Abstract

We recorded local field potentials (LFPs) in a patient with implanted bilateral subthalamic nucleus (STN) and pedunculopontine nucleus (PPN) deep brain stimulation (DBS) electrodes at 2 kHz and filtered at 0.5–500 Hz. Frequency power spectra and the average power across a 1–100 Hz frequency range was calculated at rest and during passive, yaw-plane whole body rotations at 0.2 Hz and 0.4 Hz with eyes closed and then open with manifest vestibular ocular reflex activation (i.e., nystagmus) and then with eyes open but with VOR suppression (VORS). PPN LFPs showed significant modulation during vestibular activation (rotations) compared to rest with power changes circa four times larger than those found in the STN. The PPN LFP was dominated by theta (4–7 Hz) activity which was enhanced during all tasks compared to rest (including eyes open vs closed at rest) except for VORS where there was a clear reduction in theta activity and this was more prominent for fast rotations. The pattern of theta activity was the same for right and left PPN including task-dependent modulation. In summary, our data show that human PPN activity in the theta range is increased by visual and vestibular input except during VORS when there is a prominent attenuation of theta activity. An attenuation of neural activity is known to occur in primate brainstem circuits mediating the VOR during VOR suppression. Our data thus suggest a prominent role for vestibular signals in PPN functioning.