Beyond Brain Circuitry

Article excerpt

Beyond brain circuitry

The intricate maze of connections among nerve cells in the brain, although awe-inspiring, does not provide the whole story behind animal behavior. Recent evidence indicates that a hardwired electrical circuit is not an adequate model for the brain. Characteristics invariant in an electrical circuit are flexible in nervous systems, so that fixed connections can vary their output during an animal's performance of different behaviors. The best-described nerve cell circuits are those of invertebrates, whose relatively few nerve cells can be identified. The specific connections among nerve cells have been determined in a variety of invertebrates. Now novel principles are emerging from what the scientists call "the second generation' of study of small neuronal circuits.

"Cells can dramatically change their own properties,' says Peter A. Getting of the University of lowa in Lowa City. "They show personal bias.' Getting studies a circuit used in walking and swimming by a sea slug called Tritonia. The nerve cells he has examined form an anatomically fixed circuit, but at one synapse in that circuit the same neurotransmitter can have opposite effects. …