Investigation of motor self-monitoring deficits in schizophrenia with passivity experiences using a novel modified joint position matching paradigm.

Numerous studies have identified deficits in the self-monitoring system that are associated with schizophrenia. However, the tasks used in the few previous studies generally involved complex cognitive processes and rarely compared between patients with and without passivity experiences (PE). Here, we examined the deficits in internal motor predictive representation in patients with and without PE, and in healthy controls using a novel paradigm which involved minimal cognitive processes. All participants completed a modified joint position matching (mJPM) task, in which they were required to replicate a voluntary, a passive verbally-cued, and a passive tactile-cued movement under blinded conditions. The absolute difference between the target spot and replicated spot was measured and compared. We hypothesised that if there was a failure in the internal motor predictive representation, patients with PEs would replicate less accurately in the voluntary condition, relative to passive conditions while the healthy controls would be more accurate, and, therefore, significant interactions between groups and conditions would be revealed. Both healthy controls and patients without PEs replicated more accurately in the voluntary condition compared with the passive conditions. The patients with PEs were less accurate in the voluntary condition compared with the passive tactile condition. A significant interaction was observed between patients with vs. without PEs × voluntary vs. passive tactile conditions. The findings suggested the relationship between deficits in motor self-monitoring in the prediction process and PEs, thus showing the need to highlight the link between motor performance and PEs.