Vestibular-dependent surface potentials can be recorded from over the scalp following stimulation with intense air- (AC) and bone-conducted (BC) sound. However, sound-evoked responses may be confounded by parallel stimulation of the auditory system. To demonstrate the pure vestibular origin of the cortical potentials, patients with severe to profound bilateral hearing loss were stimulated with AC and BC sound. The responses had the same amplitude as those recorded in normal subjects, and were only present in patients with preserved vestibular function, confirming their vestibular origin. One negative surface potential, the N15, was largest when measured over the forehead, and detailed mapping of this potential localised it to the eyes. This extraocular response had the same polarity on each side of the eye and was altered by changing gaze direction, suggesting an extraocular muscle origin (i.e. an ocular vestibular evoked myogenic potential, or OVEMP). Galvanic vestibular stimulation (GVS) produces large eye movements with horizontal and torsional components directed away from the cathode. A modified electrode montage was used to characterise the OVEMPs produced by GVS. OVEMPs recorded from beneath the eyes had the appropriate polarity to produce the torsional eye movement and likely originated in the inferior oblique muscles. Sound-evoked OVEMPs were investigated in patients with superior canal dehiscence (SCD), as they have vestibular hypersensitivity to sound. The SCD patients had large sound-evoked OVEMPs with low threshold, similar to the VEMP. OVEMP amplitude was much larger in the patients than controls and could be an additional diagnostic marker for this condition. Although SCD patients have large VEMPs and eye movements evoked by AC sound, little is known about other vestibular reflexes. It was shown that patients also have large sound-evoked vestibulo-spinal reflexes, similar to those evoked by GVS. However, despite these large reflexes, there was little consistent whole body sway. Finally, a case is reported in which the combination of VEMP and OVEMP results indicated the location and nature of a central nervous system lesion. The patient had delayed potentials when stimulated on the left side, indicating a demyelinating lesion in the root entry zone of the left vestibulocochlear nerve.

Vestibular-dependent surface potentials can be recorded from over the scalp following stimulation with intense air- (AC) and bone-conducted (BC) sound. However, sound-evoked responses may be confounded by parallel stimulation of the auditory system. To demonstrate the pure vestibular origin of the cortical potentials, patients with severe to profound bilateral hearing loss were stimulated with AC and BC sound. The responses had the same amplitude as those recorded in normal subjects, and were only present in patients with preserved vestibular function, confirming their vestibular origin. One negative surface potential, the N15, was largest when measured over the forehead, and detailed mapping of this potential localised it to the eyes. This extraocular response had the same polarity on each side of the eye and was altered by changing gaze direction, suggesting an extraocular muscle origin (i.e. an ocular vestibular evoked myogenic potential, or OVEMP). Galvanic vestibular stimulation (GVS) produces large eye movements with horizontal and torsional components directed away from the cathode. A modified electrode montage was used to characterise the OVEMPs produced by GVS. OVEMPs recorded from beneath the eyes had the appropriate polarity to produce the torsional eye movement and likely originated in the inferior oblique muscles. Sound-evoked OVEMPs were investigated in patients with superior canal dehiscence (SCD), as they have vestibular hypersensitivity to sound. The SCD patients had large sound-evoked OVEMPs with low threshold, similar to the VEMP. OVEMP amplitude was much larger in the patients than controls and could be an additional diagnostic marker for this condition. Although SCD patients have large VEMPs and eye movements evoked by AC sound, little is known about other vestibular reflexes. It was shown that patients also have large sound-evoked vestibulo-spinal reflexes, similar to those evoked by GVS. However, despite these large reflexes, there was little consistent whole body sway. Finally, a case is reported in which the combination of VEMP and OVEMP results indicated the location and nature of a central nervous system lesion. The patient had delayed potentials when stimulated on the left side, indicating a demyelinating lesion in the root entry zone of the left vestibulocochlear nerve.

Introduction: In gymnastics, athletes perform twisting and flipping skills at high angular velocities. These athletes rely heavily on sensory information from the visual, proprioceptive, and vestibular systems. The vestibulo-ocular reflex (VOR) is responsible for stabilizing the visual field on the retina during head movement. To accomplish this, the eyes are reflexively moved in a direction opposite the head. In a twisting gymnast, this actually reduces the ability of gymnasts to see the landing during airborne skills. Hence it becomes necessary for the gymnasts to cancel or suppress their VOR in order to view the landing. Objective: The purpose of this research is to investigate the relationship between gymnastics skill level and their ability to suppress the VOR. Methods: Ten female gymnasts (mean age 15±2.2) were obtained via a sample of convenience from a local club. The sample included both competitive and recreational gymnasts. Subjects were asked to wear a measurement system that could track head and eye movements as they performed a series of visual tasks. Three experiments were performed: (1) a saccadic experiment – two horizontally fixed LEDs (±10°) were alternately lit in a non-predictable pattern to provide visual cues, (2) a VOR experiment – the subject was asked to perform yawl head movements to an audible metronome beat 11 while visually fixating on an LED target 1m away, and (3) a vestibulo-ocular reflex suppression/cancellation (VORc) experiment – a laser pointer was fixed to the subject‟s helmet close to the cyclopean eye (slaving the target to the head movement) and the subject was again asked to perform head movements to a metronome while visually fixating on the target. In both VOR experiments, the metronome frequency varied from 72 to 196 beats per minute. Eye and head position data were synchronously sampled at 250 and 100Hz respectively. Data were post-processed using MATLAB. Periodic calibrations were performed throughout the experiment to test the continued reliability of the data. Results: Saccadic peak velocities and latencies were calculated for the sample population. Their performance did not differ from the normal population. VOR and VORc gains were also calculated and compared. The higher level (competitive) gymnasts were better at suppressing their VOR. In addition, left/right VOR gain asymmetries correlated highly with twist direction in seven of the competitive gymnasts. Discussion/Conclusions: There is a correlation between VOR performance and gymnastic level. These results do not suggest that VOR differences develop as a result of practice. These differences may simply allow some individuals to become better performers. A longitudinal study on a larger population would be required to test the causal relationship between these variables.

Freiburg (Breisgau), Universiẗat, Diss., 2007. / Dateien im PDF-Format. - Enth.: Bd. 1. Text. Bd. 2. Katalog. Bd. 3. Tafeln. - Erscheinungsjahr an der Haupttitelstelle: 2006.

Hannover, Universiẗat, Diss., 2004.

No description available.

Purpose: This study asks whether active horizontal angular Vestibulo-Ocular Reflex (VOR) gain is capable of monocular adaptation after 4 hours of wearing 10 dioptres (D) of induced anisometropia in healthy human adults. Method: The participants (average age 28 years) wore a contact lenses/spectacles combination for 4 hours. The power of the spectacle was +5. 00D (magnified images 8. 65%) in front of the right eye and ?5. 00D (minified images 5. 48%) for the left eye, while the power of the contact lenses was equal to the subjects? habitual correction, summed with the opposite power of the spectacle lens. Eye and head position data was collected in complete darkness, in one-minute trials before adaptation and every 30 minutes for 2 hours after adaptation. Eye and head position data obtained using a video-based eye tracking system, was analyzed offline using Fast Fourier Transform in MATHCADTM 11. 1 software to calculate VOR gain. The VOR gain was compared between the right eyes and left eyes for the trials before and after adaptation. Results: In the first post-adaptation trial, a significant decrease in VOR gain (? 6%) occurred in the left eye in response to the miniaturizing lens. The right eye VOR gain did not show a significant change in the first post-adaptation trial (?2% decrease). During the remaining trials in the 2 hour follow-up time, both eyes showed a significant decrease compared to the baseline trial. This might indicate habituation of the VOR from repeated testing, or fatigue. Conclusion: There was monocular adaptation of VOR in response to the combined contact lenses/spectacles, but it was not complete and it was not as we expected. However, trying different amounts of anisometropia in one or two directions, a longer adaptation period (more than 4 hours) or monitoring the gain for more than 2 hours after adaptation with a longer separation between trials, might show different results.

Purpose: This study asks whether active horizontal angular Vestibulo-Ocular Reflex (VOR) gain is capable of monocular adaptation after 4 hours of wearing 10 dioptres (D) of induced anisometropia in healthy human adults. Method: The participants (average age 28 years) wore a contact lenses/spectacles combination for 4 hours. The power of the spectacle was +5. 00D (magnified images 8. 65%) in front of the right eye and ?5. 00D (minified images 5. 48%) for the left eye, while the power of the contact lenses was equal to the subjects? habitual correction, summed with the opposite power of the spectacle lens. Eye and head position data was collected in complete darkness, in one-minute trials before adaptation and every 30 minutes for 2 hours after adaptation. Eye and head position data obtained using a video-based eye tracking system, was analyzed offline using Fast Fourier Transform in MATHCADTM 11. 1 software to calculate VOR gain. The VOR gain was compared between the right eyes and left eyes for the trials before and after adaptation. Results: In the first post-adaptation trial, a significant decrease in VOR gain (? 6%) occurred in the left eye in response to the miniaturizing lens. The right eye VOR gain did not show a significant change in the first post-adaptation trial (?2% decrease). During the remaining trials in the 2 hour follow-up time, both eyes showed a significant decrease compared to the baseline trial. This might indicate habituation of the VOR from repeated testing, or fatigue. Conclusion: There was monocular adaptation of VOR in response to the combined contact lenses/spectacles, but it was not complete and it was not as we expected. However, trying different amounts of anisometropia in one or two directions, a longer adaptation period (more than 4 hours) or monitoring the gain for more than 2 hours after adaptation with a longer separation between trials, might show different results.

Zugl.: Freiburg (Breisgau), Univ., Diss., 2006

Doct. diss.--Department of Ancient Culture--Göteborg, 1992.