How Brain Detects Short Sounds.

• Position: COMMUNICATION

For humans to understand speech and for other animals to know each other's calls, the brain must distinguish short sounds from longer ones. By studying frogs, researchers at the University of Utah, Salt Lake City, figured out how certain brain cells compute the length of sounds and detect short sounds.

In addition to pitch and loudness, "sound duration is of universal importance," says Gary Rose, professor of biology and senior author of a study published in Proceedings of the National Academy of Sciences. "Its important to frogs. It's important to humans. It's important to all animals that use sound to communicate."

Researchers long ago discovered that different neurons or nerve cells in the brain "selectively respond to sounds of a certain duration, but we didn't know until now how they computed the lengths of sounds."

Rose and neuroscience doctoral student Rishi Alluri used a novel combination of recording electrical activity of single brain cells and blocking neurotransmitter chemicals that carry nerve signals from one nerve cell or neuron to the next. It already was known that short sounds are discriminated from longer sounds by individual brain cells in the inferior colliculus, the auditory part of the midbrain.

The researchers found that, for a frog brain cell to recognize a short sound, it is inhibited from firing a nerve signal while the sound is occurring, then is excited...