Brain circuit that supports smoking cessation identified.

Diseases related to tobacco smoking have been shown to kill approximately half of long-term smokers when compared to average mortality rates faced by non-smokers. Giving up smoking has huge benefits and it’s never too late to stop the killer weed, however, quitting can be extremely difficult due to the highly addictive properties of tobacco and its casing.  Now, a study from researchers at the Medical University of South Carolina shows success is more likely with strong communication between parts of the brain known to inhibit and execute automated behavior.  The team states their study is the first to link the strength of communication in a brain circuit inhibiting automated behavior with the ability to give up smoking.  The study is published in JAMA Psychiatry.

Previous studies show in the brain, smoking becomes automated.  One way the brain has been shown to inhibit automated behavior is through a pathway called the inhibitory control network, which starts in the right inferior frontal gyrus and travels through the prefrontal cortex to the thalamus. Communication through this pathway is often disrupted in the brains of smokers, leading to addictive behavior when smoking tobacco prodicts. The current study investigates whether this pathway is involved when smokers attempt to quit.

The current study examines the inhibitory control networks in the brains of 81 nicotine-dependent adults committed to a ten-week smoking cessation program. The researchers used fMRI to monitor brain activity while patients perform a task of inhibitory control where the patients were instructed to strike a computer key each time a colored circle appeared on-screen or omit to strike the keyboard when a rare circle of a certain color appeared. Results show when a higher blood oxygenation level-dependent (BOLD) response in the inhibitory control circuit is exhibited, the brain is using more resources to inhibit the automatic response of striking the key when the rare circle appears.

After ten weeks, approximately half of the smokers had quit successfully. Data findings show the smokers who successfully quit had lower BOLD responses in their inhibitory control networks before trying to quit. The lab states successful quitters’ BOLD responses were lower in the right inferior frontal gyrus and right thalamus, they also had stronger functional connections between those regions. They observed the patients who relapsed had scored just as well on the inhibition control task as those who quit successfully, however, it appeared their automated behavior may have required more effort to inhibit.

The team then investigated BOLD responses in smokers who had not committed to quitting.  The group measured BOLD signals in 26 smokers performing the same task; each person was then presented with an open pack of their preferred brand of cigarettes, a lighter, and an ashtray. They were paid one dollar for every six minutes they did not smoke as a small incentive for an hour.  The lab notes in general, the lower the BOLD response during the task of inhibitory control, the longer the person resisted smoking. They go on to add the smokers who resisted temptation longer also had stronger functional connections in their inhibitory control networks.

The team surmises their findings show corticothalamic circuitry function during inhibitory control is associated with smoking relapse vulnerability. For the future, the researchers are now evaluating the potential of certain behavioral and pharmacological treatments to strengthen communication in the inhibitory control pathway of people who smoke.

Source: Medical University of South Carolina (MUSC)

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