Scientists investigating bipolar disorder invited participants to make safe or risky gambles as they spun the wheel in a game of roulette.
Brain activity was measured using a functional magnetic resonance imaging (fMRI) scan that monitors blood flow in the brain.
Professor Wael el-Deredy, from the University of Manchester, said in the journal Brain:
The greater buzz that people with bipolar disorder get from reward is a double-edged sword.
On the one hand, it helps people strive towards their goals and ambitions ...
However, it comes at a cost; these same people may be swayed more by immediate rewards when making decisions and less by the long-term consequences of these actions.
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Gary Davies, 50, is believed to have known the victim, 56.
The couple, married for more than half a century, had recently retired to Mount Pleasant.
Four EU countries in eastern Europe refused to take part in the meeting