Neuroscience 2003 Abstract
| Presentation Number: | 77.10 |
|---|---|
| Abstract Title: | Corticospinal transmission to ankle extensor motoneurones in relation to an anticipatory postural reaction. |
| Authors: |
Nielsen, J. B.*1
; Petersen, N. T.1
1Med. Physiol, Univ. Copenhagen, DK-2200 Copenhagen, Denmark |
| Primary Theme and Topics |
Motor Systems - Cortex and Thalamus -- Physiology |
| Secondary Theme and Topics | Motor Systems<br />- Brainstem<br />-- Physiology |
| Session: |
77. Cortical Control of Movement I Poster |
| Presentation Time: | Saturday, November 8, 2003 2:00 PM-3:00 PM |
| Location: | Morial Convention Center - Hall F-I, Board # I68 |
| Keywords: | POSTURE, REFLEX, ELECTRICAL STIMULATION, HUMAN |
A standing subject, who pulls a handle by flexing the elbow, will force the body forward unless muscles, which oppose the forward movement, are activated. The prime mover in that case is the biceps brachii while the ankle extensors are subject to an anticipatory activation and precedes the biceps activation (Nashner 1982). The mechanisms for this anticipatory activation are not fully understood. Here we investigate the corticospinal activation of the soleus muscle by transcranial magnetic stimulation (TMS) when the muscle is activated as part of an anticipatory response and when the muscle is activated by volition as a prime mover. Seven subjects participated in the experiments. In the anticipatory task subjects were instructed to stand on both legs and hold a handle in their right hand which they were to pull by performing an elbow flexion on an auditory go-signal. During the prime mover task the subjects were told to match by volition the soleus EMG activity observed during the anticipatory response. Alternating with TMS we elicted H reflexes by application of an electrical stimulus to the tibial nerve. H reflexes and EMG activity served as control of the spinal motoneuronal excitability. Both MEPs and H reflexes were adjusted to a size around 5% Mmax when the subjects were at rest. In both tasks the soleus H reflex showed a steep increase in size just prior (0 - 50 ms) to the onset of EMG activity in the soleus muscle. The amplitude of the soleus MEPs clearly increased around 100 ms prior to the onset of EMG activity during both tasks, but it was significantly larger (p < 0.05, two-way ANOVA) when soleus was activated as a prime mover. This difference in amplitude remained through the contraction.
The findings suggest a difference in corticospinal transmission during the two tasks. The exact nature of this difference will have to await additional studies.
Refererences
Nashner LM. Trends Neurosci 1982; 5:358-361.
The findings suggest a difference in corticospinal transmission during the two tasks. The exact nature of this difference will have to await additional studies.
Refererences
Nashner LM. Trends Neurosci 1982; 5:358-361.
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2003 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2003. Online.
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