The finding, which appears in the journal Science, may well have a major impact on both research into addiction and treatment. Future therapies might focus on the insula, a prune-size region under the frontal lobes that is thought to be associated with visceral states - gut feelings.
The researchers, from the University of Iowa and the University of Southern California, examined 32 former smokers, all of whom had suffered a brain injury. The men and women were lucid enough to answer a battery of questions about their habits, and to rate how hard it was to quit and the strength of their subsequent urges to smoke. All had smoked at least five cigarettes a day for two years or more, and 16 of them said they had quit with ease, losing their cravings entirely.
The researchers performed M.R.I. scans on all of the patients’ brains and found that the 16 who had quit easily were far more likely to have an injury to their insula than any other area. The researchers found no association between a diminished urge to smoke and injuries to other regions of the brain, including tissue surrounding the insula.
“There’s a whole neural circuit critical to maintaining addiction, but if you knock out this one area, it appears to wipe out the behavior,” said Dr. Antoine Bechara, a senior author of the new paper. The patients’ desire to eat, by contrast, was intact. This suggests that the insula is critical for behaviors whose bodily effects become pleasurable because they are learned, like cigarette smoking.
The insula has widely distributed connections, both in the cortex and subcortical areas, like the brain stem, that maintain heart rate, blood pressure and body temperature. It would appear that it integrates signals from these “lower brain” areas, so that the conscious brain can interpret them as a coherent emotion. This could explain why cravings are physical, and so hard to shake.
Other researchers have advised that a degree of caution should be exercised: “One has to be careful not to extrapolate too much based on brain injuries to what’s going on in all addictive behavior, in healthy brains,” said Dr. Martin Paulus, a psychiatric researcher at the University of California, San Diego. However the study “opens up a whole new way to think about addiction.”
I found this article fascinating for two reasons:
- Brain research has come on in leaps and bounds since my brief foray into neurophysiology as a student back in the early/mid 80s.
- I was a 30 a day smoker for over two decades. Until I quit five years ago (and put on a shed load of weight I haven’t yet lost)