Abstract
Needle electrodes were used to record action potentials of motor units of the rectus femoris muscle during isometric contraction (up to 50% of maximal). Up to 10 motor units working simultaneously could be identified. Under strictly stable conditions of muscular contraction the recruitment order of the motoneurons was constant. The firing rate was inversely proportional as a rule to this recruitment order. As a rule the changes in frequency connected with voluntary contraction of measured strength were in the same direction for different motoneurons. Statistical analysis of the frequency fluctuations observed during contraction of constant strength revealed direct correlation between them. The behavior of the motoneurons as described above is regarded as the result of the diffuse, indeterminate distribution of the synaptic input in the group of motoneurons innervating the muscle studied. It was also shown that even under stable conditions individual motoneurons or groups of them sometimes fired independently. During the performance of different types of movements, the firing rates of the recruited motoneurons varied in different directions and some motoneurons were replaced by others. This shows that when motoneurons function under natural conditions they use not only a common (indeterminate) but also a determinate input.
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Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 5, No. 1, pp. 77–87, January–February, 1973.
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Person, R.S., Kudina, L.P. Work organization of a group of human motoneurons during voluntary muscular contraction. Neurophysiology 5, 63–70 (1973). https://doi.org/10.1007/BF01065214
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DOI: https://doi.org/10.1007/BF01065214