Pupil size modulation drives retinal activity in mice and shapes human perception

Area of Science:

• Neuroscience
• Vision Science
• Ophthalmology

Background:

• The pupil's role in vision is primarily considered passive, regulating light entry to prevent retinal overstimulation.
• Neuronal activity in the retina is typically assumed to be independent of pupillary dynamics.

Purpose of the Study:

• To investigate whether the pupillary light reflex (PLR) actively influences retinal ganglion cell (RGC) activity.
• To determine if pupil-driven neural responses are relayed to the visual cortex and consciously perceived.

Main Methods:

• In vivo electrophysiological recordings from mouse RGCs.
• Electrophysiology in the mouse visual cortex.
• Psychophysical experiments in human volunteers.

Main Results:

• Pupillary constriction (PLR) induced significant neural activity in all studied RGC types in mice.
• This pupil-driven activity was transmitted to the visual cortex.
• Consensual PLR enabled binocular responses to monocular luminance changes.
• Human participants reported perceptual dimming correlating with PLR-induced responses.

Conclusions:

• The pupillary light reflex is not merely a passive light regulator but an active driver of RGC activity.
• Pupil dynamics directly contribute to visual processing and are consciously perceived.
• The pupil plays an active role in encoding perceived ambient luminance.