Spontaneous Eye Blink Rate Connects Missing Link between Aerobic Fitness and Cognition

Abstract

Purpose: Higher aerobic fitness, a physiological marker of habitual physical activity, is likely to predict higher executive function based on the prefrontal cortex (PFC), according to current cross-sectional studies. The exact biological link between the brain and the brawn remains unclear, but the brain dopaminergic system, which acts as a driving force for physical activity and exercise, can be hypothesized to connect the missing link above. Recently, spontaneous eye blink rate (sEBR) was proposed and has been used as a potential, noninvasive marker of brain dopaminergic activity in the neuroscience field. To address the hypothesis above, we sought to determine whether sEBR is a mediator of the association between executive function and aerobic fitness. Methods: Thirty-five healthy young males (18-24 yr old) had their sEBR measured while staring at a fixation cross while at rest. They underwent an aerobic fitness assessment using a graded exercise test to exhaustion and performed a color-word Stroop task as an index of executive function. Stroop task-related cortical activation in the left dorsolateral PFC (l-DLPFC) was monitored using functional near-infrared spectroscopy. Results: Correlation analyses revealed significant correlations among higher aerobic fitness, less Stroop interference, and higher sEBR. Moreover, mediation analyses showed that sEBR significantly mediated the association between aerobic fitness and Stroop interference. In addition, higher sEBR was correlated with higher neural efficiency of the l-DLPFC (i.e., executive function was high, and the corresponding l-DLPFC activation was relatively low). Conclusion: These results indicate that the sEBR mediates the association between aerobic fitness and executive function through prefrontal neural efficiency, which clearly supports the hypothesis that brain dopaminergic function works to connect, at least in part, the missing link between aerobic fitness and executive function.

Relationship between Eye Blink Frequency and Incremental Exercise among Young Healthy Men

“…The study involved an analysis of the blink rate based on the position of the pupil while watching a stereoscopic film, using an infra-red camera and an infra-red light source. The final results show high variability in the blink rate over time; therefore, they are not consistent with those studies that indicate an increased blink rate associated with fatigue [ 20 , 23 , 28 ]. Another study [ 38 ] involved a measurement of the number of blinks during a conversation via a camera mounted on the face.…”

“…The relationship between eye blink frequency and incremental exercise is relatively unknown. Recent findings include that spontaneous eye blinking is the missing link between aerobic fitness and cognitive function [ 23 ]. In our study, blink frequency and eye closure time were determined by a group of somatic and physiological factors.…”

“…A number of works have been carried out on the analysis of the impact of fatigue on the frequency of blinking [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. This research could lead to the development of innovative non-contact and non-invasive methods of measuring effort and fatigue.…”

Cognitive fatigue due to exercise under normobaric hypoxia is related to hypoxemia during exercise

“…The correct answer rate assigned to "yes" and "no" was 50%. Each stimulus was separated by an inter-stimulus interval showing a xation cross for 9-13 seconds to avoid predicting the timing of the subsequent trial [1,2,4,8,[21][22][23]25] . The stimulus remained on the screen until a response was given or for 2 seconds.…”

“…This method allowed us to calculate signals re ecting the oxy-Hb, deoxy-Hb, and total hemoglobin concentration changes, calculated in millimolar-millimeters (mM⋅mm) [27] . The composition of the fNIRS probe holder and its placement followed the same procedure used in our previous studies [1][2][3][4][21][22][23]28] . To register fNIRS data in the Montreal Neurological Institute (MNI) space, we used virtual registration [29,30] .…”