Timing of Voluntary Movement in Patients With Tourette Syndrome and Chronic Tic Disorder Using EEG and Surface EMG

OBJECTIVES: The purpose of this study is to determine how the subjective sense of willing and initiating an action is altered in patients with Tourette Syndrome and Chronic Tic Disorder. Although many definitions of the disease include the characterization of tics as 'involuntary', some patients claim that these movements are voluntarily made, or are unable to decide if they are voluntary or involuntary. Recent studies have shown that the time order in which someone wills a voluntary movement and begins that movement is central to the subjective sense of causality. We propose to examine tics as well as normal, voluntary movements in patients with Tourette Syndrome and Chronic Tic Disorder to identify the time course between the decision to move and the onset of movement. Using Libet's paradigm, we intend to have subjects watch a fast-rotating clock to report the times associated with willing (time W) and initiating (time M) movement; we will also determine 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 a tic disorder and frequent tics as well as normal, healthy volunteers as controls. DESIGN: We will ask tic patients to rate the "voluntariness" of their tics using a rating scale. We will ask tics patients to look at a fast-rotating clock on a computer screen and note when their movements were willed (time W) and were initiated (time M), for tics as well as normal voluntary movements. 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. The design will be the same for the normal volunteers with the exception that the volunteers will not complete rating scales and will not be experiencing tics. OUTCOME MEASURES: The primary outcome measure of this study is the latency of times W and M (before EMG onset) in tics patients as correlated with the voluntariness the patients associate with their tics, compared to the time W and M reported for normal voluntary movements in the normal volunteers.