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Sökning: WFRF:(Kalpouzos Grégoria) > Karolinska Institutet

  • Resultat 1-10 av 37
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1.
  • Becker, Nina, et al. (författare)
  • Structural brain correlates of associative memory in older adults
  • 2015
  • Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 118, s. 146-153
  • Tidskriftsartikel (refereegranskat)abstract
    • Associative memory involves binding two or more items into a coherent memory episode. Relative to memory for single items, associative memory declines greatly in aging. However, older individuals vary substantially in their ability to memorize associative information. Although functional studies link associative memory to the medial temporal lobe (MTL) and prefrontal cortex (PFC), little is known about how volumetric differences in MTL and PFC might contribute to individual differences in associative memory. We investigated regional gray-matter volumes related to individual differences in associative memory in a sample of healthy older adults (n = 54; age = 60 years). To differentiate item from associative memory, participants intentionally learned face-scene picture pairs before performing a recognition task that included single faces, scenes, and face-scene pairs. Gray-matter volumes were analyzed using voxel-based morphometry region-of-interest (ROI) analyses. To examine volumetric differences specifically for associative memory, item memory was controlled for in the analyses. Behavioral results revealed large variability in associative memory that mainly originated from differences in false-alarm rates. Moreover, associative memory was independent of individuals' ability to remember single items. Older adults with better associative memory showed larger gray-matter volumes primarily in regions of the left and right lateral PFC. These findings provide evidence for the importance of PFC in intentional learning of associations, likely because of its involvement in organizational and strategic processes that distinguish older adults with good from those with poor associative memory.
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2.
  • Brehmer, Yvonne, et al. (författare)
  • Plasticity of brain and cognition in older adults
  • 2014
  • Ingår i: Psychological Research. - : Springer Science and Business Media LLC. - 0340-0727 .- 1430-2772. ; 78:6, s. 790-802
  • Forskningsöversikt (refereegranskat)abstract
    • Aging is typically related to changes in brain and cognition, but the aging process is heterogeneous and differs between individuals. Recent research has started investigating the influence of cognitive and physical training on cognitive performance, functional brain activity, and brain structure in old age. The functional relevance of neural changes and the interactions among these changes following interventions is still a matter of debate. Here we selectively review research on structural and functional brain correlates of training-induced performance changes in healthy older adults and present exemplary longitudinal intervention studies sorted by the type of training applied (i.e., strategy-based training, process-specific training, and physical exercise). Although many training studies have been conducted recently, within each task domain, the number of studies that used comparable methods and techniques to assess behavioral and neural changes is limited. We suggest that future studies should include a multimodal approach to enhance the understanding of the relation between different levels of brain changes in aging and those changes that result from training. Investigating inter-individual differences in intervention-induced behavioral and neuronal changes would provide more information about who would benefit from a specific intervention and why. In addition, a more systematic examination of the time course of training-related structural and functional changes would improve the current level of knowledge about how learning is implemented in the brain and facilitate our understanding of contradictory results.
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3.
  • Dintica, Christina S., et al. (författare)
  • Tooth loss is associated with accelerated cognitive decline and volumetric brain differences : a population-based study
  • 2018
  • Ingår i: Neurobiology of Aging. - : Elsevier BV. - 0197-4580 .- 1558-1497. ; 67, s. 23-30
  • Tidskriftsartikel (refereegranskat)abstract
    • Tooth loss has been related to cognitive impairment; however, its relation to structural brain differences in humans is unknown. Dementia-free participants (n = 2715) of age >= 60 years were followed up for up to 9 years. A subsample (n = 394) underwent magnetic resonance imaging at baseline. Information on tooth loss was collected at baseline, and cognitive function was assessed using the Mini-Mental State Examination at baseline and at follow-ups. Data were analyzed using linear mixed effects models and linear regression models. At baseline, 404 (14.9%) participants had partial tooth loss, and 206 (7.6%) had complete tooth loss. Tooth loss was significantly associated with a steeper cognitive decline (beta: -0.18, 95% confidence interval [CI]: -0.24 to -0.11) and remained significant after adjusting for or stratifying by potential confounders. In cross-sectional analyses, persons with complete or partial tooth loss had significantly lower total brain volume (beta: -28.89, 95% CI: -49.33 to -8.45) and gray matter volume (beta: -22.60, 95% CI: -38.26 to -6.94). Thus, tooth loss may be a risk factor for accelerated cognitive aging.
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4.
  • Dong, Yi, et al. (författare)
  • Anosmia, mild cognitive impairment, and biomarkers of brain aging in older adults
  • 2023
  • Ingår i: Alzheimer's & Dementia. - : Wiley. - 1552-5260 .- 1552-5279. ; 19:2, s. 589-601
  • Tidskriftsartikel (refereegranskat)abstract
    • Olfactory impairment is a potential marker for prodromal dementia, but the underlying mechanisms are poorly understood. This population-based study included 4214 dementia-free participants (age ≥65 years). Olfaction was assessed using the 16-item Sniffin’ Sticks identification test. In the subsamples, we measured plasma amyloid beta (Aβ)40, Aβ42, total tau, and neurofilament light chain (NfL; n = 1054); and quantified hippocampal, entorhinal cortex, and white matter hyperintensity (WMH) volumes, and Alzheimer's disease (AD)-signature cortical thickness (n = 917). Data were analyzed with logistic and linear regression models. In the total sample, mild cognitive impairment (MCI) was diagnosed in 1102 persons (26.2%; amnestic MCI, n = 931; non-amnestic MCI, n = 171). Olfactory impairment was significantly associated with increased likelihoods of MCI, amnestic MCI, and non-amnestic MCI. In the subsamples, anosmia was significantly associated with higher plasma total tau and NfL concentrations, smaller hippocampal and entorhinal cortex volumes, and greater WMH volume, and marginally with lower AD-signature cortical thickness. These results suggest that cerebral neurodegenerative and microvascular lesions are common neuropathologies linking anosmia with MCI in older adults.
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5.
  • Ferencz, Beata, et al. (författare)
  • Promising Genetic Biomarkers of Preclinical Alzheimer's Disease : The Influence of APOE and TOMM40 on Brain Integrity
  • 2012
  • Ingår i: International Journal of Alzheimer's Disease. - : Hindawi Limited. - 2090-8024 .- 2090-0252. ; 2012
  • Forskningsöversikt (refereegranskat)abstract
    • Finding biomarkers constitutes a crucial step for early detection of Alzheimer's disease (AD). Brain imaging techniques have revealed structural alterations in the brain that may be phenotypic in preclinical AD. The most prominent polymorphism that has been associated with AD and related neural changes is the Apolipoprotein E (APOE) ε4. The translocase of outer mitochondrial membrane 40 (TOMM40), which is in linkage disequilibrium with APOE, has received increasing attention as a promising gene in AD. TOMM40 also impacts brain areas vulnerable in AD, by downstream apoptotic processes that forego extracellular amyloid beta aggregation. The present paper aims to extend on the mitochondrial influence in AD pathogenesis and we propose a TOMM40-induced disconnection of the medial temporal lobe. Finally, we discuss the possibility of mitochondrial dysfunction being the earliest pathophysiological event in AD, which indeed is supported by recent findings.
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6.
  • Ferencz, Beata, et al. (författare)
  • The Benefits of Staying Active in Old Age : Physical Activity Counteracts the Negative Influence of PICALM, BIN1, and CLU Risk Alleles on Episodic Memory Functioning
  • 2014
  • Ingår i: Psychology and Aging. - : American Psychological Association (APA). - 0882-7974 .- 1939-1498. ; 29:2, s. 440-449
  • Tidskriftsartikel (refereegranskat)abstract
    • PICALM, BIN1, CLU, and APOE are top candidate genes for Alzheimer's disease, and they influence episodic memory performance in old age. Physical activity, however, has been shown to protect against age-related decline and counteract genetic influences on cognition. The aims of this study were to assess whether (a) a genetic risk constellation of PICALM, BIN1, and CLU polymorphisms influences cognitive performance in old age; and (b) if physical activity moderates this effect. Data from the SNAC-K population-based study were used, including 2,480 individuals (age range = 60 to 100 years) free of dementia at baseline and at 3- to 6-year follow-ups. Tasks assessing episodic memory, perceptual speed, knowledge, and verbal fluency were administered. Physical activity was measured using self-reports. Individuals who had engaged in frequent health-or fitness-enhancing activities within the past year were compared with those who were inactive. Genetic risk scores were computed based on an integration of risk alleles for PICALM (rs3851179 G allele, rs541458 T allele), BIN1 (rs744373 G allele), and CLU (rs11136000 T allele). High genetic risk was associated with reduced episodic memory performance, controlling for age, education, vascular risk factors, chronic diseases, activities of daily living, and APOE gene status. Critically, physical activity attenuated the effects of genetic risk on episodic memory. Our findings suggest that participants with high genetic risk who maintain a physically active lifestyle show selective benefits in episodic memory performance.
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7.
  • Garzon, Benjamin, et al. (författare)
  • Automated segmentation of midbrain structures with high iron content
  • 2018
  • Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 170, s. 199-209
  • Forskningsöversikt (refereegranskat)abstract
    • The substantia nigra (SN), the subthalamic nucleus (STN), and the red nucleus (RN) are midbrain structures of ample interest in many neuroimaging studies, which may benefit from the availability of automated segmentation methods. The high iron content of these structures awards them high contrast in quantitative susceptibility mapping (QSM) images. We present a novel segmentation method that leverages the information of these images to produce automated segmentations of the SN, STN, and RN. The algorithm builds a map of spatial priors for the structures by non-linearly registering a set of manually-traced training labels to the midbrain. The priors are used to inform a Gaussian mixture model of the image intensities, with smoothness constraints imposed to ensure anatomical plausibility. The method was validated on manual segmentations from a sample of 40 healthy younger and older subjects. Average Dice scores were 0.81 (0.05) for the SN, 0.66 (0.14) for the STN and 0.88 (0.04) for the RN in the left hemisphere, and similar values were obtained for the right hemisphere. In all structures, volumes of manual and automatically obtained segmentations were significantly correlated. The algorithm showed lower accuracy on R-2* and T-2-weighted Fluid Attenuated Inversion Recovery (FLAIR) images, which are also sensitive to iron content. To illustrate an application of the method, we show that the automated segmentations were comparable to the manual ones regarding detection of age-related differences to putative iron content.
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8.
  • Garzón, Benjamin, et al. (författare)
  • Can transverse relaxation rates in deep gray matter be approximated from functional and T-2-weighted FLAIR scans for relative brain iron quantification?
  • 2017
  • Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 0730-725X .- 1873-5894. ; 40, s. 75-82
  • Tidskriftsartikel (refereegranskat)abstract
    • Alterations in iron concentration in certain deep gray matter regions are known to occur in aging and several clinical conditions. In vivo measurements of R-2* transverse relaxation rates and quantitative susceptibility mapping (QSM) have been shown to be strongly correlated with iron concentration in tissue, but their calculation requires the acquisition of a multi-echo gradient recalled echo sequence (MGRE). In the current study, we examined the feasibility of approximating R-2* rates using metrics derived from fMRI-EPI and T-2-weighted FLAIR images, which are widely available. In a sample of 40 healthy subjects, we obtained these metrics (v(EPI) and v(FLAIR)), as well as R-2* rates and QSM estimates, and found significant correlations between v(EPI) and v(FLAIR) and R-2* rates in several subcortical gray matter regions known to accumulate iron, but not in a control corticospinal white matter region. These relationships were preserved after referencing v(EPI) and v(FLAIR) with respect to the values in the control region. Effect sizes (above 0.5 for some of the regions, particularly the largest ones) were calculated and put in relation to those of the correlation between QSM and R-2* rates. We propose that the metrics described here may be applied, possibly in a retrospective fashion, to analyze datasets with available EPI or T-2-weighted FLAIR scans (and lacking a MGRE sequence), to devise new hypotheses regarding links between iron concentration in brain tissue and other variables of interest.
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9.
  • Gerritsen, L., et al. (författare)
  • The influence of negative life events on hippocampal and amygdala volumes in old age : a life-course perspective
  • 2014
  • Ingår i: Psychological Medicine. - 0033-2917 .- 1469-8978. ; 45:6, s. 1219-1228
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Psychosocial stress has been related to changes in the nervous system, with both adaptive and maladaptive consequences. The aim of this study was to examine the relationship of negative events experienced throughout the entire lifespan and hippocampal and amygdala volumes in older adults.METHOD: In 466 non-demented old adults (age range 60-96 years, 58% female), hippocampal and amygdala volumes were segmented using Freesurfer. Negative life events and the age at which these events occurred were assessed by means of a structured questionnaire. Using generalized linear models, hippocampal and amygdala volumes were estimated with life events as independent variables. The statistical analyses were adjusted for age, gender, intracranial volume, lifestyle factors, cardiovascular risk factors, depressive symptoms, and cognitive functioning.RESULTS: Total number of negative life events and of late-life events, but not of early-life, early-adulthood, or middle-adulthood events, was related to larger amygdala volume. There were interactions of early-life events with age and gender. Participants who reported two or more early-life events had significantly smaller amygdala and hippocampal volumes with increasing age. Furthermore, smaller hippocampal volume was found in men who reported two or more early-life events, but not in women.CONCLUSIONS: These results suggest that the effect of negative life events on the brain depends on the time when the events occurred, with the strongest effects observed during the critical time periods of early and late life.
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10.
  • Gonneaud, Julie, et al. (författare)
  • Distinct and shared cognitive functions mediate event- and time-based prospective memory impairment in normal ageing
  • 2011
  • Ingår i: Memory. - : Informa UK Limited. - 0965-8211 .- 1464-0686. ; 19:4, s. 360-377
  • Tidskriftsartikel (refereegranskat)abstract
    • Prospective memory (PM) is the ability to remember to perform an action at a specific point in the future. Regarded as multidimensional, PM involves several cognitive functions that are known to be impaired in normal ageing. In the present study we set out to investigate the cognitive correlates of PM impairment in normal ageing. Manipulating cognitive load, we assessed event- and time-based PM, as well as several cognitive functions, including executive functions, working memory, and retrospective episodic memory, in healthy participants covering the entire adulthood. We found that normal ageing was characterised by PM decline in all conditions and that event-based PM was more sensitive to the effects of ageing than time-based PM. Whatever the conditions, PM was linked to inhibition and processing speed. However, while event-based PM was mainly mediated by binding and retrospective memory processes, time-based PM was mainly related to inhibition. The only distinction between high- and low-load PM cognitive correlates lies in an additional, but marginal, correlation between updating and the high-load PM condition. The association of distinct cognitive functions, as well as shared mechanisms with event- and time-based PM, confirm that each type of PM relies on a different set of processes.
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  • Resultat 1-10 av 37

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