Smokers with a damaged insula – a region in the brain linked to emotion and feelings – quit smoking easily and immediately, according to a study in the Jan. 26 issue of the journal Science.
The study provides direct evidence of smoking's grip on the brain.
It also raises the possibility that other addictive behaviors may have an equally strong hold on neural circuits for pleasure.
The senior authors of the study are Antoine Bechara and Hanna Damasio, both faculty in the year-old Brain and Creativity Institute at the University of Southern California, in collaboration with graduate students Nasir Naqvi, who was first author on the study, and David Rudrauf, both from the University of Iowa.
"This is the first study of its kind to use brain lesions to study a drug addiction in humans," Naqvi said.
In the 1990s, Antonio Damasio proposed the insula, a small island enclosed by the cerebral cortex, as a "platform for feelings and emotion." The Science study shows that the pleasure of smoking appears to rest on this platform.
"It's really intriguing to think that disrupting this region breaks the pleasure feelings associated with smoking," said Damasio, director of the institute and holder of the David Dornsife Chair in Neuroscience at USC.
"It is immediate. It's not that they smoke less. They don't smoke, period."
Strokes damage many different areas of the brain. A subset of all stroke patients happen to experience damage to their insulas and a reduction in their cravings for cigarettes.
The study, pubished today in the journal Science, was inspired by a patient who smoked 40 cigarettes a day before having a stroke that damaged his insula. He quit immediately, telling doctors that he “forgot the urge to smoke”.
The scientists then turned to a database of stroke patients held by the University of Iowa and identified 69 who had smoked at least five cigarettes a day for at least two years before they suffered brain damage. They found that 19 of these patients had damage to the insula and 13 of them had given up smoking, 12 of them quickly and easily. The other six continued to smoke — possibly reflecting damage to different parts of the insula.
Comparisons of insulas done with brain scanning technologies such as functional magnetic resonance (fMRI) may lead to identification of exactly where the insula must get damaged to stop cigarette craving. I bet some smokers will subject themselves to brain surgery to damage a part of their insula if they could be assured of little or no side effects aside from a decreased desire to smoke.
The patients’ desire to eat, by contrast, was intact. This suggests, the authors wrote, that the insula is critical for behaviors whose bodily effects become pleasurable because they are learned, like cigarette smoking.
The insula, for years a wallflower of brain anatomy, has emerged as a region of interest based in part on recent work by Dr. Antonio Damasio, a neurologist and director of the Brain and Creativity Institute. The insula has widely distributed connections, both in the thinking cortex above, and down below in subcortical areas, like the brain stem, that maintain heart rate, blood pressure and body temperature, the body’s primal survival systems.
Based on his studies and others’, Dr. Damasio argues that the insula, in effect, maps these signals from the body’s physical plant, and integrates them so the conscious brain can interpret them as a coherent emotion.
The search will now start in earnest: Scientists will look for drugs or try biofeedback training methods or try transcranial magnetic stimulation or other therapies in order to tweak the insula to reduce cravings.
|Share |||Randall Parker, 2007 January 25 10:52 PM Brain Addiction|