The discovery of individuals with brain damage who give up smoking with ease could point the way to a surgical 'cure' for smoking, US scientists say.
The insula sits deep in the brain
The particular brain area damaged - called the insula - appears to be central to the urge to smoke, a team told the journal Science.
One man had smoked 40 cigarettes a day but quit immediately after his insula was damaged by a stroke.
Surgery on that part of the brain may help beat addictions, they suggest.
But lead author Antoine Bechara of the University of Southern California and the University of Iowa cautioned: "The insula also carries out lots of normal everyday functions so we would want to make sure we only interfere with functions that disrupt bad habits like smoking."
In recent years, doctors have been using "functional neurosurgery" - causing intentional damage to very well-defined brain regions - to relieve pain and the tremor of Parkinson's disease and treat stubborn depression.
The insula receives information from other parts of the body and is thought to help translate those signals into something that is subjectively felt, such as hunger, pain, or a craving.
Dr Bechara's team studied 69 brain-damaged smokers - 19 who had suffered insula injury.
Of these, 13 had also given up smoking, all but one quickly and easily with no cravings.
The researchers do not know why the six others failed to quit smoking.
Professor Paul Matthews, an expert in neuroscience from Oxford University and Imperial College London, said: "The problem people have in 'kicking' the smoking habit is cigarette craving - the urge to smoke.
"The most remarkable finding in this study is that damage to a particular brain area may block this urge.
"Now we can ask, 'Could a functional neurosurgeon implant stimulation electrodes to do the same thing? Could there be a surgical 'cure' for smoking?'"