Published papers

Self-disturbance, a core feature of schizophrenia, recently has been explained from the standpoint of an abnormal sense of agency (SoA). Previous studies showed that aberrant SoA in schizophrenia arise from imprecise predictions about the sensory consequences of actions. However, the nature of the malfunctioning predictions remains unclear. We examined the temporally "delayed" nature of inadequate predictions. We studied 30 patients with schizophrenia and 30 healthy controls. Our original SoA task evaluates explicit experience of the temporal causal relationship between an intentional action and an effect on a computer screen under the presence of temporal biases. We introduced an adaptation with a "trial-by-trial" method that prolonged or shortened the temporal biases. We hypothesized that delayed prediction signals in schizophrenia could lead to a match in timing between predictions and actual outcomes, resulting in self-agency. The adjustment courses to changing temporal biases were evaluated. Patients with schizophrenia continued to feel self-agency even when the adjusted temporal bias was longer than 1000. ms. This result indicated that patient's prediction would be delayed in each trial. Our study empirically showed behavioral evidence for "delayed" prediction signals in a SoA paradigm for the first time.

In the present study, we used the typical false recognition paradigm to test a hypothesis that the ventromedial prefrontal cortex (VMPFC) mediates event-category judgement and retrieving past similar events. Eight VMPFC patients and 10 normal subjects were first requested to learn 18 sets of 14 semantic associates. In the test phase, participants were asked to recognize paired words including true words, related lures, and unrelated lures. The VMPFC patients showed significantly higher false alarm rates than the normal subjects for lure words. A further analysis suggests that the VMPFC patients succeeded in judging the event category, yet they were more likely to fail to retrieve past similar events. © 2001 Academic Press.