Reflexes to Toe Muscles in the Cat's Hindlimb

Engberg, I.

doi:10.1016/s0079-6123(08)60628-7

Cited by 39 publications

(69 citation statements)

References 4 publications

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“…Our view is that the stumbling corrective reactions evoked during the swing and stance phases are cutaneous reflexes. Because they can be fully activated by only a limited set of afferents, we think that they are examples of a "private" reflex pathway originally described for reflexes around the foot (Engberg 1964;Hongo et al 1990) or of "local sign" (Hagbarth 1952) and not flexion reflexes (see McCrea 1992). The details of the responses evoked during stumbling correction will, however, depend on the complement of afferents activated.…”

Section: Shaping and Modulating Sp Reflexes During Fictive Locomotionmentioning

confidence: 92%

Intracellular Analysis of Reflex Pathways Underlying the Stumbling Corrective Reaction During Fictive Locomotion in the Cat

Quevedo

Stecina²,

McCrea³

2005

Journal of Neurophysiology

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. Intracellular analysis of reflex pathways underlying the stumbling correction reaction during fictive locomotion in the cat. J Neurophysiol 94: 2053-2062. First published May 25, 2005 doi:10.1152/jn.00176.2005. In cat and humans, contact between an obstacle and the dorsum of the foot evokes the stumbling corrective reaction (reflex) that lifts the foot to avoid falling. This reflex can also be evoked by short trains of stimuli to the cutaneous superficial peroneal (SP) nerve in decerebrate cats during the flexion phase of fictive locomotion. Here we examine intracellular events in hindlimb motoneurons accompanying stumbling correction. SP stimulation delivered during the flexion phase excites knee flexor motoneurons at short latency [minimum excitatory postsynaptic potential (EPSP) latency 1.8 ms; mean 2.7 ms]. Although a similar short latency excitation occurs in ankle extensors (mean latency, 2.8 ms), recruitment is delayed until successive shocks in the stimulus train overcome the locomotor-related hyperpolarization of ankle extensors. In ankle flexor motoneurons, SP stimulation evokes an inhibition (mean latency, 2.7 ms) that briefly reduces or stops their firing during the flexion phase. There is a phase-dependent modulation of SP-evoked EPSP amplitude as well as latency during locomotion. However, the more obvious change in SP reflex pathways with the onset of fictive locomotion is the reduced inhibition of ankle extensor motoneurons and the increased inhibition of ankle flexors. These results show that the characteristic pattern of hindlimb motoneuron activation during SP nerve-evoked stumbling correction results from 1) di-and trisynaptic excitation of knee flexor and ankle extensor motoneurons; 2) increased inhibitory postsynaptic potentials in ankle flexors and a suppression of inhibition in extensors, 3) sculpting of the short-latency SP postsynaptic effects by motoneuron membrane potential, and 4) longer latency excitatory effects that are likely evoked by lumbar interneurons involved in the generation of fictive locomotion.

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Section: Shaping and Modulating Sp Reflexes During Fictive Locomotionmentioning

confidence: 92%

Intracellular Analysis of Reflex Pathways Underlying the Stumbling Corrective Reaction During Fictive Locomotion in the Cat

Quevedo

Stecina²,

McCrea³

2005

Journal of Neurophysiology

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“…Then VRS1 stimulation was discontinued, and the plantar cushion stimulated, both electrically and tactilely. If the motoneurone under study was activated by low to moderate intensity tactile probing of the plantar cushion, sufficient to elicit a reflex (Engberg, 1964;Egger & Wall, 1971, Egger, 1978, but well below the threshold for a flexor withdrawal reflex (Egger et al 1976), and if it was also driven by electrical stimulation at a threshold approximately equal to that of the plantar cushion reflex threshold, the motoneurone was then electrophoretically injected with HRP. Before these injections, however, seven of the motoneurones identified as mediating the plantar cushion reflex were examined for the presence of recurrent inhibition.…”

Section: Methodsmentioning

confidence: 99%

“…Firm pressure on the central foot pad of the hind limb of the cat results in reflex plantar flexion (extension) of the toes (Engberg, 1964;Egger & Wall, 1971) produced by the intrinsic plantar muscles, the flexors digitorum brevis and longus, and the 350 M. D. EGGER, N. C. G. FREEMAN AND E. PROSHANSKY plantaris muscle. Motoneurones innervating these muscles were found by Romanes (1951) to be located in the dorsolateral portion of the ventral horn in the first sacral segment of the spinal cord.…”

Section: Introductionmentioning

confidence: 99%

Morphology of spinal motoneurones mediating a cutaneous spinal reflex in the cat.

Egger¹,

Freeman²,

Proshansky³

1980

The Journal of Physiology

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SUMMARY1. Intracellular injections of horseradish peroxidase were made in a functionally identified population of motoneurones in spinal cords of cats. These motoneurones were activated by tactile stimulation of the hind-limb central foot pad.2. Cell bodies of twenty-two such motoneurones were located in the dorsolateral portion of the ventral horn in the first sacral segment. The mean diameter of the major axis of transverse sections through twelve of these cell bodies was 68-2 /tm, the mean diameter of the minor axis was 48 7 /tm. The major axis tended to be oriented dorsomedially-ventrolaterally.3. In the transverse plane, the dendrites had a characteristic configuration, with a prominent group of dendrites travelling from the cell body dorsomedially into the dorsal horn, entering Rexed's lamina VI. For seventeen motoneurones with well stained dendrites, the mean medial spread of the dendrites was 960 #um. Though the mean lateral spread was only 508 /im, all of these motoneurones sent dendritic projections into the lateral white matter. The mean dorsal spread of the dendrites was 693 /tm, the mean ventral spread, 748 /tm. In the rostrocaudal direction, the mean spread rostrally was 911 1em, the mean spread caudally was 998 /tm. The maximum dendritic spread for a single motoneurone was 2,940 4am, in the rostrocaudal direction. The sum of dendritic lengths over an entire dendritic tree for the best-stained motoneurones exceeded 13,000 /tm.4. The mean diameter of the initial segment of axons of nineteen motoneurones was 4-3 gtm. These axons were notable for the lack or paucity of axon collaterals. Only five of twenty-one axons possessed collaterals; of these, only one possessed more than a single collateral system. This sparseness of the collateral system was reflected in a low level of recurrent inhibition.5. A possible relationship is discussed between the prominent dorsomedially oriented dendritic bundles of the motoneurones and the axon collaterals of dorsal horn cells mediating cutaneous stimulation which can activate these motoneurones.

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“…The observation that a-motoneurones supplying the short plantar muscles seem to lack axon collaterals deserves some comments on the physiology of these muscles with special reference to theories of the function of the recurrent axon collateral pathway. Reflex studies have indicated that the plantar muscles of the cat should be classified as physiological extensors (Engberg, 1964). The a-motoneurones of particularly the deep plantar muscles receive only little heteronymous excitation from Ia afferents (Engberg, 1964), which contrasts to the more diverse Ia connexions to the motoneurones of the hip, knee and ankle muscles (Eccles, Eccles & Lundberg, 1957;.…”

Section: S Cullheim and J-o Kellerthmentioning

confidence: 99%

“…Reflex studies have indicated that the plantar muscles of the cat should be classified as physiological extensors (Engberg, 1964). The a-motoneurones of particularly the deep plantar muscles receive only little heteronymous excitation from Ia afferents (Engberg, 1964), which contrasts to the more diverse Ia connexions to the motoneurones of the hip, knee and ankle muscles (Eccles, Eccles & Lundberg, 1957;. The function of recurrent inhibition of ax-motoneurones has been proposed to be to limit the extent of diverse Ia effects, thus acting as a lateral inhibition (Brooks & Wilson, 1959;Wilson et al 1960;Granit & Renkin, 1961).…”

Section: S Cullheim and J-o Kellerthmentioning

confidence: 99%

A morphological study of the axons and recurrent axon collaterals of cat alpha‐motoneurones supplying different hind‐limb muscles.

Cullheim¹,

Kellerth²

1978

The Journal of Physiology

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SUMMARY1. Intracellular injections with horseradish peroxidase were performed in cat a-motoneurones supplying various hind-limb muscles.2. Ten a-motoneurones from each of the quadriceps, posterior biceps, gastroenemius-soleus and anterior tibial pools as well as from the pool supplying the short plantar muscles were collected for morphological analysis of the intramedullary axonal systems including the recurrent axon collaterals.3. The diameter of the a-motor axons showed considerable variation within each motoneurone pool, the total range being from 4 6 to 9 0 ,tm. No significant difference in mean axon diameter was obtained between the different pools.4. All a-motoneurones supplying the short plantar muscles and one single amotoneurone supplying the quadriceps muscle lacked collaterals completely, while the remaining motoneurones gave off one to five collaterals.5. The number of axon collateral outbulgings, interpreted as synaptic boutons, which originated from a single a-motoneurone showed large variation within each pool that possessed axon collaterals, the total range being from seventeen to 158. The mean number varied from forty-four (quadriceps) to eighty-two (anterior tibial).6. The axon collateral outbulgings were distributed not only in the Renshaw cell area ventromedial to the main motor nuclei but also in those parts of the motor nuclei which were located in the vicinity of the parent cell bodies. In the rostrocaudal direction, the outbulgings were distributed within a distance of less than 1 mm around the position of the parent cell bodies.7. Some physiological implications of the lack of axon collaterals from a-motoneurones supplying the short plantar muscles were discussed in relation to the functional characteristics of plantar muscles and motor units.

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Reflexes to Toe Muscles in the Cat's Hindlimb

Cited by 39 publications

References 4 publications

Intracellular Analysis of Reflex Pathways Underlying the Stumbling Corrective Reaction During Fictive Locomotion in the Cat

Intracellular Analysis of Reflex Pathways Underlying the Stumbling Corrective Reaction During Fictive Locomotion in the Cat

Morphology of spinal motoneurones mediating a cutaneous spinal reflex in the cat.

A morphological study of the axons and recurrent axon collaterals of cat alpha‐motoneurones supplying different hind‐limb muscles.

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