NEW YORK: A location in between the ears in the brain holds the key to addiction to smoking, according to new research.
Neuroscientists, who undertook a study of people with brain damage, in most cases caused by a strike, found that the urge to light up a fag could be ignited by a lesser-studied region of the brain called the insula, which also helps the humans to realize hunger, nervous twitches and several other body signals.
Researchers said the findings point to an important new target for research into the biological underpinning of addiction, particularly into how people who try to quit a bad habit are vulnerable to relapse. They say it could even lead to put a bar on cravings, or just monitor them in a more precise manner, or even evolve therapies targeting the insula to bring down the craving.
The insula, better known in medical terminology as insular cortex, is located on either side of the head, beneath the outer neocortex. Scientists have associated it with several important functions of the body including experiencing emotions, pain, speech planning and movement. But, so far it is not studied in relation to the center associated with addiction.
Researchers at the University of Southern California and University of Iowa found that smokers, who are into the activity for a long time, could give up the habit much easily when they have some damage of insula. Antoine Bechara, an associate professor at the Brain and Creativity Institute of the University of Southern California, and lead author of the study, feels that smoking and other forms of addiction can be compared to a contest between the decision-making front part of the brain and the cravings-generating insula.
Bechara said, "it turns out it's the insula that is the culprit," as he found the insula-damaged study subjects received phenomenal relief from nicotine cravings.
There are other brain regions, like those involved in memory and reward, which are also responsible for creating the habit of smoking, but the researchers found that insula collaborates with these systems and in most cases cause the relapse in smokers who try to quit smoking.
The finding could pave the way for deactivating a vicious cycle of late state addiction, craving and relapse, the scientists feel.
Bechara said addiction is acquired and maintained by a neural circuitry and it involves a lot of parts of the brain. The question is whether one can disrupt that circuitry if one knocks out one critical area.
The study looked at 19 longtime smokers who had sustained insular damage -- six with damage on the right side and 13 with damage on the left. All of them had been smoking more than five cigarettes a day for at least two years before their strokes. These smokers were compared with 50 other smokers who had damage to other parts of the brain but not their insula. All the study subjects were asked whether they had quit smoking, how soon afterward the brain damage occurred and whether they experienced any relapse or strong cravings to take up the habit. Thirteen of the 19 people who had their insula damaged had quit smoking and 12 reported they had quit easily and immediately after the damage to the brain. The scientists found that possibility of such a disruption in the addiction is much less among those, who had other parts of their brain damaged.
The findings of the study have been reported in the latest issue of the journal Science.
Scientists now feel the study can throw up new ways of developing programs for smokers who want to quit by targeting the insula.
The insula's role in addiction to other materials, including liquor and drugs, is yet to be studied.
The Brain and Creativity Institute had been carrying out several studies on insula for years, especially under Dr Antonio Damasio, a neurologist and the institute's director. The studies have found that it has several connections, both in the thinking cortex above and down below in subcortical areas, like the brain stem that maintains heart rate, blood pressure and body temperature. Damasio says that the insula maps such signals from the physical part of the body and integrates them so the conscious brain can interpret them as a coherent emotion.
