Not only do we mentally connect the enjoyment of certain foods with unrelated stimuli, our brains can also relax these connections once we're full of that food, the researchers discovered. They report their findings in the journal Science, published by AAAS, the science society.

If that mental relaxing process doesn't happen properly, it might leave us with the urge to eat even once we're full. An inability to disconnect the anticipation of food from various sights, sounds, or other stimuli may play a role in compulsive eating, according to author Jay Gottfried of the Institute of Neurology in London.

The brain's connection-making tendencies, or "conditioning," may extend to other substances that also trigger the brain's reward circuitry, Gottfried said. The ease with which we seem to associate pleasure-giving substances with other items supports the idea that one reason it's so hard for addicts to stay clean is that the smallest signs can bring back the cravings for drugs or alcohol.

The ability to make connections between eating and various stimuli in one's environment is a fundamental part of learning that is probably common, to some degree, in all animals.

"Say a rabbit is hopping around its little grassy patch and he's learned how to find clover," Gottfried explained. "So, if he sees a particular tree stump, or rocky slope, that predicts clover."

As if nature knew we wouldn't just stop eating when we were full, it also evolved a "brake system" for the conditioning process. Gottfried and his colleagues discovered that the brain tones down certain associations, once a person is full of the desired substance.

Such a system spares the rabbit, for example, from spending all its wa
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Contact: Christina Smith
ccsmith@aaas.org
202-326-7088
American Association for the Advancement of Science
21-Aug-2003