Synchronized. Interconnected fast-spiking cells, in red and green, may time incoming signals.

Synchronizing the Brain's Signals

Sometimes neurons get so excited that they sing in harmony. Researchers aren't sure just how these brain cells synchronize their firing, but a new study shows that one type of neuron might have the abilities necessary for orchestrating the performance.

Synchronized neural firing has long excited neuroscientists, but they aren't sure what it means. Some have suggested that it allows the brain to perform sophisticated computations over disparate regions of the brain. For instance, watching a red caboose rattle down a railroad track activates color-, shape-, and motion-sensitive parts of the brain; perhaps synchronous firing across these regions tells the brain to unite these features into one image. But the theory still has a lot of holes in it. For starters: How do neurons determine that two or more signals have arrived at the same time?

Now, neuroscientists Mario Galarreta and Shaul Hestrin of Stanford University may have provided a partial answer. In the 22 June issue of Science, they report that a type of neuron called a fast-spiking cell could play a central role in detecting synchrony in the brain. They teased interconnected pairs of these cells out of a slice of rat brain and artificially stimulated each one. When inputs to two cells were 5 milliseconds apart, the cells were less likely to fire than if just one cell had been activated. But if both cells were stimulated within 1 millisecond of each other, they fired strongest.

The new study "offers a system that's exquisitely sensitive to timing," says neuroscientist Barry Connors of Brown University in Providence, Rhode Island, and therefore it's "plausible" that networks of fast-spiking cells could detect and pass along synchronized signals.

Related site

A review of some neural synchrony theories