Why do we sometimes keep eating even when we're full and other times turn down food completely? Why do we crave salty things at certain times, and sweets at other times? The answers, according to new neuroscience research at the University of Delaware, may lie in a tiny brain in an organism you might not expect.

Lisha Shao, assistant professor in the Department of Biological Sciences in the College of Arts and Sciences, has uncovered a neural network in the brains of fruit flies that represents a very early step in how the brain decides - minute by minute - whether a specific food is worth eating. The work was published in the journal Current Biology on Jan. 29.

"Our goal is to understand how the brain assigns value - why sometimes eating something is rewarding and other times it's not," Shao said.

Until this discovery, scientists knew very little about the connection between taste and the systems in the brain that determine which foods we pursue, learn and remember.

Although they are the size of a pinpoint, the brains of fruit flies use many of the same kinds of chemical messengers and basic building blocks that are found in mammals and humans, making the work a useful window into the general rules the human brain uses to begin processing rewards.