STUDY 1: Event-Related Potential Study of Psychomotor Slowing in Bipolar Disorder `

Many psychiatric disorders affecting mood, and among them bipolar disorder (BD), are associated with distinct patterns of psychomotor slowing that can be revealed during behavioral tests. This pilot study investigated how the brain reacts to sensory signals, and why reactions to such stimuli are impaired in patients with BD even when they do not present symptoms of mood disturbances. Eventrelated potential (ERP) recording technique was used to analyze time course of information processing stages and reveal timing and topography of processing abnormalities in psychopathologies. Reaction time (RT) is used to assess motor response speed during behavioral tests. The purpose of this study was to evaluate the role of perceptual and motor demands of the task on cognitive processes and behavioral performance in group of patients with bipolar disorder and collect pilot data. Eleven euthymic patients with BD and eleven healthy subjects participated in the study. The experiment represented a modification of visual target detection task and examined the differential cortical reactivity to task demands (overt motor vs. silent count) and signal features (masked vs. non-masked). We used Electrical Geodesics Inc. electroencephalograph to record brain waves from 128 location of the scalp. The group of bipolar patients compared to controls in our study showed longer RT and delayed cognitive ERPs in oddball task with motor demands. ERP indices of stimulus property evaluation and classification speed were different between groups regardless of the type of response demands. These ERP findings suggest that slow speed of response-related processes, along with the slow perceptual stimulus-evaluation processes, might be important components of the psychomotor impairments in patients with BD.