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Participants viewed flashes, triggering an initial burst of retinal activity followed by pupil constriction. We then 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. 2/4 🧵

We observed a similar (but weaker) constriction-locked response 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. 3/4 🧵