The wave

Neuroscientists have known for more than a century that the nerve cells of the brain can team up to generate rhythmic waves of electrical current. Sometimes, as in the electrical tsunamis of epileptic seizures, the waves are a sign of disease. But waves often show up in healthy brains, and researchers have been hard-pressed to find a reason for the synchrony.

A new study by Yale neurobiologists David McCormick and Flavio Fröhlich, in Neuron, has shown for the first time that these synchronous electrical currents serve a function. "These general fields are not just a passive phenomenon," says McCormick. "They're actively involved in guiding the activity of the brain."

The paper argues that the electric fields have an amplifying effect. McCormick and Fröhlich subjected slices of living tissue from ferret brains to a series of electrical charges that mimicked electrical patterns in the brains of anesthetized ferrets. They found that the electrical waves worked to synchronize neural circuit activity in the brain tissue, and, in turn, the neural activity strengthened the electrical waves in the tissue. McCormick likens the phenomenon to the way the roar of a crowd tends to get everyone in the stadium cheering louder and more in unison: think of a well-executed "wave" at a baseball or football game.

This finding may explain why therapies that use electrical fields can be effective treatments for depression, schizophrenia, tremor, and other "parasitic neural patterns," says McCormick. He speculates that the therapies may work by somehow altering abnormal wave rhythms that have become persistent in sick brains.

But the study also suggests that everyday electrical fields could also influence brain activity. McCormick worries about the possible untoward effects of such devices as cell phones and power lines, though he has not yet studied their effects.