We predicted volunteers should see more of this "perceptual dimming" in low contrast than in high, and with kinetics matching the 1-second delayed pupil. And indeed this is what we saw, suggesting that the pupil-induced activity we found in the mouse is also present—and perceived—in humans.

Well, it turns out that when our collaborators in Finland Petri Ala-Laurila and Gabriel Peinado Allina (not on Bluesky) replicated our exact mouse stimulus in humans, the pupil kinetics were indistinguishable, both in terms of the slower kinetics and ability to track slowly changing stimuli.

In addition, we found that the pupil taking about 1 second to respond to light meant that it uniquely shaped responses to slowly changing visual stimulus, so an amplitude ramp stimulus at 0.5Hz induced strong binocular modulations, but one at 2Hz didn't.

But what does this do, then? What kind of visual signal does this pupil-induced response alter? We found that it preferentially boosts low contrast stimulus over high contrast, and stimulus that matches the slow pupil kinetics, which takes about 1 second to react to the light flash.

Now this could still be "just" a retina thing, like saccadic responses that the brain subtracts away with the help of corollary discharge. Not the case with these pupil-induced responses, which we still detected in LGN axons and layer 2/3 V1 cells.

And pupil-induced responses are present in every RGC type, with amplitudes comparable to their canonical responses, in both awake and anesthetized mice.

Importantly, if we disrupted the pupil's ability to constrict with atropine (see image), the effect disappeared, suggesting a causal link here.

This would have other repercussions too, since the pupillary reflex is a consensual effect, stimulating one eye causes both pupils to change. We predicted we could stimulate the *opposite* eye and get responses, even if the recorded eye only saw a constant grey screen. And again this is what we saw.

We predicted that shining light on one eye would induce a strong pupillary constriction, or pupillary light response (PLR), that could then dim the stimulus, causing a light response change with the kinetics of the closing pupil--which we saw! See in the figure an example OFF cell showing this.

We recorded activity from retinal ganglion cell axons in the LGN of the mouse in vivo using 2-photon imaging, allowing us to stimulate either eye (or both) and record retinal activity that gets transmitted to the visual thalamus, and ultimately to the primary visual cortex.

I think I went overboard for the institute's secret santa party. BUT I did follow the rule of less than 2.5 bucks per present (labor not included).

Below is a full list of the invited speakers--and nearly half the program is for speakers selected from abstracts, so coming gives you a very good chance of talking as well!

Can I please be added? Happy to show off our beautiful NLW 2p rig (we have two of them!)