| 1. |
- Kalpouzos, Grégoria, et al.
(författare)
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Higher Striatal Iron Concentration is Linked to Frontostriatal Underactivation and Poorer Memory in Normal Aging
- 2017
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Ingår i: Cerebral Cortex. - : Oxford University Press. - 1047-3211 .- 1460-2199. ; 27:6, s. 3427-3436
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Tidskriftsartikel (refereegranskat)abstract
- In the brain, intracellular iron is essential for cellular metabolism. However, an overload of free iron is toxic, inducing oxidative stress and cell death. Although an increase of striatal iron has been related to atrophy and impaired cognitive performance, the link between elevated iron and altered brain activity in aging remains unexplored. In a sample of 37 younger and older adults, we examined whether higher striatal iron concentration could underlie age-related differences in frontostriatal activity induced by mental imagery of motor and non-motor scenes, and poorer recall of the scenes. Higher striatal iron concentration was linked to underrecruitment of frontostriatal regions regardless of age and striatal volume, the iron-activity association in right putamen being primarily driven by the older adults. In older age, higher striatal iron was related to poorer memory. Altered astrocytic functions could account for the link between brain iron and brain activity, as astrocytes are involved in iron buffering, neurovascular coupling, and synaptic activity. Our preliminary findings, which need to be replicated in a larger sample, suggest a potential frontostriatal target for intervention to counteract negative effects of iron accumulation on brain function and cognition.
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| 2. |
- Li, Xin, et al.
(författare)
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Influence of the DRD2/ANKK1 Taq1A polymorphism on caudate volume in older adults without dementia
- 2018
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Ingår i: Brain Structure and Function. - : Springer. - 1863-2653 .- 1863-2661. ; 223:6, s. 2653-2662
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Tidskriftsartikel (refereegranskat)abstract
- Dopaminergic neuromodulation is critically important for brain and cognitive integrity. The DRD2/ANKK1 Taq1A polymorphism is associated with striatal dopamine (DA) D2 receptor availability. Some previous studies have found that the A allele of the Taq1A polymorphism influences brain structure, but the results are inconsistent, likely due to population heterogeneity and small sample sizes. We investigated the genetic effect on caudate volume in a large sample of older adults without dementia. Results show that A-allele carriers have smaller caudate volume compared to non-carriers in relatively older adults (n = 167; Mage = 77.8 years), whereas the genotype did not influence caudate volume in a younger age group (n = 220; Mage = 62.8 years). Cognitive performance was not significantly affected by the DRD2 gene. Our findings extend previous observations by showing magnified genetic effects on brain volume in old age, and provide evidence for a link between a DA-related genetic polymorphism and grey matter volume in a brain region within the nigrostriatal dopaminergic pathway.
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| 3. |
- Li, Xin, et al.
(författare)
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The relationship of age and DRD2 polymorphisms to frontostriatal brain activity and working memory performance
- 2019
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Ingår i: Neurobiology of Aging. - : Elsevier. - 0197-4580 .- 1558-1497. ; 84, s. 189-199
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Tidskriftsartikel (refereegranskat)abstract
- Dopamine (DA) in both prefrontal cortex (PFC) and caudate nucleus is critical for working memory (WM) function. The C957T and Taq1A polymorphisms of the DRD2 gene are related to DA D2 receptor densities in PFC and striatum. Using functional MRI, we investigated the relationship of age and these 2 DRD2 gene polymorphisms to WM function and examined possible age by gene interactions. Results demonstrated less caudate activity for older adults (70-80 years; n = 112) compared with the younger age group (25-65 years; n = 191), suggesting age-related functional differences in this region. Importantly, there was a gene-related difference regarding WM performance and frontostriatal brain activity. Specifically, better WM performance and greater activity in PFC were found among C957T C allele carriers. Combined genetic markers for increased DA D2 receptor density were associated with greater caudate activity and higher WM updating performance. The genetic effects on blood oxygen level-dependent activity were only observed in older participants, suggesting magnified genetic effects in aging. Our findings emphasize the importance of DA-related genes in regulating WM functioning in aging and demonstrate a positive link between DA and brain activation in the frontostriatal circuitry.
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| 4. |
- Papenberg, Goran, et al.
(författare)
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Genetics and Functional Imaging : Effects of APOE, BDNF, COMT, and KIBRA in Aging
- 2015
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Ingår i: Neuropsychology Review. - : Springer. - 1040-7308 .- 1573-6660. ; 25:1, s. 47-62
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Forskningsöversikt (refereegranskat)abstract
- Increasing evidence from cross-sectional and longitudinal molecular-genetic studies suggests that effects of common genetic variations on cognitive functioning increase with aging. We review the influence of candidate genes on brain functioning in old age, focusing on four genetic variations that have been extensively investigated: APOE, BDNF, COMT, and KIBRA. Similar to the behavioral evidence, there are reports from age-comparative studies documenting stronger genetic effects on measures of brain functioning in older adults compared to younger adults. This pattern suggests disproportionate impairments of neural processing among older individuals carrying disadvantageous genotypes. We discuss various factors, including gene-gene interactions, study population characteristics, lifestyle factors, and diseases, that need to be considered in future studies and may help understand inconsistent findings in the extant literature.
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| 5. |
- Persson, Jonas, et al.
(författare)
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Influences of a DRD2 polymorphism on updating of long-term memory representations and caudate BOLD activity : magnification in aging
- 2015
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Ingår i: Human Brain Mapping. - : Wiley. - 1065-9471 .- 1097-0193. ; 36:4, s. 1325-1334
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Tidskriftsartikel (refereegranskat)abstract
- A number of genetic polymorphisms are related to individual differences in cognitive performance. Striatal dopamine (DA) functions, associated with cognitive performance, are linked to the TaqIA polymorphism of the DRD2/ANKK1 gene. In humans, presence of an A1 allele of the DRD2/ANKK1-TaqIA polymorphism is related to reduced density of striatal DA D2 receptors. The resource-modulation hypothesis assumes that aging-related losses of neurochemical and structural brain resources modulate the extent to which genetic variations affect cognitive functioning. Here, we tested this hypothesis using functional MRI during long-term memory (LTM) updating in younger and older carriers and noncarriers of the A1-allele of the TaqIa polymorphism. We demonstrate that older A1-carriers have worse memory performance, specifically during LTM updating, compared to noncarriers. Moreover, A1-carriers exhibited less blood oxygen level-dependent (BOLD) activation in left caudate nucleus, a region critical to updating. This effect was only seen in older adults, suggesting magnification of genetic effects on functional brain activity in aging. Further, a positive relationship between caudate BOLD activation and updating performance among non-A1 carriers indicated that caudate activation was behaviorally relevant. These results demonstrate a link between the DRD2/ANKK1-TaqIA polymorphism and neurocognitive deficits related to LTM updating, and provide novel evidence that this effect is magnified in aging.
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| 6. |
- Samrani, George, et al.
(författare)
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Age-Differences in the Temporal Properties of Proactive Interference in Working Memory
- 2017
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Ingår i: Psychology and Aging. - : American Psychological Association (APA). - 0882-7974 .- 1939-1498. ; 32:8, s. 722-731
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Tidskriftsartikel (refereegranskat)abstract
- The inability to suppress irrelevant information has been suggested as a primary cause of proactive interference (PI), and this deficit may be enhanced in aging. The current study examines age differences and temporal boundaries of PI, by manipulating lure distances in a verbal 2-back working memory task. Both younger and older adults showed effects of interference for proximal 3-and 4-back lures, and this effect was greater for older adults. Whereas younger adults showed less interference during 4-back compared to 3-back lures, in both reaction times and accuracy, older adults improved only in accuracy. For distant lures, when the time between the 1st presentation of an item to its reappearance as a lure item was longer (e.g., 5-to 10-back lures), younger adults were no longer affected by PI. However, older adults were affected by PI throughout all distant lures, up to the most distant lure (9-/10-back). The results suggest that older adults were less successful in resolving interference from both proximal and distant familiar lures. Further, younger adults were able to overcome the effects of PI completely after a specific lure distance. The age differences in temporal properties of PI may therefore highlight a unique component linked to impaired interference control and aging.
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| 7. |
- Samrani, George, et al.
(författare)
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Interference Control in Working Memory Is Associated with Ventrolateral Prefrontal Cortex Volume
- 2019
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Ingår i: Journal of cognitive neuroscience. - : MIT Press - Journals. - 0898-929X .- 1530-8898. ; 31:10, s. 1491-1505
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Tidskriftsartikel (refereegranskat)abstract
- Goal-irrelevant information may interfere with ongoing task activities if not controlled properly. Evidence suggests that the ability to control interference is connected mainly to the prefrontal cortex (pFC). However, it remains unclear whether gray matter (GM) volume in prefrontal regions influences individual differences in interference control (IC) and if these relationships are affected by aging. Using cross-sectional and longitudinal estimates over a 4- to 5-year period, we examined the relationship between relative IC scores, obtained from a 2-back working memory task, GM volumes, and performance in different cognitive domains. By identifying individuals with either no or high levels of interference, we demonstrated that participants with superior IC had larger volume of the ventrolateral pFC, regardless of participant demographics. The same pattern was observed both at baseline and follow-up. Cross-sectional estimates further showed that interference increased as a function of age, but interference did not change between baseline and follow-up. Similarly, across-sample associations between IC and pFC volume were found in the cross-sectional data, along with no longitudinal change-change relationships. Moreover, relative IC scores could be linked to composite scores of fluid intelligence, indicating that control of interference may relate to performance in expected cognitive domains. These results provide new evidence that a relative IC score can be related to volume of specific and relevant regions within pFC and that this relationship is not modulated by age. This supports a view that the GM volume in these regions plays a role in resisting interference during a working memory task.
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| 8. |
- Sibeck, Lennart, et al.
(författare)
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Högpresterande gjutna aluminiumkomponenter
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Projektet är en fortsättning och avrapportering av 3 års G-projekt inom högpresterande Al-legeringar, HPAL.Arbetet har fokuserat på att få ökad kunskap framförallt inom två områden; hur man kan öka hållfasthet respektive seghet hos kommersiella Al-Si-legeringar vid förhöjda temperaturer resp. rumstemperatur. En litteraturstudie har visat hur man genom tillsats av olika legeringstillsatser och användning av mer specialanpassade legeringar kan uppnå mycket goda egenskaper. I detta projekt har utgångspunkten varit konventionella legeringar. Bättre egenskaper skulle åstadkommas både genom optimering av legeringselement hos dessa och genom att minimera defektnivåer med förbättrad ingjutsteknik.Inför arbetet togs en ny provstavsmodell fram i CAD. För att visa flödets inverkan på defekter, och därmed hållfasthet, gjordes modellen i två versioner; bra resp. mindre bra ingjutssystem. Sandformarna togs fram med hjälp av 3D-skrivare. Resultaten av dragprovningen blev oväntade; skillnaden mellan grupperna var mycket liten.I arbetet med legeringar med förbättrad duktilitet valdes en legering från litteraturen, där man använt Cr för att till viss del ersätta Mg. Som utgångsmaterial valdes AlSi7Mg. Prover togs fram med hjälp av en gradientugn, där en kontrollerad stelning bidrar till att minimera defekter. Resultatet visar att Cr-tillsatsen gav en ganska liten ökning av segheten, däremot fick man efter konventionell åldring en ordentlig sänkning av brott- och sträckgräns. Åldring vid längre tider gav hållfasthet jämförbara med grundlegeringen utan Cr, men lägre än legeringen från litteraturen.Gradientstelningsförsök har visat att kisel bidrar starkt till varmhållfastheten vid 230 C för legeringen STENAL 460. En ökning av kiselhalten från 9,1 till 12,4 % ger bättre mekaniska egenskaper(Rm, Rp0.2 och A5) vid såväl rumstemperatur som vid 230 C. Jämfört med baslegeringen erhölls förbättring av sträck- och brottgräns vid 230 C med 49 respektive 17 % samtidigt som brottförlängningen ökade med 20 %. Motsvarande förbättring av sträck- och brottgräns samt brottförlängning vid rumstemperatur var 16, 22 respektive 69 %. Ett examensarbete utfört vid JU visar intressanta resultat hur kisel, cobolt och nickel var för sig och tillsammans bidrar till varmhållfastheten för Al-Si-legeringar.
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| 9. |
- Wittgren, Hans Bertil, et al.
(författare)
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A tool to support upstream work
- 2017
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Konferensbidrag (refereegranskat)abstract
- Theupstream work at utilities can be facilitated by a tool for calculatingpollution loads. A web application for mapping sources and performing substanceflow analysis is being developed. It aims to support location of sources,planning of measurement campaigns and evaluation of specific measures.
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