| 1. |
- Jonasson Stiernman, Lars, 1983-, et al.
(författare)
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Dissociations between glucose metabolism and blood oxygenation in the human default mode network revealed by simultaneous PET-fMRI
- 2021
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 118:27
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Tidskriftsartikel (refereegranskat)abstract
- The finding of reduced functional MRI (fMRI) activity in the default mode network (DMN) during externally focused cognitive control has been highly influential to our understanding of human brain function. However, these negative fMRI responses, measured as relative decreases in the blood-oxygenation-level-dependent (BOLD) response between rest and task, have also prompted major questions of interpretation. Using hybrid functional positron emission tomography (PET)-MRI, this study shows that task-positive and -negative BOLD responses do not reflect antagonistic patterns of synaptic metabolism. Task-positive BOLD responses in attention and control networks were accompanied by concomitant increases in glucose metabolism during cognitive control, but metabolism in widespread DMN remained high during rest and task despite negative BOLD responses. Dissociations between glucose metabolism and the BOLD response specific to the DMN reveal functional heterogeneity in this network and demonstrate that negative BOLD responses during cognitive control should not be interpreted to reflect relative increases in metabolic activity during rest. Rather, neurovascular coupling underlying BOLD response patterns during rest and task in DMN appears fundamentally different from BOLD responses in other association networks during cognitive control.
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| 2. |
- Simonsson, Emma, et al.
(författare)
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Dopamine d2/3-receptor availability and its association with autonomous motivation to exercise in older adults : an exploratory [11c]-raclopride study
- 2022
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Ingår i: Frontiers in Human Neuroscience. - : Frontiers Media S.A.. - 1662-5161. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- Background: Autonomous motivation to exercise occurs when the activity is voluntary and with a perceived inherent satisfaction from the activity itself. It has been suggested that autonomous motivation is related to striatal dopamine D2/3-receptor (D2/3R) availability within the brain. In this study, we hypothesized that D2/3R availability in three striatal regions (nucleus accumbens, caudate nucleus, and putamen) would be positively associated with self-reported autonomous motivation to exercise. We also examined this relationship with additional exploratory analyses across a set of a priori extrastriatal regions of interest (ROI).Methods: Our sample comprised 49 older adults (28 females) between 64 and 78 years of age. The D2/3R availability was quantified from positron emission tomography using the non-displaceable binding potential of [11C]-raclopride ligand. The exercise-related autonomous motivation was assessed with the Swedish version of the Behavioral Regulations in Exercise Questionnaire-2.Results: No significant associations were observed between self-reported autonomous motivation to exercise and D2/3R availability within the striatum (nucleus accumbens, caudate nucleus, and putamen) using semi-partial correlations controlling for ROI volume on D2/3R availability. For exploratory analyses, positive associations were observed for the superior (r = 0.289, p = 0.023) and middle frontal gyrus (r = 0.330, p = 0.011), but not for the inferior frontal gyrus, orbitofrontal cortex, anterior cingulate cortex, or anterior insular cortex.Conclusion: This study could not confirm the suggested link between striatal D2/3R availability and subjective autonomous motivation to exercise among older adults. The exploratory findings, however, propose that frontal brain regions may be involved in the intrinsic regulation of exercise-related behaviors, though this has to be confirmed by future studies using a more suitable ligand and objective measures of physical activity levels.
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| 3. |
- Stiernman Jonasson, Lars, 1983-, et al.
(författare)
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Impact of aerobic exercise on brain structure in models of aging : Hippocampus and beyond
- 2021
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Ingår i: Factors Affecting Neurological Aging. - : Elsevier. - 9780128179901 ; , s. 403-413
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Bokkapitel (refereegranskat)abstract
- Evidence from multiple scientific disciplines indicates that aerobic exercise could be effective in enhancing brain health and function in aging, and reducing the risk for cognitive impairment and dementia. Animal models have provided convincing evidence that exercise increases the expression of growth factors involved in neuroplasticity. By triggering signaling cascades in the brain, these growth factors promote proliferation, neurogenesis, neural differentiation, and cell survival in the hippocampus, and angiogenesis and/or synaptic plasticity and neural growth throughout the brain more generally. These growth factor-induced effects partly explain why exercise improves memory. Furthermore, they engender neuroprotective effects by influencing regeneration, remyelination, cell survival, and waste removal. Whereas human intervention evidence supports hippocampal plasticity, cross-sectional studies highlight effects in the cortex too, indicating that exercise-induced gross morphological changes may be regionally specific. Aerobic exercise is a promising nonpharmacological therapy to maintain brain health, although knowledge about the effects of specific exercise parameters (i.e., intensity) on different populations is still lacking.
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