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Sökning: WFRF:(Johansson Jarkko)

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1.
  • Alakurtti, Kati, et al. (författare)
  • Long-term test-retest reliability of striatal and extrastriatal dopamine D-2/3 receptor binding : study with [C-11]raclopride and high-resolution PET
  • 2015
  • Ingår i: Journal of Cerebral Blood Flow and Metabolism. - : SAGE Publications. - 0271-678X .- 1559-7016. ; 35:7, s. 1199-1205
  • Tidskriftsartikel (refereegranskat)abstract
    • We measured the long-term test-retest reliability of [C-11]raclopride binding in striatal subregions, the thalamus and the cortex using the bolus-plus-infusion method and a high-resolution positron emission scanner. Seven healthy male volunteers underwent two positron emission tomography (PET) [C-11]raclopride assessments, with a 5-week retest interval. D-2/3 receptor availability was quantified as binding potential using the simplified reference tissue model. Absolute variability (VAR) and intraclass correlation coefficient (ICC) values indicated very good reproducibility for the striatum and were 4.5%/0.82, 3.9%/0.83, and 3.9%/0.82, for the caudate nucleus, putamen, and ventral striatum, respectively. Thalamic reliability was also very good, with VAR of 3.7% and ICC of 0.92. Test-retest data for cortical areas showed good to moderate reproducibility (6.1% to 13.1%). Our results are in line with previous test-retest studies of [C-11]raclopride binding in the striatum. A novel finding is the relatively low variability of [C-11]raclopride binding, providing suggestive evidence that extrastriatal D-2/3 binding can be studied in vivo with [C-11]raclopride PET to be verified in future studies.
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2.
  • Bäckman, Lars, et al. (författare)
  • Effects of working-memory training on striatal dopamine release
  • 2011
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 333:6043, s. 718-
  • Tidskriftsartikel (refereegranskat)abstract
    • Updating of working memory has been associated with striato-frontal brain regions and phasic dopaminergic neurotransmission. We assessed raclopride binding to striatal dopamine (DA) D2 receptors during a letter-updating task and a control condition before and after 5 weeks of updating training. Results showed that updating affected DA activity before training and that training further increased striatal DA release during updating. These findings highlight the pivotal role of transient neural processes associated with D2 receptor activity in working memory.
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3.
  • Bäckman, Lars, et al. (författare)
  • Increased dopamine release after working-memory updating training : Neurochemical correlates of transfer
  • 2017
  • Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • Previous work demonstrates that working-memory (WM) updating training results in improved performance on a letter-memory criterion task, transfers to an untrained n-back task, and increases striatal dopamine (DA) activity during the criterion task. Here, we sought to replicate and extend these findings by also examining neurochemical correlates of transfer. Four positron emission tomography (PET) scans using the radioligand raclopride were performed. Two of these assessed DAD2 binding (letter memory; n-back) before 5 weeks of updating training, and the same two scans were performed post training. Key findings were (a) pronounced training-related behavioral gains in the lettermemory criterion task, (b) altered striatal DAD2 binding potential after training during letter-memory performance, suggesting training-induced increases in DA release, and (c) increased striatal DA activity also during the n-back transfer task after the intervention, but no concomitant behavioral transfer. The fact that the training-related DA alterations during the transfer task were not accompanied by behavioral transfer suggests that increased DA release may be a necessary, but not sufficient, condition for behavioral transfer to occur.
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4.
  • Ekblad, Laura L., et al. (författare)
  • Midlife insulin resistance, APOE genotype, and late-life brain amyloid accumulation
  • 2018
  • Ingår i: Neurology. - : Lippincott Williams & Wilkins. - 0028-3878 .- 1526-632X. ; 90:13, s. e1150-e1157
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective To examine whether midlife insulin resistance is an independent risk factor for brain amyloid accumulation in vivo after 15 years, and whether this risk is modulated by APOE epsilon 4 genotype. Methods This observational study examined 60 elderly volunteers without dementia (mean age at baseline 55.4 and at follow-up 70.9 years, 55.5% women) from the Finnish population-based, nationwide Health2000 study with [C-11]Pittsburgh compound B-PET imaging in 2014-2016. The participants were recruited according to their homeostatic model assessment of insulin resistance (HOMA-IR) values in the year 2000, and their APOE epsilon 4 genotype. The exposure group (IR+, n = 30) consisted of individuals with HOMA-IR > 2.17 at baseline (highest tertile of the Health2000 study population), and the control group (IR-, n = 30) consisted of individuals with HOMA-IR < 1.25 at baseline (lowest tertile). The groups were enriched for APOE epsilon 4 carriers, resulting in 50% (n = 15) APOE epsilon 4 carriers in both groups. Analyses were performed with multivariate logistic and linear regression. Results An amyloid-positive PET scan was found in 33.3% of the IR-group and 60.0% of the IR+ group (odds ratio 3.0, 95% confidence interval 1.1-8.9, p = 0.04). The increased risk was seen in carriers and noncarriers of APOE epsilon 4 genotype. Higher midlife, but not late-life continuous HOMA-IR was associated with a greater brain amyloid burden at follow-up after multivariate adjustments for other cognitive and metabolic risk factors (ss = 0.11, 95% confidence interval 0.002-0.22, p = 0.04). Conclusions These results indicate that midlife insulin resistance is an independent risk factor for brain amyloid accumulation in elderly individuals without dementia.
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5.
  • Erikshammar, Jarkko, Teknologie doktor, 1971-, et al. (författare)
  • En konceptuell logistikmodell för planering inom anläggning
  • 2020
  • Ingår i: PLANs forsknings- och tillämpningskonferens 2020. - : KTH Royal Institute of Technology.
  • Konferensbidrag (refereegranskat)abstract
    • Bygg- och anläggningsbranschen har, förutom en låg produktivitet där icke-värdeskapande aktiviteter uppgår till 30–35% av projektets totala produktionskostnad, en påverkan av det globala utsläppet av växthusgaser på upp till 40%. Utsläpp av växthusgaser, såsom koldioxid och metan, och förbrukningen av resurser inom byggbranschen måste minska kraftigt på kort tid för att branschen ska bidra till det svenska och europeiska klimatmålet. I anläggningsprojekt är det ofta problem med stora projektytor och svåråtkomlig terräng, men det kan även vara problem med trånga utrymmen runt projektet. Dessutom innebär projekt i anläggningsbranschen ofta omfattande hantering av massor vilket innebär en logistisk utmaning i planeringsfasen då hela området inte är undersökt. Företag inom anläggningssektorn arbetar sällan med tydliga modeller för logistik inom planering vilket kan potentiellt ytterligare öka slöseriet i processerna. Studiens syfte har varit att undersöka planeringsfasen och utveckla en konceptuell logistiskmodell för anläggningsprojekt. Logistikmodellen har utvecklats från befintlig teori och testats i fokusgrupper. Modellen består av sjutton komponenter som innehåller aktiviteter och verktyg samt beskriver de förutsättningar som krävs för en effektiv logistik i anläggningsprojekt. Fokusgruppernas svar indikerar att logistik inte är företagens huvudfokus; respondenterna har svårt att se fördelarna med att använda logistik som begrepp och de aktiviteter som lyfts fram i modellen förekommer sällan i praktiken. Studien indikerar att genom att ta fram standardiserade processer för logistik inom anläggningsbranschen och organisera ansvarsområdet inom processen och öka kompetensen, finns det därmed en möjlighet att effektivisera produktionen och minska miljöbelastningen.
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6.
  • Farnsworth von Cederwald, Bryn, et al. (författare)
  • White matter lesion load determines exercise-induced dopaminergic plasticity and working memory gains in aging
  • 2023
  • Ingår i: Translational Psychiatry. - : Springer Nature. - 2158-3188. ; 13:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Age-related dopamine reductions have been suggested to contribute to maladaptive working memory (WM) function in older ages. One promising intervention approach is to increase physical activity, as this has been associated with plasticity of the striatal dopamine system and WM improvements, however with individual differences in efficacy. The present work focused on the impact of individual differences in white-matter lesion burden upon dopamine D2-like receptor (DRD2) availability and WM changes in response to a 6 months physical activity intervention. While the intervention altered striatal DRD2 availability and WM performance in individuals with no or only mild lesions (p < 0.05), no such effects were found in individuals with moderate-to-severe lesion severity (p > 0.05). Follow-up analyses revealed a similar pattern for processing speed, but not for episodic memory performance. Linear analyses further revealed that lesion volume (ml) at baseline was associated with reduced DRD2 availability (r = −0.41, p < 0.05), and level of DRD2 change (r = 0.40, p < 0.05). Taken together, this study underlines the necessity to consider cerebrovascular health in interventions with neurocognitive targets. Future work should assess whether these findings extend beyond measures of DRD2 availability and WM.
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7.
  • Grill, Filip, et al. (författare)
  • Dissecting Motor and Cognitive Component Processes of a Finger-Tapping Task With Hybrid Dopamine Positron Emission Tomography and Functional Magnetic Resonance Imaging
  • 2021
  • Ingår i: Frontiers in Human Neuroscience. - : Frontiers Media S.A.. - 1662-5161. ; 15
  • Tidskriftsartikel (refereegranskat)abstract
    • Striatal dopamine is involved in facilitation of motor action as well as various cognitive and emotional functions. Positron emission tomography (PET) is the primary imaging method used to investigate dopamine function in humans. Previous PET studies have shown striatal dopamine release during simple finger tapping in both the putamen and the caudate. It is likely that dopamine release in the putamen is related to motor processes while dopamine release in the caudate could signal sustained cognitive component processes of the task, but the poor temporal resolution of PET has hindered firm conclusions. In this study we simultaneously collected [11C]Raclopride PET and functional Magnetic Resonance Imaging (fMRI) data while participants performed finger tapping, with fMRI being able to isolate activations related to individual tapping events. The results revealed fMRI-PET overlap in the bilateral putamen, which is consistent with a motor component process. Selective PET responses in the caudate, ventral striatum, and right posterior putamen, were also observed but did not overlap with fMRI responses to tapping events, suggesting that these reflect non-motor component processes of finger tapping. Our findings suggest an interplay between motor and non-motor-related dopamine release during simple finger tapping and illustrate the potential of hybrid PET-fMRI in revealing distinct component processes of cognitive functions.
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8.
  • Grill, Filip, et al. (författare)
  • Dopamine release in human associative striatum during reversal learning
  • 2024
  • Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The dopaminergic system is firmly implicated in reversal learning but human measurements of dopamine release as a correlate of reversal learning success are lacking. Dopamine release and hemodynamic brain activity in response to unexpected changes in action-outcome probabilities are here explored using simultaneous dynamic [11C]Raclopride PET-fMRI and computational modelling of behavior. When participants encounter reversed reward probabilities during a card guessing game, dopamine release is observed in associative striatum. Individual differences in absolute reward prediction error and sensitivity to errors are associated with peak dopamine receptor occupancy. The fMRI response to perseverance errors at the onset of a reversal spatially overlap with the site of dopamine release. Trial-by-trial fMRI correlates of absolute prediction errors show a response in striatum and association cortices, closely overlapping with the location of dopamine release, and separable from a valence signal in ventral striatum. The results converge to implicate striatal dopamine release in associative striatum as a central component of reversal learning, possibly signifying the need for increased cognitive control when new stimuli-responses should be learned.
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9.
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10.
  • Gustavsson, Jonatan, et al. (författare)
  • The iron-dopamine D1 coupling modulates neural signatures of working memory across adult lifespan
  • 2023
  • Ingår i: NeuroImage. - : Elsevier. - 1053-8119 .- 1095-9572. ; 279
  • Tidskriftsartikel (refereegranskat)abstract
    • Brain iron overload and decreased integrity of the dopaminergic system have been independently reported as brain substrates of cognitive decline in aging. Dopamine (DA), and iron are co-localized in high concentrations in the striatum and prefrontal cortex (PFC), but follow opposing age-related trajectories across the lifespan. DA contributes to cellular iron homeostasis and the activation of D1-like DA receptors (D1DR) alleviates oxidative stress-induced inflammatory responses, suggesting a mutual interaction between these two fundamental components. Still, a direct in-vivo study testing the iron-D1DR relationship and their interactions on brain function and cognition across the lifespan is rare. Using PET and MRI data from the DyNAMiC study (n=180, age=20-79, %50 female), we showed that elevated iron content was related to lower D1DRs in DLPFC, but not in striatum, suggesting that dopamine-rich regions are less susceptible to elevated iron. Critically, older individuals with elevated iron and lower D1DR exhibited less frontoparietal activations during the most demanding task, which in turn was related to poorer working-memory performance. Together, our findings suggest that the combination of elevated iron load and reduced D1DR contribute to disturbed PFC-related circuits in older age, and thus may be targeted as two modifiable factors for future intervention.
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