Dopamine Dependency of Oscillations between Subthalamic Nucleus and Pallidum in Parkinson's Disease

TLDR

Synchronization between basal ganglia nuclei in Parkinson’s disease is poorly understood but is important because it can enhance postsynaptic efficacy at downstream targets. Local potentials were simultaneously recorded from the globus pallidus interna and subthalamic nucleus in six ipsilateral GPi–STN pairs in four awake Parkinson’s patients. In the absence of medication, GPi–STN activity and coherence were dominated by frequencies below 30 Hz, but levodopa shifted the dominant rhythm to ~70 Hz, demonstrating that synchronization between these nuclei is strongly modulated by dopaminergic activity.

Abstract

The extent of synchronization within and between the nuclei of the basal ganglia is unknown in Parkinson9s disease. The question is an important one because synchronization will increase postsynaptic efficacy at subsequent projection targets. We simultaneously recorded local potentials (LPs) from the globus pallidus interna (GPi) and subthalamic nucleus (STN) in four awake patients after neurosurgery for Parkinson9s disease. Nuclei from both sides were recorded in two patients so that a total of six ipsilateral GPi–STN LP recordings were made. Without medication, the power within and the coherence between the GPi and STN was dominated by activity with a frequency <30 Hz. Treatment with the dopamine precursor levodopa reduced the low-frequency activity and resulted in a new peak at ∼70 Hz. This was evident in the power spectrum from STN and GPi and in the coherence between these nuclei. The phase relationship between the nuclei varied in a complex manner according to frequency band and the presence of exogenous dopaminergic stimulation. Synchronization of activity does occur between pallidum and STN, and its pattern is critically dependent on the level of dopaminergic activity.