Brains of smokers may be made up in a way which makes them more likely to pick up the habit, according to new research.
The finding comes from a new study that helps explain why some behaviours are linked with particular areas of the mind.
Experts analysed molecules produced at connection points between nerve cells - called synapses - which are key to sending messages around the brain.
The team, based at the University of Edinburgh, found patterns varied between different areas and were able to categorise them into different functions.
Using their new map, the scientists were able to investigate where genes linked to smoking have their influence.
The findings pinpointed the same region that has previously been identified in brain imaging studies.
Professor Seth Grant, of the Centre for Clinical Brain Sciences at the university, who led the study, said: "This is an important step toward understanding the molecular basis of human thought."
The work was based on post-mortem brain tissue samples from healthy people held in the Medical Research Council's (MRC) Edinburgh Brain Bank.