The neural basis of aberrant salience attribution in unmedicated patients with schizophrenia spectrum disorders

University essay from Högskolan Kristianstad/Sektionen för lärande och miljö

Abstract: Due to abnormal functioning of the brain’s reward and prediction system patients with schizophrenia spectrum disorders are thought to assign salience to non-relevant objects and events and to form context-inappropriate associations. The brain’s ventral striatum is critical in the formation of associations, and aberrant associations are believed to create delusional content during psychosis. The study wanted to examine the neural response, particularly in the ventral striatum, combined with subjective reports as patients learn associations in an aversive Pavlovian conditioning paradigm. The stimuli were randomized and involved circles of different colors. The conditioned stimuli (CS+) was followed by an unconditioned stimuli (US), consisting of an unpleasant sound, in 50% of events. The unconditioned (CS-) stimuli was followed by a low, not unpleasant sound in 50% of events. The degree of striatal activation was thought to be associated with the severity of patient’s illness. Functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) responses were examined in eleven unmedicated non-institutionalized patients with schizophrenia spectrum disorders and 15 matched healthy controls. No significant within group differences in neural or subjective response to the [CS+ > CS-] contrast were found. No significant associations between severity of illness and degree of striatal activation in response to CS+ or CS- were found. Significant differences in neural activation for the [CS+ > CS-] contrast were found in the ventral striatum, the right inferor frontal gyrus, and the right angular gyrus, with patients exhibiting stronger activation compared to controls. The results and implications are discussed along with suggestions for future research.

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