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Peaks and troughs of three-dimensional vestibulo-ocular reflex in humans.

Goumans J, Houben MM, Dits J, van der Steen J - J. Assoc. Res. Otolaryngol. (2010)

Bottom Line: Vestibulo-ocular responses only partially fulfill this ideal behavior.In the dark and in response to transients, gain of all components had lower values.In combination with the relatively low torsion gain, this horizontal component has a relative large effect on the alignment of the eye rotation axis with respect to the head rotation axis.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands.

ABSTRACT
The three-dimensional vestibulo-ocular reflex (3D VOR) ideally generates compensatory ocular rotations not only with a magnitude equal and opposite to the head rotation but also about an axis that is collinear with the head rotation axis. Vestibulo-ocular responses only partially fulfill this ideal behavior. Because animal studies have shown that vestibular stimulation about particular axes may lead to suboptimal compensatory responses, we investigated in healthy subjects the peaks and troughs in 3D VOR stabilization in terms of gain and alignment of the 3D vestibulo-ocular response. Six healthy upright sitting subjects underwent whole body small amplitude sinusoidal and constant acceleration transients delivered by a six-degree-of-freedom motion platform. Subjects were oscillated about the vertical axis and about axes in the horizontal plane varying between roll and pitch at increments of 22.5 degrees in azimuth. Transients were delivered in yaw, roll, and pitch and in the vertical canal planes. Eye movements were recorded in with 3D search coils. Eye coil signals were converted to rotation vectors, from which we calculated gain and misalignment. During horizontal axis stimulation, systematic deviations were found. In the light, misalignment of the 3D VOR had a maximum misalignment at about 45 degrees . These deviations in misalignment can be explained by vector summation of the eye rotation components with a low gain for torsion and high gain for vertical. In the dark and in response to transients, gain of all components had lower values. Misalignment in darkness and for transients had different peaks and troughs than in the light: its minimum was during pitch axis stimulation and its maximum during roll axis stimulation. We show that the relatively large misalignment for roll in darkness is due to a horizontal eye movement component that is only present in darkness. In combination with the relatively low torsion gain, this horizontal component has a relative large effect on the alignment of the eye rotation axis with respect to the head rotation axis.

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Example of 3D eye movements in response to sinusoidal stimulation about different axes. A Vertical axis in the light (upper panels) and in the dark while the subject imagined a target (lower panels). B Horizontal axis oriented at 45° azimuth. Upper panels, light; lower panels, dark. Left side panels in A and B show the stimulus (S), torsion (T), vertical (V), and horizontal (H) eye position signals. The right side panels show the corresponding angular velocities. Saccadic peak velocities are clipped in the plots. In this and all subsequent figures, eye positions and velocities are expressed in a right-handed, head-fixed coordinate system. In this system clockwise, down and left eye rotations viewed from the perspective of the subject are defined as positive values (see also Fig. 1). Note that for easier comparison, the polarity of the stimulus signal has been inverted.
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Fig2: Example of 3D eye movements in response to sinusoidal stimulation about different axes. A Vertical axis in the light (upper panels) and in the dark while the subject imagined a target (lower panels). B Horizontal axis oriented at 45° azimuth. Upper panels, light; lower panels, dark. Left side panels in A and B show the stimulus (S), torsion (T), vertical (V), and horizontal (H) eye position signals. The right side panels show the corresponding angular velocities. Saccadic peak velocities are clipped in the plots. In this and all subsequent figures, eye positions and velocities are expressed in a right-handed, head-fixed coordinate system. In this system clockwise, down and left eye rotations viewed from the perspective of the subject are defined as positive values (see also Fig. 1). Note that for easier comparison, the polarity of the stimulus signal has been inverted.

Mentions: Sinusoidal stimulation about the vertical axis in the light resulted in smooth compensatory eye movements occasionally interrupted by saccades. The mean gain ± one standard deviation (N = 6) was 1.02 ± 0.06 in the light. The responses were restricted to the horizontal eye movement component, with very small vertical and torsion components (gain, <0.05). In darkness, compensatory eye movements were more frequently interrupted by saccades, and in most subjects, there was a small drift of the other components (see Fig. 2A). The standard deviation of the horizontal position change during the 14 s of stimulation was 1.54° in the light and 1.45° in darkness (N = 6). Position changes of the vertical and torsion components were <0.28° in the light. Standard deviations of position changes in darkness of the vertical and torsion components were 0.84° for the vertical and 0.38° for the torsion component.FIG. 2


Peaks and troughs of three-dimensional vestibulo-ocular reflex in humans.

Goumans J, Houben MM, Dits J, van der Steen J - J. Assoc. Res. Otolaryngol. (2010)

Example of 3D eye movements in response to sinusoidal stimulation about different axes. A Vertical axis in the light (upper panels) and in the dark while the subject imagined a target (lower panels). B Horizontal axis oriented at 45° azimuth. Upper panels, light; lower panels, dark. Left side panels in A and B show the stimulus (S), torsion (T), vertical (V), and horizontal (H) eye position signals. The right side panels show the corresponding angular velocities. Saccadic peak velocities are clipped in the plots. In this and all subsequent figures, eye positions and velocities are expressed in a right-handed, head-fixed coordinate system. In this system clockwise, down and left eye rotations viewed from the perspective of the subject are defined as positive values (see also Fig. 1). Note that for easier comparison, the polarity of the stimulus signal has been inverted.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2914236&req=5

Fig2: Example of 3D eye movements in response to sinusoidal stimulation about different axes. A Vertical axis in the light (upper panels) and in the dark while the subject imagined a target (lower panels). B Horizontal axis oriented at 45° azimuth. Upper panels, light; lower panels, dark. Left side panels in A and B show the stimulus (S), torsion (T), vertical (V), and horizontal (H) eye position signals. The right side panels show the corresponding angular velocities. Saccadic peak velocities are clipped in the plots. In this and all subsequent figures, eye positions and velocities are expressed in a right-handed, head-fixed coordinate system. In this system clockwise, down and left eye rotations viewed from the perspective of the subject are defined as positive values (see also Fig. 1). Note that for easier comparison, the polarity of the stimulus signal has been inverted.
Mentions: Sinusoidal stimulation about the vertical axis in the light resulted in smooth compensatory eye movements occasionally interrupted by saccades. The mean gain ± one standard deviation (N = 6) was 1.02 ± 0.06 in the light. The responses were restricted to the horizontal eye movement component, with very small vertical and torsion components (gain, <0.05). In darkness, compensatory eye movements were more frequently interrupted by saccades, and in most subjects, there was a small drift of the other components (see Fig. 2A). The standard deviation of the horizontal position change during the 14 s of stimulation was 1.54° in the light and 1.45° in darkness (N = 6). Position changes of the vertical and torsion components were <0.28° in the light. Standard deviations of position changes in darkness of the vertical and torsion components were 0.84° for the vertical and 0.38° for the torsion component.FIG. 2

Bottom Line: Vestibulo-ocular responses only partially fulfill this ideal behavior.In the dark and in response to transients, gain of all components had lower values.In combination with the relatively low torsion gain, this horizontal component has a relative large effect on the alignment of the eye rotation axis with respect to the head rotation axis.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands.

ABSTRACT
The three-dimensional vestibulo-ocular reflex (3D VOR) ideally generates compensatory ocular rotations not only with a magnitude equal and opposite to the head rotation but also about an axis that is collinear with the head rotation axis. Vestibulo-ocular responses only partially fulfill this ideal behavior. Because animal studies have shown that vestibular stimulation about particular axes may lead to suboptimal compensatory responses, we investigated in healthy subjects the peaks and troughs in 3D VOR stabilization in terms of gain and alignment of the 3D vestibulo-ocular response. Six healthy upright sitting subjects underwent whole body small amplitude sinusoidal and constant acceleration transients delivered by a six-degree-of-freedom motion platform. Subjects were oscillated about the vertical axis and about axes in the horizontal plane varying between roll and pitch at increments of 22.5 degrees in azimuth. Transients were delivered in yaw, roll, and pitch and in the vertical canal planes. Eye movements were recorded in with 3D search coils. Eye coil signals were converted to rotation vectors, from which we calculated gain and misalignment. During horizontal axis stimulation, systematic deviations were found. In the light, misalignment of the 3D VOR had a maximum misalignment at about 45 degrees . These deviations in misalignment can be explained by vector summation of the eye rotation components with a low gain for torsion and high gain for vertical. In the dark and in response to transients, gain of all components had lower values. Misalignment in darkness and for transients had different peaks and troughs than in the light: its minimum was during pitch axis stimulation and its maximum during roll axis stimulation. We show that the relatively large misalignment for roll in darkness is due to a horizontal eye movement component that is only present in darkness. In combination with the relatively low torsion gain, this horizontal component has a relative large effect on the alignment of the eye rotation axis with respect to the head rotation axis.

Show MeSH
Related in: MedlinePlus