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1.
  • Alakurtti, Kati, et al. (creator_code:aut_t)
  • 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
  • record:In_t: Journal of Cerebral Blood Flow and Metabolism. - : SAGE Publications. - 0271-678X .- 1559-7016. ; 35:7, s. 1199-1205
  • swepub:Mat_article_t (swepub:level_refereed_t)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.
  • Andersson, Linus, et al. (creator_code:aut_t)
  • Brain responses to olfactory and trigeminal exposure in idiopathic environmental illness (IEI) attributed to smells : An fMRI study
  • 2014
  • record:In_t: Journal of Psychosomatic Research. - : Elsevier. - 0022-3999 .- 1879-1360. ; 77:5, s. 401-408
  • swepub:Mat_article_t (swepub:level_refereed_t)abstract
    • OBJECTIVE: Idiopathic environmental intolerance (IEI) to smells is a prevalent medically unexplained illness. Sufferers attribute severe symptoms to low doses of non-toxic chemicals. Despite the label, IEI is not characterized by acute chemical senses. Theoretical models suggest that sensitized responses in the limbic system of the brain constitute an important mechanism behind the symptoms. The aim was to investigate whether and how brain reactions to low-levels of olfactory and trigeminal stimuli differ in individuals with and without IEI. METHODS: Brain responses to intranasally delivered isoamyl acetate and carbon dioxide were assessed in 25 women with IEI and 26 non-ill controls using functional magnetic resonance imaging. RESULTS: The IEI group had higher blood-oxygenated-level-dependent (BOLD) signal than controls in the thalamus and a number of, mainly, parietal areas, and lower BOLD signal in the superior frontal gyrus. The IEI group did not rate the exposures as more intense than the control group did, and there were no BOLD signal differences between groups in the piriform cortex or olfactory regions of the orbitofrontal cortex. CONCLUSIONS: The IEI reactions were not characterized by hyper-responsiveness in sensory areas. The results can be interpreted as a limbic hyperreactivity and speculatively as an inability to inhibit salient extemal stimuli.
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3.
  • Andersson, Linus, 1979-, et al. (creator_code:aut_t)
  • Neurocognitive processes underlying heuristic and normative probability judgments
  • 2020
  • record:In_t: Cognition. - : ELSEVIER. - 0010-0277 .- 1873-7838. ; 196, s. 1-7
  • swepub:Mat_article_t (swepub:level_refereed_t)abstract
    • Judging two events in combination (A&B) as more probable than one of the events (A) is known as a conjunction fallacy. According to dual-process explanations of human judgment and decision making, the fallacy is due to the application of a heuristic, associative cognitive process. Avoiding the fallacy has been suggested to require the recruitment of a separate process that can apply normative rules. We investigated these assumptions using functional magnetic resonance imaging (fMRI) during conjunction tasks. Judgments, whether correct or not, engaged a network of brain regions identical to that engaged during similarity judgments. Avoidance of the conjunction fallacy additionally, and uniquely, involved a fronto-parietal network previously linked to supervisory, analytic control processes. The results lend credibility to the idea that incorrect probability judgments are the result of a representativeness heuristic that requires additional neurocognitive resources to avoid.
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4.
  • Andersson, Linus, et al. (creator_code:aut_t)
  • Short-term olfactory sensitization involves brain networks relevant for pain, and indicates chemical intolerance
  • 2017
  • record:In_t: International journal of hygiene and environmental health (Print). - : Elsevier. - 1438-4639 .- 1618-131X. ; 220:2, s. 503-509
  • swepub:Mat_article_t (swepub:level_refereed_t)abstract
    • Chemical intolerance is a medically unexplained affliction that implies deleterious reactions to non-toxic everyday chemical exposure. Sensitization (i.e. increased reactivity to repeated, invariant stimulation) to odorous stimulation is an important component in theoretical explanations of chemical intolerance, but empirical evidence is scarce. We hypothesized that (1) individuals who sensitize to repeated olfactory stimulation, compared with those who habituate, would express a lower blood oxygenated level dependent (BOLD) response in key inhibitory areas such as the rACC, and higher signal in pain/saliency detection regions, as well as primary and/or secondary olfactory projection areas; and (2) olfactory sensitization, compared with habituation, would be associated with greater self-reported chemical intolerance. More-over, we assessed whether olfactory sensitization was paralleled by comparable trigeminal processing - in terms of perceptual ratings and BOLD responses. We grouped women from a previous functional magnetic imaging study based on intensity ratings of repeated amyl acetate exposure over time. Fourteen women sensitized to the exposure, 15 habituated, and 20 were considered "intermediate" (i.e. neither sensitizers nor habituaters). Olfactory sensitizers, compared with habituaters, displayed a BOLD-pattern in line with the hypothesis, and reported greater problems with odours in everyday life. They also expressed greater reactions to CO2 in terms of both perceived intensity and BOLD signal. The similarities with pain are discussed.
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5.
  • Athanasiu, L., et al. (creator_code:aut_t)
  • A genetic association study of CSMD1 and CSMD2 with cognitive function
  • 2017
  • record:In_t: Brain Behavior and Immunity. - : Elsevier BV. - 0889-1591 .- 1090-2139. ; 61, s. 209-216
  • swepub:Mat_article_t (swepub:level_refereed_t)abstract
    • The complement cascade plays a role in synaptic pruning and synaptic plasticity, which seem to be involved in cognitive functions and psychiatric disorders. Genetic variants in the closely related CSMD1 and CSMD2 genes, which are implicated in complement regulation, are associated with schizophrenia. Since patients with schizophrenia often show cognitive impairments, we tested whether variants in CSMD1 and CSMD2 are also associated with cognitive functions per se. We took a discovery-replication approach, using well-characterized Scandinavian cohorts. A total of 1637 SNPs in CSMD1 and 206 SNPs in CSMD2 were tested for association with cognitive functions in the NCNG sample (Norwegian Cognitive NeuroGenetics; n = 670). Replication testing of SNPs with p-value < 0.001 (7 in CSMD1 and 3 in CSMD2) was carried out in the TOP sample (Thematically Organized Psychosis; n =1025) and the BETULA sample (Betula Longitudinal Study on aging, memory and dementia; n = 1742). Finally, we conducted a meta-analysis of these SNPs using all three samples. The previously identified schizophrenia marker in CSMD1 (SNP rs10503253) was also included. The strongest association was observed between the CSMDI SNP rs2740931 and performance in immediate episodic memory (p-value = 5 Chi 10(-6), minor allele A, MAF 0.48-0.49, negative direction of effect). This association reached the study-wide significance level (p <= 1.2 Chi 10(-5)). SNP rs10503253 was not significantly associated with cognitive functions in our samples. In conclusion, we studied n = 3437 individuals and found evidence that a variant in CSMD1 is associated with cognitive function. Additional studies of larger samples with cognitive phenotypes will be needed to further clarify the role of CSMD1 in cognitive phenotypes in health and disease. (C) 2016 The Authors. Published by Elsevier Inc.
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6.
  • Avelar-Pereira, Bárbara, et al. (creator_code:aut_t)
  • Age-Related Differences in Dynamic Interactions Among Default Mode, Frontoparietal Control, and Dorsal Attention Networks during Resting-State and Interference Resolution
  • 2017
  • record:In_t: Frontiers in Aging Neuroscience. - : Frontiers Media S.A.. - 1663-4365 .- 1663-4365. ; 9
  • swepub:Mat_article_t (swepub:level_refereed_t)abstract
    • Resting-state fMRI (rs-fMRI) can identify large-scale brain networks, including the default mode (DMN), frontoparietal control (FPN) and dorsal attention (DAN) networks. Interactions among these networks are critical for supporting complex cognitive functions, yet the way in which they are modulated across states is not well understood. Moreover, it remains unclear whether these interactions are similarly affected in aging regardless of cognitive state. In this study, we investigated age-related differences in functional interactions among the DMN, FPN and DAN during rest and the Multi-Source Interference task (MSIT). Networks were identified using independent component analysis (ICA), and functional connectivity was measured during rest and task. We found that the FPN was more coupled with the DMN during rest and with the DAN during the MSIT. The degree of FPN-DMN connectivity was lower in older compared to younger adults, whereas no age-related differences were observed in FPN-DAN connectivity in either state. This suggests that dynamic interactions of the FPN are stable across cognitive states. The DMN and DAN were anti correlated and age-sensitive during the MSIT only, indicating variation in a task-dependent manner. Increased levels of anticorrelation from rest to task also predicted successful interference resolution. Additional analyses revealed that the degree of DMN-DAN anticorrelation during the MSIT was associated to resting cerebral blood flow (CBF) within the DMN. This suggests that reduced DMN neural activity during rest underlies an impaired ability to achieve higher levels of anticorrelation during a task. Taken together, our results suggest that only parts of age-related differences in connectivity are uncovered at rest and thus, should be studied in the functional connectome across multiple states for a more comprehensive picture.
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7.
  • Avelar-Pereira, Barbara, et al. (creator_code:aut_t)
  • Increased functional homotopy of the prefrontal cortex is associated with corpus callosum degeneration and working memory decline
  • 2020
  • record:In_t: Neurobiology of Aging. - : Elsevier. - 0197-4580 .- 1558-1497. ; 96, s. 68-78
  • swepub:Mat_article_t (swepub:level_refereed_t)abstract
    • Functional homotopy reflects the link between spontaneous activity in a voxel and its counterpart in the opposite hemisphere. Alterations in homotopic functional connectivity (FC) are seen in normal aging, with highest and lowest homotopy being present in sensory-motor and higher-order regions, respectively. Homotopic FC relates to underlying structural connections, but its neurobiological underpinnings remain unclear. The genu of the corpus callosum joins symmetrical parts of the prefrontal cortex (PFC) and is susceptible to age-related degeneration, suggesting that PFC homotopic connectivity is linked to changes in white-matter integrity. We investigated homotopic connectivity changes and whether these were associated with white-matter integrity in 338 individuals. In addition, we examined whether PFC homotopic FC was related to changes in the genu over 10 years and working memory over 5 years. There were increases and decreases in functional homotopy, with the former being prevalent in subcortical and frontal regions. Increased PFC homotopic FC was partially driven by structural degeneration and negatively associated with working memory, suggesting that it reflects detrimental age-related changes. (C) 2020 The Author(s). Published by Elsevier Inc.
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8.
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9.
  • Awad, Amar, 1988- (creator_code:aut_t)
  • Functional brain imaging of sensorimotor dysfunction and restoration : investigations of discomplete spinal cord injury and deep brain stimulation for essential tremor
  • 2022
  • swepub:Mat_doctoralthesis_t (swepub:level_scientificother_t)abstract
    • The nervous system exists to generate adaptive behaviour by processing sensory input from the body and the environment in order to produce appropriate motor output, and vice versa. Consequently, sensorimotor dysfunction is the basis of disability in most neurological pathologies. In the current thesis, I explore two conditions with different types and degrees of sensorimotor dysfunction by means of functional magnetic resonance imaging (fMRI). In part 1, I assess residual sensory connections to the brain in clinically complete spinal cord injury (SCI) with seemingly complete loss of sensorimotor function below the injury level. In part 2, fMRI is combined with deep brain stimulation (DBS) to investigate interventional mechanisms of restoring dysfunctional sensorimotor control in essential tremor (ET).Part 1: SCI disrupts the communication between the brain and below-injury body parts, but rarely results in complete anatomical transection of the spinal cord. In studies I and II, we demonstrate somatosensory cortex activation due to somatosensory (tactile and nociceptive) stimulation on below-level insensate body parts in clinically complete SCI. The results from studies I and II indicate preserved somatosensory conduction across the spinal lesion in some cases of clinically complete SCI, as classified according to international standards. This subgroup is referred to as sensory discomplete SCI, which represents a distinct injury phenotype with an intermediate degree of injury severity between clinically complete and incomplete SCI.Part 2: ET is effectively treated with DBS in the caudal zona incerta, but the neural mechanisms underlying the treatment effect are poorly understood. By exploring DBS mechanisms with fMRI, DBS was shown to cause modulation in the activity of the sensorimotor cerebello-cerebral regions during motor tasks (study III), but did not modulate the functional connectivity during resting-state (study IV).fMRI is a valuable tool to investigate sensorimotor dysfunction and restoration in SCI and DBS-treated ET. There is evidence for sensory discomplete SCI in about half of the patients with clinically complete SCI. DBS modulates DBS modulation of the activity in the sensorimotor cerebello-cerebral circuit during motor tasks, but not during resting-state, is action-dependent.
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10.
  • Awad, Amar, et al. (creator_code:aut_t)
  • Preserved somatosensory conduction in a patient with complete cervical spinal cord injury
  • 2015
  • record:In_t: Journal of Rehabilitation Medicine. - : Foundation of Rehabilitation Information. - 1650-1977 .- 1651-2081. ; 47:5, s. 426-431
  • swepub:Mat_article_t (swepub:level_refereed_t)abstract
    • Objective: Neurophysiological investigation has shown that patients with clinically complete spinal cord injury can have residual motor sparing ("motor discomplete"). In the current study somatosensory conduction was assessed in a patient with clinically complete spinal cord injury and a novel ethodology for assessing such preservation is described, in this case indicating "sensory discomplete" spinal cord injury. Methods: Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD fMRI) was used to examine the somatosensory system in a healthy subject and in a subject with a clinically complete cervical spinal cord injury, by applying tactile stimulation above and below the level of spinal cord injury, with and without visual feedback. Results: In the participant with spinal cord injury, somatosensory stimulation below the neurological level of the lesion gave rise to BOLD signal changes in the corresponding areas of the somatosensory cortex. Visual feedback of the stimulation strongly modulated the somatosensory BOLD signal, implying that cortico-cortical rather than spino-cortical connections can drive activity in the somatosensory cortex. Critically, BOLD signal change was also evident when the visual feedback of the stimulation was removed, thus demonstrating sensory discomplete spinal cord injury. Conclusion: Given the existence of sensory discomplete spinal cord injury, preserved but hitherto undetected somatosensory conduction might contribute to the unexplained variability related to, for example, the propensity to develop decubitus ulcers and neuropathic pain among patients with clinically complete spinal cord injury.
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