AI Article Synopsis
- The study explored how low-threshold afferent signals from the extensor carpi radialis (ECR) affect motoneurons that control the intrinsic muscles of the hand using PSTH and EMG-A methods.
- Electrical stimulation of the radial nerve showed occasional facilitation in motor units, indicating that ECR can influence hand muscle motoneurons, but this connection is infrequent and weak.
- The research implies that while there is a monosynaptic link from ECR to hand muscle motoneurons in humans, its weakness may facilitate more dexterous, manipulatory hand movements.
Article Abstract
The projection pattern of low-threshold afferents from the extensor carpi radialis (ECR) to motoneurons supplying intrinsic hand muscles was investigated using the post-stimulus time-histogram (PSTH) and electromyogram-averaging (EMG-A) methods. Electrical conditioning stimulation was applied to the radial nerve branch innervating the ECR. In the PSTH study, changes in the firing probability of single motor units following the stimulation were examined. An early and significant peak (facilitation) was induced in the motoneurons innervating the muscles, but the facilitation was induced infrequently. The central latency of the facilitation was equivalent to that of homonymous facilitation through monosynaptic path in the spinal cord. In the EMG-A study, changes in the rectified and averaged electromyograms following the conditioning stimulation were examined. An early and significant peak (facilitation) was also induced. The facilitation disappeared after withdrawal of the vibration to the ECR muscle belly. Cutaneous nerve stimulation overlaying ECR never induced such facilitation in the PSTH and EMG-A studies. These findings suggest that monosynaptic facilitation mediated by group Ia afferents of ECR to the motoneurons supplying intrinsic hand muscles exists in humans, but the connection seems to be weak. This weakness might allow manipulatory movements of the hand.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9413870 | PMC |
| http://dx.doi.org/10.14814/phy2.15431 | DOI Listing |
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