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  • Brandt, Christine Lycke, et al. (författare)
  • Cognitive effort and schizophrenia modulate large-scale functional brain connectivity
  • 2015
  • Ingår i: Schizophrenia Bulletin. - 0586-7614 .- 1745-1701. ; 41:6, s. 1360-1369
  • Tidskriftsartikel (refereegranskat)abstract
    • Schizophrenia (SZ) is characterized by cognitive dysfunction and disorganized thought, in addition to hallucinations and delusions, and is regarded a disorder of brain connectivity. Recent efforts have been made to characterize the underlying brain network organization and interactions. However, to which degree connectivity alterations in SZ vary across different levels of cognitive effort is unknown. Utilizing independent component analysis (ICA) and methods for delineating functional connectivity measures from functional magnetic resonance imaging (fMRI) data, we investigated the effects of cognitive effort, SZ and their interactions on between-network functional connectivity during 2 levels of cognitive load in a large and well-characterized sample of SZ patients (n = 99) and healthy individuals (n = 143). Cognitive load influenced a majority of the functional connections, including but not limited to fronto-parietal and default-mode networks, reflecting both decreases and increases in between-network synchronization. Reduced connectivity in SZ was identified in 2 large-scale functional connections across load conditions, with a particular involvement of an insular network. The results document an important role of interactions between insular, default-mode, and visual networks in SZ pathophysiology. The interplay between brain networks was robustly modulated by cognitive effort, but the reduced functional connectivity in SZ, primarily related to an insular network, was independent of cognitive load, indicating a relatively general brain network-level dysfunction.
  • Lycke Brandt, Christine, et al. (författare)
  • Working memory networks and activation patterns in schizophrenia and bipolar disorder : comparison with healthy controls
  • 2014
  • Ingår i: British Journal of Psychiatry. - 0007-1250 .- 1472-1465. ; 204:4, s. 290-298
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Schizophrenia and bipolar disorder are severe mental disorders with overlapping genetic and clinical characteristics, including cognitive impairments. An important question is whether these disorders also have overlapping neuronal deficits.AIMS: To determine whether large-scale brain networks associated with working memory, as measured with functional magnetic resonance imaging (fMRI), are the same in both schizophrenia and bipolar disorder, and how they differ from those in healthy individuals.METHOD: Patients with schizophrenia (n = 100) and bipolar disorder (n = 100) and a healthy control group (n = 100) performed a 2-back working memory task while fMRI data were acquired. The imaging data were analysed using independent component analysis to extract large-scale networks of task-related activations.RESULTS: Similar working memory networks were activated in all groups. However, in three out of nine networks related to the experimental task there was a graded response difference in fMRI signal amplitudes, where patients with schizophrenia showed greater activation than those with bipolar disorder, who in turn showed more activation than healthy controls. Secondary analysis of the patient groups showed that these activation patterns were associated with history of psychosis and current elevated mood in bipolar disorder.CONCLUSIONS: The same brain networks were related to working memory in schizophrenia, bipolar disorder and controls. However, some key networks showed a graded hyperactivation in the two patient groups, in line with a continuum of neuronal abnormalities across psychotic disorders.
  • Welander-Vatn, Audun, et al. (författare)
  • The neural correlates of cognitive control in bipolar I disorder : an fMRI study of medial frontal cortex activation during a Go/No-go task
  • 2013
  • Ingår i: Neuroscience Letters. - 0304-3940 .- 1872-7972. ; 549, s. 51-56
  • Tidskriftsartikel (refereegranskat)abstract
    • In addition to dysregulation of mood, bipolar I disorder (BD I) is characterized by abnormalities in the execution of cognitive control. Hypoactivation of a specific sub-region in the cognitive control network, located in the medial frontal cortex, has been described among BD I patients. The aim of this study was to investigate whether patients with BD I showed decreased activation in this brain region as compared to healthy controls when performing a cognitive control task. Twenty-four BD I patients and 24 healthy controls performed a Go/No-go task during a functional magnetic resonance imaging (fMRI) session. Performance and response times were recorded. The BD I subjects had significantly slower response times and more patients made errors of omission compared to the healthy controls during the task. Both BD I subjects and healthy controls demonstrated activations in the brain region of interest during the task, but analyses revealed no statistically significant differences between groups. Although the patients display some deviances in behavioural measures, this study reveals no significant differences between BD I subjects and healthy controls in recruitment of the medial frontal cortex during a Go/No-go task.
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