David Lovinger, Karl Deisseroth, Charu Ramakrishnan, Rachael Neve, Guoxiang Luo, Brady Atwood and Jessica Chancey. The research team included members from the University of California San Diego, the Champalimaud Center for the Unknown, the National Institutes of Health's National Institute on Alcohol Abuse and Alcoholism, the Massachusetts Institute of Technology and Stanford University.
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