Effect of Eye Opening on Single-Unit Activity and Local Field Potentials in the Subthalamic Nucleus.

BACKGROUND: Subthalamic nucleus deep brain stimulation (STN DBS) is an established treatment in Parkinson's disease (PD). We investigate the effect of eye opening on neuronal activity and local field potentials (LFPs) in the STN.

METHODS: We prospectively enrolled 25 PD patients undergoing STN DBS in our institution. During DBS, single-unit activity (SUA) and LFPs were measured when eyes were open and closed. As movement is known to result in changes in LFPs, we tested response to eye opening in the presence and absence of movement.

RESULTS: Neither eye state nor arm movement has a significant influence on SUA recordings. There is a statistically significant interaction between eye state and arm movement (p < 0.05). In the presence of movement, STN SUA increase when eyes open (p < 0.05). When eyes are closed, STN SUA decrease with movement (p < 0.05). STN theta LFP oscillations decrease when eyes are open compared to closed, irrespective of movement status (p < 0.05).

DISCUSSION: STN activity is influenced by eye state and arm movement. It is unclear whether this is attributed to a change in the STN's role in oculomotor control or from a change in attentional state. Understanding how physiologic normal activity alters neural activity is critical for the optimization of DBS therapy, particularly in closed-loop neuromodulation.