Responses of caudal medullary raphe neurons to natural vestibular stimulation

1993 ◽  
Vol 70 (3) ◽  
pp. 938-946 ◽  
Author(s):  
B. J. Yates ◽  
T. Goto ◽  
I. Kerman ◽  
P. S. Bolton
Keyword(s):  
Spinal Cord ◽  
Cervical Spinal Cord ◽  
Semicircular Canals ◽  
Vestibular Stimulation ◽  
Whole Body ◽  
Otolith Organs ◽  
Medullary Raphe ◽  
Vestibular Endorgans ◽  
Vector Orientation ◽  
Raphe Neurons

1. Over two thirds of caudal medullary raphespinal neurons respond to electrical stimulation of the vestibular nerve, and it has been suggested that these neurons may participate in the generation of vestibulospinal and vestibulosympathetic reflexes. The objective of the present study was to determine which vestibular endorgans (semicircular canals or otolith organs) provide inputs to these cells. 2. Experiments were conducted on decerebrate cats that were baroreceptor denervated and vagotomized, and that had a cervical spinal cord transection so that inputs from tilt-sensitive receptors outside of the labyrinth did not influence the units we recorded. 3. In most experiments, vertical vestibular stimulation was used to stimulate the anterior and posterior semicircular canals and the otolith organs. The plane of whole body rotation that produced maximal modulation of a neuron's firing rate (response vector orientation) was measured at one or more frequencies between 0.1 and 0.5 Hz. Neuron dynamics were then studied with sinusoidal (0.02-1 Hz) stimuli aligned with this orientation. Alternatively, in two animals horizontal rotations at 0.5 and 1.0 Hz were employed to stimulate the horizontal semicircular canals. 4. The properties of raphespinal neurons were similar to those of a larger sample of raphe neurons studied that either could not be antidromically activated from the cervical spinal cord or were not tested for a spinal projection. In response to vertical vestibular stimulation, > 85% of caudal medullary raphe neurons had response gains that remained relatively constant across stimulus frequencies, like regularly firing otolith afferents.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of vestibular neurons to head rotations in vertical planes. I. Response to vestibular stimulation

1988 ◽  
Vol 60 (5) ◽  
pp. 1753-1764 ◽  
Author(s):  
J. Kasper ◽  
R. H. Schor ◽  
V. J. Wilson
Keyword(s):  
Vestibular Nucleus ◽  
Semicircular Canals ◽  
Vestibular Nuclei ◽  
Vestibular Stimulation ◽  
Excitatory Input ◽  
Whole Body ◽  
Otolith Organs ◽  
Vertical Semicircular Canal ◽  
Vector Orientation ◽  
Response Vector

1. We have studied, in decerebrate cats, the responses of neurons in the lateral and descending vestibular nuclei to whole-body rotations in vertical planes that activated vertical semicircular canal and utricular receptors. Some neurons were identified as vestibulospinal by antidromic stimulation with floating electrodes placed in C4. 2. The direction of tilt that caused maximal excitation (response vector orientation) of each neuron was determined. Neuron dynamics were then studied with sinusoidal stimuli closely aligned with the response vector orientation, in the range 0.02-1 Hz. A few cells, for which we could not identify a response vector, probably had spatial-temporal convergence. 3. On the basis of dynamics, neurons were classified as receiving their input primarily from vertical semicircular canals, primarily from the otolith organs, or from canal+otolith convergence. 4. Response vector orientations of canal-driven neurons were often near +45 degrees or -45 degrees with respect to the transverse (roll) plane, suggesting these neurons received excitatory input from the ipsilateral anterior or posterior canal, respectively. Some neurons had canal-related dynamics but vector orientations near roll, presumably because they received convergent input from the ipsilateral anterior and posterior canals. Few neurons had their vectors near pitch. 5. In the lateral vestibular nucleus, neurons with otolith organ input (pure otolith or otolith+canal) tended to have vector orientations closer to roll than to pitch. In the descending nucleus the responses were evenly divided between the roll and pitch quadrants. 6. We conclude that most of our neurons have dynamics and response vector orientations that make them good candidates to participate in vestibulospinal reflexes acting on the limbs, but not those acting on the neck.

Responses of interneurons in the cat cervical cord to vestibular tilt stimulation

1986 ◽  
Vol 56 (4) ◽  
pp. 1147-1156 ◽  
Author(s):  
R. H. Schor ◽  
I. Suzuki ◽  
S. J. Timerick ◽  
V. J. Wilson
Keyword(s):  
Cervical Spinal Cord ◽  
Semicircular Canals ◽  
Body Tilt ◽  
Whole Body ◽  
Cervical Cord ◽  
Otolith Organs ◽  
Phase Lag ◽  
Response Dynamics ◽  
Decerebrate Cat ◽  
Propriospinal Neurons

The responses of interneurons in the cervical spinal cord of the decerebrate cat to whole-body tilt were studied with a goal of identifying spinal elements in the production of forelimb vestibular postural reflexes. Interneurons both in the cervical enlargement and at higher levels, from which propriospinal neurons have been identified, were examined, both in animals with intact labyrinths and in animals with nonfunctional semicircular canals (canal plugged). Most cervical interneurons responding to tilt respond best to rotations in vertical planes aligned within 30 degrees of the roll plane. Two to three times as many neurons are excited by side-up roll tilt as are excited by side-down roll. In cats with intact labyrinths, most responses have dynamics proportional either to (and in phase with) the position of the animal or to a sum of position and tilt velocity. This is consistent with input from both otolith organs and semicircular canals. In animals without functioning canals, the "velocity" response is absent. In a few cells (8 out of 76), a more complex response, characterized by an increasing gain and progressive phase lag, was observed. These response dynamics characterize the forelimb reflex in canal-plugged cats and have been previously observed in vestibular neurons in such preparations.

Probing the human vestibular system with galvanic stimulation

2004 ◽  
Vol 96 (6) ◽  
pp. 2301-2316 ◽  
Author(s):  
Richard C. Fitzpatrick ◽  
Brian L. Day
Keyword(s):  
Balance Control ◽  
Semicircular Canals ◽  
Vestibular Nuclei ◽  
Vestibular Stimulation ◽  
Otolith Organs ◽  
Sources Of Information ◽  
Electrophysiological Studies ◽  
Human Balance ◽  
Cortical Inputs ◽  
Vestibular Organs

Galvanic vestibular stimulation (GVS) is a simple, safe, and specific way to elicit vestibular reflexes. Yet, despite a long history, it has only recently found popularity as a research tool and is rarely used clinically. The obstacle to advancing and exploiting GVS is that we cannot interpret the evoked responses with certainty because we do not understand how the stimulus acts as an input to the system. This paper examines the electrophysiology and anatomy of the vestibular organs and the effects of GVS on human balance control and develops a model that explains the observed balance responses. These responses are large and highly organized over all body segments and adapt to postural and balance requirements. To achieve this, neurons in the vestibular nuclei receive convergent signals from all vestibular receptors and somatosensory and cortical inputs. GVS sway responses are affected by other sources of information about balance but can appear as the sum of otolithic and semicircular canal responses. Electrophysiological studies showing similar activation of primary afferents from the otolith organs and canals and their convergence in the vestibular nuclei support this. On the basis of the morphology of the cristae and the alignment of the semicircular canals in the skull, rotational vectors calculated for every mode of GVS agree with the observed sway. However, vector summation of signals from all utricular afferents does not explain the observed sway. Thus we propose the hypothesis that the otolithic component of the balance response originates from only the pars medialis of the utricular macula.

Subgroups of Rostral Ventrolateral Medullary and Caudal Medullary Raphe Neurons Based on Patterns of Relationship to Sympathetic Nerve Discharge and Axonal Projections

1997 ◽  
Vol 77 (1) ◽  
pp. 65-75 ◽  
Author(s):  
Susan M. Barman ◽  
Gerard L. Gebber
Keyword(s):  
Spinal Cord ◽  
Sympathetic Nerve ◽  
Cell Types ◽  
Vagus Nerves ◽  
Thoracic Spinal Cord ◽  
Axonal Projections ◽  
Thoracic Spinal ◽  
Medullary Raphe ◽  
Raphe Neurons ◽  
Nerve Discharge

Barman, Susan M. and Gerard L. Gebber. Subgroups of rostral ventrolateral medullary and caudal medullary raphe neurons based on patterns of relationship to sympathetic nerve discharge and axonal projections. J. Neurophysiol. 77: 65–75, 1997. This study was designed to answer three questions concerning rostral ventrolateral medullary (RVLM) and caudal medullary raphe (CMR) neurons with activity correlated to sympathetic nerve discharge (SND). 1) What are the proportions of RVLM and CMR neurons that have activity correlated to both the cardiac-related and 10-Hz rhythms in SND, to only the 10-Hz rhythm, and to only the cardiac-related rhythm? 2) Which of these cell types project to the spinal cord? 3) Do the outputs of the cardiac-related and 10-Hz rhythm generators converge at the level of bulbospinal neurons or their antecedent interneurons? To address these issues we recorded from 44 RVLM and 48 CMR neurons with sympathetic nerve–related activity in urethan-anesthetized cats with intact carotid sinus nerves, but sectioned aortic depressor and vagus nerves. Spike-triggered averaging, arterial pulse-triggered analysis, and coherence analysis revealed that the naturally occurring discharges of 24 of these RVLM neurons and 41 of these CMR neurons were correlated to both the 10-Hz and cardiac-related rhythms in inferior cardiac postganglionic SND. The discharges of the other neurons were correlated to only the 10-Hz rhythm (15 RVLM and 6 CMR neurons) or to only the cardiac-related rhythm (5 RVLM neurons and 1 CMR neuron) in SND. The time-controlled collision test verified that 16 of 18 RVLM and 31 of 34 CMR neurons with activity correlated to both rhythms were antidromically activated by stimulation of the white matter of the first thoracic (T1) segment of the spinal cord. In contrast, only 1 of 10 RVLM neurons and 0 of 4 CMR neurons with activity correlated to only the 10-Hz rhythm could be antidromically activated by stimulation at T1. Also 0 of 3 RVLM neurons with activity correlated to only the cardiac-related rhythm in SND were antidromically activated by spinal stimulation. These data show for the first time that bulbospinal sympathetic pathways emanating from the RVLM and CMR are comprised almost exclusively of neurons whose discharges are correlated to both the cardiac-related and 10-Hz rhythms in SND. Moreover, the data support the hypothesis that the outputs of the cardiac-related and 10-Hz rhythm generators converge on RVLM and CMR bulbospinal neurons rather than on their antecedent interneurons. Finally, the data demonstrate that a substantial proportion of RVLM neurons and a small group of CMR neurons with activity correlated to SND do not project to the thoracic spinal cord. Their discharges were correlated to only one of the rhythms in SND. Their axonal trajectories and functions are unknown.

scholarly journals Pulsed Infrared Stimulation of Vertical Semicircular Canals Evokes Cardiovascular Changes in the Rat

2021 ◽  
Vol 12 ◽  
Author(s):  
Darrian Rice ◽  
Giorgio P. Martinelli ◽  
Weitao Jiang ◽  
Gay R. Holstein ◽  
Suhrud M. Rajguru
Keyword(s):  
Heart Rate ◽  
Nervous System ◽  
Semicircular Canal ◽  
Parasympathetic Nervous System ◽  
Semicircular Canals ◽  
Whole Body ◽  
Experimental Session ◽  
Otolith Organs ◽  
Vertical Semicircular Canals ◽  
Stimulation Of

A variety of stimuli activating vestibular end organs, including sinusoidal galvanic vestibular stimulation, whole body rotation and tilt, and head flexion have been shown to evoke significant changes in blood pressure (BP) and heart rate (HR). While a role for the vertical semicircular canals in altering autonomic activity has been hypothesized, studies to-date attribute the evoked BP and HR responses to the otolith organs. The present study determined whether unilateral activation of the posterior (PC) or anterior (AC) semicircular canal is sufficient to elicit changes in BP and/or HR. The study employed frequency-modulated pulsed infrared radiation (IR: 1,863 nm) directed via optical fibers to PC or AC of adult male Long-Evans rats. BP and HR changes were detected using a small-animal single pressure telemetry device implanted in the femoral artery. Eye movements evoked during IR of the vestibular endorgans were used to confirm the stimulation site. We found that sinusoidal IR delivered to either PC or AC elicited a rapid decrease in BP and HR followed by a stimulation frequency-matched modulation. The magnitude of the initial decrements in HR and BP did not correlate with the energy of the suprathreshold stimulus. This response pattern was consistent across multiple trials within an experimental session, replicable, and in most animals showed no evidence of habituation or an additive effect. Frequency modulated electrical current delivered to the PC and IR stimulation of the AC, caused decrements in HR and BP that resembled those evoked by IR of the PC. Frequency domain heart rate variability assessment revealed that, in most subjects, IR stimulation increased the low frequency (LF) component and decreased the high frequency (HF) component, resulting in an increase in the LF/HF ratio. This ratio estimates the relative contributions of sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) activities. An injection of atropine, a muscarinic cholinergic receptor antagonist, diminished the IR evoked changes in HR, while the non-selective beta blocker propranolol eliminated changes in both HR and BP. This study provides direct evidence that activation of a single vertical semicircular canal is sufficient to activate and modulate central pathways that control HR and BP.

Impact of cervical spinal cord injury on the relationship between the metabolism and ventilation in rats

2021 ◽  
Author(s):  
Tzu-Ting Chiu ◽  
Kun-Ze Lee
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Tidal Volume ◽  
Cervical Spinal Cord ◽  
Cervical Spinal Cord Injury ◽  
Male Rats ◽  
Whole Body ◽  
Post Injury ◽  
Chronic Injury ◽  
Cord Injury

Cervical spinal cord injury typically results in respiratory impairments. Clinical and animal studies have demonstrated that respiratory function can spontaneously and partially recover over time after injury. However, it remains unclear whether respiratory recovery is associated with alterations in metabolism. The present study was designed to comprehensively examine ventilation and metabolism in a rat model of spinal cord injury. Adult male rats received sham (i.e., laminectomy) or unilateral mid-cervical contusion injury (height of impact rod: 6.25 or 12.5 mm). Breathing patterns and whole-body metabolism (O2 consumption and CO2 production) were measured using a whole-body plethysmography system conjugated with flow controllers and gas analyzer at the acute (1 day post-injury), subchronic (2 weeks post-injury), and chronic (8 weeks post-injury) injury stages. The results demonstrated that mid-cervical contusion caused a significant reduction in the tidal volume. Although the tidal volume of contused animals can gradually recover, it remains lower than that of uninjured animals at the chronic injury stage. While O2 consumption and CO2 production were similar between uninjured and contused animals at the acute injury stage, these two metabolic parameters were significantly reduced in contused animals at the subchronic to chronic injury stages. Additionally, the relationships between ventilation, metabolism, and body temperature were altered by cervical spinal cord injury. These results suggest that cervical spinal cord injury causes a complicated reconfiguration of ventilation and metabolism that may enable injured animals to maintain a suitable homeostasis for adapting to the pathophysiological consequences of injury.

Responses of neurons of the cat central cervical nucleus to natural neck and vestibular stimulation

1996 ◽  
Vol 76 (4) ◽  
pp. 2786-2789 ◽  
Author(s):  
D. B. Thomson ◽  
N. Isu ◽  
V. J. Wilson
Keyword(s):  
Vestibular Nuclei ◽  
Vestibular Stimulation ◽  
Body Tilt ◽  
Whole Body ◽  
Vestibular Input ◽  
Preferred Direction ◽  
Central Cervical Nucleus ◽  
Neck Rotation ◽  
Vector Orientation ◽  
To Receive

1. The central cervical nucleus (CCN) is known to receive neck and vestibular input and to project to the contralateral cerebellum and vestibular nuclei. To investigate the processing of neck and vestibular input by cells in the CCN, we studied their responses to sinusoidal neck rotation and to whole-body tilt in vertical planes in decerebrate, paralyzed cats. CCN neurons were identified by antidromic stimulation with electrodes placed in or near the contralateral restiform body. 2. For every neuron, we first identified the preferred direction of neck rotation (response vector orientation), then studied the neuron's dynamics with rotations in a plane close to this direction at 0.05-1 Hz. 3. Responses of CCN neurons to neck rotation resembled those of previously studied neck spindle primary afferents in terms of their dynamics and nonlinear responses to stimuli of differing amplitudes. They also resembled the neck responses of Deiters' neurons studied in similar preparations. 4. The activity of two-thirds of CCN neurons also was modulated by natural vestibular stimulation. Orientation and dynamics of vestibular responses were characterized in the same way as neck responses. Labyrinthine input originated predominantly from the contralateral vertical canals, and there was no evidence of otolith input. Neck and vestibular inputs were always antagonistic, but the gain of the vestibular response was lower than that of the neck response at all frequencies studied. 5. The quantitative aspects of the interaction between neck and vestibular inputs can be expected to vary with the type of preparation and with stimulus parameters, and its functional significance remains to be investigated.

Spatial organization of neck and vestibular reflexes acting on the forelimbs of the decerebrate cat

1986 ◽  
Vol 55 (3) ◽  
pp. 514-526 ◽  
Author(s):  
V. J. Wilson ◽  
R. H. Schor ◽  
I. Suzuki ◽  
B. R. Park
Keyword(s):  
Spatial Organization ◽  
Stimulus Frequency ◽  
Semicircular Canals ◽  
Head Rotation ◽  
Otolith Organs ◽  
Vestibular Reflexes ◽  
Decerebrate Cat ◽  
Shoulder Muscles ◽  
Long Head ◽  
Vector Orientation

EMG recording was used to study the spatial organization of vestibular and tonic neck reflexes acting on forelimb and shoulder muscles of the decerebrate cat. Neck reflexes were studied in preparations with intact labyrinths as well as those with acute or chronic labyrinthectomies. Reflexes were described by response vectors whose orientation component is aligned with the optimal excitatory direction of tilt or head rotation. A muscle's vector orientation remained reasonably stable over a period of hours, although there was sometimes drift at the beginning or end of an experiment. Orientation of muscle response vectors did not change systematically with stimulus frequency of 0.05-2.0 Hz. For vestibular reflexes this is so, although their dynamics are consistent with convergent input from semicircular canals and otolith organs. Regardless of the preparation, a consistent reflex pattern emerged. Vestibular reflexes are characterized by response vector orientation near ear-down roll. Neck vector orientation lies in the opposite direction from the vestibular vector but typically lies further from the roll plane: Nose-up pitch is excitatory for the shoulder muscles supra- and infraspinatus, and for the medial and lateral heads of triceps, whereas nose-down pitch excites the long head of triceps. Our results generally agree with the pattern proposed by Roberts (28) for neck reflexes but disagree in part with his proposed pattern of vestibular reflexes; we did not see the expected consistent excitation by nose-down pitch.

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