Spontaneous pupillary oscillations increase during mindfulness meditation

A significant body of literature has shown that pupil size varies with cognitive and perceptual states [1,2]. Furthermore, the pupil diameter oscillates spontaneously at low frequencies, sometimes referred to as pupillary hippus [3,4]. Oscillation amplitude varies with many neural factors, including arousal and cortical excitability. Here we show that pupillary oscillations are modulated by mindfulness meditation, increasing by 53% compared to pre- and post-meditation baselines. The effect occurs only in trained meditators and is specific for low frequencies (below 1 Hz), with delta frequencies (1–5 Hz) unchanged. The study suggests that pupil size may be a useful marker of the altered cortical state during meditation. Pomè et al. measured the diameter of the eye pupil in trained mindfulness meditators and found that slow spontaneous pupil oscillations are specifically enhanced during meditation, indicating that the pupils can betray the meditative state.