Friday, May 18, 2012

Dopamine and Eating Disorders: Unexpected Rewards

Each participant reclined in an scanner that uses a technique called functional magnetic-resonance imaging to peer inside the brain as their owners where presented with external stimuli. The first of these was a series of coloured geometric shapes displayed on a screen. Then, a few tablespoons of either sugar water or salt solution, made to resemble saliva, were squirted into the subject’s mouth. Alternatively, nothing was administered. In a nod to Ivan Pavlov, after a while a purple polygon, which had been systematically followed by a dose of sugar, was enough to provoke a spike in the brain activity in the reward centres. Occasionally, however, the rule was broken, either by squirting sugar following an orange snowflake, say, where none had been squirted before, or withholding it after displaying a purple shape. Imaging revealed that the three groups responded differently to such surprises. more

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