Traditionally, we think of the human brain as being "hierarchically organized," sort of like the military. Recent evolutionary additions to the brain-structure direct the rest of the human mind—a sort of neurological superego. Except, as Faith Brynie writes in Psychology Today, "any weight watcher knows ... the top-down command model of the brain doesn't explain much when it comes to appetite control."

That's where researchers Richard Thompson and Larry Swanson come in. They've traced brain circuitry in rats, and say that a network model for the brain actually makes much more sense.

The brain is usually described as hierarchically organized, although an alternative network model has been proposed. To help distinguish between these two fundamentally different structure-function hypotheses, we developed an experimental circuit-tracing strategy that can be applied to any starting point in the nervous system and then systematically expanded....the results do not support a rigidly hierarchical model of nervous system organization but instead indicate a network model of organization.

Or, as Byrnie paraphrases, "Around and around in a series of loops, messages travel in all directions." Appetite, as well as attention, arousal, and more, function through "a feedback network best compared to computer networks such as the Internet." Of course, she points out that knowing this about the brain's "appetite circuitry" might not "make resisting that juicy burger any easier."

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Heather Horn