Why habits are so hard to break

Washington: Can't stop eating junk food? This is because a habit leaves a lasting mark on specific circuits in the brain, priming us to feed our cravings, a new study has found. The research deepens scientists' understanding of how habits like sugar and other vices manifest in the brain and suggests new strategies for breaking them.

Researchers from Duke University in US trained otherwise healthy mice to form sugar habits of varying severity, a process that entailed pressing a lever to receive tiny sweets. The animals that became hooked kept pressing the lever even after the treats were removed. They then compared the brains of mice that had formed a habit to the ones that did not.

In particular, the researchers studied electrical activity in the basal ganglia, a complex network of brain areas that controls motor actions and compulsive behaviours, including drug addiction. In the basal ganglia, two main types of paths carry opposing messages - one carries a 'go' signal which spurs an action, the other a 'stop' signal.

Researchers observed that changes in go and stop activity occurred across the entire region of the basal ganglia they were studying as opposed to specific subsets of brain cells. This might relate to the observation that an addiction to onething can make a person more likely to engage in other unhealthy habits or addictions as well, researchers said.

To see if they could break a habit, researchers encouraged the mice to change their habit by rewarding them only if they stopped pressing the lever. The mice that were the most successful at quitting had weaker go cells.