Exercise and Cognition
Colcombe and Kramer (2003) Potential moderating variables
-Theoretical variables Speed hypothesis Visuospatial hypothesis Controlled processing hypothesis Executive control hypothesis -Training type Combined Aerobic only -Program duration Short (1-3 months) Medium (4-6 months) Long (6+ months) -Session duration Short (15-30 minutes) Moderate (31-45 minutes) Long (46-60 minutes) -Sex -Age Young-old (55-65) Mid-old (66-70) Old-old (71-80) -Population Clinical Non-clinical - Fitness effects
Colcombe and Kramer (2003) What confounder did this article discuss with regards to cross sectional data?
A predisposition of the exercisers toward fast and accurate responding rather than a benefit of aerobic fitness achieved through exercise
Hillman (2008) Which brain structure is shown to have disproportionate changes as a result of participation in physical activity?
Anterior cingulate cortex (ACC)
Understand the results of the Barnes longitudinal/prospective study
Barnes, et al. (2003) o N= 349 o Males and females (55 years and older at time 1) o Found that fitness level at baseline predicted higher levels of cognitive performance 6 years later o Important because it used an objective measure of aerobic functioning (VO2 max) and also assessed a wider variety of cognitive processes
Hillman (2008) The article summarizes findings of several meta-analyses on cognitive function in older adults. Describe the important findings that meta-analytic research has offered to this field.
Each of the meta-analyses has shown a significant effect of exercise on cognition. They have also shown significant results in both healthy adults and adults with early signs of Alzheimer's disease, indicating an effect on a variety of cognitive functions. They have also seen results in areas that tend to have significant age-related deterioration, indicating that even more effect area of cognition can be impacted through exercise.
Hillman (2008) Which theoretical framework does this mechanism help to support?
Executive-control processing- for tasks that always require effort and controlled thought
Colcombe and Kramer (2003) How cross sectional data cited in this article limits the ability to conclude aerobic fitness predicts higher levels of cognitive function (consider temporal sequencing)
Exercisers may experience a predisposition toward fast and accurate responding due to the overall positive effects of fitness on perceptual, cognitive, and motor processes, rather than displaying a benefit of aerobic fitness from exercise.
What is the problem with cross sectional studies?
Findings could be due to less of a research effect, and more of a cohort effect
Understand the general results of longitudinal/prospective studies
Have shown that while deficits are apparent as people ago, the most profound changes aren't seen until we reach out 60's
Hillman (2008) How/why do they propose that this relationship exists? (Consider "behavioral conflict")
It is suggested that trained individuals experience a reduction in activation and a decrease in "behavioral conflict" during tasks that require variable amounts of executive control. It is also suggested that trained individuals experience increased activation of the dorsal prefrontal and parietal brain regions which are involved with task related inhibitory functioning (help bias task-relevant activation).
Why was it relevant to discuss the small (but significant) effects for categories like IQ score and achievement test scores in the Sibley and Etnier (2003) study?
It might be of interest to educators
Understand the results of the Laurin longitudinal/prospective study
Laurin, et al. (2001) o N=4615 o Compared to no exercise, PA levels at baseline were associated with lower risks of cognitive impairment, Alzheimer's disease, and dementia of any type 5 years after assessment (all were high functioning 65 years old at the baseline assessment)
Colcombe and Kramer (2003) Spirduso and Clifford (1978)- Why did we assume that smaller fitness benefits were seen with younger adults?
Less room to improve (cognition already good so harder to improve)
Hillman (2008) Is time spent in PE associated with a deficit in cognitive performance?
No, regardless of the measure used in varying studies, research has shown that an increase in time dedicated to physical health based activities, like PE, are not associated with a decline in academic performance
Colcombe and Kramer (2003) What did the Spirduso and Clifford (1978) study find about exercise and older adults?
Older athlete's performance on these tasks was substantially better than the older sedentary adults' and were similar to the performance of the young sedentary adults
Hillman (2008) Discuss the mechanism that was investigated to relate math and reading performance to increases in aerobic fitness.
Reading and math involve the prefrontal cortex and parietal/posterior cingulate cortex. Fitness is also related to the frontoparietal network and it is thought that this link helps produce the beneficial effects of exercise on academic performance.
What have cross sectional studies shown on this topic? (specific point in time)
Relatively linear declines in perceptions, cognition, and motor function from the 20's to the end of life
Hillman (2008) We are still lacking experimental evidence assessing the impact of physical activity on the cognitive function in kids. However, several studies have investigated these variables. What conclusions have they come to regarding exercise and cognitive function in children?
Research has shown an overall positive relation between physical activity and cognitive performance in school-age children. Early intervention might be important for the improvement and maintenance of cognitive health and function throughout the adult lifespan.
Understand the results of the Richards, Hardy, and Wadsworth longitudinal/prospective study
Richards, Hardy, and Wadsworth (2003) o Found that PA levels at 36 years of age was predictive of higher levels of verbal memory from 43-53 years of age o N=1919 o Other life activities such as game playing, attending religious services, or playing a musical instrument were not predictive of memory performance specific effect of PA
Colcombe and Kramer (2003) What has animal research shown us in this field?
The cellular, molecular, and neurochemical changes observed in rats and mice in response to exercise interventions may underlie the improvements in perceptual, cognitive, and motor processes in adult humans
Colcombe and Kramer (2003) Inclusion and exclusion criteria
The target populations were most often community-dwelling, "normal" older adults. Additionally, studies had to look specifically at the theoretical proposals made, had to include aerobic fitness, had to be randomized and have a control group, and participants had to be from age 55-80 years old. Articles were excluded if they were cross sectional, there was no random assignment, the exercise intervention was unsupervised, the exercise intervention did not include and aerobic aspect, and the participants were under the age of 55.
T/F: Although not all research shows a positive effect of exercise on cognitive function, there is nothing to indicate a negative effect.
True
Understand the results of the Yaffe longitudinal/prospective study
Yaffe, et al. (2001) o N= 5,925 o High functioning "community dwelling" women (65+ years) reported activities including number of blocks walked per walk o Results i. Women with greater PA levels at baseline were less likely to experience cognitive decline as assessed with the mini mental status exam (MMSE) during 6-8 years at follow up ii. The effect remained even after they adjusted for age, education level, health status, depression, diabetes, stroke, hypertension, smoking, and estrogen use
Hillman (2008) Consider early investigation of the relationship between physical activity and cognitive function: a. When did scientific research on this relationship begin? b. What was one of the first "theoretical frameworks" that was studied? When was this systematically investigated?
a. 1930s b. Relationship between physical conditioning and faster reaction times was first systematically examined in the 1970s. Findings indicated older adults who perform PA have faster psychomotor speed.
Hillman (2008) Hillman states that there is some research on young adults, but it is also lacking.
a. Although we understand that ceiling effects may exist in this population, what is most of this research used for? i. The majority of this research is focused on cognitive aging. There is a need for research in this area because of the declining health of children today, so we can understand times during the lifespan that are characterized by peak cognitive health.
Hillman (2008) List/describe at least 3 suggestions for future research in this area that your group proposes
a. Are there specific dietary recommendations to provide a protective effect on cognition? b. What are the effects of participant characteristics such as gender, socioeconomic status, ethnicity? c. How long are the protective effects of exercise on cognition seen? Are these effects diminished after days, weeks, or months of inactivity?
Hillman (2008) Consider the "Neuroimaging studies of physical activity in humans" section. List (at least) FIVE specific potential mechanisms that are discussed here that could be considered the "causal agent" between exercise and improvements in cognitive function.
a. Baseline electrocortical function b. Increased top down control c. Smaller error related negativity d. Activation of middle frontal gyrus and superior parietal cortex and decreased activation in ACC e. Increased cerebral blood volume in dentate gyrus of hippocampus f. Larger volumes of prefrontal and temporal grey matter, anterior white matter
Colcombe and Kramer (2003) What are physiologic adaptations to exercise that animal studies have shown to explain the relationship between exercise/aerobic fitness and cognitive function? Why have fitness interventions in humans produced less reliable results?
a. Cellular and molecular mechanisms i. Increased capillary density in cerebellum when rats exercised on a wheel ii. Increased aerobic fitness (running) increased cortical high affinity choline uptake and dopamine receptor density in the brain of older rats iii. Increased BDNF in rats iv. Increased new cells in the hippocampus of mice b. Within studies on humans the results are not as reliable in comparison to the animal studies. This is hypothesized to be due to methodological reasons regarding intensity, length, and type of aerobic fitness interventions, as well as initial fitness level, gender, cognitive function tests, and control groups. There also have been differences in theoretical framework that affect the tasks chosen to determine the fitness effects.
Colcombe and Kramer (2003) What are the four theoretical frameworks that are presented in this article as approaches to studying the effects of fitness on cognition? (Please list and give a brief explanation of what each theoretical framework represents) Which hypothesis did the authors support?
a. Executive-Control Processing i. Exercise improves executive controlled processing in tasks that will never be automatic and always require effort & controlled thought. b. Controlled Processing i. Fitness has a greater effect on movement that requires thought, effort, and control than on movement that is automatic ii. Exercise will improve the ability to acquire skills that require a large amount of effort & control iii. These tasks are not yet automatic c. Visuospatial Processing i. In comparison to verbal skills, visuospatial are more likely to decline with age ii. Hypothesis: Exercise will help with visuospatial skills because they are less likely to decline with fitness d. Speed i. Fitness in relation to reaction time (or other activities such as the quickness of tapping a finger) ii. The goal is to test the CNS function without having it impacted by cognition. iii. Hypothesis: Exercise helps cognition because it quickens reaction time e. Which Hypothesis did the authors support? i. Executive control process showed the greatest benefits ii. Controlled & Visuospatial all show benefits as well (just not as large as executive control)
Colcombe and Kramer (2003) Which cognitive processes had the highest effect from aerobic training? Did this fit the predictions of the authors?
a. Exercise had the greatest effect on executive control processing that was significantly greater than any other cognitive process. b. Exercise also was better than the control group at controlled, spatial, and speed tasks.
Hillman (2008) How might genetic variability moderate the effects between exercise and cognition?
a. Genetic variability in terms of the presence of a certain allele (the e4 allele) on the APOE (apolipoprotein E) gene may influence the relationship between fitness and cognition b. Future research would benefit from the examination of the influence of genetic variability on relevant target systems
Hillman (2008) We have discussed many different cognitive tests that are often used in research to assess a wide variety of cognitive functions. What are some recent methods utilized (in humans) to effectively assess the overall impact of exercise on cognition?
a. Neuroimaging techniques, such as ERP (event-related brain potentials) and structural and functional MRI tests can be used to examine changes in the brain structure and function and therefore the relationship between exercise and cognition b. Perceptual skills, intelligence quotient, achievement, verbal tests, mathematic tests, memory, developmental level/academic readiness
Colcombe and Kramer (2003) Overall effect of exercise on cognitive function (effect size)
a. Overall ES: 0.478 b. Overall exercise had a positive effect on cognitive function of sedentary adults regardless of the type of cognitive task.
Hillman (2008) What other lifestyle factors are discussed that may be influential in promoting a healthy brain/cognitive function?
a. The researchers looked at diet and cognition, as well as the interaction between diet and exercise- some research has shown a negative effect of high fat diets on BDNF levels and learning b. They have also looked at social interaction/isolation and exercise and cognition- found that older adults at risk for dementia who scored high in physical, cognitive, and social engagement had the greatest benefits in decreasing dementia risk.
Colcombe and Kramer (2003) Significant moderating variables (specific with overall category and specific sub category)
a. Theoretical variables → executive processing had significantly better results compared to the other cognitive variables b. Type of fitness training→ combined strength and aerobic training (better than aerobic training alone) c. Program duration→ long-term training programs (better than brief or moderate) d. Training-session duration→ bouts of exercise greater than 30 minutes (but moderate better than long) e. Gender→ females better than males f. Age→ over 65 y/o showed greater benefits
Hillman (2008) List at least 3 suggestions for future research the article proposes
a. What are the best varieties, intensities, frequencies, and durations of exercise? b. Is it ever too late to start an exercise program? c. Can exercise be used to reduce the negative effects of neurodegenerative diseases?
Hillman (2008) How is aerobic fitness related to cognition? What about BMI? Were muscle strength and flexibility related to academic achievement in the study discussed?
i. Aerobic fitness has a small positive relationship to academic achievement ii. BMI has a negative relationship with cognition iii. Muscle strength and flexibility are unrelated to academic achievement
Hillman (2008) What cognitive functions is this structure associated with?
i. Executive control ii. Connected to other brain structures that process sensory, motor, emotional and cognitive information
Hillman (2008) Describe each mechanism and relevant findings associated with each: Increases in BDNF
i. Exercise has consistently been shown to increase BDNF, ii. BDNF is associated with long term memory formation, and the growth and survival of new neurons as well as with enhanced learning and memory processes iii. This increase in BDNF seen in animals may be important since low levels of BDNF has been linked to Alzheimer's, Parkinson's, depression, anorexia, and other disease
Hillman (2008) Describe each mechanism and relevant findings associated with each: Increase in blood vessels, VEGF, and IGF1
i. Stimulated by the need for nutrients that comes with the increase in proliferation and cell survival ulin-like growth factor 1. ii. Blood vessel growth may be dependent on VEGF (vascular endothelial growth factor and IGF1 (insulin growth factor 1) iii. In rodents exercise increases the production of IGF1 and VEGF, which creates new blood vessels
Hillman (2008) Animal studies have provided a body of evidence to support the relationship between exercise/aerobic fitness and cognitive function. Describe each mechanism and relevant findings associated with each: Increase in cell proliferation and cell survival
i. There was an increase found in the hippocampus ii. It is one of the most consistently observed effects iii. In pups where the mom had exercise, there was a larger increase in cell survival and proliferation iv. The cells are thought to improve behavioral performance
Why is exercise and its effects on cognition such an important topic?
• As we age, we see declines in "fluid abilities" o Reasoning o Speed of processing o Things not based on experience o Executive control- planning, multi-tasking • Exercise slows these declines as we age
Colcombe and Kramer (2003) What were the results?
• Exercise had the greatest effect on executive processes • Combined strength and aerobic training regimens improved to a reliably greater degree than those in aerobic training alone • Relatively brief training programs provided at least as much benefit as moderate training, but not quite as much as long-term training programs • Short bouts of exercise had very little impact of cognitive function • When the population was more than half female, the group as a whole showed greater benefit than if the population was at least half male • Mid-old category seemed to benefit most from exercise • In the control group o Performance of the young-old and middle-old increased much more than performance of the old-old
Colcombe and Kramer (2003) What significant effect did they find for the control groups?
• Found that the "young-old" and "mid-old" showed the greatest improvements in cognition in the control groups (from not exercising) o Likely due to attention effect, social effects
What are some proposed mechanisms for why exercise impacts cognition?
• Increased cerebral blood flow • Alterations in brain neurotransmitters • Structural changes in the CNS • Modified arousal/ anxiety levels (increased focus) • Increased neurogenesis • Increases in BDNF • Learning experiences • Skills and relationship building
Understand the information discussed from the Etnier (1997) meta analysis. Be aware of the population, overall effect size, number of studies, and the moderating variable discussed.
• Meta-analysis on all of the PA and cognition literature • Population: kids and adults • Overall ES: 0.25 • Number of studies: 134 • Moderating variable discussed: age large effect for elementary aged children (6-13) and high school children
Colcombe and Kramer (2003) What was the overall effect? What about that of control groups?
• Overall ES: 0.478 o Exercise had a positive effect on cognitive function of sedentary adults regardless of the type of cognitive task • ES for control groups: 0.164 on all cognitive tasks o Improvement was about 1/8 a standard deviation
What are some ways that they test cognition in this research?
• Perceptual skills tests • IQ • Achievement tests (standardized tests) • Verbal tests • Math tests • Memory • Developmental readiness/ academic level • Stroop test, creativity, concentration • Reaction time
Understand the information from the Sibley and Etnier (2003) meta analysis. Be aware of the population, overall effect size, number of studies, and moderators.
• Population: kids • Overall ES: 0.32 • Number of studies: 44 • Moderators o Age largest effects in middle school aged students (may have been lowest to begin with) o Cognitive test perceptual skills test o Publication status
Understand the information from the Chang, et al. (2012) meta analysis. Be aware of the population, overall effect size, number of studies, number of participants, and moderators.
• Population: kids and adults • Overall effect size: 0.097 (small, positive ES) • Number of studies: 79 • Number of participants: 2072 • Moderators during exercise o Executive control function o High fit • Moderators immediately following o Intensity (very light, light, moderate) o Type of test (attention, crystallized intelligence, executive function) o Fitness (low fit and high fit) • Moderators after a delay o Intensity (very light intensity was the WORST, light, moderate, hard, very hard, maximal all significant positive effects) o Type of test (crystallized intelligence and executive function)
Colcombe and Kramer (2003) How did they code the studies?
• Theoretical variables o Speed category- measure of low-level neurological functioning (simple RT) o Visuospatial category- transform or remember visual and spatial information o Controlled- some cognitive control (choice RT) o Executive category- planning, inhibition, scheduling of mental procedures • Participant characteristics o Age i. Young-old- 55-65 ii. Middle-old- 66-70 iii. Old-old- 71+ o Sex i. High male- greater than or equal to 50% male ii. High female- greater than 50% female o Target population i. Clinical- in some way representative of a particular clinical population ii. Nonclinical • Training interventions o Type i. Aerobic- emphasized cardiovascular fitness in isolation ii. Combination- combined cardiovascular fitness training with strength training o Duration i. Short- 15-30 min ii. Moderate- 31-45 min iii. Long- 45-60 min o Length i. Short- 1-3 months ii. Medium- 4-6 months iii. Long- 6+ months o Cardiovascular improvement i. Unreported ii. Moderate- 5-11% iii. Large- 12-25%
Colcombe and Kramer (2003) What were the methodological issues with past research?
• Widely varying age groups • Differed with respect to the nature, intensity, and length of the aerobic fitness manipulations • Type of fitness measures employed • General health and fitness level of the partcipants at the beginning of the study • Subjects' gender • Tasks used to measure aspects of cognition • Nature of the control groups