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Sökning: WFRF:(Duzel Emrah)

  • Resultat 1-10 av 27
  • [1]23Nästa
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1.
  • Maass, Anne, et al. (författare)
  • Relationships of peripheral IGF-1, VEGF and BDNF levels to exercise-related changes in memory, hippocampal perfusion and volumes in older adults
  • 2016
  • Ingår i: NeuroImage. - 1053-8119 .- 1095-9572. ; 131, s. 142-154
  • Tidskriftsartikel (refereegranskat)abstract
    • Animal models point towards a key role of brain-derived neurotrophic factor (BDNF), insulin-like growth factor-I (IGF-I) and vascular endothelial growth factor (VEGF) in mediating exercise-induced structural and functional changes in the hippocampus. Recently, also platelet derived growth factor-C (PDGF-C) has been shown to promote blood vessel growth and neuronal survival. Moreover, reductions of these neurotrophic and angiogenic factors in old age have been related to hippocampal atrophy, decreased vascularization and cognitive decline. In a 3-month aerobic exercise study, forty healthy older humans (60 to 77 years) were pseudo-randomly assigned to either an aerobic exercise group (indoor treadmill, n=21) or to a control group (indoor progressive-muscle relaxation/stretching, n=19). As reported recently, we found evidence for fitness-related perfusion changes of the aged human hippocampus that were closely linked to changes in episodic memory function. Here, we test whether peripheral levels of BDNF, IGF-I, VEGF or PDGF-C are related to changes in hippocampal blood flow, volume and memory performance. Growth factor levels were not significantly affected by exercise, and their changes were not related to changes in fitness or perfusion. However, changes in IGF-I levels were positively correlated with hippocampal volume changes (derived by manual volumetry and voxel-based morphometry) and late verbal recall performance, a relationship that seemed to be independent of fitness, perfusion or their changes over time. These preliminary findings link IGF-I levels to hippocampal volume changes and putatively hippocampus-dependent memory changes that seem to occur over time independently of exercise. We discuss methodological shortcomings of our study and potential differences in the temporal dynamics of how IGF-1, VEGF and BDNF may be affected by exercise and to what extent these differences may have led to the negative findings reported here.
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2.
  • Lövdén, Martin, et al. (författare)
  • Performance-Related Increases in Hippocampal N-acetylaspartate (NAA) Induced by Spatial Navigation Training Are Restricted to BDNF Val Homozygotes
  • 2011
  • Ingår i: Cerebral Cortex. - : Oxford University Press. - 1047-3211 .- 1460-2199. ; 21:6, s. 1435-1442
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent evidence indicates experience-dependent brain volume changes in humans, but the functional and histological nature of such changes is unknown. Here, we report that adult men performing a cognitively demanding spatial navigation task every other day over 4 months display increases in hippocampal N-acetylaspartate (NAA) as measured with magnetic resonance spectroscopy. Unlike measures of brain volume, changes in NAA are sensitive to metabolic and functional aspects of neural and glia tissue and unlikely to reflect changes in microvasculature. Training-induced changes in NAA were, however, absent in carriers of the Met substitution in the brain-derived neurotrophic factor (BDNF) gene, which is known to reduce activity-dependent secretion of BDNF. Among BDNF Val homozygotes, increases in NAA were strongly related to the degree of practice-related improvement in navigation performance and normalized to pretraining levels 4 months after the last training session. We conclude that changes in demands on spatial navigation can alter hippocampal NAA concentrations, confirming epidemiological studies suggesting that mental experience may have direct effects on neural integrity and cognitive performance. BDNF genotype moderates these plastic changes, in line with the contention that gene–context interactions shape the ontogeny of complex phenotypes.
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3.
  • Wenger, Elisabeth, et al. (författare)
  • Cortical thickness changes following spatial navigation training in adulthood and aging
  • 2012
  • Ingår i: NeuroImage. - : Elsevier. - 1053-8119 .- 1095-9572. ; 59:4, s. 3389-3397
  • Tidskriftsartikel (refereegranskat)abstract
    • A widespread network involving cortical and subcortical brain structures forms the neural substrate of human spatial navigation. Most studies investigating plasticity of this network have focused on the hippocampus. Here, we investigate age differences in cortical thickness changes evoked by four months of spatial navigation training in 91 men aged 20-30 or 60-70 years. Cortical thickness was automatically measured before, immediately after, and four months after termination of training. Younger as well as older navigators evidenced large improvements in navigation performance that were partly maintained after termination of training. Importantly, training-related cortical thickening in left precuneus and paracentral lobule were observed in young navigators only. Thus, spatial navigation training appears to affect cortical brain structure of young adults, but there is reduced potential for experience-dependent cortical alterations in old age.
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4.
  • Düzel, E., et al. (författare)
  • European Ultrahigh-Field Imaging Network for Neurodegenerative Diseases (EUFIND)
  • 2019
  • Ingår i: Alzheimer's and Dementia: Diagnosis, Assessment and Disease Monitoring. - : Elsevier. - 2352-8729. ; 11, s. 538-549
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduction: The goal of European Ultrahigh-Field Imaging Network in Neurodegenerative Diseases (EUFIND) is to identify opportunities and challenges of 7 Tesla (7T) MRI for clinical and research applications in neurodegeneration. EUFIND comprises 22 European and one US site, including over 50 MRI and dementia experts as well as neuroscientists. Methods: EUFIND combined consensus workshops and data sharing for multisite analysis, focusing on 7 core topics: clinical applications/clinical research, highest resolution anatomy, functional imaging, vascular systems/vascular pathology, iron mapping and neuropathology detection, spectroscopy, and quality assurance. Across these topics, EUFIND considered standard operating procedures, safety, and multivendor harmonization. Results: The clinical and research opportunities and challenges of 7T MRI in each subtopic are set out as a roadmap. Specific MRI sequences for each subtopic were implemented in a pilot study presented in this report. Results show that a large multisite 7T imaging network with highly advanced and harmonized imaging sequences is feasible and may enable future multicentre ultrahigh-field MRI studies and clinical trials. Discussion: The EUFIND network can be a major driver for advancing clinical neuroimaging research using 7T and for identifying use-cases for clinical applications in neurodegeneration. © 2018 The Authors
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5.
  • Guitart-Masip, Marc, et al. (författare)
  • Action versus valence in decision making
  • 2014
  • Ingår i: Trends in cognitive sciences. - 1364-6613 .- 1879-307X. ; 18:4, s. 194-202
  • Forskningsöversikt (refereegranskat)abstract
    • The selection of actions, and the vigor with which they are executed, are influenced by the affective valence of predicted outcomes. This interaction between action and valence significantly influences appropriate and inappropriate choices and is implicated in the expression of psychiatric and neurological abnormalities, including impulsivity and addiction. We review a series of recent human behavioral, neuroimaging, and pharmacological studies whose key design feature is an orthogonal manipulation of action and valence. These studies find that the interaction between the two is subject to the critical influence of dopamine. They also challenge existing views that neural representations in the striatum focus on valence, showing instead a dominance of the anticipation of action.
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6.
  • Guitart-Masip, Marc, et al. (författare)
  • Differential, but not opponent, effects of L-DOPA and citalopram on action learning with reward and punishment
  • 2014
  • Ingår i: Psychopharmacology. - 0033-3158 .- 1432-2072. ; 231:5, s. 955-966
  • Tidskriftsartikel (refereegranskat)abstract
    • Decision-making involves two fundamental axes of control namely valence, spanning reward and punishment, and action, spanning invigoration and inhibition. We recently exploited a go/no-go task whose contingencies explicitly decouple valence and action to show that these axes are inextricably coupled during learning. This results in a disadvantage in learning to go to avoid punishment and in learning to no-go to obtain a reward. The neuromodulators dopamine and serotonin are likely to play a role in these asymmetries: Dopamine signals anticipation of future rewards and is also involved in an invigoration of motor responses leading to reward, but it also arbitrates between different forms of control. Conversely, serotonin is implicated in motor inhibition and punishment processing. To investigate the role of dopamine and serotonin in the interaction between action and valence during learning. We combined computational modeling with pharmacological manipulation in 90 healthy human volunteers, using levodopa and citalopram to affect dopamine and serotonin, respectively. We found that, after administration of levodopa, action learning was less affected by outcome valence when compared with the placebo and citalopram groups. This highlights in this context a predominant effect of levodopa in controlling the balance between different forms of control. Citalopram had distinct effects, increasing participants' tendency to perform active responses independent of outcome valence, consistent with a role in decreasing motor inhibition. Our findings highlight the rich complexities of the roles played by dopamine and serotonin during instrumental learning.
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7.
  • Kuehn, Simone, et al. (författare)
  • Brain Areas Consistently Linked to Individual Differences in Perceptual Decision-making in Younger as well as Older Adults before and after Training
  • 2011
  • Ingår i: Journal of Cognitive Neuroscience. - Cambridge, Mass. : MIT Press. - 1530-8898 .- 0898-929X. ; 23:9, s. 2147-2158
  • Tidskriftsartikel (refereegranskat)abstract
    • Perceptual decision-making performance depends on several cognitive and neural processes. Here, we fit Ratcliff's diffusion model to accuracy data and reaction-time distributions from one numerical and one verbal two-choice perceptual-decision task to deconstruct these performance measures into the rate of evidence accumulation (i.e., drift rate), response criterion setting (i.e., boundary separation), and peripheral aspects of performance (i.e., nondecision time). These theoretical processes are then related to individual differences in brain activation by means of multiple regression. The sample consisted of 24 younger and 15 older adults performing the task in fMRI before and after 100 daily 1-hr behavioral training sessions in a multitude of cognitive tasks. Results showed that individual differences in boundary separation were related to striatal activity, whereas differences in drift rate were related to activity in the inferior parietal lobe. These associations were not significantly modified by adult age or perceptual expertise. We conclude that the striatum is involved in regulating response thresholds, whereas the inferior parietal lobe might represent decision-making evidence related to letters and numbers.
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8.
  • Loh, Eleanor, et al. (författare)
  • Parsing the Role of the Hippocampus in Approach-Avoidance Conflict
  • 2017
  • Ingår i: Cerebral Cortex. - 1047-3211 .- 1460-2199. ; 27:1, s. 201-215
  • Tidskriftsartikel (refereegranskat)abstract
    • The hippocampus plays a central role in the approach-avoidance conflict that is central to the genesis of anxiety. However, its exact functional contribution has yet to be identified. We designed a novel gambling task that generated approach-avoidance conflict while controlling for spatial processing. We fit subjects' behavior using a model that quantified the subjective values of choice options, and recorded neural signals using functional magnetic resonance imaging (fMRI). Distinct functional signals were observed in anterior hippocampus, with inferior hippocampus selectively recruited when subjects rejected a gamble, to a degree that covaried with individual differences in anxiety. The superior anterior hippocampus, in contrast, uniquely demonstrated value signals that were potentiated in the context of approach-avoidance conflict. These results implicate the anterior hippocampus in behavioral avoidance and choice monitoring, in a manner relevant to understanding its role in anxiety. Our findings highlight interactions between subregions of the hippocampus as an important focus for future study.
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9.
  • Lövdén, Martin, et al. (författare)
  • Experience-dependent plasticity of white-matter microstructure extends into old age
  • 2010
  • Ingår i: Neuropsychologia. - : Elsevier. - 0028-3932 .- 1873-3514. ; 48:13, s. 3878-3883
  • Tidskriftsartikel (refereegranskat)abstract
    • Experience-dependent alterations in the human brain's white-matter microstructure occur in early adulthood, but it is unknown whether such plasticity extends throughout life. We used cognitive training, diffusion-tensor imaging (DTI), and structural MRI to investigate plasticity of the white-matter tracts that connect the left and right hemisphere of the frontal lobes. Over a period of about 180 days, 20 younger adults and 12 older adults trained for a total of one hundred and one 1-h sessions on a set of three working memory, three episodic memory, and six perceptual speed tasks. Control groups were assessed at pre- and post-test. Training affected several DTI metrics and increased the area of the anterior part of the corpus callosum. These alterations were of similar magnitude in younger and older adults. The findings indicate that experience-dependent plasticity of white-matter microstructure extends into old age and that disruptions of structural interhemispheric connectivity in old age, which are pronounced in aging, are modifiable by experience and amenable to treatment.
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10.
  • Lövdén, Martin, et al. (författare)
  • Spatial navigation training protects the hippocampus against age-related changes during early and late adulthood
  • 2012
  • Ingår i: Neurobiology of Aging. - : Elsevier. - 0197-4580 .- 1558-1497. ; 33:3, s. 620.e9-620.e22
  • Tidskriftsartikel (refereegranskat)abstract
    • It is unknown whether lifestyle, including mental stimulation, and appropriate training interventions, may directly improve spatial navigation performance and its underlying neural substrates. Here we report that healthy younger and older men performing a cognitively demanding spatial navigation task every other day over 4 months display navigation-related gains in performance and stable hippocampal volumes that were maintained 4 months after termination of training. In contrast, control groups displayed volume decrements consistent with longitudinal estimates of age-related decline. Hippocampal barrier density, as indicated by mean diffusivity estimated from diffusion tensor imaging, showed a quadratic shape of increased density after training followed by a return to baseline in the right hippocampus, but declined in the control groups and in the left hippocampus. We conclude that sustained experiential demands on spatial ability protect hippocampal integrity against age-related decline. These results provide the first longitudinal evidence indicating that spatial navigation experience modifies hippocampal volumes in humans, and confirm epidemiological results suggesting that mental stimulation may have direct effects on neural integrity.
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  • Resultat 1-10 av 27
  • [1]23Nästa

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