Recent U of M research on time helps explain why this afternoon is going to feel so long

Categories: Science, U of M
RhesusMonkey.jpg
Wikimedia Commons and PLOS Biology
A rhesus macaque, the kind of monkey brain the researchers studied, roaming in India. Right, a diagram of what happened in the U experiment.
A lot of us are fascinated by time: How we measure it, or why it seems to fly at a fantastic concert but crawl at work on, say, the afternoon before Thanksgiving.

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Geoff Ghose wonders about these questions too -- but he's a neuroscientist, so he gets to try to answer them. And after he published new research in the journal PLOS Biology at the end of October, some science writers started speculating that down the road, Ghose's findings could lead to pills that alter how we perceive time.

The research started about four years ago, when Ghose, along with one of his then-students, Blaine Schneider, wanted to look at how the brain keeps time.

"We look at a clock or a watch or sunlight," Ghose explains. "But we also have a thing separate from that, like 'Gee, it's getting late,'" an innate ability to distinguish between a minute and an hour, or a day.

These are big questions, and other scientists had looked at them before. Those researchers had found that in monkey brains, neuron activity builds over time, until it finally reaches a point that signals, for instance, 'It's time to go.'

But in many of those experiments, the monkeys would also get rewarded. Ghose and Schneider speculated that this impending reward could be triggering an anticipation build-up that skewed results away from just measuring time-tracking.

So they devised an experiment in which monkeys could only get a task right by keeping time, and in which they didn't have any outside help to generate a timing pattern.

The scientists worked with two rhesus macaque monkeys, and trained them to move their eyes between dots on a screen at regular one-second intervals. After three months, the monkeys could keep the time within fractions of a second.

Here's the breakthrough: Using electrodes to eavesdrop on the monkeys' brains, the researchers found that neuron activity actually decreased -- not increased, like previous results -- between each interval, and that the more activity dropped, the faster the monkeys were.

In other words, the monkeys' sense of time was linked to the activity they were doing, and those neuron circuits, as opposed to some general brain clock. "The animals' relationship to timing actually switched depending on the particular task the animal was doing," Ghose explains. "It's not consistent with a single clock mechanism." That is, the brain has time zones.

So what practical applications does this have? One idea is that every activity might have its own highly precise neuron decay rate, and that training can hone this task-specific time keeping. For instance, a drummer might improve his rhythm through practice, but still have poor timing during other tasks.

"It might be that you just make a small population of neurons that are appropriate for the task really good," says Ghose. "That's a fundamentally different notion of how you get good at things, how you learn things."

Ghose plans on devoting his next experiments to unpacking the question of how this kind of precision, like rhythm, develops -- i.e., what's going on in the monkeys' brains while they're learning to keep these intervals -- and how flexible it is.

From a macro perspective, learning more about how and why neuron activity is linked to time could translate into a better understanding of why neurodegenerative diseases, like Parkinson's, can skew a person's sense of time.

Figuring out "how the brain represents information is the first step," says Ghose.

The new research also hints at explaining the staple "time flies when you're having fun" saying. Hormones like adrenaline are known to affect how neuron activity decays. If this decay rate is linked to our sense of what time it is, it follows that it could be possible to play with these hormonal signals in order to alter our perceptions.

Some popular science writers are latching onto this to take these results even further. "As the findings unfold, it ought to be possible to manipulate these states to change how time is perceived," writes Mother Nature Network. "In other words, in the future there may actually be pills you can take to alter your perception of time just like there are mind-altering pills for various other purposes."

Ghose cautions that this is speculative. "A pill has a diffuse effect on a lot of neurons in the brain," he says, in contrast to his findings, which show results linked to very specific neurons. Which is to say, when it comes to the mysteries of time, "Looking for a pill might not even be the right way to think about things."



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