How do we sense time? The brain’s specialist cells that order our memories

Recent studies suggest there is not one part of the brain dedicated to measuring duration, as there is for senses like taste and smell. Instead, the passage of time is tracked by a network of “time cells”

By Helen Thomson

EVER WALKED INTO the kitchen at the exact moment the oven beeps to say your dinner is ready? Most of us can estimate time passing with amazing precision thanks to a complex network of neural mechanisms. Over the past five years, our understanding of these has expanded rapidly, making it clear there is no single timekeeper in our brains. Nor is there a particular neural pathway that relates to time, as there is for other senses, such as smell or sight.

Some timekeeping happens unconsciously – our bodies have circadian rhythms that help biological processes occur at the right time of day (see “Can we live without time?”, page 47). But mechanisms in our brain also contribute to our ability to sense the passing of time.

Let’s start with “time cells”. These reside in the hippocampus – a brain region involved in memory – and were first discovered in rats in 2018. Recently, time cells were also identified in humans by Bradley Lega at the University of Texas Southwestern Medical Center and his colleagues. Lega says that to understand what time cells do, first we need to consider “place cells” – brain cells that mark where in a spatial environment an animal is. If the animal walks along a linear tunnel, place cells would fire in a linear manner. Time cells do something similar, but for the passage of time.

When you are at an event – a movie or a dinner party, for instance – your brain will recognise this as a specific, or notable, chunk of time that neuroscientists call an “episode”. In many cases, our brains know how …