Orientation of Listing's plane after hypergravity in humans

2008 ◽  
Vol 18 (2-3) ◽  
pp. 97-105
Author(s):  
Suzanne A.E. Nooij ◽  
Jelte E. Bos ◽  
Eric L. Groen
Keyword(s):  
Supine Position ◽  
Head Tilt ◽  
Frame Of Reference ◽  
Otolith Organs ◽  
Inertial Acceleration ◽  
Listing's Plane ◽  
Before And After ◽  
Fixed Orientation ◽  
Orientation Vector ◽  
Listing’S Plane

Adaptation to a novel gravitational state involves adaptation of vestibular mediated responses, in particular those mediated by the otolith organs. The present paper investigates whether the orientation of Listing's plane, which is under control of otolith signals, is affected by sustained exposure to hypergravity. Subjects were exposed to four G-loads differing in duration (45 or 90 min) and magnitude (2 or 3G). During centrifugation subjects were in a supine position, directing the gravito-inertial acceleration along the naso-occipetal axis. We determined the orientation of Listing's plane before and after each centrifuge run, with the head erect and tilted in pitch. Head tilt in pitch induced a counter-pitch of Listing's plane, which was found to be less pronounced after centrifugation. In addition, exposure to 3G for 90~min induced a small backward tilt of Listing's plane compared to the pretest orientation (head erect). In order to explain these results a hypothesis is discussed, proposing that the orientation of Listing's plane in the head is governed by a head fixed orientation vector that is modulated by the direction of gravity relative to the head. Sustained centrifugation is proposed to decrease this gravitational modulation, leading to the effects observed. This could reflect a shift towards a more body centered frame of reference.

scholarly journals Decreased otolith-mediated vestibular response in 25 astronauts induced by long-duration spaceflight

2016 ◽  
Vol 115 (6) ◽  
pp. 3045-3051 ◽  
Author(s):  
Emma Hallgren ◽  
Ludmila Kornilova ◽  
Erik Fransen ◽  
Dmitrii Glukhikh ◽  
Steven T. Moore ◽  
...  
Keyword(s):  
Orthostatic Intolerance ◽  
Balance Control ◽  
Head Tilt ◽  
Otolith Organs ◽  
Negative Effects ◽  
Spatial Disorientation ◽  
Long Duration ◽  
Before And After ◽  
Ocular Counterrolling ◽  
Otolith System

The information coming from the vestibular otolith organs is important for the brain when reflexively making appropriate visual and spinal corrections to maintain balance. Symptoms related to failed balance control and navigation are commonly observed in astronauts returning from space. To investigate the effect of microgravity exposure on the otoliths, we studied the otolith-mediated responses elicited by centrifugation in a group of 25 astronauts before and after 6 mo of spaceflight. Ocular counterrolling (OCR) is an otolith-driven reflex that is sensitive to head tilt with regard to gravity and tilts of the gravito-inertial acceleration vector during centrifugation. When comparing pre- and postflight OCR, we found a statistically significant decrease of the OCR response upon return. Nine days after return, the OCR was back at preflight level, indicating a full recovery. Our large study sample allows for more general physiological conclusions about the effect of prolonged microgravity on the otolith system. A deconditioned otolith system is thought to be the cause of several of the negative effects seen in returning astronauts, such as spatial disorientation and orthostatic intolerance. This knowledge should be taken into account for future long-term space missions.

Central Positional Nystagmus Simulated by a Mathematical Ocular Motor Model of Otolith-Dependent Modification of Listing's Plane

2001 ◽  
Vol 86 (4) ◽  
pp. 1546-1554 ◽  
Author(s):  
S. Glasauer ◽  
M. Dieterich ◽  
Th. Brandt
Keyword(s):  
Eye Movements ◽  
Neural Control ◽  
Position Control ◽  
Three Dimensional ◽  
Head Tilt ◽  
Eye Position ◽  
Positional Nystagmus ◽  
Listing's Plane ◽  
Head Positions ◽  
Listing’S Plane

To find an explanation of the mechanisms of central positional nystagmus in neurological patients with posterior fossa lesions, we developed a three-dimensional (3-D) mathematical model to simulate head position-dependent changes in eye position control relative to gravity. This required a model implementation of saccadic burst generation, of the neural velocity to eye position integrator, which includes the experimentally demonstrated leakage in the torsional component, and of otolith-dependent neural control of Listing's plane. The validity of the model was first tested by simulating saccadic eye movements in different head positions. Then the model was used to simulate central positional nystagmus in off-vertical head positions. The model simulated lesions of assumed otolith inputs to the burst generator or the neural integrator, both of which resulted in different types of torsional-vertical nystagmus that only occurred during head tilt in roll plane. The model data qualitatively fit clinical observations of central positional nystagmus. Quantitative comparison with patient data were not possible, since no 3-D analyses of eye movements in various head positions have been reported in the literature on patients with positional nystagmus. The present model, prompted by an open clinical question, proposes a new hypothesis about the generation of pathological nystagmus and about neural control of Listing's plane.

Modulation of carotid baroreflex responsiveness in man: effects of posture and propranolol

1976 ◽  
Vol 41 (3) ◽  
pp. 383-387 ◽  
Author(s):  
D. L. Eckberg ◽  
F. M. Abboud ◽  
A. L. Mark
Keyword(s):  
Angina Pectoris ◽  
Supine Position ◽  
Baroreflex Sensitivity ◽  
Pulse Interval ◽  
Upright Posture ◽  
Adrenergic Stimulation ◽  
Interval Prolongation ◽  
Carotid Baroreflex ◽  
Before And After ◽  
Autonomic Blockade

Carotid baroreceptors were stimulated with graded neck suction in supine and standing volunteers, before and after autonomic blockade, to determine the influence of posture on baroreflex responsiveness. Propranolol significantly augmented baroreflex pulse interval prolongation in the supine position. Upright posture did not modify baroreflex pulse interval responses prior to propranolol, but significantly augmented responses after propranolol. The results suggest that standing enhances baroreflex sensitivity, but that under normal circumstances, this effect is masked by beta-adrenergic stimulation. Augmentation of baroreflex pulse interval prolongation in the supine and standing positions by propranolol may contribute to the effectiveness of this drug in angina pectoris and labile hypertension.

scholarly journals Symmetry of oculomotor burst neuron coordinates about Listing's plane

1992 ◽  
Vol 68 (2) ◽  
pp. 432-448 ◽  
Author(s):  
J. D. Crawford ◽  
T. Vilis
Keyword(s):  
Emergent Behavior ◽  
Medial Longitudinal Fasciculus ◽  
Anatomic Landmarks ◽  
Electrical Microstimulation ◽  
Listing's Plane ◽  
Unilateral Stimulation ◽  
Eye Rotation ◽  
Burst Neuron ◽  
Listing’S Plane ◽  
Stimulation Of

1. The purpose of this investigation was to determine the axes of eye rotation generated by oculomotor burst neuron populations and the coordinate system that they collectively define. In particular, we asked if such coordinates might be related to constraints in the emergent behavior, i.e., Listing's law for saccades. 2. The mesencephalic rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) was identified in four monkeys with the use of single-unit recording, and then explored with the use of electrical microstimulation and pharmacological inactivation with the inhibitory gamma-aminobutyric acid (GABA) agonist muscimol. Three-dimensional (3-D) eye positions and velocities were recorded in one or both eyes while alert animals made eye movements in response to visual stimuli and head rotation. 3. Unilateral stimulation of the riMLF (20 microA, 200 Hz, 300-600 ms) produced conjugate, constant velocity eye rotations, which then stopped abruptly and held their final positions. This is expected if the riMLF produces phasic signals upstream from the oculomotor integrator. 4. Units that burst before upward or downward saccades were recorded intermingled in each side of the riMLF. Unilateral stimulation of the same riMLF sites produced eye rotations about primarily torsional axes, clockwise (CW) during right riMLF stimulation and counterclockwise (CCW) during left stimulation. Only small and inconsistent vertical components were observed, supporting the view that the riMLF carries intermingled up and down signals. 5. The torsional axes of eye rotation produced by riMLF stimulation did not correlate to external anatomic landmarks. Instead, stimulation axes from both riMLF sides aligned with the primary gaze direction orthogonal to Listing's plane of eye positions recorded during saccades. 6. Injection of muscimol into one side of the riMLF produced a conjugate deficit in saccades and quick phases, including a 50% reduction in all vertical velocities and complete loss of one torsional direction. CW was lost after right riMLF inactivation, and CCW was lost after left inactivation. 7. The plane that separated the intact torsional axes from the missing axes correlated with the orientation of Listing's plane. Thus, during left or right riMLF inactivation, the vertical axes of intact horizontal saccades were abnormally aligned with Listing's plane. The orientation of these axes was not correlated with external anatomic landmarks. 8. As suggested by their alignment with Listing's plane, the intact vertical axes of horizontal saccades following riMLF inactivation were orthogonal to torsional riMLF stimulation axes.(ABSTRACT TRUNCATED AT 400 WORDS)

Plasma cyclic nucleotides and plasma catecholamines before and after prolonged treatment with clonidine in hypertensive patients

1981 ◽  
Vol 97 (3) ◽  
pp. 405-411 ◽  
Author(s):  
Per Manhem ◽  
Lise Heding ◽  
Jörgen Malmquist ◽  
Bernt Hökfelt
Keyword(s):  
Physical Exercise ◽  
Supine Position ◽  
Cyclic Nucleotides ◽  
Plasma Catecholamines ◽  
Prolonged Treatment ◽  
Hypertensive Patients ◽  
Noradrenaline Concentration ◽  
Before And After ◽  
Plasma Camp ◽  
Response To Exercise

Abstract. The effect of standing and physical exercise on catecholamines and cyclic nucleotides in plasma was measured in 8 patients with essential hypertension under standardized conditions before and after prolonged treatment with clonidine. Before clonidine medication noradrenaline, adrenaline and cyclic AMP (cAMP) increased in response to standing and bicycling for 20 min. No significant correlation was found between their absolute levels nor was the increase in cAMP following exercise correlated to the increase in noradrenaline. Standing and physical exercise were without effect on cyclic GMP (cGMP). Clonidine reduced the plasma noradrenaline concentration in supine position and the noradrenaline and the adrenaline response to standing and exercise. Plasma cAMP was uneffected by clonidine under basal conditions but the response to exercise was slightly reduced initially. During clonidine there was a positive correlation between the plasma levels of cAMP and noradrenaline following work. Clonidine produced an increase in plasma cGMP in supine position, immediately prior to bicycling and after 5 min of exercise.

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