scholarly journals A Re-evaluation of Whether Non-monosynaptic Homonymous H Reflex Facilitation Tests Propriospinal Circuits

2021 ◽  
Vol 15 ◽  
Author(s):  
Karen M. Fisher ◽  
Stuart N. Baker
Keyword(s):  
Median Nerve ◽  
Human Subjects ◽  
Conditioning Stimulus ◽  
Macaque Monkey ◽  
H Reflex ◽  
Healthy Human ◽  
Median Nerve Stimulation ◽  
Important Pathway ◽  
Peripheral Axon ◽  
Forearm Flexor

The C3–C4 propriospinal system is an important pathway mediating movement in cats; it contributes to movements in primates (including humans), and may have a role in recovery after lesion. Validated clinical tests of this system would find many applications, therefore we sought to test whether non-monosynaptic homonymous facilitation of the forearm flexor H reflex is mediated solely via a C3–C4 propriospinal pathway. In one anesthetized macaque monkey, median nerve stimulation elicited an H reflex in the flexor carpi radialis (FCR). Median nerve conditioning stimuli at sub-threshold intensities facilitated the H reflex, for inter-stimulus intervals up to 30 ms. Successive spinal surgical hemisections were then made. C2 lesion left the homonymous facilitation intact, suggesting mediation by spinal, not supraspinal pathways. Facilitation also remained after a second lesion at C5, indicating a major role for segmental (C7–C8) rather than propriospinal (C3–C4) interneurons. In separate experiments in five healthy human subjects, a threshold tracking approach assessed changes in peripheral axon excitability after conditioning stimulation. This was found to be enhanced up to 20 ms after the conditioning stimulus, and could partly, although not completely, underlie the H reflex facilitation seen. We conclude that homonymous facilitation of the H reflex in FCR can be produced by segmental spinal mechanisms, as well as by a supranormal period of nerve excitability. Unfortunately, this straightforward test cannot therefore be used for selective assessment of propriospinal circuits.

Dynamics of mu-rhythm suppression caused by median nerve stimulation: a magnetoencephalographic study in human subjects

2000 ◽  
Vol 294 (3) ◽  
pp. 163-166 ◽  
Author(s):  
Vadim V Nikouline ◽  
Klaus Linkenkaer-Hansen ◽  
Heidi Wikström ◽  
Martti Kesäniemi ◽  
Elena V Antonova ◽  
...  
Keyword(s):  
Median Nerve ◽  
Nerve Stimulation ◽  
Human Subjects ◽  
Mu Rhythm ◽  
Median Nerve Stimulation

scholarly journals Multimodal stimuli modulate rapid visual responses during reaching

2019 ◽  
Vol 122 (5) ◽  
pp. 1894-1908 ◽  
Author(s):  
Isabel S. Glover ◽  
Stuart N. Baker
Keyword(s):  
Median Nerve ◽  
Reticular Formation ◽  
Visual Target ◽  
Human Subjects ◽  
Vestibular Stimulation ◽  
Auditory Stimuli ◽  
Visual Responses ◽  
Healthy Human ◽  
Reaching Task ◽  
Upper Limb Function

The reticulospinal tract plays an important role in primate upper limb function, but methods for assessing its activity are limited. One promising approach is to measure rapid visual responses (RVRs) in arm muscle activity during a visually cued reaching task; these may arise from a tecto-reticulospinal pathway. We investigated whether changes in reticulospinal excitability can be assessed noninvasively using RVRs, by pairing the visual stimuli of the reaching task with electrical stimulation of the median nerve, galvanic vestibular stimulation, or loud sounds, all of which are known to activate the reticular formation. Surface electromyogram (EMG) recordings were made from the right deltoid of healthy human subjects as they performed fast reaching movements toward visual targets. Stimuli were delivered up to 200 ms before target appearance, and RVR was quantified as the EMG amplitude in a window 75–125 ms after visual target onset. Median nerve, vestibular, and auditory stimuli all consistently facilitated the RVRs, as well as reducing the latency of responses. We propose that this facilitation reflects modulation of tecto-reticulospinal excitability, which is consistent with the idea that the amplitude of RVRs can be used to assess changes in brain stem excitability noninvasively in humans. NEW & NOTEWORTHY Short-latency responses in arm muscles evoked during a visually driven reaching task have previously been proposed to be tecto-reticulospinal in origin. We demonstrate that these responses can be facilitated by pairing the appearance of a visual target with stimuli that activate the reticular formation: median nerve, vestibular, and auditory stimuli. We propose that this reflects noninvasive measurement and modulation of reticulospinal excitability.

scholarly journals Intensity Sensitive Modulation Effect of Theta Burst Form of Median Nerve Stimulation on the Monosynaptic Spinal Reflex

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Kuei-Lin Yeh ◽  
Po-Yu Fong ◽  
Ying-Zu Huang
Keyword(s):  
Median Nerve ◽  
Amplitude Ratio ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
H Reflex ◽  
Spinal Reflex ◽  
M Wave ◽  
Therapeutic Benefits ◽  
Median Nerve Stimulation ◽  
Theta Burst

The effects of electrical stimulation of median nerve with a continuous theta burst pattern (EcTBS) on the spinal H-reflex were studied. Different intensities and durations of EcTBS were given to the median nerve to 11 healthy individuals. The amplitude ratio of the H-reflex to maximum M wave (H/M ratio), corticospinal excitability and inhibition measured using motor evoked potentials (MEPs), short-interval intracortical inhibition and facilitation (SICI/ICF), spinal reciprocal inhibition (RI), and postactivation depression (PAD) were measured before and after EcTBS. In result, the H/M ratio was reduced followed by EcTBS at 90% H-reflex threshold, and the effect lasted longer after 1200 pulses than after 600 pulses of EcTBS. In contrast, EcTBS at 110% threshold facilitated the H/M ratio, while at 80% threshold it had no effect. Maximum M wave, MEPs, SICI/ICF, RI, and PAD all remained unchanged after EcTBS. In conclusion, EcTBS produced lasting effects purely on the H-reflex, probably, through effects on postsynaptic plasticity. The effect of EcTBS depends on the intensity and duration of stimulation. EcTBS is beneficial to research on mechanisms of human plasticity. Moreover, its ability to modulate spinal excitability is expected to have therapeutic benefits on neurological disorders involving spinal cord dysfunction.

Spinal excitation and inhibition decrease as humans age

2004 ◽  
Vol 82 (4) ◽  
pp. 238-248 ◽  
Author(s):  
Aiko Kido ◽  
Naofumi Tanaka ◽  
Richard B Stein
Keyword(s):  
Human Subjects ◽  
Tibialis Anterior Muscle ◽  
Common Peroneal Nerve ◽  
Reciprocal Inhibition ◽  
H Reflex ◽  
Direct Stimulation ◽  
Voluntary Activity ◽  
Healthy Human ◽  
Wide Range ◽  
First Time

Although changes in the soleus H-reflex (an electrical analog of the tendon jerk) with age have been examined in a number of studies, some controversy remains. Also, the effect of age on inhibitory reflexes has received little attention. The purpose of this paper was to examine some excitatory and inhibitory reflexes systematically in healthy human subjects having a wide range of ages. We confirmed that both the maximum H-reflex (Hmax) and the maximum M-wave (Mmax) (from direct stimulation of motor axons) decrease gradually with age. The decrease in Hmax was larger so the Hmax/Mmax ratio decreased dramatically with age. Interestingly, the modulation of the H-reflex during walking was essentially the same at all ages, suggesting that the pathways that modulate the H-reflex amplitude during walking are relatively well preserved during the aging process. We showed for the first time that the short-latency, reciprocal inhibitory pathways from the common peroneal nerve to soleus muscle and from the tibial nerve to the tibialis anterior muscle also decreased with age, when measured as a depression of ongoing voluntary activity. These results suggest that there may be a general decrease in excitability of spinal pathways with age. Thus, the use of age-matched controls is particularly important in assessing abnormalities resulting from disorders that occur primarily in the elderly.Key words: H-reflex, reciprocal inhibition, age.

scholarly journals Indirect Vibration of the Upper Limbs Alters Transmission Along Spinal but Not Corticospinal Pathways

2021 ◽  
Vol 15 ◽  
Author(s):  
Trevor S. Barss ◽  
David F. Collins ◽  
Dylan Miller ◽  
Amit N. Pujari
Keyword(s):  
Median Nerve ◽  
Presynaptic Inhibition ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
H Reflex ◽  
Cutaneous Reflexes ◽  
Spinal Pathways ◽  
Median Nerve Stimulation ◽  
The Right ◽  
Stimulation Of

The use of upper limb vibration (ULV) during exercise and rehabilitation continues to gain popularity as a modality to improve function and performance. Currently, a lack of knowledge of the pathways being altered during ULV limits its effective implementation. Therefore, the aim of this study was to investigate whether indirect ULV modulates transmission along spinal and corticospinal pathways that control the human forearm. All measures were assessed under CONTROL (no vibration) and ULV (30 Hz; 0.4 mm displacement) conditions while participants maintained a small contraction of the right flexor carpi radialis (FCR) muscle. To assess spinal pathways, Hoffmann reflexes (H-reflexes) elicited by stimulation of the median nerve were recorded from FCR with motor response (M-wave) amplitudes matched between conditions. An H-reflex conditioning paradigm was also used to assess changes in presynaptic inhibition by stimulating the superficial radial (SR) nerve (5 pulses at 300Hz) 37 ms prior to median nerve stimulation. Cutaneous reflexes in FCR elicited by stimulation of the SR nerve at the wrist were also recorded. To assess corticospinal pathways, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation of the contralateral motor cortex were recorded from the right FCR and biceps brachii (BB). ULV significantly reduced H-reflex amplitude by 15.7% for both conditioned and unconditioned reflexes (24.0 ± 15.7 vs. 18.4 ± 11.2% Mmax; p < 0.05). Middle latency cutaneous reflexes were also significantly reduced by 20.0% from CONTROL (−1.50 ± 2.1% Mmax) to ULV (−1.73 ± 2.2% Mmax; p < 0.05). There was no significant effect of ULV on MEP amplitude (p > 0.05). Therefore, ULV inhibits cutaneous and H-reflex transmission without influencing corticospinal excitability of the forearm flexors suggesting increased presynaptic inhibition of afferent transmission as a likely mechanism. A general increase in inhibition of spinal pathways with ULV may have important implications for improving rehabilitation for individuals with spasticity (SCI, stroke, MS, etc.).

scholarly journals Modulation of Rapid Visual Responses during Reaching by Multimodal Stimuli

2019 ◽  
Author(s):  
Isabel S Glover ◽  
Stuart N Baker
Keyword(s):  
Median Nerve ◽  
Reticular Formation ◽  
Visual Target ◽  
Human Subjects ◽  
Vestibular Stimulation ◽  
Auditory Stimuli ◽  
Visual Responses ◽  
Healthy Human ◽  
Reaching Task ◽  
Upper Limb Function

AbstractThe reticulospinal tract plays an important role in primate upper limb function, but methods for assessing its activity are limited. One promising approach is to measure rapid visual responses (RVRs) in arm muscle activity during a visually-cued reaching task; these may arise from a tecto-reticulospinal pathway. We investigated whether changes in reticulospinal excitability can be assessed non-invasively using RVRs, by pairing the visual stimuli of the reaching task with electrical stimulation of the median nerve, galvanic vestibular stimulation or loud sounds, all of which are known to activate the reticular formation.Surface electromyogram recordings were made from the right deltoid of healthy human subjects as they performed fast reaching movements towards visual targets. Stimuli were delivered up to 200ms before target appearance and RVR was quantified as the EMG amplitude in a window 75-125ms after visual target onset. Median nerve, vestibular and auditory stimuli all consistently facilitated the RVRs, as well as reducing the latency of responses. We propose that this reflects modulation of tecto-reticulospinal excitability, suggesting that the amplitude of RVRs can be used to assess changes in brainstem excitability non-invasively in humans.New & NoteworthyShort latency responses in arm muscles evoked during a visually-driven reaching task have previously been proposed to be tecto-reticulospinal in origin. We demonstrate that these responses can be facilitated by pairing the appearance of a visual target with stimuli that activate the reticular formation – median nerve, vestibular and auditory stimuli. We propose that this reflects non-invasive measurement and modulation of reticulospinal excitability.

scholarly journals Indirect Vibration of the Upper Limbs Alters Transmission Along Spinal but not Corticospinal Pathways

2020 ◽  
Author(s):  
Trevor S. Barss ◽  
David F. Collins ◽  
Dylan Miller ◽  
Amit N. Pujari
Keyword(s):  
Median Nerve ◽  
Presynaptic Inhibition ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
H Reflex ◽  
Cutaneous Reflexes ◽  
Spinal Pathways ◽  
Median Nerve Stimulation ◽  
The Right ◽  
Stimulation Of

AbstractThe aim of this study was to investigate whether indirect upper limb vibration (ULV) modulates transmission along spinal and corticospinal pathways that control the human forearm. All measures were assessed under CONTROL (no vibration) and ULV (30 Hz; 0.4 mm displacement) conditions while participants maintained a small contraction of the right flexor carpi radialis (FCR) muscle. To assess spinal pathways, Hoffmann reflexes (H-reflexes) elicited by stimulation of the median nerve were recorded from FCR with motor response (M-wave) amplitudes matched between conditions. An H-reflex conditioning paradigm was also used to assess changes in presynaptic inhibition by stimulating the superficial radial (SR) nerve (5 pulses at 300Hz) 37 ms prior to median nerve stimulation. Cutaneous reflexes in FCR elicited by stimulation of the SR nerve at the wrist were also recorded. To assess corticospinal pathways, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation of the contralateral motor cortex were recorded from the right FCR and biceps brachii (BB). ULV significantly reduced H-reflex amplitude by 15.7% for both conditioned and unconditioned reflexes (24.0±15.7 vs 18.4±11.2 % Mmax; p<0.05). Middle latency cutaneous reflexes were also significantly reduced by 20.0% from CONTROL (−1.50 ± 2.1 % Mmax) to ULV (−1.73 ± 2.2 % Mmax; p<0.05). There was no significant effect of ULV on MEP amplitude (p>0.05). Therefore, ULV inhibits cutaneous and H-reflex transmission without influencing corticospinal excitability of the forearm flexors suggesting increased presynaptic inhibition of afferent transmission as a likely mechanism. A general increase in inhibition of spinal pathways with ULV may have important implications for improving rehabilitation for individuals with spasticity (SCI, stroke, MS, etc).

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