Biology subjects

Weiden, D.

Publications and source records attributed to Weiden, D..

2 recordsLinked to original sources

bioRxiv2026

Pupil Constriction Causes Activity in the Human Retina and Visual System

Pupil responses shape the earliest stages of visual perception by regulating the amount of light that enters the eye. How this affects visual processing is still poorly understood. Here we present evidence that pupil constriction causes activity in the human retina and visual system, independently of visual stimulation. Healthy human participants (N=119) viewed brief visual stimuli (light increments or decrements) while pupil size, retinal activity (electroretinogram), and brain activity (electroencephalogram) were recorded. As expected, visual stimulation triggered an initial burst of retinal activity followed by pupil constriction (the pupil light response). Importantly, we used trial-to-trial variability in constriction latency to reveal a previously unknown retinal response that is locked to pupil constriction, rather than to visual stimulation. Presumably, and in line with similar findings in mice, this constriction-locked retinal activity is a response to the sudden decrease in retinal light exposure that accompanies pupil constriction (although contribution of iris muscle activity is not conclusively ruled out). A similar constriction-locked response emerged later over visual cortex. Given these findings, an important open question is how the visual system maintains brightness constancy despite pupil-induced retinal and cortical activity.

neuroscience↗

bioRxiv2024

Spontaneous Fluctuations in Pupil Size Shape Retinal Responses to Visual Stimuli

Visual perception is shaped at the earliest stage by the size of the eyes pupil, which determines how much light enters the eye and how well this light is focused. But the exact role of pupil size in visual perception is still poorly understood. We recorded pupil size and electrical activity from the retina and brain while healthy human participants viewed full-screen flashes. We found that early retinal responses, which peaked {+/-}25 ms after stimulus onset and predicted subsequent activity over visual cortex, were strongly affected by stimulus intensity. Importantly, pupil size, at least within the range of naturally occurring fluctuations, did not affect the amplitude of these early retinal responses, despite resulting in substantial changes in retinal light exposure. However, the direction of pupil-size change at the moment of stimulus presentation did modulate the amplitude of early retinal responses, which were enhanced during phases of dilation as compared to constriction. Based on these results, we suggest that fast-acting adaptation processes may normalize early retinal responses with respect to changes in retinal light exposure that result from spontaneous changes in pupil size: an initial form of brightness constancy. These results shed new light on, and raise important and previously unasked questions about, the role of pupil size in visual perception.

neuroscience↗