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Do you like a flutter? The levels of dopamine in your brain might be affecting how likely you are to gamble or take risks.

Dopamine is a signalling molecule released by nerve cells known to be involved in predicting reward. While its role is often misunderstood 鈥� it has been blamed for everything from drug addiction to Facebook鈥檚 popularity 鈥� the听compound plays an important role in the brain. Last year鈥檚 听鈧�1 million Brain Prize was given to three scientists who helped discover what it does.

Now, for the first time, scientists have been able to see how risk-taking is affected by the activity of dopamine-using nerve cells in part of the brain that is involved in decision-making.

People who had lower background levels of activity were slightly more likely to take a risky decision in a gambling task in the lab.

Because the effect was small, this could only sometimes influence our decisions in real life, says of University College London, who did the work. He estimates that when facing the same choice we would make the same decision roughly eight times out of ten 鈥� but the other times it would be affected by dopamine fluctuations.

To find out more, Chew鈥檚 team got 43 people to lie in a brain scanner while playing a gambling task, shown on a screen inside. In one version, for instance, they had to choose between definitely getting 拢2.70 or taking a 50-50 chance of a 拢6 pay-out, which over several rounds should result in more money but is riskier in the short term.

People made the riskier choice 56 per cent of the time when they had high activity levels in part of the brain where dopamine neurons are concentrated. This rose to 59 per cent when they had low levels, Chew reported at the University College London Neuroscience Symposium last month.

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Chew says our background dopamine activity can be affected by external factors, such as the time of day, and how long it is since we鈥檝e eaten.听 鈥淢oment to moment fluctuations of dopamine influence your choice,鈥� he says.

But of the University of Nottingham, who wasn鈥檛 involved in the work, says the findings are hard to interpret. Complicating matters is the fact that dopamine nerve cells have a slow background rate of firing 鈥� up to once every 20 seconds 鈥� which is thought to affect our motivation.

On top of this, they also fire in fast bursts to signal unexpected rewards, responding within milliseconds. 鈥淭hat signals ,鈥� says Humphries

He thinks the activity levels seen in the brain scanner would be a combination of the slow and fast firing. 鈥淎ll they can see is a long-term average of what the dopamine neurons are doing.鈥� The type of brain scanner used only tracks blood flow, it cannot reveal nerve cell firing rates directly.

Another puzzle is the fact that when people with Parkinson鈥檚 disease take medicines that raise their dopamine levels 鈥� because dopamine neurons have a third role, in controlling physical movements 鈥� they sometimes become gambling addicts.

This would suggest that higher dopamine leads to risky choices, which would seem to contradict Chew鈥檚 results. 鈥淭his group鈥檚 next step has to be to reconcile the two findings,鈥� says Humphries.

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