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:

  1. 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.
  2. 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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  4. Hillman, C. H., Kamijo, K., & Scudder, M. (2011). A review of chronic and acute physical activity participation on neuroelectric measures of brain health and cognition during childhood. Preventive Medicine, 52(Suppl. 1), S21–S28.
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  6. Spirduso, W., Francis, K., & MacRae, P. (2004). Physical dimensions of aging (2nd ed.). Champaign, IL: Human Kinetics.
  7. Tomporowski, P. D., Lambourne, K., & Okumura, M. S. (2011). Physical activity interventions and children’s mental function: An introduction and overview. Preventive Medicine, 52(Suppl. 1), S3–S9.

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