title: Blocking central pathways in the primate motor system using high-frequency sinusoidal current.
abstract: Electrical stimulation with high-frequency (2-10 kHz) sinusoidal currents has previously been shown to produce a transient and complete nerve block in the peripheral nervous system. Modeling and in vitro studies suggest that this is due to a prolonged local depolarization across a broad section of membrane underlying the blocking electrode. Previous work has used cuff electrodes wrapped around the peripheral nerve to deliver the blocking stimulus. We extended this technique to central motor pathways, using a single metal microelectrode to deliver focal sinusoidal currents to the corticospinal tract at the cervical spinal cord in anesthetized adult baboons. The extent of conduction block was assessed by stimulating a second electrode caudal to the blocking site and recording the antidromic field potential over contralateral primary motor cortex. The maximal block achieved was 99.6%, similar to findings of previous work in peripheral fibers, and the optimal frequency for blocking was 2 kHz. Block had a rapid onset, being complete as soon as the transient activation associated with the start of the sinusoidal current was over. High-frequency block was also successfully applied to the pyramidal tract at the medulla, ascending sensory pathways in the dorsal columns, and the descending systems of the medial longitudinal fasciculus. High-frequency sinusoidal stimulation produces transient, reversible lesions in specific target locations and therefore could be a useful alternative to permanent tissue transection in some experimental paradigms. It also could help to control or prevent some of the hyperactivity associated with chronic neurological disorders.
authors.affiliation: Institute of Neuroscience, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom; and.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Fisher
authors.affiliation: Institute of Primate Research, National Museums of Kenya, Karen, Nairobi, Kenya.
authors.forename: Ngalla E
authors.initials: NE
authors.lastname: Jillani
authors.affiliation: Institute of Primate Research, National Museums of Kenya, Karen, Nairobi, Kenya.
authors.forename: George O
authors.initials: GO
authors.lastname: Oluoch
authors.affiliation: Institute of Neuroscience, Medical School, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom; and stuart.baker@ncl.ac.uk.
authors.forename: Stuart N
authors.initials: SN
authors.lastname: Baker
mesh_terms: D000818:Animals; D004558:Electric Stimulation / Q000379:methods*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D010215:Papio; D010525:Peripheral Nerves / Q000502:physiology
keywords: corticospinal; high-frequency block