Abstract
It has recently been suggested that schizophrenia involves dysfunction in brain connectivity at a neural level, and a dysfunction in reward processing at a behavioral level. The purpose of the present study was to link these two levels of analyses by examining effective connectivity patterns between brain regions mediating reward learning in patients with schizophrenia and healthy, age-matched controls. To this aim, we used functional magnetic resonance imaging and galvanic skin recordings (GSR) while patients and controls performed an appetitive conditioning experiment with visual cues as the conditioned (CS) stimuli, and monetary reward as the appetitive unconditioned stimulus (US). Based on explicit stimulus contingency ratings, conditioning occurred in both groups; however, based on implicit, physiological GSR measures, patients failed to show differences between CS+ and CS− conditions. Healthy controls exhibited increased blood-oxygen-level dependent (BOLD) activity across striatal, hippocampal, and prefrontal regions and increased effective connectivity from the ventral striatum to the orbitofrontal cortex (OFC BA 11) in the CS+ compared to the CS− condition. Compared to controls, patients showed increased BOLD activity across a similar network of brain regions, and increased effective connectivity from the striatum to hippocampus and prefrontal regions in the CS− compared to the CS+ condition. The findings of increased BOLD activity and effective connectivity in response to the CS− in patients with schizophrenia offer insight into the aberrant assignment of motivational salience to non-reinforced stimuli during conditioning that is thought to accompany schizophrenia.
Highlights
The name “schizophrenia” was first introduced by Bleuler (1911) as a splitting and disintegration of conscious experience
In the present functional magnetic resonance imaging (fMRI) study, we investigated reward learning and group differences in effective connectivity employing an appetitive conditioning paradigm in which visual stimuli were associated with rewards and, as a consequence, became imbued with motivational salience
The group by condition interaction was primarily driven by the larger percentage of trials exhibiting increased galvanic skin recordings (GSR) values in the unpaired CS+ condition in controls compared to patients
Summary
The name “schizophrenia” was first introduced by Bleuler (1911) as a splitting and disintegration of conscious experience. Recent studies examined the hypothesis of “disconnectivity” in schizophrenia by investigating temporally coherent brain activity derived from functional magnetic resonance imaging (fMRI) data (for a review, see Calhoun et al, 2009). Jensen et al (2008) suggested that, based on the implicit physiological measure of skin conductance, patients with schizophrenia demonstrated abnormal aversive learning patterns, and could not reliably distinguish between neutral stimuli and stimuli linked to aversive outcomes.Accompanying these behavioral deficits, patients with schizophrenia exhibited increased blood-oxygen-level dependent (BOLD) activity in the ventral striatum (VS; Juckel et al, 2006; Jensen et al, 2008; Schlagenhauf et al, 2009) and hippocampus (Schmajuk, 2001; Meyer-Lindenberg et al, 2005) in response to non-reinforced stimuli
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