Low- and high-frequency subcortical SEP amplitude reduction during pure passive movement.

Objectives: To investigate the effect of pure passive movement on both cortical and subcortical\r\nsomatosensory evoked potentials (SEPs).\r\nMethods: Median nerve SEPs were recorded in 8 patients suffering from Parkinson’s disease (PD) and two\r\npatients with essential tremor. PD patients underwent electrode implantation in the subthalamic (STN)\r\nnucleus (3 patients) and pedunculopontine (PPTg) nucleus (5 patients), while 2 patients with essential\r\ntremor were implanted in the ventral intermediate nucleus (VIM) of the thalamus. In anesthetized\r\npatients, SEPs were recorded at rest and during a passive movement of the thumb of the stimulated wrist\r\nfrom the intracranial electrode contacts and from the scalp. Also the high-frequency oscillations (HFOs)\r\nwere analyzed.\r\nResults: Amplitudes of both deep and scalp components were decreased during passive movement, but\r\nthe reduction was higher at cortical than subcortical level. Also the HFOs were reduced by movement.\r\nConclusion: The different amount of the movement-related decrease suggests that the cortical SEP gating\r\nis not only the result of a subcortical somatosensory volley attenuation, but a further mechanism acting\r\nat cortical level should be considered.\r\nSignificance: Our results are important for understanding the physiological mechanism of the sensory–\r\nmotor interaction during passive movement.\r\n 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights\r\nreserved.