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We have previously shown that sinusoidal galvanic vestibular stimulation (sGVS), a means of a selectively modulating vestibular afferent input without affecting other inputs, can cause partial entrainment of muscle sympathetic nerve activity (MSNA). Given that motion sickness causes sweating and pallor, we tested the hypothesis that sGVS also entrains skin(More)
We have previously demonstrated that selective modulation of vestibular inputs, via sinusoidal galvanic vestibular stimulation (GVS) delivered at 0.5-0.8 Hz, can cause partial entrainment of muscle sympathetic nerve activity (MSNA). Given that we had seen interaction between the dynamic vestibular input and the normal cardiac-locked MSNA rhythm, we tested(More)
We tested the hypothesis that vestibular and cardiac rhythms compete to modulate muscle sympathetic nerve activity (MSNA) in human subjects. Sinusoidal galvanic vestibular stimulation was applied across the mastoid processes at each subject's cardiac frequency and at ±0.1, ±0.2, ±0.3 and ±0.6 Hz. Cyclic modulation of MSNA was weakest at this central(More)
There is controversy as to whether the vestibulosympathetic reflexes demonstrated in experimental animals actually exist in human subjects. While head-down neck flexion and off-vertical axis rotation can increase muscle sympathetic nerve activity (MSNA) in awake subjects, we recently showed that bipolar galvanic vestibular stimulation (GVS) does not.(More)
1. The discharge behaviour of fourteen single sympathetic vasoconstrictor efferents was studied using a tungsten microelectrode inserted percutaneously into a motor fascicle of the radial or peroneal nerve in eight awake supine subjects. Units were classified as vasoconstrictor because their firing properties correlated appropriately to changes in cardiac(More)
1. Single motor axons innervating human toe extensor muscles were selectively stimulated through a tungsten microelectrode inserted percutaneously into the peroneal nerve. Twitch and tetanic forces were measured from a strain gauge over the proximal phalanx of the toe generating the greatest force. Twitch data were obtained from 19 single motor units in(More)
1. While it is known that the average firing rate of a population of motoneurones declines with time during a maximal voluntary contraction, at least for many muscles, it is not known how the firing patterns of individual motoneurones adapt with fatigue. To address this issue we used tungsten microelectrodes to record spike trains (mean +/- s.e.m., 183 +/-(More)
1. Single-unit recordings were made from 19 postganglionic muscle vasoconstrictor axons via tungsten microelectrodes in the peroneal nerve in seven healthy subjects with many multi-unit sympathetic discharges at rest ('high group', 75 +/- 5 multi-unit bursts per 100 heart beats, mean +/- s.e.m.). The results were compared with previous data from 14 units in(More)
The most obvious impairments associated with spinal cord injury (SCI) are loss of sensation and motor control. However, many subjects with SCI also develop persistent neuropathic pain below the injury which is often severe, debilitating and refractory to treatment. The underlying mechanisms of persistent neuropathic SCI pain remain poorly understood.(More)
Unexpected pulling and pushing loads exerted by an object held with a precision grip evoke automatic and graded increases in the grip force (normal to the grip surfaces) that prevent escape of the object; unloading elicits a decrease in grip force. Anesthesia of the digital nerves has shown that these grip reactions depend on sensory signals from the(More)