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Pupil Size during Very Light Exercise Predicts Benefits to Prefrontal Function

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Researchers from the University of Tsukuba investigated the impact of 10-min very light exercise on pupil size and prefrontal function. Their findings provide the first evidence that changes in pupil size during exercise can serve as an indicator for the enhancement of cognitive function associated with the prefrontal cortex resulting from very light exercise.

Tsukuba, Japan—Recent studies have revealed that mild forms of exercise, such as yoga or walking, can improve mood and enhance executive function, which involves the brain's prefrontal cortex and refers to the ability to control one's behavior to achieve a goal. However, the specific neural activity in the human brain that leads to the improvement of executive function during exercise has remained poorly understood due to tecFhnical limitations.

It is often said that the eyes are a part of the brain and can effectively reflect a person's mental state. In recent years, there has been growing interest in investigating pupil size variations as these are closely linked to the neural activity associated with the brain's noradrenergic arousal system. Pupillometry, a noninvasive and contactless measurement technique, allows for the assessment of neural activity during aerobic exercise and could serve as an indicator of arousal neural activity. Based on this premise, a research team led by KUWAMIZU Ryuta and SOYA Hideaki hypothesized that changes in pupil size during very light exercise could predict improvement in prefrontal executive function after a single exercise session.

To test this theory, the research team asked a group of healthy young adults to participate in 10-min very light exercise followed by an executive function task. The findings revealed that pupils dilated during the exercise, and the extent of the dilation was an indicator of a subsequent improvement in executive function. Prefrontal cortex activity during the executive function task was examined using functional near-infrared spectroscopy, demonstrating an increase in the activity of the left dorsolateral prefrontal cortex, a region associated with executive function.

These results strongly suggest that the enhancement of prefrontal executive function resulting from very light exercise can be attributed to pupil-linked neural activity, specifically the activation of the brain's noradrenergic arousal system. Looking ahead, pupil diameter holds promising potential as a novel biomarker that can be used to predict the effects of exercise on the brain.

This work was supported in part by the Japan Society for the Pro- motion of Science (JSPS) 16H06405 (H.S), 18H04081 (H.S.), 21H04858 (H.S.), 20J20893 (R.K.), and 23KJ1169 (R.K.); the Japan Science and Technology Agency (JST) Grant JPMJMI19D5 (H.S.); and the Meiji Ya- suda Life Foundation of Health and Welfare Grant (R.K.). This work was also supported in part by the Inviting Overseas Educational Research Units in University of Tsukuba ( 2016-2023) (to H.S.).

Original Paper

Title of original paper:
Pupil dynamics during very light exercise predict benefits to prefrontal cognition


Professor SOYA Hideaki
Advanced Research Initiative for Human High Performance (ARIHHP), Institute of Health and Sport Sciences, University of Tsukuba

Post-doc Researcher KUWAMIZU Ryuta
Graduate School of Letters, Kyoto University

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