Dean and Vice President of Medical Affairs FAU Boca Raton, Florida, United States
Introduction: Phase-amplitude coupling (PAC) is one of the most well-studied interactions between oscillations at different frequency bands; however, limited research has explored the functional use of directional local field potentials (LFPs) using PAC in the subthalamic nucleus (STN) in Parkinson’s disease (PD) and the ventral intermediate nucleus of the thalamus (VIM) in essential tremor (ET). We investigated whether PAC could identify sub-territories of the basal ganglia structures and guide selection of stimulation direction to assist device programming.
Methods: Participants were recruited from patients diagnosed with tremor-dominant PD or ET and scheduled to undergo DBS surgery at Albany Medical Center. Directional LFPs were re-referenced to their common average and time-frequency analysis was computed using a Welch periodogram method on MATLAB. PAC for nonlinear interactions between the phase of beta and amplitude of high frequency oscillations (HFOs) was investigated using a Modulation Index (MI) approach.
Results: LFPs in two subjects (2 male) from directional DBS leads were successfully obtained and processed. In ET case, direction of the lead on the intraoperative fluoroscopy image was not clear. However, the strongest PAC was localized to 2B, where C+3B- were the programming contacts selected by physician. In PD case, strongest PAC was found in the contact facing anterior and, as shown by our previous study, PAC was localized to the dorsal STN with amplitude frequency at slow HFO (200-400Hz) with C+2- as the programming contacts.
Conclusion : To our knowledge, this is the first time that beta-HFO has been demonstrated in LFP recordings from directional leads in an ET case. These preliminary data suggest that beta power or beta-HFO PAC could be used to guide optimal contact selection when directional leads are used. Such findings could improve efficiency of DBS programming. We will further investigate these interactions in a larger cohort.
