Summary
The firing patterns of α and γ efferent fibres and of group I and group II afferent fibres innervating the gastrocnemius muscle were observed during spontaneous locomotor movements in the thalamic cat. Multi-unit discharges of each kind of fibre were obtained by electronic sorting of the action potentials from the whole activity of a thin branch of gastrocnemius lateralis or medialis nerve. The main results were: (1) During the locomotor cycle the activity of the afferent and efferent populations was highly modulated. (2) α- and γ-motoneurones were co-activated within the locomotor cycle during ankle plantar-flexion. The γ discharge began to rise earlier and to fall later than did the α discharge. The amplitude of the γ discharge, unlike that of the α discharge, was largely independent of the vigour of walking. Between the cyclic discharges, most of γ populations were tonically active whereas α populations were silent. Subgroups of the α and γ populations were not usually activated according to the cell-size principle, but, the activation of the latest γ subgroup always preceded that of the earliest α subgroup. (3) Modulation of the group I and II afferent discharges was closely related to the cyclic length changes of the parent muscle. Fusimotor activation during the active shortening of gastrocnemius muscle prevented the afferent discharges from pausing. (4) The pattern of afferent and efferent activity during selective curarisation of the extrafusal junctions indicated that the discharge of static γ-motoneurones is modulated during the locomotor cycle. After curarisation of both extrafusal and intrafusal junctions, an efferent-discharge pattern of central origin persisted alternately in extensor- and flexor-muscle nerves (fictive locomotion). The durations of the fictive locomotor cycle and of the cyclic discharge in the sartorius nerve were increased as a consequence of the suppression of phasic afferent inputs to the C.N.S. (5) Maintained ankle dorsi-flexion slowed the fictive locomotor rhythm and elicited opposite effects, respectively excitation and depression, on the magnitude of the α and γ discharges. Maintained ankle plantar-flexion scarcely perturbed the duration of the fictive locomotor cycle, but the duration of the sartoriusnerve discharge lengthened at the expense of that of the gastrocnemius discharge. Both gastrocnemius α-and γ-motoneurones were depressed, the former considerably more than the latter. (6) The roles of the gastrocnemius afferents and γ-efferents during the locomotor cycle are discussed in the light of these results.
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References
Appelberg B, Bessou P, Laporte Y (1966) Action of static and dynamic fusimotor fibres on secondary endings of cat's spindles. J Physiol (Lond) 185: 160–171
Appelberg B, Hulliger M, Johansson H, Sojka P (1983a) Actions on γ-motoneurones elicited by electrical stimulation of group I muscle afferent fibres in the hind limb of the cat. J Physiol (Lond) 335: 237–253
Appelberg B, Hulliger M, Johansson H, Sojka P (1983b) Actions on γ-motoneurones elicited by electrical stimulation of group II muscle afferent fibres in the hind limb of the cat. J Physiol (Lond) 335: 255–273
Appenteng K, Prochazka A, Proske U, Wand P (1982) Fusimotor stimulation can maintain cat soleus Ia firing even during very rapid muscle shortening. J Physiol (Lond) 326: 51–52P
Bessou P, Emonet-Dénand F, Laporte Y (1965) Motor fibres innervating extrafusal and intrafusal fibres in the cat. J Physiol (Lond) 180: 649–672
Bessou P, Joffroy M, Montoya R, Pagès B (1984a) Effects of triceps stretch by ankle flexion on intact afferents and efferents of gastrocnemius in the decerebrate cat. J Physiol (Lond) 346: 73–91
Bessou P, Joffroy M, Montoya R, Pagès B (1984b) Action réflexogène des fibres afférents musculaires des groupes I et II sur les motoneurones γ homonymes. J Physiol (Paris) 79: 39A
Bessou P, Joffroy M, Pagès B (1981) Efferents and afferents in an intact muscle nerve: background activity and effects of sural nerve stimulation in the cat. J Physiol (Lond) 320: 81–102
Burke RE (1981) Motor units: anatomy, physiology and functional organisation. In: Brooks VB (ed) Handbook of physiology, Sect 1, Vol II. American Physiological Society, Bethesda, pp 345–422
Burke D, Hagbarth KE, Löfstedt L (1978) Muscle spindle activity in man during shortening and lengthening contractions. J Physiol (Lond) 277: 131–142
Cabelguen J-M (1981) Static and dynamic fusimotor controls in various hindlimb muscles during locomotor activity in the decorticate cat. Brain Res 213: 83–97
Crowe A, Matthews PBC (1964) Further studies of static and dynamic fusimotor fibres. J Physiol (Lond) 174: 132–151
Emonet-Dénand F, Houk J (1968) Etude comparative de la curarisation des synapses neuromusculaires des fibres fusimotrices gamma dynamiques et statiques chez le chat. J Physiol (Paris) 60: 367–372
Forssberg H, Grillner S, Rossignol S (1975) Phase dependent reflex reversal during walking chronic spinal cat. Brain Res 85: 103–107
Goslow GE, Reinking RM, Stuart DG (1973) The cat step cycle: hind-limb joint angles and muscle lengths during unrestrained locomotion. J Morph 141: 1–42
Grillner S (1981) Control of locomotion in biped, tetrapods, and fish. In: Brooks VB (ed) Handbook of physiology, Sect 1, Vol II. American Physiological Society, Bethesda, pp 1179–1236
Gustafsson B, Pinter MJ (1984) An investigation of threshold properties among cat spinal α-motoneurones. J Physiol (Lond) 357: 453–483
Gustafsson B, Pinter MJ (1985) On factors determining orderly recruitment of motor units: a role for intrinsic membrane properties. Trends Neurosci 8: 431–433
Henneman E, Somjen G, Carpenter DO (1965) Functional significance of cell size in spinal motoneurones. J Neurophysiol 28: 560–580
Henneman E, Olson CB (1965) Relations between structure and function in the design of skeletal muscles. J Neurophysiol 28: 581–598
Joffroy M (1975) Méthode de discrimination des potentiels unitaires constituant l'activité complexe d'un filet nerveux non sectionné. J Physiol (Paris) 70: 239–252
Kuffler SW, Hunt CC (1952) The mammalian small-nerve fibres: a system for efferent nervous regulation of muscle spindle discharge. Res Publs Ass Res Nerv Ment Dis 30: 24–37
Loeb GE, Duysens J (1979) Activity patterns in individual hindlimb primary and secondary muscle spindle afferents during normal movements in unrestrained cats. J Neurophysiol 42: 420–440
Loeb GE, Hoffer JA (1985) Activity of spindle afferents from cat anterior thigh muscles. II. Effects of fusimotor blockade. J Neurophysiol 54: 565–577
Loeb GE, Hoffer JA, Pratt CA (1985) Activity of spindle afferents from cat anterior thigh muscles. I. Identification and patterns during normal locomotion. J Neurophysiol 54: 549–564
Matthews PBC (1970) The origin and functional significance of stretch reflex. In: Andersen P, Jansen JKS (eds) Excitatory synaptic mechanisms. Universitetsforlaget, Oslo, pp 301–315
Morgan DL, Prochazka A, Proske U (1985) Action of single dynamic fusimotor neurones on cat soleus Ia afferents during muscle shortening. Exp Brain Res 58: 56–61
Murphy PR, Stein RB, Taylor J (1984) Phasic and tonic modulation of impulse rates in gamma motoneurones during locomotion in premammillary cats. J Neurophysiol 52: 228–243
Orlovsky GN (1969) Spontaneous and induced locomotion of the thalamic cat. Biophysics 14: 1154–1162
Pearson KG, Duysens J (1976) Function of segmental reflexes in the control of stepping in cockroaches and cats. In: Herman RM, Grillner S, Stein PSG, Stuart DG (eds) Neural control of locomotion. Plenum Press, New York, pp 519–535
Perret C (1976) Neural control of locomotion in the decorticate cat. In: Herman RM, Grillner S, Stein PSG, Stuart DG (eds) Neural control of locomotion. Plenum Press, New York, pp 587–615
Perret C (1983) Centrally generated pattern of motoneurone activity during locomotion in the cat. In: Roberts A, Roberts B (eds) Neural origin of rhythmic movements. Society for Experimental Biology Symposium XXXVII, pp 405–422
Perret C, Buser P (1972) Static and dynamic fusimotor activity during locomotor movements in the cat. Brain Res 40: 165–169
Prochazka A, Westerman RA, Ziccone SP (1976) Discharge of single hindlimb afferents in the freely moving cat. J Neurophysiol 39: 1090–1104
Severin FV (1970) The role of the gamma motor system in the activation of the extensor alpha motor neurones during controlled locomotion. Biophysics 15: 1138–1145
Sjöström A, Zangger P (1976) Muscle spindle control during locomotor movements generated by the deafferented spinal cord. Acta Physiol Scand 97: 281–291
Taylor J, Stein RB, Murphy PR (1985) Impulse rates and sensitivity to stretch of soleus muscle spindle afferent fibers during locomotion in premammillary cats. J Neurophysiol 53: 341–360
Vallbo AB (1971) Muscle spindle response at the onset of isometric voluntary contractions in man. Time differences between fusimotor and skelemotor effects. J Physiol (Lond) 318: 405–431
Windhorst U, Schwestka R (1982) Interactions between motor units in modulating discharge patterns of primary muscle spindle endings. Exp Brain Res 45: 417–427
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Bessou, P., Cabelguen, J.M., Joffroy, M. et al. Efferent and afferent activity in a gastrocnemius nerve branch during locomotion in the thalamic cat. Exp Brain Res 64, 553–568 (1986). https://doi.org/10.1007/BF00340493
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DOI: https://doi.org/10.1007/BF00340493