Saccade-related potentials recorded from human subthalamic nucleus

Objective To investigate an ocular motor role for the STN in Parkinson’s disease (PD) patients. Methods Potentials were recorded from deep brain stimulation (DBS) electrodes implanted in the vicinity of STN in five PD patients, while patients simultaneously performed visually cued saccades, self-paced saccades and in two patients self-paced wrist extensions. Results Premovement potentials related to visually cued saccades were found in 4/5 patients and 56% (5/9) of potentials showed phase reversal indicating a local generator. Onsets of these potentials began closer to saccade initiation from STN contacts (0.88 ± 0.30 s) than thalamic ones (1.39 ± 0.28 s). Self-paced saccade-related potentials were found in 4/4 patients. Self-paced saccade potential onsets (1.82 ± 0.88 s) were not different from self-paced wrist extension onsets (1.27 ± 0.98 s), suggesting a non-specific mechanism could be responsible for both potentials. 50% (3/6) of potentials to self-paced saccades and 66% (2/3) of potentials to self-paced wrist extensions showed phase reversal. Potentials could be found either ipsilaterally or contralaterally with respect to saccade direction. Conclusions These subcortical premovement potentials to saccades are similar to Bereitschaftspotentials and contingent negative variations to limb movements recorded in cortical and subcortical regions. Significance These studies further support a role of STN in ocular motor control and suggest a common mechanism of motor preparation for both eye and limb movements in the basal ganglia.