DYING FOR a smoke but trying to give them up? Battling with the urge must be hard work for the brain as it uses 20 per cent of the body’s energy despite weighing only 2.5 per cent of our total weight.
It appears that the feeling we often have of two voices arguing over the pros and cons of something we want to consume are indeed represented by two different parts of the brain.
The pre-frontal cortex to the front governs behaviour, while the striatum, deep within the brain, handles rewarding feelings.
Smokers, ex-smokers and those who’ve never smoked are being sought by PhD student Brendan Behan at Trinity College Dublin for a study into how different parts of the brain battle it out when faced with something we’d like to have.
It’s this “antagonism” which Behan is hoping to gain a greater understanding of by using fMRI brain imaging scans to see how the two areas react to certain tasks on a computer screen. fMRI scans measure blood flow and it’s known that oxygenated blood rushes to the part of the brain being actively used.
Ex-smokers are found to show greater activity in the prefrontal cortex than in those who’ve never smoked as a result of all the exercising of control over the urge to smoke. So it appears that learning skills to combat drug desires actually changes the brain itself.
A previous study, by Dr Liam Nestor, has demonstrated that conscious control is indeed very much a part of successful abstinence. Behan’s study will examine whether or not greater prefrontal activity is matched by decreased striatal activity and whether a lack of prefrontal control gives rise to impulsivity.
There’s evidence of deficits in the prefrontal areas of gamblers and the obese also but these are not well researched yet, according to Prof Hugh Garavan, of the School of Psychology in Trinity College and the Departments of Psychiatry and Psychology at the University of Vermont.
For example, obese women have been found to be poorer at delaying gratification in a test which offers a smaller financial reward immediately compared with a larger reward in the future.
Research in the US has found that both drug addicts and the pathologically obese share a reduction in striatal dopamine receptors. It’s suggested that decreased levels of these receptors in the brain encourage subjects to search for reinforcers – in the case of drug addicts for a drug and food for the obese – as a means to temporarily compensate for this decreased sensitivity in this reward area of the brain.
In both obesity and drug addiction, overconsumption can trigger a gradual increase in the reward threshold, requiring more and more palatable high fat food or reinforcing a drug to satisfy the craving over time, according to research published two years ago by Nida, the US National Institute on Drug Abuse.
“Obese people do show similar differences in the striatal system that have been observed in drug users and there is evidence of increased impulsivity related to prefrontal function in gamblers,” says Garavan.
“We are about to start a study soon looking into these same systems in people who have managed to successfully diet. My expectation is that we’ll see similar effects in successful dieters.”
A comprehensive set of questions to assess everything from impulsivity to IQ will be given to each candidate beforehand. Only one’s head needs to go into the scanner and there’s no radiation involved, just magnetism.
Each test, including assessment beforehand, takes about two and a half hours and participants will get paid a small fee for their trouble, plus an image of their brain scan to keep.
Those aged 20-40 interested in taking part can contact Brendan Behan at
[ tcd.nicOpens in new window ]
otine@gmail.com
