Histological analysis of cat muscle spindles following direct observation of the effects of stimulating dynamic and static motor axons.

Banks, Robert W.; Barker, David J.; Bessou, P; Pagès, B; Stacey, Michael

doi:10.1113/jphysiol.1978.sp012522

Cited by 38 publications

(28 citation statements)

References 17 publications

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“…The increase in dynamic and static sensitivities during the speed task may be seen as the result of a mixed activation of ␥ dynamic (␥d) and ␥ static (␥s) fusimotor neurons. But, thanks to animal studies, it is known that purely dynamic actions are very rare because most ␥d-axons make contact not only on bag1 but also on bag2 and/or chain intrafusal muscle fibers (Banks et al 1978;Durbaba et al 2001;Emonet-Dénand et al 1977). Therefore it is probable that the simultaneous increase in the afferent static and dynamic sensitivity observed in the present task was related to the involvement of such ␥d neurons in humans.…”

Section: Discussionmentioning

confidence: 78%

Fusimotor Drive May Adjust Muscle Spindle Feedback to Task Requirements in Humans

Ribot-Ciscar¹,

Hospod²,

Roll³

et al. 2009

Journal of Neurophysiology

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Ribot-Ciscar E, Hospod V, Roll JP, Aimonetti JM. Fusimotor drive may adjust muscle spindle feedback to task requirements in humans. J Neurophysiol 101: 633-640, 2009. First published November 26, 2008 doi:10.1152/jn.91041.2008. The aim of the present study was to investigate whether the fusimotor control of muscle spindle sensitivity may depend on the movement parameter the task is focused on, either the velocity or the final position reached. The unitary activities of 18 muscle spindle afferents were recorded by microneurography at the common peroneal nerve. We compared in two situations the responses of muscle spindle afferents to ankle movements imposed while the subject was instructed not to pay attention to or to pay attention to the movement, both in the absence of visual cues. In the two situations, three ramp-and-hold movements were imposed in random order. In one situation, the three movements differed by their velocity and in the other by the final position reached. The task consisted in ranking the three movements according to the parameter under consideration (for example, slow, fast, and medium). The results showed that paying attention to movement velocity gave rise to a significant increase in the dynamic and static responses of muscle afferents. In contrast, focusing attention on the final position reached made the muscle spindle feedback better discriminate the different positions and depressed its capacity to discriminate movement velocities. Changes are interpreted as reflecting dynamic and static gamma activation, respectively. The present results support the view that the fusimotor drive depends on the parameter the task is focused on, so that the muscle afferent feedback is adjusted to the task requirements.

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Section: Discussionmentioning

confidence: 78%

Fusimotor Drive May Adjust Muscle Spindle Feedback to Task Requirements in Humans

Ribot-Ciscar¹,

Hospod²,

Roll³

et al. 2009

Journal of Neurophysiology

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“…A considerable body of evidence indicates that in most mammalian muscle spindles the bag, intrafusal fibre is innervated exclusively by dynamic fusimotor axons, while static axons innervate both bag2 and chain fibres (Boyd, Gladden, McWilliam & Ward, 1977;Banks, Barker, Bessou, Pages & Stacey, 1978). Therefore it should be possible to test for after-effects acting on the bag, fibre by examining the responses of primary endings to stimulation of dynamic fusimotor axons.…”

Section: Introductionmentioning

confidence: 99%

Fusimotor after‐effects on responses of primary endings to test dynamic stimuli in cat muscle spindles.

Emonet-Dénand¹,

Hunt²,

Laporte³

1985

The Journal of Physiology

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SUMMARY1. Conditioning stimulation of individual dynamic fusimotor axons, either y or , leaves after-effects which enhance the responses ofprimary endings to test stimulation of the same axon applied during slow ramp stretch. These after-effects have a long duration, persisting well over 5 min, but are abolished by stretch of large amplitude.2. The dynamic after-effects also enhance frequencygrams elicited by lowfrequency repetitive stimulation during slow ramp stretch, causing single stimuli to become much more effective.3. When several dynamic axons to the same spindle are isolated, conditioning stimulation of one leaves an after-effect to test stimulation of itself and of all other dynamic axons. When two dynamic axons are used for conditioning stimulation, facilitation or occlusion can be demonstrated in their interaction, indicating that they converge on the same intrafusal element.4. Dynamic after-effects persist during background static fusimotor activity of considerable amplitude, suggesting that static and dynamic actions are quite independent.5. Dynamic after-effects appear to result from residual changes in the bag, fibre, probably from a persistent increase in the number of cross-bridges between thick and thin filaments. These after-effects produce a large increase in the response of primary endings to dynamic fusimotor activity and probably have an important functional role.

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“…One point remains controversial, that is whether some static fusimotor axons also innervate bag1 fibres in addition to chain and bag2 fibres. Microscopic observations of living spindles have so far not shown bag1 contraction elicited by static axons or, more exactly poles of bag1 fibres activated by dynamic axons have not been seen to be also supplied by static axons (Bessou & Pages, 1975;Boyd & Ward, 1975;Boyd, 1976;Boyd, Gladden, McWilliam & Ward, 1977;Barker, Bessou, Jankowska, Pages & Stacey, 1978;Banks, Barker, 312 F. EMONET-DJNAND, L. JAMI, Y. LAPORTE AND N. TANKOV Bessou, Pages & Stacey, 1978). However two pieces of experimental evidence support the view that static axons may supply some bag1 fibres.…”

Section: Introductionmentioning

confidence: 99%

Glycogen depletion of bag1 fibers elicited by stimulation of static gamma axons in cat peroneus brevis muscle spindles.

Emonet-Dénand¹,

Jami²,

Laporte³

et al. 1980

The Journal of Physiology

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1. The distribution of static fusimotor axons to intrafusal muscle fibres in cat peroneus brevis spindles has been studied with the glycogen depletion method. 2. In each of six experiments three to seven static axons were stimulated. The muscle was subsequently quick-frozen and cut in serial transverse sections that were stained for glycogen. In each muscle, nearly all the spindles were examined for depletion. 3. Intrafusal muscle fibres displaying zones of complete glycogen depletion were observed in fifty-two whole spindles and seven half-spindles. Chain fibres were depleted in forty-eight (92%) of the whole spindles, bag2 fibres in thirty-five spindles (67%) and bag1 fibres in nineteen spindles (36%). 4. Seven other experiments were performed to test whether small amplitude sinusoidal stretching (30--100 Hz) of the muscle might produce glycogen depletion in bag1 fibres. Two hundred and seven spindles were examined. In nearly all of them the glycogen content of the intrafusal muscle fibres was normal. Two muscles had limited atrophic portions within which a few depleted spindles were found. 5. These experiments show that the intrafusal distribution of static gamma axons is not restricted to chain and bag2 fibres but that in a significant number of spindles the bag1 fibres are also supplied by static gamma axons.

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Histological analysis of cat muscle spindles following direct observation of the effects of stimulating dynamic and static motor axons.

Cited by 38 publications

References 17 publications

Fusimotor Drive May Adjust Muscle Spindle Feedback to Task Requirements in Humans

Fusimotor Drive May Adjust Muscle Spindle Feedback to Task Requirements in Humans

Fusimotor after‐effects on responses of primary endings to test dynamic stimuli in cat muscle spindles.

Glycogen depletion of bag1 fibers elicited by stimulation of static gamma axons in cat peroneus brevis muscle spindles.

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