Welcome to Quantum Magazine's podcast.

Each episode we bring you stories about developments in science and mathematics.

I'm Susan Vallett.

Our brain doesn't have the equivalent of a clock for telling the time directly, so it can't

directly put time stamps on memories of events.

But researchers have been trying to figure out a mathematical model of our brain's way of time

processing. How do we neurologically represent the past?

It all began about a decade ago at Syracuse University with a set of equations scrawled

on a blackboard.

Cognitive neuroscientist Mark Howard, who's now at Boston University, and then postdoctoral

student, Kartik Shankar, wanted to figure out a mathematical model of time processing. It's a neurologically

computable function for representing the past, like a mental canvas onto which the brain

could paint memories and perceptions. In effect, they were trying to work out a theory about

how the brain puts the paint on that canvas. It's fairly

straightforward to represent a tableau of visual information as functions of certain variables. Think of how

we represent light intensity or brightness as wavelength. That's because dedicated receptors in our eyes

directly measure those qualities in what we see.

But the brain doesn't have such receptors for time.

Masamiche Hayashi is a cognitive neuroscientist at the Center for Information and Neural Networks,

a neuroscience technology research institute in Osaka, Japan.

The problem is that time is such an elusive property of a perception, while color or shapes are quite obvious.

There's a long history of studies on shape perception or color perception or something.

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