Carefully Timed Sequences Create Neuron "Songs"

Photon micrograph of a brain slice from a mouse visual cortex. Image courtesy of Rafael Yuste

Nerve cells in the brain are organized into networks that carry information by firing in carefully timed sequences, researchers have reported in the 23 April 2004 issue of the journal Science. Their new data challenges conventional wisdom, which dictates that nerves in the cerebral cortex fire in a more arbitrary fashion.

Such nerve cell activity in the cortex is the source of memories, imagination, language, control of voluntary movements, and other functions. Yuji Ikegaya and colleagues studied nerve activity in slices of cortical tissue and found evidence supporting the existence of so-called "synfire chains." Each chain is composed of distinct groups of nerve cells, which could represent one piece of information. One group fires first, stimulating a second group of neurons, which fire in unison, stimulating a third group, and so on. A group also may send feedback messages to those that fired earlier, or it may activate a new group of neurons in a separate chain.

The scientists also reported evidence that combined firing of such chains can create "songs" in the cortex. A related "Perspective" discusses why the discovery of precise firing times is important in neuroscience research.

26 April 2004

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