Brain activity (above) corresponds to pupil dilation in a sleeping mouse's eye (below).ÖZGE YÜZGEÇ, MARIO PRSA, ROBERT ZIMMERMANN, DANIEL HUBER
Swiss scientists developed a novel method of studying pupil dilation when they noticed their laboratory mice slept with their eyes open. It uses an infrared light to image the back of the eye. They discovered that pupil size changes rhythmically during sleep, and the dilation correlates with changes in sleep states.
Ö Yüzgeç, et al. “Pupil size coupling to cortical states protects the stability of deep sleep via parasympathetic modulation,” Curr Biol, doi:10.1016/j.cub.2017.12.049, 2018.
