Tonic and phasic changes in anteromedial globus pallidus activity in Tourette syndrome

Background: Tourette syndrome is a hyperkinetic neurodevelopmental disorder characterized by tics. Objective: Assess the neuronal changes in the associative/limbic GP associated with Tourette syndrome. Methods: Neurophysiological recordings were performed from the anterior (associative/limbic) GPe and GPi of 8 awake patients during DBS electrode implantation surgeries. Results: The baseline firing rate of the neurons was low in a state-dependent manner in both segments of the GP. Tic-dependent transient rate changes were found in the activity of individual neurons of both segments around the time of the tic. Neither oscillatory activity of individual neurons nor correlations in their interactions were observed. Conclusions: The results demonstrate the involvement of the associative/limbic pathway in the underlying pathophysiology of Tourette syndrome and point to tonic and phasic modulations of basal ganglia output as a key mechanisms underlying the abnormal state of the disorder and the expression of individual tics, respectively.