Journal of Vestibular Research - Volume 5, issue 3

Authors: Wilson, V.J. | Boyle, R. | Fukushima, K. | Rose, P.K. | Shinoda, Y. | Sugiuchi, Y. | Uchino, Y.

Article Type: Review Article

Abstract: Stabilization of the head is required not only for adequate motor performance, such as maintaining balance while standing or walking, but also for the adequate reception of sensory inputs such as visual and auditory information. The vestibular organs, which consist of three approximately orthogonal semicircular canals (anterior, horizontal, posterior) and two otolith organs (utriculus, sacculus), provide the most important input for the detection of head movement. Activation of afferents from these receptors evokes the vestibulocollic reflex (VCR), which stabilizes bead position in space. In this review, which is the outgrowth of a session of the vestibular symposium held in Hawaii …in April, 1994, we discuss the neural substrate of this reflex and some aspects of the central processing involved in its production. Some topics are not considered, in particular the important interaction between the VCR and the cervicocollic reflex evoked by activation of neck afferents (70,119), and attempts to model the reflex (69). Show more

Keywords: neck, afferents, efferents, neural, processing

DOI: 10.3233/VES-1995-5301

Citation: Journal of Vestibular Research, vol. 5, no. 3, pp. 147-170, 1995

Authors: Kröller, J. | Behrens, F.

Article Type: Research Article

Abstract: A moving random dot pattern was projected onto a tangent screen in front of awake untrained monkeys that were always placed in upright position. Eye movements were recorded in two dimensions to study the oblique optokinetic nystagmus (OKN) and compare it to the horizontal and vertical OKN. Any direction of pattern movement across the screen could be achieved. The angular velocity of pattern movement was varied between 6 and 180°/s. To display off-horizontal and off-vertical eye movements, the instantaneous direction and velocity of the eye movements were computed from the horizontal and vertical search coil voltages. At pattern velocities below …90°/s, stimulus-direction and direction of the OKN slow phase matched very precisely. Above 90°/s the slow-phase eye movement direction was systematically shifted toward the horizontal except for pure vertical stimulation. The slow-phase eye velocity at off-horizontal stimulation was inconstant, however; stable periods occurred repeatedly that were used to define the gain of OKN. Up to stimulus speeds of about 90°/s the OKN gain did not depend on the direction of stimulation and of OKN. At higher velocities the gain decreased with the increasing angle between stimulus direction and horizontal. Practically no vertical optokinetic afternystagmus (OKAN) could be observed, in either the up or down direction. At the onset of afternystagmus after oblique stimulation the direction of the OKAN slow phase immediately shifted over to the horizontal. The data indicate that the slow-phase direction and gain of oblique OKN with the monkey’s head upright can be described by the sum of a horizontal and a vertical velocity vector obtained during stimulation in these cardinal directions. Show more

Keywords: optokinetic nystagmus, OKN, optokinetic afternystagmus, OKAN, oblique, vector sum

DOI: 10.3233/VES-1995-5302

Citation: Journal of Vestibular Research, vol. 5, no. 3, pp. 171-186, 1995

Authors: Tighilet, Brahim | Lacour, Michel

Article Type: Research Article

Abstract: Locomotor balance recovery after unilateral vestibular neurectomy bas been found strongly accelerated in the cat when the animals received a postoperative treatment with Ginkgo biloba Extract (EGb 761: 50 mg/kg/d, i.p.), a result due to the improvement of plasticity mechanisms involved in vestibular compensation. The aim of this study was to determine which of the two main biochemical components (terpenes vs. flavonoids) contained in the extract was the most active in the recovery process, to test the influence of the route of administration, and to look for dose-dependent effects. Experiments were performed in six experimental groups of cats that were …compared witb each other and with three control groups. Comparisons were done on the recovery profile and time course of equilibrium function restoration, as quantified by the rotating beam test. Four experimental groups were treated with the standardized extract EGb 761 given orally (p.o.: 2 groups; 40 mg and 80 mg/kg) or intraperitoneally (i.p.: 2 groups; 50 mg and 25 mg/kg), whereas the two others received only a special extract that did not contain the terpenes (i.p. administration: 25 mg and 10 mg/kg). Treatment was always given until complete recovery of locomotor balance function. The control groups received either no treatment (untreated cats), an oral vehicle (placebo cats), or a sham i.p. injection (sham cats). Results showed that locomotor balance recovery was significantly improved in all the experimental groups as compared to the control groups of cats, which recovered similarly and more slowly. Efficacy of the special extract without the terpenes was comparable to that of the total extract, indicating that the nonterpenic fraction was the most active biochemical constituent in this experimental model of central nervous system (CNS) plasticity. Pharmacological activity of the extract was also significantly better when given i.p. as compared to the p.o. route of administration, and dose-dependent effects were evidenced with the i.p. administration of the special extract without the terpenes, with a lower efficacy for the lowest dose (10 mg/kg). These data confirm that EGb 761 treatment serves as useful therapy in supporting brain functional recovery in this animal model of vestibular compensation and lead to a more precise understanding of the biochemical component that is active in this recovery process. Show more

Keywords: vestibular compensation, locomotor balance function, Ginkgo biloba extract (EGb 761), cat

DOI: 10.3233/VES-1995-5303

Citation: Journal of Vestibular Research, vol. 5, no. 3, pp. 187-200, 1995

Authors: Fetter, Michael | Misslisch, Hubert | Sievering, Doris | Tweed, Douglas

Article Type: Research Article

Abstract: The three-dimensional (3-D) properties of the vestibuloocular reflex (VOR) were studied in six normal human subjects during passive whole-body rotations in darkness and with full-field visual input in light. Subjects were asked to fixate a point target stationary in space straight ahead or to imagine such a target in darkness. Using a 3-D rotating chair, subjects were rotated sinusoidally (frequency .3 Hz, maximum speed 37.5°/s) about an earth-vertical axis for horizontal stimulation and about an earth-horizontal axis for vertical and torsional stimulation. The subject faced forward for vertical stimulation, 90° to the side for torsional stimulation, or 15° to the right or …left side for combined vertical and torsional stimulation. Left eye position was measured using 3-D search coils. The VOR response was quantified using the 3-D analogue of gain, a 3 × 3 matrix where each element describes the dependence of one component – torsional, vertical, or horizontal – of eye velocity on one component of head velocity. Average gain matrices were calculated for three cycles of rotation (10 s). Major findings were: (1) Gain values for the VOR were higher in light than in darkness for all directions. In light, vertical and horizontal responses were fully compensatory in both magnitude and direction, whereas the torsional responses were still weak. (2) Intersubject variability, large in the dark, was very small in the light for the vertical and horizontal responses but still considerable for the torsional. (3) Crosscoupling, in the form of partially horizontal eye movements in response to a torsional head rotation, was present in darkness but disappeared in light. (4) The VOR showed the same eye position dependence in darkness and in light; that is, if the eye is looking x° away from straight ahead, the eye rotation axis in response to a horizontal or vertical head rotation tilts about x°/4 in the same direction as the gaze line. These axis tilts are incompatible with perfect stabilization of the retinal image, but they are qualitatively appropriate for preserving Listing’s law. Show more

Keywords: three-dimensional vestibuloocular reflex, three-dimensional eye movements, Listing’s law, magnetic search-coil

DOI: 10.3233/VES-1995-5304

Citation: Journal of Vestibular Research, vol. 5, no. 3, pp. 201-209, 1995

Authors: Massion, Jean | Fabre, Jean-Claude | Mouchnino, Laurence | Obadia, Annie

Article Type: Research Article

Abstract: Professional divers were instructed to adopt a vertical posture under water with their feet fixed to the ground and to perform a fast forward or backward upper trunk bending movement in response to a tone. Kinematic and EMG analyses were performed. It was first noted that the divers adopted a forward inclined, erect posture, suggesting that the verticality was misevaluated, although the effects of gravity were still exerted on the otoliths. Second, the upper trunk movements were still accompanied by opposite movements of lower segments and, as a result, the center of gravity displacement was still minimized, although not so …accurately as on the ground. The EMG pattern consisting of early activation of a set of trunk, thigh, and shank muscles continued to occur under water. These results suggest that “axial synergies” associated with upper trunk movements are learned motor habits that regulate the center of gravity position regardless of the equilibrium constraints. Show more

Keywords: posture, movement, center of gravity

DOI: 10.3233/VES-1995-5305

Citation: Journal of Vestibular Research, vol. 5, no. 3, pp. 211-221, 1995

Authors: Schor, Robert H. | Yates, Bill J.

Article Type: Research Article

Abstract: This study examines the response of neurons in the medullary reticular formation of the decerebrate cat to sinusoidal yaw rotations in the plane of the horizontal semicircular canals. Responsive neurons that could be antidromically activated from the spinal cord appeared to be less sensitive to the rotary stimulus than the rest of the population of responsive neurons. Most neurons had response dynamics similar to those of semicircular canal afferents.

Keywords: reticulospinal, vestibulospinal reflexes, horizontal rotation

DOI: 10.3233/VES-1995-5306

Citation: Journal of Vestibular Research, vol. 5, no. 3, pp. 223-228, 1995