New experiments explore how the timekeepers in our heads help us make sense of the world

How the brain perceives time

By Laura Sanders

9:10am, July 15, 2015

CLOCKING IN To perceive time, the brain relies on internal clocks that precisely orchestrate movement, sensing, memories and learning.

Tang Yau Hoong

Magazine issue: Vol. 188 No. 2, July 25, 2015, p. 20

Everybody knows people who seem to bumble through life with no sense of time — they dither for hours on a “quick” e-mail or expect an hour’s drive to take 20 minutes. These people are always late. But even for them, such minor lapses in timing are actually exceptions. We notice these flaws precisely because they’re out of the ordinary.

Humans, like other animals, are quite good at keeping track of passing time. This talent does more than keep office meetings running smoothly. Almost everything our bodies and brains do requires precision clockwork — down to milliseconds. Without a sharp sense of time, people would be reduced to insensate messes, unable to move, talk, remember or learn.

“We don’t think about it, but just walking down the street is an exquisitely timed operation,” says neuroscientist Lila Davachi of New York University. Muscles fire and joints steady themselves in a precisely orchestrated time series that masquerades as an unremarkable part of everyday life. A sense of time, Davachi says, is fundamental to how we move, how we act and how we perceive the world.

Yet for something that forms the bedrock of nearly everything we do, time perception is incredibly hard to study. “It’s a quagmire,” says cognitive neuroscientist Peter Tse of Dartmouth College.

The problem is thorny because there are thousands of possible intricate answers, all depending on what exactly scientists are asking. Their questions have begun to reveal an astonishingly complex conglomerate of neural timekeepers that influence each other.

New findings hint that the brain has legions of assorted clocks, all tick-tocking at different rates. Some parts of the brain handle milliseconds and others keep track of decades. Some neural timers handle body movements; others monitor information streaming in from the senses. Some brain departments make timing predictions for the future, while timing of memories is handled elsewhere.

This diversity has led some scientists to focus on figuring out how the brain stitches together the results from its many clocks to reflect the outside world accurately. A deeper understanding of how the brain’s timekeepers work might also shed light on something much more profound: how the brain constructs its own reality. The brain sometimes squishes, expands or warps time, some studies suggest. Subtle timing slips have been linked to emotions, attention, drugs and disorders such as schizophrenia. Those tweaks hint at how the brain normally counts seconds and milliseconds.

Time warp To the chagrin of people looking for simple solutions, there is no tiny clock tucked beneath the skull that marks the passing seconds, Tse says. And the brain’s timekeeping is not always as reliable as the steady tapping of a metronome. Instead, time can sometimes be experienced as stretched out lulls followed by torrential bursts.

Distortions Drugs, disorders and emotions can stretch or shrink time, depending on the neural system they target. Studying these subtle timing deficits may help reveal how the brain detects and responds to time.

Drugs

Stimulants Stimulant dependence makes it hard to distinguish durations and tap fingers to a beat

Psilocybin People taking this component of psychedelic mushrooms have trouble producing time intervals longer than a few seconds and are worse at tapping along with a slow beat

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