2098 Movement Decreases Synchronization Between Beta Band Local Field Potential and Single-Unit Activity in Parkinson's Disease

INTRODUCTION: Beta band (12-30 Hz) oscillations are thought to maintain the current sensorimotor state and have been shown to be modulated during movement. Pathologically increased beta power and abnormalities in single-unit spiking have been characterized in the subthalamic nucleus (STN) of Parkinson’s Disease patients. Despite these findings, the relationship between single-unit activity and beta oscillations during movement remains unclear. METHODS: Microelectrode recordings were obtained from 16 subjects undergoing stereotactic DBS implantation surgery. Recordings were taken after implantation in the STN while the patient was awake and performing a center-out reach task. Four conditions were studied: Rest (prior to task start), preparatory (400-50 ms before reach), Reach (50 to 400 ms after reach start), and hold (50-400 ms after hold start). RESULTS: Relative beta power was significantly lower during reaches than in any other epoch and spike-field coherence (SFC) in high-beta (20-30 Hz) was lowest during reach. Relative power was also low during rest, however SFC was highest. Preferred phases of coherence were most consistent throughout the beta band during rest and least consistent during reaches from 20-30 Hz. Spike-triggered averaging (STA) magnitude decreased during reach in high beta. CONCLUSIONS: During movement, relative beta power, spike-field coherence, spike-triggered average amplitude and phase consistency decreased. This supports previous findings suggesting that the relationship between beta oscillations and single-units in the STN are modulated during movement. Decreased SFC and STA-LFP amplitude from 20-30 Hz demonstrate that single-units in the STN are more likely to fire independently during movement and synchronously during hold and preparation. During rest, power was lower than during hold or preparation, but synchronization with spikes was higher, suggesting beta power and single-unit activity may be decoupled during rest and are more strongly coupled during maintenance of position.