Studying Pupils

Have you ever seen someone’s pupil suddenly shrink when the lights turn on in a dark room? Our pupils change size constantly throughout the day, adjusting to light levels and responding to shifts in attention. But what happens at night? Hidden behind closed eyelids, sleeping pupil activity has always been a mystery. Now researchers have managed to film a mouse’s pupil overnight. An infrared light shines on the back of the eye, making the pupil glow white on an infrared camera. The recordings revealed that pupil size fluctuates, precisely matching the state of sleep at any given time. The deeper the mice’s slumber, the narrower the pupils, suggesting they’re blocking out intrusive light during important deep sleep – thought to be the key time for memory consolidation. Furthermore, tracking pupils is a new approach to monitoring sleep, so could one day help people plagued by insomnia get a good night’s rest.

Written by Anthony Lewis

Anthony Lewis

Writer

Ant was the web editor in the early days of BPoD, and has since worked with the UK’s top science organisations as a writer and multimedia producer. He now splits his time between freelance work and managing multimedia at The Lancet.

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• Video from work by Özge Yüzgeç, Mario Prsa and Robert Zimmermann, and Daniel Huber
• Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland
• Video originally published under a Creative Commons Licence (BY-NC-ND 4.0)
• Published in Current Biology, January 2018