ISSN:
1432-0770
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Computer Science
,
Physics
Notes:
Abstract Comparison of the discharge patterns of soleus motor units with associated changes in force exerted by foot during quiet stance have already demonstrated the following facts. In the initial stage of standing, the motor units exhibited stationary and asynchronous discharges. The force showed a sporadic presence of the high frequency oscillation in the 8–10 Hz band. After five to ten minutes of standing, the firing rate of individual motor unit discharges increased to about 10 spikes/sec and discharges of each motor unit were synchronized and phase-locked to each of the accompanying force oscillation. During this transitional stage, the discharges of motor units were characterized by spike dropouts from an otherwise regular spike train. To simulate the changes in the discharge characteristics, we have proposed a parallel feedback model of the stretch reflex arc. This was made of multiple α-motoneurons, motor units and muscle spindles. And motor units interact each other through group Ia afferent signals. As a result of simulation, motor units were found to exhibit stationary and asynchronous discharges when feedback gain was kept small. With an increase of feedback gain, the firing rate of individual motor units increased and finally the discharges of them were synchronized. During this transitional stage, the spike dropouts were observed in accordance with the experimental results. The neuronal mechanism of synchronization may partly be explained by the interactions of motor neurons through the above stated parallel feedback system.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01259393
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