Timing of Voluntary Movement in Patients With Schizophrenia

Objectives The purpose of this study is to determine how the subjective sense of willing and initiating an action is altered in schizophrenic patients. One proposed explanation for characteristic symptoms of schizophrenia ("passivity phenomena") is a defect in the forward model of movement that the brain receives as the motor signal is generated. We propose to examine this forward model using Libet's paradigm, in which normal subjects gave evidence for a forward model in their anticipatory reports of initiation of movement. We intend to determine the times associated with willing (W), initiating (M), and electroencephalographic/electromyographic (EEG/EMG) measures of movement. Study Population We intend to study adult patients with a Diagnostic and Statistical Manual of Mental Disorders diagnosis of schizophrenia. These patients provide a unique population for this study because they often do not have the sense that they direct their own movement or author their own thoughts (passivity phenomena). Studies have shown that schizophrenics have movement-related cortical potentials on EEG, but it is not known when the subjective sense of initiating movement occurs for these patients. As the order of mental events in time has been shown to contribute to the sense of agency, it is important to know how the timing of voluntary movement is altered in schizophrenia. Design We will ask patients to look at a fast-rotating clock on a computer screen and note when their movements were willed, instigated by an external agent if they have such delusions, and were initiated. Patients will also report the time of a somatosensory stimulus. Surface EMG will determine the time of actual movement, and EEG will record brain potentials associated with movement. Eligible patients with schizophrenia and passivity phenomena will be recruited from the Clinical Brain Disorders Branch, NIMH. Outcome Measures The primary outcome measure of this study is the absence of time W in some schizophrenics, the latency of W in other schizophrenics compared to normal subjects, and the latency of M in schizophrenics compared to normals. Any effect of medication status or symptoms on performance in the study will be considered exploratory data.