| 1. |
- Böhme, Rebecca, et al.
(författare)
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Reversal learning strategy in adolescence is associated with prefrontal cortex activation
- 2017
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Ingår i: European Journal of Neuroscience. - : WILEY-BLACKWELL. - 0953-816X .- 1460-9568. ; 45:1, s. 129-137
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Tidskriftsartikel (refereegranskat)abstract
- Adolescence is a critical maturation period for human cognitive control and executive function. In this study, a large sample of adolescents (n=85) performed a reversal learning task during functional magnetic resonance imaging. We analyzed behavioral data using a reinforcement learning model to provide individually fitted parameters and imaging data with regard to reward prediction errors (PE). Following a model-based approach, we formed two groups depending on whether individuals tended to update expectations predominantly for the chosen stimulus or also for the unchosen one. These groups significantly differed in their problem behavior score obtained using the child behavior checklist (CBCL) and in a measure of their developmental stage. Imaging results showed that dorsolateral striatal areas covaried with PE. Participants who relied less on learning based on task structure showed less prefrontal activation compared with participants who relied more on task structure. An exploratory analysis revealed that PE-related activity was associated with pubertal development in prefrontal areas, insula and anterior cingulate. These findings support the hypothesis that the prefrontal cortex is implicated in mediating flexible goal-directed behavioral control.
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| 2. |
- Nickchen, Katharina, et al.
(författare)
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Reversal learning reveals cognitive deficits and altered prediction error encoding in the ventral striatum in Huntingtons disease
- 2017
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Ingår i: Brain Imaging and Behavior. - : SPRINGER. - 1931-7557 .- 1931-7565. ; 11:6, s. 1862-1872
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Tidskriftsartikel (refereegranskat)abstract
- Huntingtons disease (HD) is an autosomal dominant neurodegenerative condition characterized by a triad of movement disorder, neuropsychiatric symptoms and cognitive deficits. The striatum is particularly vulnerable to the effects of mutant huntingtin, and cell loss can already be found in presymptomatic stages. Since the striatum is well known for its role in reinforcement learning, we hypothesized to find altered behavioral and neural responses in HD patients in a probabilistic reinforcement learning task performed during functional magnetic resonance imaging. We studied 24 HD patients without central nervous system (CNS)-active medication and 25 healthy controls. Twenty HD patients and 24 healthy controls were able to complete the task. Computational modeling was used to calculate prediction error values and estimate individual parameters. We observed that gray matter density and prediction error signals during the learning task were related to disease stage. HD patients in advanced disease stages appear to use a less complex strategy in the reversal learning task. In contrast, HD patients in early disease stages show intact encoding of learning signals in the degenerating left ventral striatum. This effect appears to be lost with disease progression.
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