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Methods to Quantify Pharmacologically Induced Alterations in Motor Function in Human Incomplete SCI
Published on: April 18, 2011
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Modulation of spinal motor output by initial arm postures in anesthetized monkeys
Hiroaki Yaguchi1, Tomohiko Takei2, David Kowalski3
1Department of Neurophysiology, National Institute of Neuroscience, Tokyo 187-8502, Japan, Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 113-8656, Japan.
Summary
Spinal cord reflexes adjust muscle activity based on initial arm posture. This spinal reflex pathway influences voluntary movement by modifying motor commands relative to limb position.
Area of Science:
- Neuroscience
- Motor Control
- Spinal Cord Physiology
Background:
- Voluntary movement necessitates sensorimotor transformations adapting to initial limb states.
- Muscle recruitment patterns vary with limb position at movement onset for tasks like reaching.
Purpose of the Study:
- To investigate if sensorimotor transformations for movement control occur at the spinal cord level.
- To determine if cervical spinal cord stimulation can elicit posture-dependent motor responses in the upper limb.
Main Methods:
- Cervical spinal cord (C6 segment) stimulation in anesthetized monkeys using microelectrode arrays.
- Electromyography (EMG) recorded from 12 upper limb muscles (hand, elbow, shoulder).
- Systematic manipulation of initial arm posture (nine positions) to assess modulation of evoked muscle twitches.
Main Results:
- 61% of electrode-muscle pairs showed posture-dependent modulation in twitch magnitude or latency.
- Posture dependency was more pronounced in distal muscles compared to proximal muscles.
- Spinalization at C2 did not affect the observed posture dependency, indicating spinal reflex involvement.
Conclusions:
- Cervical spinal cord excitability is modulated by initial arm posture via spinal reflex pathways.
- This posture-dependent spinal motor output can influence voluntary arm movements.
- Spinal reflexes contribute to adjusting motor commands based on the limb's starting configuration.
