Brain time

Some of the brain’s multitude of timekeepers are listed below. Studies suggest that several brain areas handle aspects of explicit timing — when a person is asked to estimate a certain duration (left). Other areas (right, there’s some overlap) are involved in implicit timing — making timing predictions for durations of events without being directly asked to do so.

F. PIRAS ET AL/FRONTIERS IN NEUROLOGY 2014

Nerve cells removed from a rat’s cortex, the brain’s outer layer, will respond in complex ways to the tempo of music, neuroscientist Antonius VanDongen of Duke-NUS Graduate Medical School Singapore and colleagues have found. After genetically engineering a network of nerve cells to respond to blue light, the team regaled the cells with “music” — carefully timed patterns of light based on the rhythm and notes of songs. Upon “hearing” the songs, the cells’ electrical reactions could usually determine whether ragtime or classical music was playing at any given moment. And the cells got better as the seconds ticked by, hinting that they could hold a memory of the tempo information for about six seconds.

Those results show that time processing is fundamental in the brain, says VanDongen. “This is a very basic thing,” he says. A small group of neurons is the building block that may enable more sophisticated time processing.

Of course, nerve cells don’t usually live in lab dishes. The cells are housed in complex and diverse networks in the brain. Studies from human brain scans have also revealed clues about how the brain handles various aspects of time, suggesting roles for the cerebral cortex, the basal ganglia and the cerebellum. Activity in the insula (part of the cortex) changes when people are asked to estimate time by clicking a button at the end of an interval, for instance. And a recent study of people listening to snippets of foreign speech found a brain region, the superior temporal sulcus, that responds to increasingly longer sections of speech.

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