NeuronalOscillationsintheBasalGangliaand MovementDisorders:EvidencefromWholeAnimaland HumanRecordings

Neuronal oscillations underlie a number of physiological processes, such as respiration, diurnal rhythms of the sleep–wake cycle, and gait. Oscillatory activity can be observed in many different brain regions and can be synchronized across these different regions or nuclei. Oscillatory activity has long been recognized in the electroencephalogram (EEG), in which synchrony between thalamus and cortex can be observed at different frequencies. These oscillations are generally subdivided into types onthebasisoftheircharacteristicfrequencyandlocation,suchas theta(2–7Hz),alpha(7–13Hzinvisualcortex),beta(11–30Hz), gamma (30–80 Hz), and mu (7–12 Hz, sensorimotor). Recent studies in animals and humans have revealed the existence of several types of oscillatory activity in the various nuclei of the basal ganglia and, although still poorly understood, are believed toplayanimportantfunctioninboththenormalphysiologyand pathophysiology of this system. This mini-symposium will describe the findings of recent studies that have examined various aspects of oscillatory activity in the basal ganglia. In the past decade, there has been an increase in basal ganglia surgery for movement disorders, primarily for Parkinson’s disease, but also dystonia and Huntington’s disease, which has provided a unique opportunity for neurophysiologists such as William Hutchison and Jonathan Dostrovsky to probe these subcortical structures in the clinical setting. Although previous surgeries involved the stereotactic placement of lesions in the brain,theeraofneuroablativeprocedureshasgivenwayto“neuroaugmentive procedures” involving chronic indwelling electrodes implanted for deep brain stimulation. Many centers use microelectrodes to map the basal ganglia targets in the internal globus pallidum (GPi) and, more recently, the subthalamic nucleus (STN). During the course of these mapping procedures, it became evident that oscillatory activity could be detected in the firingofindividualneuronsinthesestructures,particularlyinthe