Co-modulation of finely tuned high-gamma band activity across hemispheres in Parkinson's disease

Objective: Dopaminergic treatment of patients with Parkinson's disease can be associated with a finely tuned high-gamma (FTG) band oscillation between 60 and 90. Hz in the basal ganglia (BG) nuclei. This activity, together with suppression of excessive neural synchrony in the beta frequency band (15-30. Hz), is hypothesized to contribute to the pro-kinetic effects of dopaminergic medication. Beta activity, which high-gamma replaces, has been shown to be bilaterally coherent, but whether sub-cortical FTG activity is in some way linked across hemispheres remains unknown. Methods: We analyse bilateral local field potential activity recorded from the subthalamic nuclei of 10 patients on dopaminergic medication while at rest, following surgery for deep brain stimulation. Results: In three of these patients FTG activities were coherent across the hemispheres. Short duration (≤18. s) bilateral amplitude and frequency co-modulation were recorded in all subjects, although the two phenomena were independent in time and independent of similar episodes in other frequency bands. Conclusions: FTG co-modulation can be independent of movement and of co-modulation episodes at other frequencies. Significance: Relatively independent organisation of processing through amplitude and frequency modulation within different frequency bands potentially affords opportunities for functional segregation and multiplexing of processing streams within the BG. © 2013 International Federation of Clinical Neurophysiology.