What a brain does when it sees doughnuts

CHICAGO, March 7 (UPI) -- Chicago researchers explain why the sight of chocolate-frosted doughnuts in a bakery window can propel people to buy doughnuts they hadn't expected to buy.

Researchers at Northwestern University's Feinberg School of Medicine had study subjects tested twice -- once after eating up to eight Krispy Kreme doughnuts until they could eat no more, and on another day after fasting for eight hours.

In both sessions, people were shown pictures of doughnuts and screwdrivers, while researchers examined their brains in using functional magnetic resonance imaging. When the study participants saw pictures of doughnuts after the eating binge, their brains didn't register much interest, but for those who had been fasting, two areas of the brain lit up.

First, the limbic brain lit up -- it says "I am hungry and there is food." Next the brain's spatial attention network shifted the hungry subject's focus on the doughnuts.

"There's a very complex system in the brain that helps to direct our attention to items in our environment that are relevant to our needs, for example, food when we are hungry but not when we are full," lead author Aprajita Mohanty, a post-doctoral fellow at the Feinberg School.

The study was published in the journal Cerebral Cortex.