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Smokers may be able to learn to smoke less by being exposed to the smells of tobacco and rotten eggs or fish in their sleep, according to Weizmann Institute of Science research.Findings of the study by Dr. Anat Arzi, who is part of Prof. Noam Sobel’s group at the Rehovot institute’s neurobiology department, were published Wednesday in the latest issue of The Journal of Neuroscience.They suggest that certain kinds of conditioning during sleep could induce us to change behaviors.The researchers exposed smokers to pairs of smells – cigarettes together with rotten food – as the subjects slept, and then asked them to record how many cigarettes they smoked in the following week. The study showed a significant reduction in smoking following the conditioning during sleep.The team previously had demonstrated that associative conditioning – Pavlovian-type learning in which the brain is trained to subconsciously associate one stimulus with another – could occur during sleep if odors were used as the unconditioned stimulus. Although the volunteers did not remember the odors they had smelled during the night, their sniffing gave them away as the next morning they reacted unconsciously to tones that had been paired with bad smells by taking short, shallow breaths. The use of smell, explained Arzi, is key; unlike other types of sensory stimuli, even very bad odors do not wake us up.“We have not yet invented a way to quit smoking as you sleep. That will require a different kind of study altogether,” Arzi said.The new research was performed on 66 volunteers who wanted to quit smoking but were not being treated.Cigarette smoking was chosen because it is a behavior that can be quantified simply and the target stimulus was another smell, Arzi said.Those in the sleep group spent a night in the department’s special sleep lab during which their sleep patterns were monitored closely. At certain stages of sleep, they were exposed to paired smells – cigarettes and a foul odor – one right after the other, repeatedly throughout the night.Although they did not remember smelling the odors, the subjects reported smoking less over the course of the next week. In contrast, subjects who were exposed to the paired smells when awake or exposed to cigarette smells and the two repulsive smells unpaired at random times, did not.Sobel and Arzi suggested that olfactory conditioning may be a promising direction for addiction research because the brain’s reward center, which is involved in such addictive behavior as smoking, is closely interconnected with the regions that process smell and that some of these regions not only remain active when we sleep, the information they absorb may even be