Distinct patterns of dysfunctional appetitive and aversive motivation in bipolar disorder versus schizophrenia: An event-related potential study

Schizophrenia and bipolar disorder are associated with different clinical profiles of disturbances in motivation, yet few studies have compared the neurophysiological correlates of such disturbances. Outpatients with schizophrenia (n = 34), or bipolar disorder I (n = 33), and healthy controls (n = 31) completed a task in which the late positive potential (LPP), an index of motivated attention, was assessed along motivational gradients determined by apparent distance from potential rewards or punishments. Sequences of cues signaling possible monetary gains or losses appeared to loom progressively closer to the viewer; a reaction time (RT) task after the final cue determined the outcome. Controls showed the expected pattern with LPPs for appetitive and aversive cues that were initially elevated, smaller during intermediate positions, and escalated just prior to the RT task. The clinical groups showed different patterns in the final positions just prior to the RT task: the bipolar group's LPPs to both types of cues peaked relatively early during looming sequences and subsequently decreased, whereas the schizophrenia group showed relatively small LPP escalations, particularly for aversive cues. These distinct patterns suggest that the temporal unfolding of attentional resource allocation for motivationally significant events may qualitatively differ between these disorders.