Smokers' brains may be made up in a way that 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 at Edinburgh University analysed molecules produced at connection points between nerve cells - called synapses - which are key to sending messages around the brain.
The team 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."
'This innovative study enriches our understanding of the human brain.'Dr Kate Adcock
The work was based on post-mortem brain tissue samples from healthy people held in the Medical Research Council's (MRC) Edinburgh Brain Bank.
Scientists from the study claim their findings provide a "powerful tool" for investigating how diseases affect different parts of the brain, with all of their data made available to facilitate such research.
Dr Kate Adcock, MRC head of neurosciences and mental health, said: "This innovative study enriches our understanding of the human brain through its use of samples from the Medical Research Council's Edinburgh Brain Bank.
"The information that Professor Grant and his team has generated provide an excellent opportunity for researchers to gain further insight into how the brain works."