Analysis of the fast afferent impulses from thigh muscles

Abstract

Recently, when investigating the effect of graded stimulus strengths on the size of the conducted monophasic spike in muscle afferent fibres, Brock, Eccles & Rall (1951) found that with biceps-semitendinosus nerve the range of stimulus strengths from threshold to that giving the maximum group I spike was much larger than with other muscle nerves. There was a three-to fourfold increase of strength in contrast to an increment of 1-6-2-3 for other nerves. It has also been an almost invariable finding that, when recorded triphasically (a contact electrode against an indifferent electrode), an afferent volley from the biceps-semitendinosus or quadriceps nerves showed a double negative spike (cf. Brock, Coombs & Eccles, 1952, fig. 9), which was never observed for afferent volleys from the leg muscles-gastrocnemius, flexor digitorum longus, extensor digitorum longus, etc. Since the fast afferent fibres of muscle (the group I) are known to have two major components of quite different reflex function, which respectively may be designated group I a from the annulo-spiral endings and group I b from the Golgi tendon organs (Matthews, 1933;Barker, 1948;Granit, 1950; Granit & Strom, 1951; Hunt & Kuffler, 1951 a, b;Hunt, 1951 Hunt, , 1952Laporte & Lloyd, 1951, 1952Hagbarth & Naess, 1950), it was of interest to determine whether the double negative spike was attributable to this dual composition. If this was so, then the discrimination between the reflex functions of groups Ia and Ib would become simpler because the relative group I a and I b composition of an afferent volley would be directly determinable. METHODCats, anaesthetized with pentobarbitone sodium (Nembutal), have been used in all experiments. The method, and the dissection of nerves and their mounting on electrodes, have resembled in general those procedures described by Brock et al. (1951). Special precautions have been taken to ensure that the stimulus did not 'escape' to nerves other than those on the electrodes. For example the sartorius and saphenous components of the femoral nerve were dissected up and cut about 2 cm proximal to the cathodal electrode on quadriceps nerve. The stimuli were brief

Spinal cord potentials generated by volleys in the large muscle afferents

“…Optimum conditions were thus secured for illustrating the interneuronal and motoneuronal responses. As shown by Bradley & Eccles (1953), it is possible with many quadriceps and biceps-semitendinosus nerves to choose a strength of stimulus that excites most of the group Ia afferent fibres (originating from the annulo-spiral endings of muscle spindles) and virtually none of the group Ib afferents (originating from the Golgi tendon organs). The response evoked by a group Ia volley was usually compared with that evoked by a volley just maximal for groups Ia and Ib, but exciting few of group II and none of group III muscle afferents.…”

“…the group I afferent fibres of muscle nerves, are separable into two quite distinct groups, I a and I b, the former arising from the annulo-spiral endings of the muscle spindles, the latter from the Golgi tendon organs (Matthews, 1933;Bairker, 1948;Hunt & Kuffler, 1951;Hunt, 1952Hunt, , 1953. Furthermore, impulses in the group Ia and Ib afferent fibres have quite distinct actions within the spinal cord (Granit, 1950(Granit, , 1952 Laporte & Lloyd, 1952;Bradley & Eccles, 1953;Hunt & Kuffler, 1951;Hunt, 1952). However, almost all of this functional specification has depended on an analysis of input-output investigations on spinal reflexes; hence very little is known about the functional pathways within the spinal cord, though the number of synaptic linkages on such pathways has been inferred from the central delay between input and output.…”

“…the group I afferent fibres of muscle nerves, are separable into two quite distinct groups, I a and I b, the former arising from the annulo-spiral endings of the muscle spindles, the latter from the Golgi tendon organs (Matthews, 1933; Bairker, 1948; Hunt & Kuffler, 1951; Hunt, 1952 Hunt, , 1953. Furthermore, impulses in the group Ia and Ib afferent fibres have quite distinct actions within the spinal cord (Granit, 1950(Granit, , 1952Laporte & Lloyd, 1952;Bradley & Eccles, 1953; Hunt & Kuffler, 1951; Hunt, 1952 Renshaw, 1946) has shown that with microelectrode recording it is possible to identify the pre-and post-synaptic components of the monosynaptic myotatic reflex, and to subdivide the total central delay of this reflex into a pre-synaptic conduction time, a true synaptic delay in the initiation ofthe synaptic potential, and finally post-synaptic events.The present investigation is an extension of this earlier work; not only is there a study of the time relations of the synaptic events evoked by group Ia and I b afferent volleys, but there has been approximate mapping of the potential fields generated in the spinal cord by their respective synaptic actions. In 1945 Campbell published elaborate maps of the potential fields generated in the spinal cord by an afferent volley, but unfortunately this volley was com-…”

Medullary reticulospinal tract mediating a generalized motor inhibition in cats: iii. functional organization of spinal interneurons in the lower lumbar segments

“…Group Ia afferents of these nerves may be expected only with stimulus intensities within the lower ranges for the first component of the incoming volleys, or up to approximately 1.2-1.3 times the threshold. Group Ib afferents were evoked by higher stimulus intensities, ranging from 1.4 to 1.5 times threshold, and appeared in parallel with the second component of the afferent volleys (Bradley and Eccles, 1953;Coppin et al, 1969;Jankowska et al, 1981b).…”

“…The strength of the incoming Ia and Ib volley was determined by the double volley technique (Bradley and Eccles, 1953). Group Ia afferents of these nerves may be expected only with stimulus intensities within the lower ranges for the first component of the incoming volleys, or up to approximately 1.2-1.3 times the threshold.…”