Inhibition of monosynaptic reflexes in the human lower limb.

Iles, J. F.; Roberts, R C

doi:10.1113/jphysiol.1987.sp016484

Cited by 104 publications

(85 citation statements)

References 42 publications

(47 reference statements)

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“…The variability is about three times greater than in the same subject sitting and performing a small voluntary contraction (compare with Fig. 1A in Iles & Roberts, 1987 (Fig. 3A).…”

Section: Soleus H Reflex Testingmentioning

confidence: 92%

“…2 where individual reflexes were measured, groups of sixty-four reflexes were averaged before measurement. These averages were repeated in order to estimate the standard error of the mean (see Iles & Roberts, 1987). Subjects could tolerate recording sessions lasting 1-15 h in which time some seven to ten data points of the type illustrated in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…These inhibitory pathways are also modulated during voluntary isometric contraction of soleus (see Iles, 1986;Iles & Roberts, 1987;Pisini, 1987). During strong soleus contraction inhibitory transmission operates at a low level, weaker soleus contraction (analogous to the forward sway response) is associated with a higher level of inhibitory transmission.…”

Section: Spatial Facilitation Using the H Reflexmentioning

confidence: 99%

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Vestibular‐evoked postural reactions in man and modulation of transmission in spinal reflex pathways.

Iles¹,

Pisini²

1992

The Journal of Physiology

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SUMMARY1. The effects of galvanic stimulation of the vestibular apparatus (with electrodes on the mastoid processes) have been studied in standing human subjects. With the head turned to one side, subjects swayed towards the anode.2. Forwards sway was preceded by electromyographic (EMG) activity in quadriceps and tibialis anterior muscles. Backwards sway was preceded by EMG activity in soleus and hamstring muscles.3. Using the method of H reflex conditioning, forward sway was found to be preceded by inhibition of soleus motoneurones.4. Interaction between the vestibular-evoked inhibition of soleus motoneurones preceding forwards sway and peripheral reflex inhibition was examined by a spatial facilitation method.5. Interaction was found between vestibular-evoked inhibition and la reciprocal, group I non-reciprocal and group Ia-Ia presynaptic inhibitory pathways. It is concluded that vestibular signals converge on spinal interneurones subserving these inhibitory actions. 6. A 'decoupling' of soleus motoneurones and soleus-coupled Renshaw cells was found in the period of soleus activation preceding backwards sway.

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“…The variability is about three times greater than in the same subject sitting and performing a small voluntary contraction (compare with Fig. 1A in Iles & Roberts, 1987 (Fig. 3A).…”

Section: Soleus H Reflex Testingmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Spatial Facilitation Using the H Reflexmentioning

confidence: 99%

See 1 more Smart Citation

Vestibular‐evoked postural reactions in man and modulation of transmission in spinal reflex pathways.

Iles¹,

Pisini²

1992

The Journal of Physiology

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“…Therefore the differences in response to perturbation may be assumed to be due in part to underlying differences in central and segmental control of flexor versus extensor muscles. (Iles and Roberts, 1987;Dietz et. al., 1989) This is likely to be particularly true for the TA muscle which is thought to be under a greater cortical control than is the GM (Schubert et al, 1997;.…”

Section: Autonomy Of the Spinal Cord To Generate Compensatory Responsmentioning

confidence: 99%

Single joint perturbation during gait: Preserved compensatory response pattern in spinal cord injured subjects

Field-Fote¹,

Dietz²

2007

Clinical Neurophysiology

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Objective-Responses to afferent input during locomotion are organized at the spinal level but modulated by supraspinal centers. The study aim was to examine whether supraspinal influences affect the behavior of complex electromyographic (EMG) responses to single limb perturbations during walking.Methods-Subjects with motor-complete (MCSCI), motor-incomplete spinal cord injury (MISCI), and non-disabled (ND) subjects participated. Hip or knee joint trajectory was briefly arrested by a robotic device at early or late swing phase. EMG responses from muscles of both legs were analyzed.Results-Perturbation-induced EMG responses of spinal cord injured and ND individuals were similar in basic structure, with the exception that tibialis anterior onset times were delayed for SCI subjects. Across all groups, perturbations in late swing (i.e., near the swing-to-stance transition) were associated with shorter muscle onset times and higher EMG amplitudes. Knee perturbations were associated with shorter muscle response onset times, while hip perturbations were elicited higher response amplitudes. EMG responses were also evoked in muscles contralateral to the perturbation.Conclusions-These data indicate that neuronal circuits within the spinal cord deprived of normal supraspinal input respond to swing phase perturbations in a manner that is similar to that of the intact spinal cord.Significance-The adult human spinal cord is capable of generating complex, phase-appropriate responses much as has been observed in studies of human infants and in spinal animals.

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“…Two further phases were termed D1 and D2 inhibition by Mizuno et al (1971). The strength of D1 changes during voluntary movement (Iles & Roberts, 1987). The present experiments were intended to disclose any facilitation of this inhibition by the corticospinal route.…”

mentioning

confidence: 99%

Proceedings of the Physiological Society, 10‐11 February 1989, Royal College of Surgeons, London, Meeting: Communications

1989

The Journal of Physiology

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The human motor cortex can be excited by both electromagnetic and percutaneous electrical stimulation. The latencies of EMG responses in arm muscles are 1P4-2-7 ms longer with electromagnetic stimulation. The reason for this difference remains unclear; it has been proposed that electromagnetic stimulation indirectly excites corticospinal neurones, whilst electrical stimulation activates them directly (Day et al. 1987; see also Amassian et al. 1987). We have examined the corticospinal volleys excited by electromagnetic stimulation in the macaque monkey.In the first experiment, a monkey was anaesthetized with alfentanil (150 mg/kg per h) combined with midazolan (1 mg/kg per h, i.v.). Tungsten electrodes were placed in the hand area of the left motor cortex and in the left medullary pyramid.The cervical (C7) and thoracic (T9) spinal segments were exposed by laminectomy and electrodes placed on the right dorsolateral funiculus (DLF). After surgery the monkey was paralysed with Flaxedil (20 mg/h) and ventilated. The anaesthetic iinfusion was maintained at the same rate and the level of anaesthesia assessed from heart rate and blood pressure. The left motor cortex was activated with a Novametrix MagStim 200 stimulator with the coil tangential to the scalp. The latencies of the evoked volley were as follows: left pyramid at 0 7 ms; right DLF at C7, 1-4 ms and right DLF at T9, 2-6 ms. The corticospinal origin of this volley was confirmed by its collision with volleys evoked from the pyramid (1 shock, 300 PsA) 0-14 ms before the electromagnetic stimulus. The latency of the antidromic volley from C7 to cortex was 1-4 ms. No significant indirect responses (I-waves) were seen after electromagnetic stimulation.The second experiment was conducted on a conscious monkey which had previously had tungsten electrodes implanted in the left pyramidal tract under full Halothane anaesthesia (Lemon et al. 1986). While the monkey performed a precision grip task with the right hand, electromagnetic stimuli were delivered to the cortex with the coil held tangentially above the head. A volley was evoked in the pyramid at 0-8 ms. Clear responses were observed in the EMG of forearm muscles (latencies 7-0-775 ms) and of intrinsic hand muscles (10-0-10-4 ms). The latencies of EMG responses following single shock (200 ,sA) stimulation of the pyramid were 6-5 and 9-5 ms in forearm and hand, respectively.We conclude that in these experiments tangential electromagnetic stimulation of the cortex activated corticospinal neurones directly.

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Inhibition of monosynaptic reflexes in the human lower limb.

Cited by 104 publications

References 42 publications

Vestibular‐evoked postural reactions in man and modulation of transmission in spinal reflex pathways.

Vestibular‐evoked postural reactions in man and modulation of transmission in spinal reflex pathways.

Single joint perturbation during gait: Preserved compensatory response pattern in spinal cord injured subjects

Proceedings of the Physiological Society, 10‐11 February 1989, Royal College of Surgeons, London, Meeting: Communications

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