New research by Chin-An Wang and Douglas Munoz, at Queen’s University, shows that a brain region called the intermediate superior colliculus (SCi) helps regulate the size of the pupil to optimize visual sensitivity and sharpness. Interestingly, brain processing of an object begins even before one shifts their gaze towards the object. This research shows that the size of the pupil is adjusted to the light level of the target, independent of the general light level, before the movement of the eyes towards this target.
Wang and Munoz showed that the predictive pupil response is coordinated by the SCi by specifically stimulating this region, resulting in a pupil response. They also showed they could inhibit the pupil response by injecting lidocaine in the SCi, thereby inactivating it.
This research demonstrates that tiny pupil movements are part of top-down control of behavior to optimize vision and adapt to the light in the environment.
Read the original research paper:
Wang CA, Munoz DP. Neural basis of location-specific pupil luminance modulation. Proc Natl Acad Sci U S A. 2018 Sep 24. pii: 201809668. doi: 10.1073/pnas.1809668115.