A groundbreaking study has revealed that pupils change size in sync with our breathing, a response now dubbed the “pupillary respiratory phase response.” Researchers confirmed that pupils are smallest around the start of inhalation and largest during exhalation, regardless of lighting, focus, or cognitive effort. This discovery adds a fourth type of pupil response to the well-known light, focus, and mental effort triggers.
The study, conducted by researchers at the Karolinska Institute in Stockholm and the University of Groningen in the Netherlands, involved over 200 participants and five experiments. The results showed that pupil size fluctuates in sync with breathing, even when other factors such as lighting, fixation distance, and mental effort are varied.
This finding suggests a deeper connection between our internal rhythms and visual perception, potentially influencing how we experience the world with each breath. The fluctuations are only fractions of a millimeter, which is less than the pupil response to light, but similar to the pupil response to mental effort or arousal.
The discovery may have implications for both medical diagnosis and research into the human brain. Disruptions in this response may signal neurological conditions, similar to how light reflexes are used in medicine. Additionally, understanding the relationship between breathing and pupil size could lead to new insights into how bodily rhythms shape perception.
Source: https://neurosciencenews.com/breathing-pupil-size-28621