Journal of Vestibular Research - Volume 15, issue 2

Authors: Helling, Kai | Scherer, Hans | Hausmann, Stefan | Clarke, Andrew H.

Article Type: Research Article

Abstract: The otolith mass of the saccules and utricles of plaice, Pleuronectes platessa (n = 39) and turbot, Psetta maxima (n = 21) was measured using an electronic microbalance. In the right-eyed plaice, the left utricular otoliths were found to be significantly heavier than the right (p < 0.0001), whereas no significant difference was found between left and right saccular otoliths (p < 0.751). In the left-eyed turbot, both the right utricular and saccular otoliths were found to be significantly heavier (in both cases, p < 0.0001). While the gene and regulative …protein responsible for the peripheral biomineralisation process have been identified, it remains unclear how the symmetry between the right and left otoliths in fish species is regulated. Here it is likely that an additional central mechanism is involved. It must be assumed that similar processes govern the systematic asymmetry observed in flatfish such as the plaice and turbot. Taken together these findings are strongly suggestive of concomitant CNS modification and metamorphic plasticity, presumably represented in genetic code. Show more

Keywords: biomineralisation, flatfish, metamorphosis, otolith asymmetry, saccule, utricle

DOI: 10.3233/VES-2005-15201

Citation: Journal of Vestibular Research, vol. 15, no. 2, pp. 59-64, 2005

Authors: Clarke, A.H.

Article Type: Research Article

Abstract: The extensive remains of large sauropods, excavated in the Upper Jurassic layers of the Tendaguru region of Tanzania, East Africa by Janensch [15], include an intact fossil cast of a vestibular labyrinth and an endocast of the large Brachiosaurus brancai . The approximately 150 million year old labyrinth cast demonstrates clearly a form and organisation congruent in detail to those of extant vertebrate species. Besides the near-orthogonal arrangement of semicircular canals (SCCs), the superior and inferior branches of the vestibulo-acoustic nerve, the endolymphatic duct, the oval and round windows, and the cochlea can be identified. The orientation of the labyrinth …in the temporal bone is also equivalent to that of many extant vertebrates. Furthermore, the existence of the twelve cranial nerves can be identified from the endocast. The present study was initiated after the photogrammetric measurement of the skeleton volume of B. brancai [13] yielded a realistic estimate of body mass (74.42 metric tons). Dimensional analysis shows that body mass and average SCC dimensions of B. brancai generally fit with the allometric relationship found in previous studies of extant species. However, the anterior SCC is significantly larger than the allometric relationship would predict. This would indicate greater sensitivity, supporting the idea that the behavioural repertoire must have included much slower pitch movements of the head. These slower movements would most likely have involved flexion of the neck, rather than head pitching about the atlas joint. Pursuing the relationship between body mass and SCC dimensions further, the SCC frequency response is estimated by scaling up from the SCC dimensions of the rhesus monkey; this yields a range between 0.008–26 Hz, approximately one octave lower than for humans. Show more

DOI: 10.3233/VES-2005-15202

Citation: Journal of Vestibular Research, vol. 15, no. 2, pp. 65-71, 2005

Authors: Moore, Steven T. | Hirasaki, Eishi | Raphan, Theodore | Cohen, Bernard

Article Type: Research Article

Abstract: Rotation axes were calculated during active head movements using a motion analysis system. The mean rotation axis for 1 Hz head pitch when seated was posterior (6 mm) and inferior (21 mm) to the interaural axis, shifting 16 mm downwards when standing. During seated 2 Hz head pitch the rotation axis was close to the interaural axis, shifting downwards 15 mm when standing. This downward shift suggests that cervical vertebrae were recruited during head pitch with the trunk unsupported. The proximity of the pitch axis to the otoliths implies minimal otolith activation during small-amplitude, high-frequency pitch rotations, such as those …encountered during locomotion. The mean rotation axis for 1 Hz yaw rotation was located slightly posterior (10 mm) to the interaural axis at the midpoint between the vestibular labyrinths when both seated and standing. In addition, the orientation of the plane of yaw rotation relative to the stereotaxic horizontal plane (pitched 5° nose-down) was essentially fixed in head coordinates, regardless of the pitch orientation of the head, suggesting that yaw movements occur about an axis restricted by the mechanical structure of the atlanto-axial joint. The results demonstrate that the instantaneous rotation axes technique overcomes the inherent instability of the helical-axis representation for small head movements. Show more

Keywords: rotation axis, head rotation, locomotion, VOR, otoliths

DOI: 10.3233/VES-2005-15203

Citation: Journal of Vestibular Research, vol. 15, no. 2, pp. 73-80, 2005

Authors: Schmäl, Frank | Glitz, Barbara | Thiede, Oliver | Stoll, Wolfgang

Article Type: Research Article

Abstract: Both the influence of a remembered “earth-fixed” target (RT) on the vestibulo-ocular reflex and the effect of “unilateral cold caloric vestibular stimulation” on the localization of a RT have previously been proved. As “unilateral caloric stimulation” is not a physiological stimulus, the aim of the present study was to analyze whether even physiological “bilateral vestibular stimulation” (rotation) is able to affect the RT position. The pointing error (PE) towards an RT both without and following angular acceleration was investigated in 24 healthy volunteers. Postrotatory nystagmus response was recorded by electronystagmography. Evaluation parameters were “nystagmus frequency”, “total amplitude” and “velocity of …the slow phase”; the horizontal and vertical PE. The fixation of an RT led to a significant reduction of about 28% in nystagmus amplitude compared to the test condition in darkness. “After rotatory stimulation” a systematic horizontal PE in the direction of the fast phase of the postrotatory nystagmus (direction of “illusory self-rotation”) occurred and the magnitude of this PE increased significantly compared to the test situation “without vestibular stimulation”, but showed only a non-uniform negative correlation with two of the nystagmus parameters. It has to be concluded that “after rotatory stimulation”, in contrast to “unilateral cold caloric vestibular stimulation”, the subjective sense of “illusory self-motion” leads to a horizontal PE in the direction of the nystagmus fast phases. Show more

Keywords: visual vestibular interactions , rotational testing , pointing error

DOI: 10.3233/VES-2005-15204

Citation: Journal of Vestibular Research, vol. 15, no. 2, pp. 81-92, 2005

Authors: Kassemi, M. | Oas, J.G. | Deserranno, Dimitri

Article Type: Research Article

Abstract: Microgravity caloric tests aboard the 1983 SpaceLab1 mission produced nystagmus results with an intensity comparable to those elicited during post- and pre- flight tests, thus contradicting the basic premise of Barany's convection hypothesis for caloric stimulation. In this work, we present a dynamic fluid structural analysis of the caloric stimulation of the lateral semicircular canal based on two simultaneous driving forces for the endolymphatic flow: natural convection driven by the temperature-dependent density variation in the bulk fluid and expansive convection caused by direct volumetric displacement of the endolymph during the thermal irrigation. Direct numerical simulations indicate that on …earth, the natural convection mechanism is dominant. But in the microgravity environment of orbiting spacecraft, where buoyancy effects are mitigated, expansive convection becomes the sole mechanism for producing cupular displacement. A series of transient 1 g and microgravity case studies are presented to delineate the differences between the dynamics of the 1 g and microgravity endolymphatic flows. The impact of these different flow dynamics on the endolymph-cupula fluid-structural interactions is also analyzed based on the time evolutions of cupular displacement and velocity and the transcupular pressure differences. Show more

Keywords: fluid structural interaction, inner ear, vestibular system, CFD, caloric test, microgravity

DOI: 10.3233/VES-2005-15205

Citation: Journal of Vestibular Research, vol. 15, no. 2, pp. 93-107, 2005

Authors: Hegeman, J. | Honegger, F. | Kupper, M. | Allum, J.H.J.

Article Type: Research Article

Abstract: Objective: We investigated whether long-term bilateral vestibular loss subjects could combine auditory biofeedback of trunk sway with their remaining natural sensory inputs on balance to provide an improved control of trunk sway. A successful integration of natural and artificial signals would provide a basis for a balance prosthesis. Methods: Trunk sway of 6 bilateral peripheral vestibular loss subjects (BVL) was recorded using either angular position- or velocity-based auditory feedback or no feedback during stance and gait tasks. Roll and pitch trunk movements were recorded with angular velocity transducers mounted just above the waist and feedback without a delay …to 4 loudspeakers placed at the left, right, front and rear borders of the 5 m long by 4 m wide test environment. The two types of auditory feedback or no feedback were provided to the subjects in random order. In the feedback modes, sway greater than a preset angle (ca. 0.5 deg) or velocity (ca. 3 deg/s) thresholds caused a tone to be emitted from the speaker towards which the subject moved. The tone volume increased with increasing angle or angular velocity amplitude. Results: For all stance tasks BVL subjects without auditory feedback had a significantly different balance control with respect to that of normal controls. BVL sway values eyes open on a normal surface were reduced with auditory feedback with the greatest reductions in the roll plane. Specifically for the task of standing on 1 leg eyes open with position-auditory- feedback, amplitudes of pitch and roll angles and angular velocities were indistinguishable from those of normal controls. Sway during stance tasks on foam with eyes closed showed no improvement with feedback, remaining greater than normal. For some gait tasks there was a decrease in trunk sway with velocity feedback. Conclusions: These initial results indicate that subjects with vestibular loss could incorporate the auditory prosthetic sensory information into their balance commands, particularly in the roll plane if the balance task is performed with eyes open. Position information appears more useful than velocity information in reducing trunk sway during stance tasks. Future work will need to determine the effect of a training time on the improvement in balance control using such a prosthetic device and the ideal position and velocity auditory feedback combination. Show more

DOI: 10.3233/VES-2005-15206

Citation: Journal of Vestibular Research, vol. 15, no. 2, pp. 109-117, 2005