Cognitive Function

Cognitive function refers to the mental process of knowing or thinking. It involves all aspects of mental processes that enable individuals to perceive, recognize, process, and understand thoughts. Specifically, cognitive function involves processes such as action, attention, memory, learning, reasoning, planning, problem solving, decision making, and communication. These cognitive functions are not only important to daily life but are also recognized as main components in health-related quality of life.

Cognition: A Lifespan Spectrum

Although the major brain areas that are the core resource of cognition are set at birth, along with emerging and forming networks of brain cells, cognition and intelligence continuously develop throughout childhood, adolescence, and into young adulthood, thereafter declining gradually after adulthood. For example, with the exception of vocabulary, multiple cognitive functions, including the speed of information processing, reasoning, and memory, peak at 20 years of age and then decline linearly until the age of 70 years. Generally, compared to the entire population, an individual’s cognitive function at 20 years is above the 75th percentile, at 50 years it is near the 50th percentile, and at 70 years, it is in approximately the 20th percentile. This decline of cognitive function is linked to cognitive impairment in later life, such as dementia and Alzheimer’s disease.

As one can easily notice, the rate of cognitive development during early life and cognitive decline later in life exhibit marked inter-individual variability. Environmental factors and an individual’s experiences, including physical activity, intellectual engagement, social interaction, nutrition, and self-confidence, can positively influence these cognitive changes. Participation in physical activity is particularly emphasized in both lifespan phases by numerous social and health institutions and organizations, because increased physical activity has been related to multiple benefits affecting physical and mental health in children and older adults.

Physical Activity and Cognition: Different Perspectives

Early and Large-Scale Observational Studies

Physical activity and cognition were first investigated by Waneen Spirduso, Karen Francis, and Priscilla MacRae in the 1970s. While the researchers found that older adults demonstrated a longer reaction time of information processing in response to several cognitive tasks compared with younger adults, they also found that both older and younger adults showed differences based on participation in sports. The older adults who participated in sports regularly not only had a greatly increased cognitive speed compared to older sedentary adults, but also had similar cognitive performances as young sedentary adults, suggesting that participation in sports positively moderated the age-related cognitive decline.

The positive associations between physical activity and cognitive performance have also been shown in large-scale epidemiological studies. Generally, studies of older adults based on retrospective reports of physical activity have suggested protective effects against cognitive decline and cognitive impairment. However, these subjective measurements of physical activity are somewhat imprecise, and information regarding the modality, intensity, frequency, duration, and length of participation in physical activity is often deficient.

A study focusing on physical fitness, rather than physical activity, which involved approximately 900,000 California schoolchildren, demonstrated that increased physical fitness was significantly positively associated with enhanced reading and mathematics scores, regardless of gender and grade. Although a cause–effect relationship cannot be established from observational studies, the positive correlation between physical activity and cognition is promising.

Interventional Studies

Using experimental designs, particularly with randomized assignment into an exercise group or non-exercise control group, some studies have provided stronger evidence for a cause–effect relationship. Interestingly, while an older adult group with long-term physical activity improved in general cognitive performance, such as speed-, spatial-, controlled-, and executive function-related cognition compared with a sedentary control group, physical activity training also provided the greatest benefit to executive function. Executive function is a high-order type of cognition that is used to regulate, control, and manage multilevel basic information processing for purposeful and goal-directed behaviors. Therefore, older adults who participated in long-term physical activity demonstrated improved cognitive function in general, and selectively, particularly in executive function.

Long-term exercise may also benefit cognitive performance in overweight children. Research has indicated that participating in an exercise program 5 days per week over 15 weeks for 40 minutes per day at moderate intensity improves the planning aspect of cognition. It should be noted that performing this exercise protocol for 20 minutes per day had only a limited effect, suggesting that the duration of 40 minutes is the minimum threshold for cognitive function to be enhanced among children. Physical activity in school-based physical education, play during recess, classroom physical activity, and extracurricular physical activity, has either been found to be positively related to academic attitude, behavior, and achievement or to have no relationship, suggesting that participation in physical activity at school does not negatively affect student achievement.

Chronic Exercise Versus Acute Exercise

Besides studies that target long-term physical activity, known as chronic exercise, the effect of single bouts of physical activity, known as acute exercise, on cognitive function has also been investigated. Generally, when performing acute exercise, individuals with higher fitness and those who do 20 minutes or more of exercise per session show greater improvements in cognitive performance than those with low fitness and those who perform exercise of shorter durations. Similar to chronic exercise, which has been shown to benefit many types of cognition including information processing and attention, acute exercise also has a positive effect on executive function. Although the effect of acute exercise on cognition is of a somewhat short duration, higher but not extreme exercise intensity appears to prolong the positive effect to 60 minutes. The beneficial effects of acute physical activity on cognition have recently been extended to overweight children and children with attention deficit–hyperactivity disorder.

Although both chronic and acute exercise benefits cognitive function, the mechanisms are likely to be different. According to the cardiovascular fitness hypothesis, the improvement in cognitive performance following chronic exercise is mediated by gains in cardiovascular fitness. In support of this hypothesis, studies using sophisticated neuroscientific and psychophysiological methods (e.g., magnetic resonance imaging or event-related potentials) have indicated that both older adults and children with high fitness levels show larger brain volumes in areas implicated in cognitive function (including gray matter, white matter, specific cortical structures like the prefrontal cortex, and subcortical structures like the hippocampus) than their counterparts with low fitness levels. In contrast, the mechanism linking acute exercise and cognition is believed to be exercise-induced arousal or enhanced allocation of attentional resources and improved efficiency of stimulus evaluation in response to a given cognitive task.

Exercise Mode

Exercise-cognition research primarily emphasizes aerobic exercise, possibly because this exercise mode is linked to cardiovascular fitness. However, a recent line of investigation has evaluated the effect of exercise types on cognitive function. Particularly with respect to older adults, studies have demonstrated that resistance exercise training may also improve cognition. It is speculated that the ability to improve cognition through resistance exercise is based upon the increase of certain neurotrophic factors, such as insulin-like growth factor I (IGF-I), which are upregulated in response to muscle contraction. IGF-I is not only negatively related to aging but has also been linked to the promotion of neurogenesis, neuronal survival, and synaptic plasticity, which collectively can lead to improved cognitive performance. Furthermore, given that acute resistance exercise elevates physiological arousal similar to acute aerobic exercise, it is believed that acute resistance exercise can also benefit cognition. Indeed, positive effects of resistance exercise have been observed in studies evaluating executive function among young and middle-age adults.

Coordinative exercises, such as gymnastics, martial arts, soccer, or dance, have also been linked to executive function in kindergarten children. It is believed that the adaptation of coordinative exercise, which involves complex movement and cognitive demand for goal-directed behavior, may improve neuromotor abilities in both the peripheral and central levels, which in turn may enhance cognitive performance. In addition to cardiovascular fitness, coordinative exercise may also advance cognitive functions by increasing motor fitness, including movement speed, balance, motor coordination, and flexibility. In fact, individuals with better motor fitness have demonstrated to activate more cognition-related brain regions during the cognitive tasks.

Conclusion

Although cognitive functions develop and deteriorate during an individual’s lifespan, participation in physical activity may alter the rate of these сhanges. Large-scale observational and interventional studies have revealed a positive relationship between physical activity and cognitive function in older adults, as well as a positive correlation between school-based physical activity and academic achievement in children. In addition, chronic exercise has been shown to impact cognitive functions in general and also, more selectively, executive functions. Similarly, beneficial effects of acute exercise have also been identified, although the magnitude of these effects can be moderated by fitness status, exercise duration, exercise intensity, and the type of cognitive task. Notably, the biological mechanisms associating chronic and acute exercise with cognition are likely to be different. Along with the beneficial effects of aerobic exercise on cognition, studies have also demonstrated the potential of resistance exercise and coordinative exercise for enhancing cognitive activity. Taken together, this body of evidence indicates that physical activity has beneficial effects on cognitive function throughout an individual’s lifespan.

References:

Chang, Y.-K., Labban, J. D., Gapin, J. I., & Etnier, J. L. (2012). The effects of acute exercise on cognitive performance: A meta-analysis. Brain Research, 1453, 87–101.
Chang, Y.-K., Pan, C. Y., Chen, F. T., Tsai, C. L., & Huang, C. C. (2012). Effect of resistance exercise training on cognitive function in healthy older adults: A review. Journal of Aging and Physical Activity, 20, 497–516.
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