Correlated activity in globus pallidus and thalamus during voluntary reaching movement in three children with primary dystonia

Classical models of the physiology of dystonia suggest that involuntary muscle contractions are caused by inappropriately low activity in Globus Pallidus internus (GPi) that fails to adequately inhibit thalamic inputs to cortex. We test this prediction in three children with primary dystonia undergoing depth electrode recording in basal ganglia and thalamus during selection of targets for deep brain stimulation (DBS) implantation. We compare muscle activity to the power in the spectrogram of the local field potential, as well as to counts of identified spikes in GPi, subthalamic nucleus (STN), and the Ventral oralis (VoaVop) and Ventral Anterior (VA) subnuclei of the thalamus, while subjects are at rest or attempting to make active voluntary arm or leg reaching movements. In all three subjects, both spectrogram power and spike activity in GPi, STN, VoaVop, and VA are significantly positively correlated with movement. In particular, GPi and STN both increase activity during attempted movement. These results contradict the classical rate model of the physiology of dystonia, and support more recent models that propose abnormalities in the detailed pattern of activity rather than the overall lumped activity of pallidum and thalamus.