Portrait of a little girl sitting with her head on her arms, staring at an old clock.

If the day seems to be moving slowly, fatigue in a group of neurons involved in time perception might be to blame. Credit: Getty

Neuroscience

Exhausted neurons help make time seem ... to ... drag

A brain region that tires after repeated use is involved in distorted perceptions of time’s passage.

Time flies when you are busy, but when you’re bored, it seems as if the day will never end. Researchers have now found that specific neurons can grow weary if repeatedly exposed to the same stimulus — altering the brain’s perception of time.

Masamichi Hayashi at the National Institute of Information and Communications Technology in Suita, Japan, and Richard Ivry at the University of California, Berkeley, scanned volunteers’ brains while showing them a grey spot on a screen for a defined period of time, 30 times in a row. After this ‘adaptation’ phase, participants saw the grey spot again, but for different lengths of time. Then, they estimated how long the object had stayed on screen.

In some tests, the length of time that the visual stimulus was on screen was similar to that in the adaptation phase. Participants tended to respond by misjudging its duration, and activity decreased in a group of brain cells involved in time perception, indicating neuron fatigue. The activity of other neurons was unchanged, which can skew an individuals’ experience of time, the researchers say.