Pupil Diameter Tracks Statistical Structure in the Environment to Increase Visual Sensitivity

Abstract

Pupil diameter determines how much light hits the retina and, thus, how much information is available for visual processing. This is regulated by a brainstem reflex pathway. Here, we investigate whether this pathway is under the control of internal models about the environment. This would allow adjusting pupil dynamics to environmental statistics to augment information transmission. We present image sequences containing internal temporal structure to humans of either sex and male macaque monkeys. We then measure whether the pupil tracks this temporal structure not only at the rate of luminance variations, but also at the rate of statistics not available from luminance information alone. We find entrainment to environmental statistics in both species. This entrainment directly affects visual processing by increasing sensitivity at the environmentally relevant temporal frequency. Thus, pupil dynamics are matched to the temporal structure of the environment to optimize perception, in line with an active sensing account.

Memory guidance of value-based decision making at an abstract level of representation

“…Previous studies have shown that associative learning of face pairs does not lead to awareness of these associations 29 and that memory guidance occurs in the absence of explicit memory about the associations that form the basis of this guidance 14 . Similarly, we found that subjects were not better than chance in their explicit judgement whether two faces formed a pair when they actually did (mean difference − 3.68%, t (29) = − 1.44, p = 0.1606, g = − 0.2629).…”

Pupil tracks statistical regularities: behavioral and neural implications

“…Together, these findings suggest that pupil size reliably varies with the sudden changes in the environment's causal statistical structure. Schwiedrzik and Sudmann (2020) also highlight the critical finding that pupil dynamics adjust to the environment's temporal regularities. However, the way statistical regularities impact pupillary changes lacks consistency.…”

“…In a recent study, Schwiedrzik and Sudmann (2020) demonstrated that the brainstem PLR pathway that accounts for pupil dynamics adjustment is controlled by the environment's internal models derived from higher-order temporal statistics. Pupil recordings of humans and monkeys were made as they viewed faces with and without statistical regularities, referred to as random and structured streams of faces, respectively.…”

“…The most crucial finding of Schwiedrzik and Sudmann (2020) is that the brainstem PLR pathway is under the influence of brain areas that can extract environmental regularities. One possible site that mediates descending cognitive inputs to pupil cycling is locus coeruleus (LC).…”

“…Event-related measures indexing the activity in the LC-NE system (Murphy et al, 2011) are also linked with statistical learning (Jost et al, 2015), providing indirect evidence for LC role in statistical learning. However, Schwiedrzik and Sudmann (2020) suggest that their results are dissociable from the noradrenergic effects of the LC-NE system based on the argument that pupil cycling is primarily under parasympathetic control. Given the inconsistency in how regularities impact the pupillary changes, we propose another possible mechanism that interfaces pupil cycling by LC and explains the present findings, displaying a lack of pupil-based attenuation to predicted stimulus.…”