NEUROPHYSIOLOGY:
Listening In on the Brain
Marcia Barinaga
Traditional methods of recording brain activity allow neurophysiologists to record only the activity of one neuron at a time; while such techniques have provided a wealth of information about how brain neurons encode information by varying their firing rates, some neurobiologists have worried that by using just one electrode they weren't getting the full picture--the equivalent, say, of trying to record a symphony with a single microphone that can pick up the notes played by only one musician. Recent results using multiple electrodes to record from several neurons at a time now suggest that those worries were justified: Researchers are finding that neurons frequently fall into step with one another, forming ensembles that fire in relative synchrony for brief periods before some neurons drop out of synch. What's more, studies of systems as diverse as the motor cortex of monkeys and the olfactory system of honeybees indicate that these changing patterns of synchrony correlate with specific behaviors. Although the case is not yet proven, these findings suggest that the brain encodes information, not just in the firing rates of individual neurons, but also in the patterns in which groups of neurons work together.
