Summary: Spontaneous eye-blink rates could be the missing link in explaining the relationship between aerobic fitness and cognitive function.
Source: University of Tsukuba
Although exercise is known to enhance cognitive function and improve mental health, the neurological mechanisms of this link are unknown. Now, researchers from Japan have found evidence of the missing link between aerobic fitness and cognitive function.
In a study published in Medicine & Science in Sports & Exercise, researchers from the University of Tsukuba revealed that spontaneous eye blink rate (sEBR), which reflects activity of the dopamine system, could be used to understand the connection between cognitive function and aerobic fitness.
The dopaminergic system is known to be involved in physical activity and exercise, and previous researchers have proposed that exercise-induced changes in cognitive function might be mediated by activity in the dopaminergic system. However, a marker of activity in this system was needed to test this hypothesis, something the researchers at the University of Tsukuba aimed to address.
“The dopaminergic system is associated with both executive function and motivated behavior, including physical activity,” says first author of the study Ryuta Kuwamizu. “We used sEBR as a non-invasive measure of dopaminergic system function to test whether it could be the missing link between aerobic fitness and cognitive function.”
To do this, the researchers asked healthy participants to undergo a measure of sEBR, a test of cognitive function, and an aerobic fitness test. They also measured brain activity during the cognitive task using functional near-infrared spectroscopy.
“As expected, we found significant correlations between aerobic fitness, cognitive function, and sEBR,” explains Professor Hideaki Soya, senior author. “When we examined these relationships further, we found that the connection between higher aerobic fitness and enhanced cognitive function was mediated in part by dopaminergic regulation.”
Furthermore, activity in the left dorsolateral prefrontal cortex (l-DLPFC) during the cognitive task was the same or lower in participants with higher sEBR compared with lower sEBR, even though those with higher sEBR appeared to have greater executive function, and thus higher neural efficiency.
“Although previous studies have indicated that aerobic fitness and cognitive function are correlated, this is the first to provide a neuromodulatory basis for this connection in humans. Our data indicate that dopamine has an essential role in linking aerobic fitness and cognition,” says first author Kuwamizu.
Given that neural efficiency in the l-DLPFC is a known characteristic of the dopaminergic system that has been observed in individuals with higher fitness and executive function, it is possible that neural efficiency in this region partially mediates the association between aerobic fitness and executive function. Furthermore, physical inactivity may be related to dopaminergic dysfunction.
This information provides new directions for research regarding how fitness affects the brain, which may lead to improved exercise regimens. For instance, exercise that specifically focuses on improving dopaminergic function may particularly boost motivation, mood, and mental function.
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Source: University of Tsukuba Contact: Naoko Yamashina – University of Tsukuba Image: The image is in the public domain
Spontaneous Eye Blink Rate Connects Missing Link between Aerobic Fitness and Cognition
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 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, non-invasive 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.
Thirty-five healthy young males (18-24 years 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(fNIRS).
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).
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.