They got the beat

In a dish, rat neurons engineered to respond to light can tell whether they’re listening to classical or ragtime music, in part because of the different timing signals. Scientists converted a Schubert impromptu (top) into different patterns of timed light pulses (middle). As the cells “listened,” their activity was able to detect that classical music was playing as opposed to ragtime.

The brain is able to knit different signals in time together into unifying experiences in what Tse calls a buffering process. Some type of a brain buffer collects data coming in over about a quarter of a second and stitches it together into discrete events that we recognize as “now.”

H. Ju et al/J. Neurosci. 2015

New work suggests that this process goes awry in people with schizophrenia, who often report time as a jumble. “It’s actually quite fascinating,” says neuroscientist Virginie van Wassenhove of INSERM in France. People with schizophrenia “describe their world as a movie that’s segmented and they have to reconstruct the meaning of that movie, because time is not continuous for them.”

When asked to make a conscious timing judgment, people with schizophrenia merge sights and sounds over a longer window of time than people without the disorder, according to research by van Wassenhove and her colleagues. Healthy people consciously combined sights and sound over a 200-millisecond window. For people with schizophrenia, that window stays open for around 300 or 400 milliseconds.

“In a way, a moment is consciously longer for them,” van Wassenhove says. This longer-than-usual “now” applied only to timing tasks when the study’s volunteers were explicitly asked to keep track of time, the researchers found. When not explicitly asked to pay attention to a timing task, healthy volunteers noticed timing discrepancies just as often as did people without schizophrenia. For example, a badly dubbed movie would be just as bothersome for both groups.

Those puzzling results hint at some profound differences in the way people with schizophrenia might process time, van Wassenhove says. Perhaps different neural systems are responsible for keeping track of time consciously and unconsciously, and those systems are affected differently by the disorder.

So far, scientists are struggling to make sense of these sorts of hints. But experiments are becoming more sophisticated as scientists attempt to mimic real-world scenarios. “In the real world, we don’t have tunnel vision,” says Warren Meck of Duke. “We’re not timing just one thing at a time and ignoring other things.” He and his colleagues are working on how brains keep track of multiple, simultaneous events. And new techniques to manipulate neurons will allow researchers to see if they can mimic time perception in the brain.

Other researchers are exploring concepts like musical rhythm, ordering events in time, and mental time travel, in which people imagine the past and the future. “All of these aspects are possible ways of approaching the big concept of time,” van Wassenhove says. Scientists hope that these types of experiments will ultimately reveal how the brain makes and keeps its own time.

This story appears in the July 25, 2015 issue with the headline, "Clocking in: The brain has a throng of timekeepers that stitch together a coherent reality.

WORDLIST ENGLISH ARTICLES 2015

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