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| 2. |
- Rieckmann, Anna, et al.
(författare)
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Accelerated decline in white matter integrity in clinically normal individuals at risk for Alzheimer's disease
- 2016
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Ingår i: Neurobiology of Aging. - : Elsevier BV. - 0197-4580 .- 1558-1497. ; 42, s. 177-188
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Tidskriftsartikel (refereegranskat)abstract
- Prior studies have identified white matter abnormalities in Alzheimer's disease (AD). Yet, cross-sectional studies in normal older individuals show little evidence for an association between markers of AD risk (APOE4 genotype and amyloid deposition), and white matter integrity. Here, 108 normal older adults (age, 66-87) with assessments of apolipoprotein e4 (APOE4) genotype and assessment of amyloid burden by positron emission tomography underwent diffusion tensor imaging scans for measuring white matter integrity at 2 time points, on average 2.6 years apart. Linear mixed-effects models showed that amyloid burden at baseline was associated with steeper decline in fractional anisotropy in the parahippocampal cingulum (p < 0.05). This association was not significant between baseline measures suggesting that longitudinal analyses can provide novel insights that are not detectable in cross-sectional designs. Amyloid-related changes in hippocampus volume did not explain the association between amyloid burden and change in fractional anisotropy. The results suggest that accumulation of cortical amyloid and white matter changes in parahippocampal cingulum are not independent processes in individuals at increased risk for AD.
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| 3. |
- Hedden, Trey, et al.
(författare)
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Multiple Brain Markers are Linked to Age-Related Variation in Cognition
- 2016
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Ingår i: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 26:4, s. 1388-1400
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Tidskriftsartikel (refereegranskat)abstract
- Age-related alterations in brain structure and function have been challenging to link to cognition due to potential overlapping influences of multiple neurobiological cascades. We examined multiple brain markers associated with age-related variation in cognition. Clinically normal older humans aged 65-90 from the Harvard Aging Brain Study (N = 186) were characterized on a priori magnetic resonance imaging markers of gray matter thickness and volume, white matter hyperintensities, fractional anisotropy (FA), resting-state functional connectivity, positron emission tomography markers of glucose metabolism and amyloid burden, and cognitive factors of processing speed, executive function, and episodic memory. Partial correlation and mediation analyses estimated age-related variance in cognition shared with individual brain markers and unique to each marker. The largest relationships linked FA and striatum volume to processing speed and executive function, and hippocampal volume to episodic memory. Of the age-related variance in cognition, 70-80% was accounted for by combining all brain markers (but only ∼20% of total variance). Age had significant indirect effects on cognition via brain markers, with significant markers varying across cognitive domains. These results suggest that most age-related variation in cognition is shared among multiple brain markers, but potential specificity between some brain markers and cognitive domains motivates additional study of age-related markers of neural health.
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| 4. |
- Rieckmann, Anna, et al.
(författare)
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Dedifferentiation of caudate functional connectivity and striatal dopamine transporter density predict memory change in normal aging
- 2018
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Ingår i: Proceedings of the National Academy of Sciences. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 115:40, s. 10160-10165
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Tidskriftsartikel (refereegranskat)abstract
- Age-related changes in striatel function are potentially important for predicting declining memory performance over the adult life span. Here, we used fMRI to measure functional connectivity of caudate subfields with large-scale association networks and positron emission tomography to measure striatal dopamine transporter (DAT) density in 51 older adults (age 65-86 years) who received annual cognitive testing for up to 7 years (mean = 5.59, range 2-7 years). Analyses showed that cortical-caudate functional connectivity was less differentiated in older compared with younger adults (n = 63, age 18-32 years). Unlike in younger adults, the central lateral caudate was less strongly coupled with the frontal parietal control network in older adults. Older adults also showed less "decoupling" of the caudate from other networks, including areas of the default network (DN) and the hippocampal complex. Contrary to expectations, less decoupling between caudate and the DN was not associated with an age-related reduction of striatal DAT, suggesting that neurobiological changes in the cortex may drive dedifferentiation of cortical-caudate connectivity. Reduction of specificity in functional coupling between caudate and regions of the DN predicted memory decline over subsequent years at older ages. The age-related reduction in striatal DAT density also predicted memory decline, suggesting that a relation between striatal functions and memory decline in aging is multifaceted. Collectively, the study provides evidence highlighting the association of age-related differences in striatal function to memory decline in normal aging.
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| 5. |
- Rieckmann, Anna, et al.
(författare)
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Dopamine transporter availability in clinically normal aging is associated with individual differences in white matter integrity
- 2016
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Ingår i: Human Brain Mapping. - : Wiley-Blackwell. - 1065-9471 .- 1097-0193. ; 37:2, s. 621-631
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Tidskriftsartikel (refereegranskat)abstract
- Aging-related differences in white matter integrity, the presence of amyloid plaques, and density of biomarkers indicative of dopamine functions can be detected and quantified with in vivo human imaging. The primary aim of the present study was to investigate whether these imaging-based measures constitute independent imaging biomarkers in older adults, which would speak to the hypothesis that the aging brain is characterized by multiple independent neurobiological cascades. We assessed MRI-based markers of white matter integrity and PET-based marker of dopamine transporter density and amyloid deposition in the same set of 53 clinically normal individuals (age 65-87). A multiple regression analysis demonstrated that dopamine transporter availability is predicted by white matter integrity, which was detectable even after controlling for chronological age. Further post-hoc exploration revealed that dopamine transporter availability was further associated with systolic blood pressure, mirroring the established association between cardiovascular health and white matter integrity. Dopamine transporter availability was not associated with the presence of amyloid burden. Neurobiological correlates of dopamine transporter measures in aging are therefore likely unrelated to Alzheimer's disease but are aligned with white matter integrity and cardiovascular risk. More generally, these results suggest that two common imaging markers of the aging brain that are typically investigated separately do not reflect independent neurobiological processes.
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| 6. |
- Rieckmann, Anna, et al.
(författare)
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Putamen-midbrain functional connectivity is related to striatal dopamine transporter availability in patients with Lewy body diseases
- 2015
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Ingår i: NeuroImage. - : Elsevier. - 2213-1582. ; 8, s. 554-559
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Tidskriftsartikel (refereegranskat)abstract
- Prior work has shown that functional connectivity between the midbrain and putamen is altered in patients with impairments in the dopamine system. This study examines whether individual differences in midbrain-striatal connectivity are proportional to the integrity of the dopamine system in patients with nigrostriatal dopamine loss (Parkinson's disease and dementia with Lewy bodies). We assessed functional connectivity of the putamen during resting state fMRI and dopamine transporter (DAT) availability in the striatum using 11C-Altropane PET in twenty patients. In line with the hypothesis that functional connectivity between the midbrain and the putamen reflects the integrity of the dopaminergic neurotransmitter system, putamen-midbrain functional connectivity was significantly correlated with striatal DAT availability even after stringent control for effects of head motion. DAT availability did not relate to functional connectivity between the caudate and thalamus/prefrontal areas. As such, resting state functional connectivity in the midbrain-striatal pathway may provide a useful indicator of underlying pathology in patients with nigrostriatal dopamine loss.
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| 7. |
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| 8. |
- Comi, G, et al.
(författare)
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Effects of early treatment with glatiramer acetate in patients with clinically isolated syndrome
- 2013
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Ingår i: Multiple sclerosis (Houndmills, Basingstoke, England). - : SAGE Publications. - 1477-0970 .- 1352-4585. ; 19:8, s. 1074-1083
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Tidskriftsartikel (refereegranskat)abstract
- The placebo-controlled phase of the PreCISe study showed that glatiramer acetate delayed onset of clinically definite multiple sclerosis (CDMS) in patients with clinically isolated syndrome and brain lesions on MRI. Objective: To compare the effects of early versus delayed glatiramer acetate treatment in the open-label phase of PreCISe. Methods: Patients with a clinically isolated syndrome suggestive of MS with unifocal manifestation and ≥2 T2-weighted brain lesions were randomized to receive glatiramer acetate 20 mg/d (early-treatment, n=198) or placebo (delayed-treatment, n=211) for 36 months or until conversion to CDMS, followed by open-label glatiramer acetate treatment for two years. Results: Early glatiramer acetate treatment reduced CDMS conversion risk by 41% (hazard ratio 0.59, 95% confidence interval 0.44–0.80; p=0.0005) versus delayed-treatment, and was associated with a 972-day delay (185%) in conversion to CDMS, less brain atrophy (−28%, p=0.0209), fewer new T2 lesions/year (−42%, <0.0001) and lower T2 lesion volume (−22%, p=0.0005) versus delayed treatment. Adverse events were consistent with the established safety profile of glatiramer acetate. Conclusions: Effects of early glatiramer acetate treatment on the rate of conversion to CDMS and on MRI measures of disease activity and lesion burden support initiating glatiramer acetate treatment soon after the first clinical symptoms suggestive of MS and continuing treatment to sustain benefits.
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| 9. |
- Ebner, Natalie C., et al.
(författare)
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Processing own-age vs. other-age faces : Neuro-behavioral correlates and effects of emotion
- 2013
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Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 78, s. 363-371
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Tidskriftsartikel (refereegranskat)abstract
- Age constitutes a salient feature of a face and signals group membership. There is evidence of greater attention to and better memory for own-age than other-age faces. However, little is known about the neural and behavioral mechanisms underlying processing differences for own-age vs. other-age faces. Even less is known about the impact of emotion expressed in faces on such own-age effects. Using fMRI, the present study examined brain activity while young and older adult participants identified expressions of neutral, happy, and angry young and older faces. Across facial expressions, medial prefrontal cortex, insula, and (for older participants) amygdala showed greater activity to own-age than other-age faces. These own-age effects in ventral medial prefrontal cortex and insula held for neutral and happy faces, but not for angry faces. This novel and intriguing finding suggests that processing of negative facial emotions under some conditions overrides age-of-face effects.
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| 10. |
- Rypma, Bart, et al.
(författare)
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Dopamine D1 Binding Potential Predicts Fusiform BOLD Activity during Face-Recognition Performance
- 2015
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Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 35:44, s. 14702-14707
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Tidskriftsartikel (refereegranskat)abstract
- The importance of face memory in humans and primates is well established, but little is known about the neurotransmitter systems involved in face recognition. We tested the hypothesis that face recognition is linked to dopamine (DA) activity in fusiform gyrus (FFG). DA availability was assessed by measuring D1 binding potential (BP) during rest using PET. We further assessed blood-oxygen-level-dependent (BOLD) signal change while subjects performed a face-recognition task during fMRI scanning. There was a strong association between D1 BP and BOLD activity in FFG, whereasD1BPin striatal and other extrastriatal regions were unrelated to neural activity in FFG. These results suggest that D1 BP locally modulates FFG function during face recognition. Observed relationships among D1 BP, BOLD activity, and face-recognition performance further suggest that D1 receptors place constraints on the responsiveness of FFG neurons.
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