Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Pattern of projections of group I afferents from forearm muscles to motoneurones supplying biceps and triceps muscles in man

  • 128 Accesses

  • 65 Citations


(1) Two independent methods were used, in man, to assess the modifications of the excitability of biceps and triceps brachii motoneurone pools following the stimulation of group I afferents coming from muscles acting at the wrist: (a) the modifications of the excitability of a motoneuronal population were studied using a reflex technique, (b) the modifications of the excitability of an isolated motor unit were estimated using a post-stimulus time histogram (p.s.t.h.) method. (2) The activation of group I afferents contained in the median nerve, originating from wrist flexors and pronators, resulted in a strong, short-latency facilitation of the biceps brachii motoneurones. A similar effect was also evoked by stimulation of group I afferents in the radial nerve, distally to the branch supplying the brachio-radialis muscle. The latency of both median and radial-induced facilitations is compatible with a monosynaptic linkage. (3) The stimulation of group I afferents in the median or the radial nerves produced inhibition of triceps motoneurones, with a latency compatible with a disynaptic linkage. (4) The prolonged vibration of the tendon of the flexor carpi radialis (FCR) or of the extensor carpi radialis (ECR) raised the threshold for both the facilitation of biceps and the inhibition of triceps motoneurones. The same pattern of excitatory and inhibitory convergence could also be obtained when the electrical conditioning stimulus to the median or radial nerves was replaced by a tap applied to the tendons of FCR or ECR respectively. Both results suggest that the conditioning fibres were Ia fibres. (5) The pattern of distribution of Ia afferents from muscles acting at the wrist onto motoneurones of muscles acting at the elbow has been compared to that described in the cat and monkey. A comparison has also been made between Ia connections of muscles acting at different joints in the upper and lower limb in man. The differences are discussed in relation to the manipulating capacity of the hand.

This is a preview of subscription content, log in to check access.


  1. Baldissera F, Campadelli P, Cavallari P (1983) Inhibition of H-reflex in wrist flexors by group I afferents in the radial nerve. Electromyogr Clin Neurophysiol 23:187–193

  2. Bratzlavski M, Isch F, Vander Eechen H (1971) Study of evoked responses in proximal muscles of the superior and inferior limbs. Eur Neurol 5:171–186

  3. Buchtal F, Rosenfalk A (1966) Evoked action potentials and conduction velocity in human sensory nerves. Brain Res 3:1–122

  4. Cavallari P, Fournier E, Katz R, Pierrot-Deseilligny E, Shindo M (1984) Spinal projections of group I fibres from wrist flexors and extensors in man. Neurosci Lett [Suppl] 18:395

  5. Cavallari P, Fournier E, Katz R, Malmgren K, Pierrot-Deseilligny E, Shindo M (1985) Cutaneous facilitation of transmission in Ib reflex pathway in human upper limb. Exp Brain Res 60:197–199

  6. Clough JFM, Kernell D, Phillips CG (1968) The distribution of monosynaptic excitation from the pyramidal tract and from primary spindle afferents to motoneurones of the baboon's hand and forearm. J Physiol (Lond) 598:145–166

  7. Coppin CMC, Jack JJB, MacLennan CR (1970) A method for the selective electrical stimulation of tendon organ afferent fibres from the cat soleus muscle. J Physiol (Lond) 210:18p-20p

  8. Day BL, Marsden CD, Obeso JA, Rothwell JC (1984) Reciprocal inhibition between the muscles of the human forearm. J Physiol (Lond) 349:519–534

  9. Eccles JC, Eccles RM, Lundberg A (1957) The convergence of monosynaptic excitatory afferents onto many different species of alpha-motoneurones. J Physiol (Lond) 137:22–50

  10. Fetz EE, Gustafsson B (1983) Relation between shapes of postsynaptic potentials and changes in firing probability of cat motoneurones. J Physiol (Lond) 341:387–410

  11. Fetz E, Jankowska E, Johannisson T, Lipski J (1979) Autogenetic inhibition of motoneurones by impulses in group Ia muscle spindle afferents. J Physiol (Lond) 293:173–195

  12. Fournier E, Meunier S, Pierrot-Deseilligny E, Shindo M (1986) Evidence for interneuronally mediated Ia excitatory effects to human quadriceps motoneurones. J Physiol (Lond) 377:146–169

  13. Fritz N, Illert M (1981) Basic principles of Ia connections in the cat forelimb. Neurosci Lett [Suppl] 7:S347

  14. Gustafsson B, McCrea D (1984) Influence of stretch-evoked synaptic potentials on firing probability of cat spinal motoneurones. J Physiol (Lond) 347:431–451

  15. Heckman CJ, Condon MS, Hutton RS, Enoka RM (1984) Can Ib axons be selectively activated by electrical stimuli in human subjects? Exp Neurol 86:576–582

  16. Hongo T, Lundberg A, Phillips CG, Thomspon RF (1984) The pattern of monosynaptic Ia-connections to hindlimb motor nuclei in the baboon: a comparison with the cat. Proc R Soc London Ser B 221:261–289

  17. Jankowska E, McCrea D, Mackel R (1981a) Pattern of “non reciprocal” inhibition of motoneurones by impulses in group Ia muscle spindle afferents. J Physiol (Lond) 316:393–409

  18. Jankowska E, McCrea D, Mackel R (1981b) Oligosynaptic excitation of motoneurones by impulses in group Ia muscles spindle afferents in the cat. J Physiol (Lond) 316:411–425

  19. Katz R, Morin C, Pierrot-Deseilligny E, Hibino R (1977) Conditioning of H-reflex by a preceding subthreshold tendon reflex stimulus. J Neurol Neurosurg Psychiatr 40:575–580

  20. Lundberg A, Winsbury G (1960) Selective adequate activation of large afferents from muscle spindles and Golgi tendon organs. Acta Physiol Scand 49:155–164

  21. Magladery JW, Porter WE, Park AM, Tesdall RD (1951) Electrophysiological studies on nerve and reflex activity in normal man. IV. Two neurone reflex and identification of certain action potentials from spinal roots and cord. Bull Johns Hopkins Hosp 88:491–519

  22. Malmgren K, Pierrot-Deseilligny E (1988) Evidence for nonmonosynaptic Ia excitation of wrist flexor motoneurones, possibly via propriospinal neurones. J Physiol (Lond) 405:747–764

  23. Mao C, Ashby P, Wang M, McCrea D (1984) Synaptic connections from large muscle afferents to the motoneurones of various leg muscles in man. Exp Brain Res 56:341–350

  24. Pierrot-Deseilligny E, Mazières L (1984) Circuits réflexes de la moelle épinière chez l'homme: contrôle au cours du mouvement et rôle fonctionnel (2ème partie). Rev Neurol (Paris) 140:681–694

  25. Pierrot-Deseilligny E, Morin C, Bergego C, Tankov N (1981) Pattern of group I fibre projections from ankle flexor and extensor muscles in man. Exp Brain Res 42:337–350

  26. Rosen I, Sjölund D (1973) Organisation of group I activated cells in the main and external cuneate nuclei of the cat: identifications of muscle receptors. Exp Brain Res 16:221–234

  27. Schmidt RF, Willis WD (1963) Intracellular recordings from motoneurones of the cervical spinal cord of the cat. J Neurophysiol 26:28–43

  28. Stephens JA, Usherwood TP, Garnett R (1976) Technique for studying synaptic connections of single motoneurones in man. Nature 263:343–344

  29. Willis ND, Tate JW, Ashworth RD, Willis JC (1966) Monosynaptic excitation of motoneurones of individual forelimb muscles. J Neurophysiol 29:410–424

Download references

Author information

Correspondence to R. Katz.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Cavallari, P., Katz, R. Pattern of projections of group I afferents from forearm muscles to motoneurones supplying biceps and triceps muscles in man. Exp Brain Res 78, 465–478 (1989). https://doi.org/10.1007/BF00230235

Download citation

Key words

  • Ia projections
  • Monosynaptic reflex
  • Post-stimulus time histogram
  • Upper limb
  • Man