Spatial resolution and heterogeneity of local field potentials in the globus pallidus

Local field potentials (LFPs) are thought to be promising feedback signals for implementation in closed-loop deep brain stimulation (DBS) systems. However, little is known about how spectral properties of bipolar LFPs recorded along a DBS lead depend on electrode size and spacing. In this study, we recorded LFPs from two different DBS lead designs spanning the external globus pallidus (GPe) and internal globus pallidus (GPi) in two non-human primates. Bipolar electrode recording montages were progressively grouped to investigate spatial heterogeneity of oscillatory activity in the beta (10-30 Hz) and high gamma (>70 Hz) frequencies. For both DBS leads, the data showed that the highest ratio of beta to gamma activity within the GPi. The stronger ratio of beta to gamma was found for a bipolar electrode pitch of 750 μm compared to 1000 μm, while a larger inter-electrode spacing of 1.5-3 mm with one contact in the GPe and the other in the GPi produced the strongest activity. Finally, oscillatory activity recorded within the same region of globus pallidus with a bipolar electrode montage oriented longitudinally versus radially did not differ significantly. Together, these data provide important guidelines for the design of recording electrodes for use with closed-loop DBS leads in the globus pallidus.