Electrical stimulation of the posteroventral pallidum influences internally guided saccades in Parkinson's disease

Chronic electrical stimulation of the posteroventral internal pallidum, a recently developed treatment option in advanced Parkinson's disease (PD), improves bradykinesia, rigidity and medication-induced dyskinesia. Apart from disturbances of the somatic motor system, PD is also characterized by disturbances of saccadic eye movements with hypometric and delayed internally guided saccades. We examined these internally guided eye movements (memory-guided and anti-task saccades) in a patient with bilaterally implanted stimulation electrodes, when stimulation was turned on and off. The electrical stimulation not only improved the bradykinesia and rigidity, but also the internally guided saccades by shortening the latency of the anti-saccades and increasing the gain of the memory-guided saccades. This finding supports the idea that the oculomotor pathways through the basal ganglia are organized like the somatic motor pathways and that stimulation of the posteroventral pallidum influences both.