Summary
In approximately 3/4 of precollicular decerebrate (unanesthetized) cats, tetanic electrical stimulation of the sural nerve, or pinching the ankle skin innervated by the sural nerve, produced predominant excitation (overall increased force output and EMG activity) in the mixed medical gastrocnemius (MG) muscle and simultaneous inhibition in its slow twitch Synergist, soleus (Sol). The present experiments were designed to test whether, as this and other evidence suggests, certain sets of cutaneous afferents can produce activation of particular groups of motor units and simultaneous inhibition of other groups within the same motor unit pool (i.e., units belonging to a single muscle).
We recorded, in decerebrate cats, the activity of restricted sets of MG motor units using either fine bipolar EMG wire electrodes or bipolar hook electrodes on small natural filaments of the MG muscle nerve. In preparations exhibiting the differential effect of sural input noted above, we usually found that some low threshold MG motor units (i.e., those responding to stretch or vibration of the MG muscle) exhibited slowing of discharge or complete inhibition at the same time that higher threshold MG units, not responsive to stretch or vibration, were powerfully recruited by either electrical or natural stimulation of sural nerve afferents. The net balance of synaptic effects within the MG motoneuron population may thus be excitatory in some cells and simultaneously inhibitory in others. This finding, together with earlier evidence, suggests the existence of at least two patterns of organization of synaptic input to the MG motoneuron pool.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Anastasijević, R., Anojčić, M., Todorović, B., Vučo, J.: The differential reflex excitability of alpha motoneurons of decerebrate cats caused by vibration applied to the tendon of the gastrocnemius medialis muscle. Brain Res. 11, 336–346 (1968)
Bak, M.J., Schmidt, E.M.: An improved time-amplitude window discriminator. IEEE-BME In press (1977a)
Bak, M.J., Schmidt, E.M.: An analog delay circuit for on-line visual confirmation of discriminated neuroelectrical signals. IEEE-BME 24, 69–71 (1977b)
Barrett, J.N., Crill, W.E.: Specific membrane properties of cat motoneurons. J. Physiol. (Lond.) 239, 301–324 (1974)
Burke, R.E.: Group Ia synaptic input to fast and slow twitch motor units of cat triceps surae. J. Physiol. (Lond.) 196, 605–630 (1968a)
Burke, R.E.: Firing patterns of gastrocnemius motor units in the decerebrate cat. J. Physiol. (Lond.) 196, 631–654 (1968b)
Burke, R.E.: On the central nervous system control of fast and slow twitch motor units. In: New Developments in Electromyography and Clinical Neurophysiology, Vol. 3 (ed. J.E. Desmedt), pp. 69–94. Basel: Karger 1973
Burke, R.E., Edgerton, V.R.: Motor unit properties and selective involvement in movement. In: Exercise and Sport Sciences Reviews, Vol. 3 (eds. J.H. Wilmore and J.F. Keogh), pp. 31–81. New York: Academic Press 1975
Burke, R.E., Jankowska, E., Bruggencate, G. ten: A comparison of peripheral and rubrospinal synaptic input to slow and fast twitch motor units of triceps surae. J. Physiol. (Lond.) 207, 709–732 (1970)
Burke, R.E., Levine, D.N., Salcman, M., Tsairis, P.: Motor units in cat soleus muscle: Physiological, histochemical and morphological characteristics. J. Physiol. (Lond.) 238, 503–514 (1974)
Burke, R.E., Levine, D.N., Tsairis, P., Zajac, F.E.: Physiological types and histochemical profiles in motor units of the cat gastrocnemius. J. Physiol. (Lond.) 234, 723–748 (1973a)
Burke, R.E., Rymer, W.Z., Walsh, J.V.: Functional specialization in the motor unit population of cat medial gastrocnemius muscle. In: Control of Posture and Locomotion (eds. R.B. Stein, K.B. Pearson, R.S. Smith and J.B. Redford), pp. 29–44. New York: Plenum 1973b
Burke, R.E., Rymer, W.Z., Walsh, J.V.: Relative strength of synaptic input from short-latency pathways to motor units of defined type in cat medial gastrocnemius. J. Neurophysiol. 39, 447–458 (1976)
Clamann, H.P., Gillies, J.D., Henneman, E.: Effects of inhibitory inputs on critical firing level and rank order of motoneurons. J. Neurophysiol. 34, 1350–1360 (1974)
Ciamann, H.P., Henneman, E.: Electrical measurement of axon diameter and its use in relating motoneuron size to critical firing level. J. Neurophysiol. 39, 844–851 (1976)
Creed, R.S., Denny-Brown, D., Eccles, J.C., Liddell, E.G.T., Sherrington, C.S.: Reflex Activity of the Spinal Cord. Oxford: Oxford Univ. Press 1932
Denny-Brown, D.: On the nature of postural reflexes. Proc. roy. Soc. B 104, 252–301 (1929)
Eccles, J.C., Sherrington, C.S.: Numbers and contraction values of individual motor units examined in some muscles of the limb. Proc. roy. Soc. B 106, 326–357 (1930)
Freund, H.-J., Büdingen, H.-J., Dietz, V.: Activity of single motor units from human forearm muscles during voluntary isometric contractions. J. Neurophysiol. 38, 933–946 (1975)
Granit, R.: The Basis of Motor Control. New York: Academic Press 1970
Grimby, L., Hannerz, J.: Recruitment order of motor units in voluntary contraction: Changes induced by proprioceptive afferent activity. J. Neurol. Neurosurg. Psychiat. 31, 565–573 (1968)
Grimby, L., Hannerz, J.: Differences in recruitment order and discharge pattern of motor units in the early and late flexion reflex components in man. Acta physiol. scan. 90, 555–564 (1974)
Grimby, L., Hannerz, J.: Disturbances in voluntary recruitment order of low and high frequency motor units on blockade of proprioceptive afferent activity. Acta physiol. scand. 96, 207–216 (1976)
Hagbarth, K.-E.: Excitatory and inhibitory skin areas for flexor and extensor motoneurons. Acta physiol. scand. 26, Suppl. 94, 1–58 (1952)
Henneman, E., Somjen, G., Carpenter, D.O.: Functional significance of call size in spinal motoneurons. J. Neurophysiol. 28, 560–580 (1965)
Henneman, E., Clamann, H.P., Gillies, J.D., Skinner, R.D.: Rank order of motoneurons within a pool: Law of combination. J. Neurophysiol. 34, 1338–1349 (1974)
Kanda, K., Walmsley, B., Burke, R.E.: Differential recruitment of medial gastrocnemius motor units produced by cutaneous (sural nerve) input in decerebrate cats. Neuroscience Abstr. 2, 976 (1976)
Kato, M., Tanji, J.: Volitionally controlled single motor units in human finger muscles. Brain Res. 40, 345–357 (1972)
Kernell, D., Sjöholm, H.: Recruitment and firing rate modulation of motor unit tension in a small muscle of the cat's foot. Brain Res. 98, 57–72 (1975)
Milner-Brown, H.S., Stein, R.B., Yemm, R.: The orderly recruitment of human motor units during voluntary isometric contractions. J. Physiol. (Lond.) 230, 359–370 (1973)
Rall, W., Hunt, C.C.: Analysis of reflex variability in terms of partially correlated excitability fluctuations in a population of motoneurons. J. gen. Physiol. 39, 397–422 (1956)
Ryall, R.W., Piercey, M.F., Polosa, C., Goldfarb, J.: Excitation of Renshaw cells in relation to orthodromic and antidromic excitation of motoneurons. J. Neurophysiol. 35, 137–148 (1972)
Tanji, J., Kato, M.: Recruitment of motor units in voluntary contraction of a finger muscle in man. Exp. Neurol. 40, 759–770 (1973)
Wyman, R.J., Waldron, I., Wachtel, G.M.: Lack of fixed order of recruitment in cat motoneuron pools. Exp. Brain Res. 20, 101–114 (1974)
Zucker, R.S.: Theoretical implications of the size principle of motoneuron recruitment. J. theor. Biol. 38, 587–596 (1973)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Kanda, K., Burke, R.E. & Walmsley, B. Differential control of fast and slow twitch motor units in the decerebrate cat. Exp Brain Res 29, 57–74 (1977). https://doi.org/10.1007/BF00236875
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00236875