Human flexor reflexes

Shahani, Bhagwan T.; Young, Robert R.

doi:10.1136/jnnp.34.5.616

Cited by 221 publications

(125 citation statements)

References 22 publications

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“…This is in agreement with previous observations in SCI subjects (Shahani and Young 1971;Roby-Brami and Bussel 1987;Knikou and Conway 2005), and in spinal l-dopa-treated cats (Conway et al 1987;Anden et al 1966a). In the present study, the test reflex stimulus intensity was normalized to the threshold of the first evoked TA EMG activity, whether this corresponded to the early or to the late flexion reflex.…”

Section: Observations On the Two Types Of The Flexion Reflexsupporting

confidence: 79%

Modulation of flexion reflex induced by hip angle changes in human spinal cord injury

2005

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The flexion reflex can be elicited via stimulation of skin, muscle, and high-threshold afferents inducing a generalized flexion of the limb. In spinalized animal models this reflex is quite prominent and is strongly modulated by actions of hip proprioceptors. However, analogous actions on the flexion reflex in spinal cord injured (SCI) humans have not yet been examined. In this study, we investigated the effects of imposed static hip angle changes on the flexion reflex in ten motor incomplete SCI subjects when input from plantar cutaneous mechanoreceptors was also present. Flexion reflexes were elicited by low-intensity stimulation of the sural nerve at the lateral malleolus, and were recorded from the ipsilateral tibialis anterior (TA) muscle. Plantar skin stimulation was delivered through two surface electrodes placed on the metatarsals, and was initiated at different delays ranging from 3 to 90 ms. We found that non-noxious sural nerve stimulation induced two types of flexion reflexes in the TA muscle, an early, and a late response. The first was observed only in three subjects and even in these subjects, it appeared irregularly. In contrast, the second (late) flexion reflex was present uniformly in all ten subjects and was significantly modulated during hip angle changes. Flexion reflexes recorded with hip positioned at different angles were compared to the associated control reflexes recorded with hip flexed at 10°. Hip flexion (30°, 40°) depressed the late flexion reflex, while no significant effects were observed with the hip set in neutral angle (0°). Strong facilitatory effects on the late flexion reflex were observed with the hip extended to 10°. Moreover, the effects of plantar skin stimulation on the flexion reflex were also found to depend on the hip angle. The results suggest that hip proprioceptors and plantar cutaneous mechanoreceptors strongly modulate flexion reflex pathways in chronic human SCI, verifying that this type of sensory afferent feedback interact with spinal interneuronal circuits that have been considered as forerunners of stepping and locomotion. The sensory consequences of this afferent input should be considered in rehabilitation programs aimed to restore movement and sensorimotor function in these patients.

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Section: Observations On the Two Types Of The Flexion Reflexsupporting

confidence: 79%

Modulation of flexion reflex induced by hip angle changes in human spinal cord injury

2005

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“…Excitation of FRA induces two distinct responses, a short and a long reflex loop response (SRL and LRL, respectively) (Spaich et al, 2004), while their latency and amplitude depend on the stimulus intensity strength and site of stimulation (Andersen et al, 2001;Spaich et al, 2004). In spinal-intact subjects, the nociceptive flexion withdrawal reflex, which combines flight and defense movements (Sherrington, 1910), has a short central conduction time observed at latencies of 40-60 ms, while the long-latency response occurs at latencies of 85-120 ms or beyond (Shahani and Young, 1971;Hagbarth and Finer, 1963). After a spinal cord injury (SCI), the SRL response is still observable, but when non-nociceptive stimulus is employed it is rarely observed (RobyBrami and Bussel, 1987;Knikou and Conway, 2005;Knikou et al, 2006b).…”

Section: Introductionmentioning

confidence: 99%

Hip-phase-dependent flexion reflex modulation and expression of spasms in patients with spinal cord injury

Knikou

2007

Experimental Neurology

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The flexion reflex in human spinal cord injury (SCI) is believed to incorporate interneuronal circuits that consist elements of the stepping generator while ample evidence suggest that hip proprioceptive input is a controlling signal of locomotor output. In this study, we examined the expression of the non-nociceptive flexion reflex in response to imposed sinusoidal passive movements of the ipsilateral hip in human SCI. The flexion reflex was elicited by low-intensity stimulation (300 Hz, 30 ms pulse train) of the right sural nerve at the lateral malleolus, and recorded from the tibialis anterior (TA) muscle. Sinusoidal hip movements were imposed to the right hip joint at 0.2 Hz by a Biodex system while subjects were supine. The effects of leg movement on five leg muscles along with hip, knee, and ankle joint torques were established simultaneously with the modulation pattern of the flexion reflex during hip oscillations. Phase-dependent modulation of the flexion reflex was present during hip movement, with the reflex to be significantly facilitated during hip extension and suppressed during hip flexion. The phase-dependent flexion reflex modulation coincided with no changes in TA pre-and post-stimulus background ongoing activity during hip extension and flexion. Reflexive muscle and joint torque responses, induced by the hip movement and substantiated by excitation of flexion reflex afferents, were entrained to specific phases of hip movement. Joint torque responses were consistent with multi-joint spasmodic muscle activity, which was present mostly during the transition phase of the hip from flexion to extension and from mid-to peak extension. Our findings provide further evidence on the interaction of hip proprioceptors with spinal interneuronal circuits engaged in locomotor pathways, and such interaction should be considered in rehabilitation protocols employed to restore sensorimotor function in people with SCI.

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“…The studies of Makin (1958) and Tyrer and Sutherland (1961) in spastic spinocerebellar atrophy suggested a predominance of the posterior tibialis as the cause of foot deformity. Previous electromyographic studies in spastic disorders consistently mention that the muscle with the lowest threshold to exteroceptive response is the anterior tibialis (Dimitrijevic and Nathan, 1968;Shahani and Young, 1971).…”

Section: Discussionmentioning

confidence: 99%

Pes cavus and claw toes deformity in patients with spinal cord injury and multiple sclerosis

et al. 1979

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Abstract. Patients with spinal cord injur y or multiple sclerosis were surve y ed for the presence of extreme foot deformities and spasticit y . Pes cavus and claw toes were found in eight of 80 spastic spinal cord injury and two of 20 multiple sclerosis patients. Pes cavus and claw toes were not found in 2 9 flaccid spinal cord injury patients.Pes cavus and claw toes were associated with flexor reflexes which could be elicited b y pin prick proximal to the knee, suggesting extreme spasticit y -and b y low excitatory thresholds for the anterior tibialis as indicated electro m y ographicall y .Complications of severe spasticit y associated with spinal cord injur y and multiple sclerosis include pes cavus and claw toes, mediated in part b y spasms of the anterior tibialis.

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Human flexor reflexes

Cited by 221 publications

References 22 publications

Modulation of flexion reflex induced by hip angle changes in human spinal cord injury

Modulation of flexion reflex induced by hip angle changes in human spinal cord injury

Hip-phase-dependent flexion reflex modulation and expression of spasms in patients with spinal cord injury

Pes cavus and claw toes deformity in patients with spinal cord injury and multiple sclerosis

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