title: Facilitation of quadriceps motoneurones by group I afferents from pretibial flexors in man. 1. Possible interneuronal pathway.
abstract: The neuronal pathway of the facilitation of quadriceps (Q) motoneurones (MNs) evoked by stimulation of the common peroneal nerve (CPN) has been reinvestigated using both the post-stimulus time histogram (PSTH) method for measurement of the firing probability of individual units and the H reflex technique. It has been found that Ia (and to an unknown extent Ib) afferents from pretibial flexors - but not from peroneal muscles - are responsible for this excitation. The central latency of the CPN-induced excitation of Q MNs was estimated to be 3-3.7 ms longer than that of their monosynaptic Ia excitation. To further investigate the neuronal pathway of the CPN-induced excitation the spatial facilitation technique was used, the effects on the Q H reflex of two conditioning stimuli (applied to the CPN and the femoral nerve - FN) being compared when applied separately and together. When the two conditioning volleys were timed to reach the spinal cord simultaneously the facilitation of the H reflex on combined stimulation was larger than the algebraic sum of the effects by separate stimuli in 40% of the cases. It is argued that this additional facilitation reflects summation at a premotoneuronal level and it is concluded that non-monosynaptic Ia excitation of Q MNs from Q and pretibial flexors is, at least partly, mediated through a common pathway. In those individual units in which stimulation of the FN and/or the CPN evoked a non-monosynaptic Ia excitation, this excitation was reduced on combined stimulation of the two nerves. It is argued that this reflects inhibition of the interneurones mediating the excitation, i.e. consists in a disfacilitation of the MNs. It is suggested that the non-monosynaptic (homonymous and heteronymous) Ia excitation of Q MNs in man (and the inhibition of this excitation) is mediated through a system of neurones similar to the system recently described in the cat by Edgley and Jankowska (1987).
authors.affiliation: Clinical Neurophysiology, Rééducation, Hôpital de la Salpêtrière, Paris, France.
authors.forename: R
authors.initials: R
authors.lastname: Forget
authors.forename: R
authors.initials: R
authors.lastname: Pantieri
authors.forename: E
authors.initials: E
authors.lastname: Pierrot-Deseilligny
authors.forename: M
authors.initials: M
authors.lastname: Shindo
authors.forename: R
authors.initials: R
authors.lastname: Tanaka
mesh_terms: D000328:Adult; D006181:H-Reflex; D006801:Humans; D007395:Interneurons / Q000502:physiology*; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D009132:Muscles / Q000294:innervation* / Q000502:physiology; D009431:Neural Conduction; D011930:Reaction Time; D012023:Reflex, Monosynaptic; D013979:Tibial Nerve / Q000502:physiology*