title: Electrical stimulation of the human descending motor tracts at several levels.
abstract: The descending motor tracts were activated using a high voltage electrical stimulation technique at four levels: the motor cortex, brainstem (around the pyramidal decussation), and the first and sixth thoracic vertebral levels (T1, T6). Electromyographic activity was recorded from the tibialis anterior or extensor digitorum brevis muscles. Consistent motor action potentials could be evoked in all normal subjects. The conduction velocity of the descending tracts was estimated to be 62 to 79 m/s. The sum of synaptic delay and utilization time at the motoneurons (spinal delay time) was estimated to be 0.5 +/- 0.3 ms indicating a mono- or oligosynaptic connection. In patients with diffusely affected descending tracts, the technique showed slowed conduction along the descending tracts and prolonged spinal delay time which may include the time required for temporal summation of excitatory postsynaptic potentials as well as synaptic delay and utilization time. In patients with a localized lesion, localized conduction delay was found at the appropriate segment.
authors.affiliation: Department of Neurology, School of Medicine, University of Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ugawa
authors.forename: K
authors.initials: K
authors.lastname: Genba-Shimizu
authors.forename: I
authors.initials: I
authors.lastname: Kanazawa
mesh_terms: D000328:Adult; D000818:Animals; D001933:Brain Stem; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex; D009046:Motor Neurons / Q000473:pathology*; D009132:Muscles; D013116:Spinal Cord