Brightness illusions evoke pupil constriction preceded by a primary visual cortex response in rats

The mind affects the body via central nervous system (CNS) control of the autonomic nervous system (ANS). In humans, one striking illustration of the "mind-body" connection is that illusions, subjectively perceived as bright, drive pupil constriction. The CNS network driving this pupil response is unknown and requires an animal model for investigation. However, the pupil response to this illusion has long been thought to occur only in humans. Here, we report that the same brightness illusion that evokes pupil constriction in humans also does so in rats. We surveyed the role of most of rat cortex in this "mind-body" connection by recording cortex-wide EEG. These recordings revealed that, compared to a luminance-matched control stimulus, the illusion of brightness for a specific stimulus color and size, evoked a larger response in primary visual cortex (V1) and not in secondary visual, parietal, or frontal cortex. The response preceded pupil constriction suggesting a potential causal role of V1 on the pupil. Our results provide evidence that this "mind-body" connection is not confined to humans and that V1 may be part of a mammalian CNS network for bodily reactions to illusions.