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      Exercise Effects on Cognitive Function in Humans

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      Brain Plasticity

      IOS Press

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          Abstract

          Physical exercise improves memory function and mood, and may delay or prevent the onset of neurodegenerative conditions in older individuals. Understanding the effects of exercise on the underlying structural and functional neuronal mechanisms in the human brain is currently the focus of intense investigation. This Special Issue includes four research papers and three reviews addressing key issues in the human exercise and cognition field. The first article is a comprehensive review by Smith which focuses on the prevention of Alzheimer’s disease and related dementias and discusses the main risk factors: physical inactivity, ‘Western’ dietary patterns (e.g. high intake of saturated fat and complex carbohydrates, and low intake of fruits and vegetables), and poorly controlled cardiometabolic risk factors. In particular, a very clear and detailed description of the different dietary interventions that may benefit cardiovascular and cognitive health is given. Overall, combining dietary changes and exercise may effectively prevent or delay the onset of Alzheimer’s disease and related dementias [1]. The following research article by Schmitt et al. aims to understand how the relative intensity (low vs. high) of acute bouts of exercise might differentially modulate resting state functional connectivity (rs-FC) within different brain networks. The authors studied 25 trained male athletes who underwent individualized, graded fitness assessment on a treadmill. The participants also had brain MRI scans to determine rs-FC within diverse cognitive, sensorimotor, and affective networks. The study found that low-intensity exercise was associated with a significant increase in rs-FC in the left and right fronto parietal network, whereas high-intensity exercise was somewhat paradoxically linked to decreased rs-FC in the sensorimotor and dorsal attention networks, but increased connectivity in the left affective and reward network. This study is unique in being the one of the first to demonstrate differential effects of two individually-titrated exercise intensities on brain connectivity at rest. An important next step would be an elucidation of the potential neurobiological mechanisms underlying these exciting findings [2]. The second research paper in this Special Issue pertains to the link between cardiorespiratory fitness and executive function. Although it is well established that cardiorespiratory fitness conduces to improved performance on measures of executive function, an important knowledge gap relates to the potential neuronal mechanisms that support this fitness-executive function connection. To investigate this question, Peven et al. [3] recruited fifty young adults between the ages of 18 and 40 (mean age = 25.22 years, 56% female) who underwent graded maximal exercise test on a motorized treadmill and completed functional MRI scans during a Stroop color-word task. Analyses examined task-evoked functional connectivity of several brain regions. Specifically, they tested whether greater cardiorespiratory fitness would be associated with increased connectivity between brain regions that are involved with the processing of task-relevant stimuli dimensions (e.g., word color) versus whether higher cardiorespiratory fitness would be associated with diminished connectivity between brain regions that subserve the processing of task-irrelevant dimensions of the stimuli (e.g., word processing areas). They found greater support for the latter hypothesis, suggesting that one mechanism by which greater cardiorespiratory fitness confers better executive function is by suppressing the connectivity between brain regions that are involved with task-irrelevant sensory processing. A subsequent research article furthers our understanding of the neural substrates underlying effects of exercise on sleep and cognition. As individuals age, they are often likely to encounter greater disruptions in the quantity and quality of their sleep. These changes in sleep, in turn, are linked with brain changes and poorer performance on cognitive tests. In contrast, greater physical activity, even in old age, is related to better brain health and cognitive function. In their study of thirty older adults, Won and colleagues [4] examined the association between acute exercise, several sleep indices, and performance on the Stroop task. They found that, after acute exercise, longer total sleep time (TST) was related to shorter response time on the Stroop, and that this association between longer TST and faster processing speed was mediated by greater caudate volume. These findings shed light on the potential manner in which distinct lifestyle factors, such as exercise and sleep behavior, may interact to favorably promote healthy cognitive aging. In the final research paper of this Special Issue, Gaitan et al. [5] investigated the effects of exercise training on cerebral glucose metabolism (measured with FDG PET) and cognitive performance (episodic memory and executive function) in subjects with elevated risk for Alzheimer’s disease. Specifically, they examined the extent to which aerobic exercise training positively affects glucose metabolism in the posterior cingulate cortex, a region known to show hypometabolism with advancing Alzheimer’s disease. The authors found that improvements in cardiorespiratory fitness after the exercise training was associated with greater PCC glucose metabolism and enhanced executive function. The study concept and design is novel because participants in the intervention are relatively young older adults but enriched for high risk of Alzheimer’s disease (familial or genetic). This research is important because it provides a basis for subsequent studies that evaluate effects of exercise during preclinical disease periods in populations that are at high risk of accelerated decline. In their review article Boat and Cooper describe the relationship between exercise and self-control. They focus on two complementary aspects: the effects of self-control on exercise adherence and performance, and conversely how exercise may regulate self-control, as a component of executive function [6]. Finally, Gothe et al. provide a comprehensive review of the recent literature pertaining to the effects of practicing yoga on the brain. Positive effects are reported on the structure and function of brain areas such as the hippocampus, prefrontal cortex, cingulate and amygdala, responsible for memory function as well as mood regulation [7].

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          Most cited references 7

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          Modulation of Distinct Intrinsic Resting State Brain Networks by Acute Exercise Bouts of Differing Intensity

          Acute exercise bouts alter resting state functional connectivity (rs-FC) within cognitive, sensorimotor, and affective networks, but it remains unknown how these effects are influenced by exercise intensity. Twenty-five male athletes underwent individual fitness assessments using an incremental treadmill test. On separate days, they performed ‘low’ (35% below lactate threshold) and ‘high’ (20% above lactate threshold) intensity exercise bouts of 30 min. Rs-fMRI and Positive and Negative Affect Scale (PANAS) were acquired before and after each exercise bout. Networks of interest were extracted from twenty-two participants (3 dropouts). Pre-to-post changes and between conditions effects were evaluated using FSL’s randomise by applying repeated measures ANOVA. Results were reported at p < 0.05, corrected for multiple comparisons using threshold free cluster enhancement. PANAS revealed a significant increase in positive mood after both exercise conditions. Significant effects were observed between conditions in the right affective and reward network (ARN), the right fronto parietal network (FPN) and the sensorimotor network (SMN). Pre-to-post comparisons after ‘low’ exercise intensity revealed a significant increase in rs-FC in the left and right FPN, while after ‘high’-intensity exercise rs-FC decreased in the SMN and the dorsal attention network (DAN) and increased in the left ARN. Supporting recent findings, this study is the first to report distinct rs-FC alterations driven by exercise intensity: (i) Increased rs-FC in FPN may indicate beneficial functional plasticity for cognitive/attentional processing, (ii) increased rs-FC in ARN may be linked to endogenous opioid-mediated internal affective states. Finally, (iii) decreased rs-FC in the SMN may signify persistent motor fatigue. The distinct effects on rs-FC fit with theories of transient persistent network alterations after acute exercise bouts that are mediated by different exercise intensities and impact differentially on cognitive/attentional or affective responses.
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            Brain Glucose Metabolism, Cognition, and Cardiorespiratory Fitness Following Exercise Training in Adults at Risk for Alzheimer’s Disease

            Aerobic exercise has been associated with reduced burden of brain and cognitive changes related to Alzheimer’s disease (AD). However, it is unknown whether exercise training in asymptomatic individuals harboring risk for AD improves outcomes associated with AD. We investigated the effect of 26 weeks of supervised aerobic treadmill exercise training on brain glucose metabolism and cognition among 23 late-middle-aged adults from a cohort enriched with familial and genetic risk of AD. They were randomized to Usual Physical Activity (PA) or Enhanced PA conditions. Usual PA received instruction about maintaining an active lifestyle. Enhanced PA completed a progressive exercise training program consisting of 3 sessions of treadmill walking per week for 26 weeks. By week seven, participants exercised at 70– 80% heart rate reserve for 50 minutes per session to achieve 150 minutes of moderate intensity activity per week in accordance with public health guidelines. Before and after the intervention, participants completed a graded treadmill test to assess VO2peak as a measure of cardiorespiratory fitness (CRF), wore an accelerometer to measure free-living PA, underwent 18F-fluorodeoxyglucose positron emission tomography imaging to assess brain glucose metabolism, and a neuropsychological battery to assess episodic memory and executive function. VO2peak increased, sedentary behavior decreased, and moderate-to-vigorous PA increased significantly in the Enhanced PA group as compared to Usual PA. Glucose metabolism in the posterior cingulate cortex (PCC) did not change significantly in Enhanced PA relative to Usual PA. However, change in PCC glucose metabolism correlated positively with change in VO2peak. Executive function, but not episodic memory, was significantly improved after Enhanced PA relative to Usual PA. Improvement in executive function correlated with increased VO2peak. Favorable CRF adaptation after 26 weeks of aerobic exercise training was associated with improvements in PCC glucose metabolism and executive function, important markers of AD.
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              Caudate Volume Mediates the Interaction between Total Sleep Time and Executive Function after Acute Exercise in Healthy Older Adults

              Although both exercise and sleep are significant lifestyle factors in cognitive aging, the interaction of these two factors with respect to cognition remains to be determined. Also, little is known regarding the role of the basal ganglia (BG) in cognitive aging despite its involvement in both sleep and executive function. The primary objective of this study was to investigate the interaction between sleep and acute exercise on executive function performance, and secondarily, to assess if BG volume mediates this interaction. Thirty healthy older adults (65.8±7.3 years) completed 30 minutes of seated rest or moderate-intensity cycling exercise on different days. Structural MRI was used to assess the volumes of BG components including caudate, putamen, and globus pallidus shortly after the experimental conditions. Approximately 90 minutes after each condition, the Stroop task was administered to measure executive function. To examine sleep, participants wore a wrist actigraph for 8.0±3.6 days prior to the first experimental session. Results revealed that while longer total sleep time (TST) was associated with shorter Stroop response time (RT), shorter TST was associated with longer RT after exercise, compared to rest, for both congruent (p = 0.029) and incongruent (p = 0.022) trials. Longer TST was correlated with greater caudate volume, and greater caudate volume was associated with exercise-related improvement in Stroop incongruent RT. Ultimately, we found that the association between longer sleep duration and faster processing speed after acute exercise was mediated by greater caudate volume. These findings suggest that TST is an important factor for acute exercise-induced cognitive improvements in older adults, and that our study is a first step in understanding the interactive effects of these important lifestyle factors in cognitive aging that might simultaneously be addressed to promote healthy cognitive aging. Future studies should examine the interactive effects of sleep and chronic exercise on cognitive function, and whether BG volume might also mediate this interaction.
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                Author and article information

                Journal
                Brain Plast
                Brain Plast
                BPL
                Brain Plasticity
                IOS Press (Nieuwe Hemweg 6B, 1013 BG Amsterdam, The Netherlands )
                2213-6304
                2213-6312
                26 December 2019
                2019
                : 5
                : 1 , Exercise Effects on Cognitive Function in Humans
                : 1-2
                Affiliations
                [a ]Department of Medicine and Alzheimer’s Disease Research Center, University of Wisconsin School of Medicine and Public Health , WI, USA
                [b ]Department of Biomedical Science, Charles E. Schmidt College of Medicine, and Brain Institute, Florida Atlantic University , Jupiter, FL, USA
                Author notes
                [* ]Correspondence to: Henriette van Praag, Department of Biomedical Science, Charles E. Schmidt College of Medicine, and Brain Institute, Florida Atlantic University, Jupiter, FL 33458, USA. E-mail: h.vanpraag@ 123456protonmail.com .
                Article
                BPL199001
                10.3233/BPL-199001
                6971818
                © 2019 – IOS Press and the authors. All rights reserved

                This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial (CC BY-NC 4.0) License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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