Addictions, Bad Habits Can 'Highjack' Brain

Similarities found in brain scans of clinically obese and cocaine addicts.

ByABC News via logo
January 29, 2010, 1:14 PM

Jan. 31, 2010— -- By the end of January, many New Year's resolutions have been tossed out with leftover holiday cookies and unwanted gifts. It's been nearly impossible to deny that slice of cake after dinner, or to hit the treadmill instead of surfing the Internet.

Change, especially changing bad habits, is hard -- and rightly so, as any neuroscientist will tell you.

Advances in neuroimaging have enabled researchers to peer inside the brains of addicts and patients with addictive behaviors. They can see, in real-time, what gets patients hooked: how the brain's reward system -- based largely on the neurotransmitter dopamine -- thirsts for more, while inhibitory control centers experience a system failure.

The pattern is similar across all kinds of behaviors -- from cocaine and tobacco addiction to overeating. That's why changing your mind may be the first step toward breaking a habit, but altering the brain's neural machinery is the real challenge.

Highjacked Pathways

Drugs and addictive behaviors "highjack" the brain's reward system, says Dr. Petros Levounis, director of the Addiction Institute of New York at St. Luke's and Roosevelt Hospitals in Manhattan.

In normal patients, dopamine plays a major role in motivation and reward, surging before and during a pleasurable activity -- say, eating or sex -- to make patients want to repeat a behavior that's crucial to the survival of the species.

Dopaminergic pathways connect the limbic system, which is responsible for emotion, with the hippocampus, which is responsible for memory. This combination etches rewarding behaviors into the brain with strong, even seductive, memories.

The problem arises when the memory and the craving to recapture it take over a person's life.

"Imagine what a stronghold these highjacked pleasure reward pathways take on our brains and our whole existence when they're so closely connected geographically and anatomically speaking with our memories and our emotions," Levounis says.

Then, as the dopamine surge gains speed, the brakes fail. Normal function in the brain's frontal lobes, which are responsible for inhibitory control and executive functioning, or will power, tends to decrease in addicts.

"Ultimately," Levounis says, "the war on drugs is a war between the highjacked pleasure reward pathways that push the person to want to use, and the frontal lobes, which try to keep the beast at bay. That is the essence of addiction."