| 1. |
- Brandt, Christine Lycke, et al.
(författare)
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Cognitive effort and schizophrenia modulate large-scale functional brain connectivity
- 2015
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Ingår i: Schizophrenia Bulletin. - : Oxford University Press. - 0586-7614 .- 1745-1701. ; 41:6, s. 1360-1369
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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.
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| 2. |
- Welander-Vatn, Audun, et al.
(författare)
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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
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Ingår i: Neuroscience Letters. - : Elsevier Ireland Ltd. - 0304-3940 .- 1872-7972. ; 549, s. 51-56
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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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| 3. |
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| 4. |
- Haatveit, Beathe, et al.
(författare)
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Reduced load-dependent default mode network deactivation across executive tasks in schizophrenia spectrum disorders
- 2016
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Ingår i: NeuroImage Clinical. - : Elsevier BV. - 0353-8842 .- 2213-1582. ; 12, s. 389-396
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Schizophrenia is associated with cognitive impairment and brain network dysconnectivity. Recent efforts have explored brain circuits underlying cognitive dysfunction in schizophrenia and documented altered activation of large-scale brain networks, including the task-positive network (TPN) and the task-negative default mode network (DMN) in response to cognitive demands. However, to what extent TPN and DMN dysfunction reflect overlapping mechanisms and are dependent on cognitive state remain to be determined. METHODS: In the current study, we investigated the recruitment of TPN and DMN using independent component analysis in patients with schizophrenia spectrum disorders (n = 29) and healthy controls (n = 21) during two different executive tasks probing planning/problem-solving and spatial working memory. RESULTS: We found reduced load-dependent DMN deactivation across tasks in patients compared to controls. Furthermore, we observed only moderate associations between the TPN and DMN activation across groups, implying that the two networks reflect partly independent mechanisms. Additionally, whereas TPN activation was associated with task performance in both tasks, no such associations were found for DMN. CONCLUSION: These results support a general load-dependent DMN dysfunction in schizophrenia spectrum disorder across two demanding executive tasks that is not merely an epiphenomenon of cognitive dysfunction.
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| 5. |
- Haatveit, Beathe, et al.
(författare)
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Stability of executive functions in first episode psychosis : one year follow up study
- 2015
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Ingår i: Psychiatry Research. - : Elsevier Ireland Ltd. - 0165-1781 .- 1872-7123. ; 228:3, s. 475-481
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Tidskriftsartikel (refereegranskat)abstract
- Executive functioning is a multi-dimensional construct covering several sub-processes. The aim of this study was to determine whether executive functions, indexed by a broad range of executive measures remain stable in first episode psychosis (FEP) over time. Eighty-two patients and 107 age and gender matched healthy controls were assessed on five subdomains of executive functioning; working memory, fluency, flexibility, and inhibitory control at baseline and at 1 year follow-up. Results showed that patients performed significantly poorer than controls on all executive measures at both assessment points. In general executive functions remained stable from baseline to follow-up, although both groups improved on measures of inhibitory control and flexibility. In phonemic fluency, controls showed a slight improvement while patients showed a slight decline. Investigation of individual trajectories revealed some fluctuations in both groups over time, but mainly supports the group level findings. The implications of these results are discussed.
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