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Motivation and value influences in the relative balance of goal-directed and habitual behaviours in obsessive-compulsive disorder
AbstractOur decisions are based on parallel and competing systems of goal-directed and habitual learning, systems which can be impaired in pathological behaviours. Here we focus on the influence of motivation and compare reward and loss outcomes in subjects with obsessive-compulsive disorder (OCD) on model-based goal-directed and model-free habitual behaviours using the two-step task. We further investigate the relationship with acquisition learning using a one-step probabilistic learning task. Forty-eight OCD subjects and 96 healthy volunteers were tested on a reward and 30 OCD subjects and 53 healthy volunteers on the loss version of the two-step task. Thirty-six OCD subjects and 72 healthy volunteers were also tested on a one-step reversal task. OCD subjects compared with healthy volunteers were less goal oriented (model-based) and more habitual (model-free) to reward outcomes with a shift towards greater model-based and lower habitual choices to loss outcomes. OCD subjects also had enhanced acquisition learning to loss outcomes on the one-step task, which correlated with goal-directed learning in the two-step task. OCD subjects had greater stay behaviours or perseveration in the one-step task irrespective of outcome. Compulsion severity was correlated with habitual learning in the reward condition. Obsession severity was correlated with greater switching after loss outcomes. In healthy volunteers, we further show that greater reward magnitudes are associated with a shift towards greater goal-directed learning further emphasizing the role of outcome salience. Our results highlight an important influence of motivation on learning processes in OCD and suggest that distinct clinical strategies based on valence may be warranted.
Hippocampus
The hippocampus (Latin for seahorse) is a structure in the medial temporal lobe, lining the temporal horn of the lateral ventricle. It has been considered part of the limbic system and plays an important role in explicit, episodic, declarative, contextual, or relational forms of rapid encoding, consolidation, and retrieval processes related to memory and emotion. Its unique highly ordered lamination, trisynaptic circuitry, and site for neurogenesis has contributed a wealth of information toward our current understanding of experience-dependent neuroplasticity at the systems, cellular, and molecular levels.
Multiple autoimmunity: neuromyelitis optica spectrum disorder with Lambert-Eaton myasthenic syndrome.
A 56-year-old woman with a background of neuromyelitis optica spectrum disorder associated with aquaporin-4 antibodies (AQ4-NMOSD) treated with azathioprine, presented with a 2-month history of declining mobility, weight loss and hoarse voice. She had a history of autoimmune thyrotoxicosis and treated hypertension. Given her smoking history, the initial clinical concern was of malignancy. Neurophysiological examination identified severely attenuated responses from the upper and lower limb motor units, with significant neurophysiological incrementation postexercise, indicating a presynaptic neuromuscular junction disorder. Antibody testing showed markedly raised antibodies to the p/q subtype voltage-gated calcium channels, and she was diagnosed with Lambert-Eaton myasthenic syndrome (LEMS). She was treated with 3,4-diaminopyridine and rituximab to maintain remission. Follow-up serial fluorodeoxyglucose positron emission tomography (FDG-PET) CT scans have yet to identify an underlying malignancy. LEMS is associated with additional autoimmune diseases in about half of cases. This case illustrates the importance of recognising other treatable autoimmune conditions in the context of NMOSD.