Researchers at Karolinska Institutet found that breathing affects the size of the pupils, which are smallest when inhaling and largest when exhaling. The discovery suggests a brainstem-controlled mechanism that could improve understanding of vision and attention and could potentially have applications in clinical treatments for neurological disorders.
Researchers at Sweden's Karolinska Institute have discovered a fundamental mechanism that affects pupil size: breathing. Their study, published in the Journal of Physiology, reveals that pupils constrict during inhalation and dilate during exhalation, a finding that could impact our understanding of vision.
The pupil, like the aperture of a camera, regulates the amount of light entering the eye and plays a vital role in vision and perception. For more than a century, scientists have recognized three main factors that influence pupil size: light exposure, focal length, and cognitive influences (such as emotion or mental effort). Now, researchers have discovered a fourth factor - breathing. Their results showed that pupils are smallest at the beginning of inhalation and largest at the time of exhalation.
Artin Arshamian, associate professor at the Department of Clinical Neuroscience at Karolinska Institutet, who led the study, explained: "What is unique about this mechanism is that it is periodic, always present, and does not require external stimulation. Since breathing affects brain activity and cognitive function, this finding may help to better understand how our vision and attention are regulated."
The researchers conducted five experiments with more than 200 participants to study the effect of breathing on pupil size under different conditions. The results showed that this effect persisted whether participants breathed quickly or slowly, breathed through their nose or mouth, whether lighting conditions or fixed distance varied, and whether they were resting or performing a visual task. Theoretically, the difference in pupil size during inhalation and exhalation is enough to affect vision.
Research has also shown that people born without olfactory bulbs, brain structures activated by nasal breathing, have this function. This suggests that the mechanism is controlled by the brainstem, a fundamental and evolutionarily conserved part of the brain.
Researchers are currently studying whether changes in pupil size during breathing also affect vision. Previous research has shown that smaller pupils make it easier to see details, while larger pupils help us detect hard-to-see objects.
"The findings suggest that our vision may switch between resolving small details when inhaling and detecting obscure objects when exhaling, and this all occurs within one breathing cycle," said Martin Schaefer, a postdoctoral researcher in the same department at Karolinska Institutet and first author of the study.
The researchers say the technology may also have clinical applications. "One potential application is a new way to diagnose or treat neurological diseases such as Parkinson's disease, since impaired pupillary function is an early sign of the disease. This is something we would like to explore in the future."
Compiled from /ScitechDaily
DOI:10.1113/JP287205