Habits help us every day, from discarding the need to remember the details of baking steps, driving to work, or performing various multi-step tasks. Bad habits, moreover, become deeply entrenched in both our minds and behaviors. They are extremely difficult to change and very easy to revive, as seen in many people addicted to drugs.
A new study published in Nature, conducted by Ann Graybiel from the McGovern Institute at the Massachusetts Institute of Technology, has now revealed the reason why: The neural activity patterns in a particular region of the brain significantly change when habits are formed, and also change when those habits are disrupted, but they quickly recover when something triggers the lost habit.
This brain region is called the basal ganglia, which plays a crucial role in habits, addiction, and learning sequences. In patients with Parkinson’s disease, obsessive-compulsive disorder, and various other mental disorders, the functioning of the basal ganglia is impaired.
In Graybiel’s experiments, mice learned a habit of finding a chocolate reward at the end of a T-shaped maze. While they were remembering this, the neurons “lit up” throughout their run in the maze, as if everything was of great importance. When the mice memorized the habit along with a cue (a sound) during their run to the chocolate, the neurons in the basal ganglia also activated.
Once the mice had memorized the cue, the related neurons only activated strongly at the most crucial points of the task—the start and end points of the maze. However, these neurons fell silent as the mice traversed the familiar maze, as if they were using their knowledge to focus more efficiently on the reward. The “irrelevant” neurons also remained quiet throughout the maze run.
Afterward, the researchers removed the reward and rendered the cues meaningless. This change made everything in the maze seem “relevant” again, and the neurons lit up throughout the run. Eventually, the mice stopped running (abandoned the habit), and the newly learned habit in the brain cells disappeared. But as soon as the research team placed the chocolate back, the learned neural pattern, with the start and end points, re-emerged.
“We attempted to simulate the learning and removal of a habit. If a learned pattern remains in the brain after the behavior disappears, it may explain why changing a habit is so difficult,” remarked Yasuo Kubota, a member of the research team.
“For some reason, the brain retains the memory of the habit, and this pattern can be restored if the cues associated with the habit reappear. This situation is similar to someone trying to lose weight, but just seeing a piece of chocolate can make them start all over again with their good intentions,” Graybiel stated.
The research team hopes that this discovery will be the key to finding ways to treat bad habits such as addiction and to encourage good habits that benefit health and happiness.
T. An (according to Physorg)
