Anodal vestibular stimulation does not suppress vestibular reflexes in human subjects

2003 ◽  
Vol 150 (4) ◽  
pp. 525-528 ◽  
Author(s):  
Ann M. Bacsi ◽  
James G. Colebatch
Keyword(s):  
Human Subjects ◽  
Vestibular Stimulation ◽  
Vestibular Reflexes

Vestibular Influence on Human Auditory Space Perception

2000 ◽  
Vol 84 (2) ◽  
pp. 1107-1111 ◽  
Author(s):  
Jörg Lewald ◽  
Hans-Otto Karnath
Keyword(s):  
Cold Water ◽  
Human Subjects ◽  
Space Perception ◽  
Median Plane ◽  
Vestibular Stimulation ◽  
Whole Body ◽  
Interaural Level Difference ◽  
Auditory Periphery ◽  
Auditory Space ◽  
Sound Image

We investigated the effect of vestibular stimulation on the lateralization of dichotic sound by cold-water irrigation of the external auditory canal in human subjects. Subjects adjusted the interaural level difference of the auditory stimulus to the subjective median plane of the head. In those subjects in whom dizziness and nystagmus indicated sufficient vestibular stimulation, these adjustments were significantly shifted toward the cooled ear compared with the control condition (irrigation with water at body temperature); i.e., vestibular stimulation induced a shift of the sound image toward the nonstimulated side. The mean magnitude of the shift was 7.3 dB immediately after vestibular stimulation and decreased to 2.5 dB after 5 min. As shown by an additional control experiment, this effect cannot be attributed to a unilateral hearing loss induced by cooling of the auditory periphery. The results indicate the involvement of vestibular afferent information in the perception of sound location during movements of the head and/or the whole body. We thus hypothesize that vestibular information is used by central-nervous mechanisms generating a world-centered representation of auditory space.

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.

Extracting phase-dependent human vestibular reflexes during locomotion using both time and frequency correlation approaches

2011 ◽  
Vol 111 (5) ◽  
pp. 1484-1490 ◽  
Author(s):  
Jean-Sébastien Blouin ◽  
Christopher J. Dakin ◽  
Kees van den Doel ◽  
Romeo Chua ◽  
Bradford J. McFadyen ◽  
...  
Keyword(s):  
Vestibular Stimulation ◽  
Time Dependent ◽  
Medial Gastrocnemius ◽  
Electromyographic Activity ◽  
Step Cycle ◽  
Vestibular Reflexes ◽  
Time Frequency ◽  
Dynamic Modulation ◽  
Frequency Decomposition ◽  
Heel Contact

Daily activities, such as walking, may require dynamic modulation of vestibular input onto motoneurons. This dynamic modulation is difficult to identify in humans due to limitations in the delivery and analysis of current vestibular probes, such as galvanic vestibular stimulation. Stochastic vestibular stimulation, however, provides an alternative method to extract human vestibular reflexes. Here, we used time-dependent coherence and time-dependent cross-correlation, coupled with stochastic vestibular stimulation, to investigate the phase dependency of human vestibular reflexes during locomotion. We found that phase-dependent activity from the medial gastrocnemius muscles is correlated with the vestibular signals over the 2- to 20-Hz bandwidth during the stance phase of locomotion. Vestibular-gastrocnemius coherence and time-dependent cross-correlations reached maximums at 21 ± 4 and 23 ± 8% of the step cycle following heel contact and before the period of maximal electromyographic activity (38 ± 5%). These results demonstrate 1) the effectiveness of these techniques in extracting the phase-dependent modulation of vestibulomuscular coupling during a cyclic task; 2) that vestibulomuscular coupling is phasically modulated during locomotion; and 3) that the period of strongest vestibulomuscular coupling does not correspond to the period of maximal electromyographic activity in the gastrocnemius. Therefore, we have shown that stochastic vestibular stimulation, coupled with time-frequency decomposition, provides an effective tool to assess the contribution of vestibular ex-afference to the muscular control during locomotion.

Subsensory galvanic vestibular stimulation augments arterial pressure control upon head-up tilt in human subjects

2012 ◽  
Vol 166 (1-2) ◽  
pp. 66-71 ◽  
Author(s):  
Kunihiko Tanaka ◽  
Chikara Abe ◽  
Yuzuru Sakaida ◽  
Mitsuhiro Aoki ◽  
Chihiro Iwata ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Human Subjects ◽  
Pressure Control ◽  
Vestibular Stimulation ◽  
Galvanic Vestibular Stimulation ◽  
Head Up Tilt

scholarly journals Three-Dimensional Binocular Kinematics of Torsional Vestibular Nystagmus During Convergence on Head-Fixed Targets in Humans

2001 ◽  
Vol 86 (1) ◽  
pp. 113-122 ◽  
Author(s):  
O. Bergamin ◽  
D. Straumann
Keyword(s):  
Human Subjects ◽  
Three Dimensional ◽  
Vertical Component ◽  
Vestibular Stimulation ◽  
Fixed Target ◽  
Healthy Human ◽  
Retinal Slip ◽  
Gain Reduction ◽  
The Right ◽  
Eye Velocity

When a human subject is oscillated about the nasooccipital axis and fixes upon targets along the horizontal head-fixed meridian, angular eye velocity includes a vertical component that increases with the horizontal eccentricity of the line-of-sight. This vertical eye movement component is necessary to prevent retinal slip. We asked whether fixation on a near head-fixed target during the same torsional vestibular stimulation would lead to differences of vertical eye movements between the right and the left eye, as the directions of the two lines-of-sight are not parallel during convergence. Healthy human subjects ( n = 6) were oscillated (0.3 Hz, ±30°) about the nasooccipital axis on a three-dimensional motor-driven turntable. Binocular movements were recorded using the dual search coil technique. A head-fixed laser dot was presented 1.4 m (far head-fixed target) or 0.25 m (near head-fixed target) in front of the right eye. We found highly significant ( P < 0.01) correlations (R binocular = 0.8, monocular = 0.59) between the convergence angle and the difference of the vertical eye velocity between the two eyes. The slope of the fitted linear regression between the two parameters ( s = 0.45) was close to the theoretical slope necessary to prevent vertical retinal slippage (predicted s = 0.5). Covering the left eye did not significantly change the slope ( s = 0.52). In addition, there was a marked gain reduction (∼35%) of the torsional vestibuloocular reflex (VOR) between viewing the far and the near targets, confirming earlier results by others. There was no difference in torsional gain reduction between the two eyes. Lenses of +3 dpt positioned in front of both eyes to decrease the amount of accommodation did not further change the gain of the torsional VOR. In conclusion, ocular convergence on a near head-fixed target during torsional vestibular stimulation leads to deviations in vertical angular velocity between the two eyes necessary to prevent vertical double vision. The vertical deviation velocity is mainly linked to the amount of convergence, since it also occurs during monocular viewing of the near head-fixed target. This suggests that convergence during vestibular stimulation automatically leads to an alignment of binocular rotation axes with the visual axes independent of retinal slip.

Responses of Reticulospinal Neurons in Intact Lamprey to Pitch Tilt

2002 ◽  
Vol 88 (3) ◽  
pp. 1136-1146 ◽  
Author(s):  
E. L. Pavlova ◽  
T. G. Deliagina
Keyword(s):  
Spinal Cord ◽  
Conduction Velocity ◽  
Longitudinal Axis ◽  
Maximal Activity ◽  
Vestibular Stimulation ◽  
Dynamic Responses ◽  
Vestibular Reflexes ◽  
Postural Control System ◽  
Roll Control ◽  
Response Group

In the swimming lamprey, a postural control system maintains a definite orientation of the animal's longitudinal axis in relation to the horizon (pitch angle). Operation of this system is based on vestibular reflexes. Important elements of the postural network are the reticulospinal (RS) neurons, which are driven by vestibular input and transmit commands for postural corrections from the brain stem to the spinal cord. Here we describe responses to vestibular stimulation (rotation of the animal in the pitch plane) in RS neurons of intact lampreys. The activity of neurons was recorded from their axons in the spinal cord by chronically implanted arrays of macroelectrodes. From the multielectrode recordings of mass activity, discharges in individual axons were extracted by means of a spike-sorting program, and the axon position in the spinal cord and its conduction velocity were determined. Vestibular stimulation was performed by rotating the animal in steps of 45° throughout 360° or by periodical “trapezoid” tilts between the nose-up and -down positions. Typically, the RS neurons exhibited both dynamic responses (activity during movement) and static responses (activity in a new sustained position). The neurons were classified into two groups according to their pattern of response. Group up neurons responded preferentially to nose-up rotation with maximal activity at 0–135° up. Group down neurons responded preferentially to nose-down rotation with maximal activity at 0–135° down. Neurons of the two groups also differed in the position of their axons in the spinal cord and axonal conduction velocity. An increase in water temperature, which presumably causes a downward turn in swimming lampreys, affected the activity in the up anddown groups differently, so that the ratio upresponses to down responses increased. We suggest that theup and down groups mediate the opposing vestibular reflexes and cause the downward and upward turns of the animal, respectively. The lamprey will stabilize the orientation in the pitch plane at which the effects of up and downgroups are equal to each other. In addition to the main test (rotation in the pitch plane), the animals were also tested by rotation in the transverse (roll) plane. It was found that 22% of RS neurons responding to pitch tilts also responded to roll tilts. The overlap between the pitch and roll populations suggests that the RS pathways are partly shared by the pitch and roll control systems.

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