From Physorg.com:
A new study in the Oct. 20 issue of Nature, led by Ann Graybiel of MIT’s McGovern Institute, now shows why. Important neural activity patterns in a specific region of the brain change when habits are formed, change again when habits are broken, but quickly re-emerge when something rekindles an extinguished habit — routines that originally took great effort to learn.
“We knew that neurons can change their firing patterns when habits are learned, but it is startling to find that these patterns reverse when the habit is lost, only to recur again as soon as something kicks off the habit again,” said Graybiel, who is also the Walter A. Rosenblith Professor of Neuroscience in MIT’s Department of Brain and Cognitive Sciences (BCS).
The patterns in question occur in the basal ganglia, a brain region that is critical to habits, addiction and procedural learning. Malfunctions in the basal ganglia occur in Parkinson’s disease, obsessive-compulsive disorder (OCD) and many neuropsychiatric disorders.
More here.