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Aerobic fitness influences working memory updating via the striatal dopaminergic system in older adults
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Umeå University, Faculty of Social Sciences, Centre for Demographic and Ageing Research (CEDAR).ORCID iD: 0000-0001-6169-5836
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).ORCID iD: 0000-0002-3367-1746
Departments of Psychology and Mechanical and Industrial Engineering, Northeastern University, Boston, MA, USA.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).ORCID iD: 0000-0002-3731-3612
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

There is much evidence that dopamine is vital for cognitive functioning in aging. Here we tested the hypothesis that aerobic exercise and fitness influences dopaminergic neurotransmission in the striatum as measured by positron emission tomography (PET) and the non-displacable binding potential (BPND ) of [11C]raclopride, and in turn performance on offline working-memory updating tasks. In a sample of 58 older sedentary adults undergoing a six-months exercise intervention, aerobic exercise compared to stretching, toning, and resistance training did not have a differential effect on BPND . At baseline, higher aerobic fitness levels (VO2peak ) were associated with higher BPND  in the striatum. Following the intervention, for both forms of training, we found reduced BPND , indicating increased dopamine (DA), in a cluster in the anterior striatum in individuals with larger improvements in VO2peak . This reduction in BPND  mediated a positive indirect effect of VO2peak  on working-memory updating performance. Collectively these findings implicate DA as a neurocognitive mechanism explaining the positive effects of staying physically active at an old age for working memory.

National Category
Neurosciences
Identifiers
URN: urn:nbn:se:umu:diva-139053OAI: oai:DiVA.org:umu-139053DiVA: diva2:1138586
Projects
PHIBRA
Funder
Västerbotten County CouncilSwedish Research Council, 2012- 00530
Available from: 2017-09-06 Created: 2017-09-06 Last updated: 2017-09-06
In thesis
1. Aerobic fitness and healthy brain aging: cognition, brain structure, and dopamine
Open this publication in new window or tab >>Aerobic fitness and healthy brain aging: cognition, brain structure, and dopamine
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Aerobisk träning och hjärnans hälsosamma åldrande : kognition, hjärnstruktur och dopamin
Abstract [en]

Background: Performing aerobic exercise and maintaining high levels of aerobic fitness may have positive effects on both brain structure and function in older adults. Despite decades of research however, there is still a rather poor understanding of the neurocognitive mechanisms explaining the positive effects of aerobic exercise on cognition. Changes in prefrontal gray matter as well as dopaminergic neurotransmission in striatum are both candidate neurocognitive mechanisms. The main aims of this thesis are: 1. To investigate the effects of aerobic exercise and fitness on cognition and magnetic resonance imaging (MRI) derived gray matter volumes using data from a 6 month physical exercise intervention in older adults (Study I). 2. To simulate the effect of atrophy in longitudinal positron emission tomography (PET) which could pose a challenge to interpreting changes in longitudinal PET imaging (Study II). 3. To study the influence of aerobic exercise and fitness on the dopamine D2-receptor (D2R) system in striatum using [11C]raclopride PET as a potential mechanism for improved cognition (Study III).

Results: In Study I, aerobic exercise was found to improve cognitive performance in a broad, rather than domain-specific sense. Moreover, aerobic fitness was related to prefrontal cortical thickness, and improved aerobic fitness over 6 months was related to increased hippocampal volume. In Study II, we identified areas in the striatum vulnerable to the effect of shrinkage, which should be considered in longitudinal PET imaging. Finally, in Study III, the effect of being aerobically fit, and improving fitness levels was found to impact dopaminergic neurotransmission in the striatum, which in turn mediated fitness-induced improvements in working memory updating performance.

Conclusion: The findings in this thesis provide novel evidence regarding the neurocognitive mechanisms of aerobic exercise-induced improvements in cognition, and impacts the interpretation of longitudinal PET imaging. Performing aerobic exercise and staying aerobically fit at an older age have positive effects on cognition and brain systems important for memory and cognition. Specifically, fitness-induced changes to the dopaminergic system stands out as one novel neurocognitive mechanism explaining the positive effects of aerobic fitness on working-memory performance in healthy older adults.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2017. 81 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1908
Keyword
Aerobic exercise, VO2, working memory, executive function, freesurfer, striatum, dopamine, D2-receptors, [11C]raclopride
National Category
Neurosciences Sport and Fitness Sciences
Identifiers
urn:nbn:se:umu:diva-139056 (URN)978-91-7601-753-1 (ISBN)
Public defence
2017-09-29, Sal 933, Building 3B, Norrland University Hospital, Umeå, 09:35 (English)
Opponent
Supervisors
Available from: 2017-09-08 Created: 2017-09-06 Last updated: 2017-09-26Bibliographically approved

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