Deep brain stimulation of the pedunculopontine region in the normal non-human primate

Lesions in the pedunculopontine nucleus (PPN) cause akinesia. The PPN degenerates in Parkinson's disease. Stimulation of the PPN region induces stepping movements in rats and cats. These findings suggest that the PPN may play an important role in akines ia and that stimulating it may alleviate akinesia.Therefore, we have stereotactically implanted a macroelectrode in the left PPN region in a normal macaque to investigate the effects of deep brain stimulation at different frequencies. Motor activity was recorded with an infra-red counter and behaviour videotaped. At frequencies above 45 Hz there was significantly more severe akinesia than at lower frequencies (paired t -test, n=15, P<0.005). At 100 Hz, there was gross impairment of postural control. At low frequencies (5-30 Hz), stimulation induced a 5-Hz tremor in the right arm. We conclude that stimulating the PPN region at high frequency causes akinesia, whereas low frequencies induce some positive motor effects.