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  • 1
    Electronic Resource
    Electronic Resource
    Three-Dimensional Eye Velocity Measurement following Postrotational Tilt in the Monkey (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 656 (1992), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1992.tb25257.x
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  • 2
    Electronic Resource
    Electronic Resource
    Humans use internal models to estimate gravity and linear acceleration (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 398 (1999), S. 615-618 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Because sensory systems often provide ambiguous information, neural processes must exist to resolve these ambiguities. It is likely that similar neural processes are used by different sensory systems. For example, many tasks require neural processing to distinguish linear acceleration from ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/19303
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  • 3
    Electronic Resource
    Electronic Resource
    Noise in human muscle spindles (1996)
    [s.l.] : Nature Publishing Group
    Nature 383 (1996), S. 769-770 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Stochastic resonance is a phenomenon in which the response of a nonlinear system to a weak input signal is optimized by the presence of a particular non-zero level of noise1'2. It has been demonstrated in several biological systems, ranging from ion channels to sensory neurons4 to human ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/383769a0
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  • 4
    Electronic Resource
    Electronic Resource
    The dynamic contributions of the otolith organs to human ocular torsion (1996)
    Springer
    Experimental brain research 110 (1996), S. 315-321 
    Details
    ISSN: 1432-1106
    Keywords: Ocular torsion ; Vestibulo-ocular reflex ; Linear vestibulo-ocular reflex ; Ocular counterroll ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We measured human ocular torsion (OT) monocularly (using video) and binocularly (using search coils) while sinusoidally accelerating (0.7 g) five human subjects along an earth-horizontal axis at five frequencies (0.35, 0.4, 0.5, 0.75, and 1.0 Hz). The compensatory nature of OT was investigated by changing the relative orientation of the dynamic (linear acceleration) and static (gravitational) cues. Four subject orientations were investigated: (1) Y-upright — acceleration along the interaural (y) axis while upright; (2) Y-supine — acceleration along the y-axis while supine; (3) Z-RED — acceleration along the dorsoventral (z) axis with right ear down; (4) Z-supine — acceleration along the z-axis while supine. Linear acceleration in the Y-upright, Y-supine and Z-RED orientations elicited conjugate OT. The smaller response in the Z-supine orientation appeared disconjugate. The amplitude of the response decreased and the phase lag increased with increasing frequency for each orientation. This frequency dependence does not match the frequency response of the regular or irregular afferent otolith neurons; therefore the response dynamics cannot be explained by simple peripheral mechanisms. The Y-upright responses were larger than the Y-supine responses (P〈0.05). This difference indicates that OT must be more complicated than a simple low-pass filtered response to interaural shear force, since the dynamic shear force along the interaural axis was identical in these two orientations. The Y-supine responses were, in turn, larger than the Z-RED responses (P〈0.01). Interestingly, the vector sum of the Y-supine responses plus Z-RED responses was not significantly different (P=0.99) from the Y-upright responses. This suggests that, in this frequency range, the conjugate OT response during Y-upright stimulation might be composed of two components: (1) a response to shear force along the y-axis (as in Y-supine stimulation), and (2) a response to roll tilt of gravitoinertial force (as in Z-RED stimulation).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228562
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  • 5
    Electronic Resource
    Electronic Resource
    The vestibulo-ocular reflex of the squirrel monkey during eccentric rotation and roll tilt (1995)
    Springer
    Experimental brain research 106 (1995), S. 111-122 
    Details
    ISSN: 1432-1106
    Keywords: Nystagmus ; Vestibular ; Semicircular canals ; VOR ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in six male squirrel monkeys during eccentric rotation. Monkeys were rotated in the dark at a constant velocity of 200°/s (centrally or 79 cm off axis) with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's orientation (facing-motion or back-to-motion) had a dramatic influence on the VOR. These experiments show that: (a) the axis of eye rotation always shifted toward alignment with gravito-inertial force; (b) the peak value of horizontal slow phase eye velocity was greater with the monkey facingmotion than with back-to-motion; and (c) the time constant of horizontal eye movement decay was smaller with the monkey facing-motion than with back-to-motion. All of these findings were statistically significant and consistent across monkeys. In another set of tests, the same monkeys were rapidly tilted about their naso-occipital (roll) axis. Tilted orientations of 45° and 90° were maintained for 1 min. Other than a compensatory angular VOR during the angular rotation, no consistent eye velocity response was observed during or following the tilt for any of the six monkeys. The absence of any eye movement response following tilt weighs against the possibility that translational linear VOR responses are due to simple high-pass filtering of the otolith signals. The VOR response during eccentric rotation was divided into the more familiar angular VOR and linear VOR components. The angular component is known to depend upon semicircular canal dynamics and central influences. The linear component of the response decays rapidly with a mean duration of only 6.6 s, while the axis of eye rotation rapidly aligns (〈10 s) with gravito-inertial force. These results are consistent with the hypothesis that the measurement of gravito-inertial force by the otolith organs is resolved into central estimates of linear acceleration and gravity, such that the central estimate of gravitational force minus the central estimate of linear acceleration approximately equals the otolith measurement of gravito-inertial force.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241361
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  • 6
    Electronic Resource
    Electronic Resource
    Vergence can be controlled by audio feedback, and induces downward ocular deviation (1994)
    Springer
    Experimental brain research 101 (1994), S. 169-172 
    Details
    ISSN: 1432-1106
    Keywords: Biofeedback ; Eye movements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We measured horizontal and vertical eye positions, using binocular search coils, in three humans. Subjects could maintain vergence by means of audio biofeedback. Feedback consisted of a pair of audio tones, one variable and one fixed at a reference frequency. The variable tone was controlled by instantaneous vergence and provided immediate feedback on the vergence state. The reference frequency, which they attempted to match, was set to correspond to a target distance of either 0.34 m or 0.14 m. Subjects could maintain vergence consistently, even while undergoing lateral motions at 0.5 Hz and 0.2 g peak acceleration in darkness. There was also a consistent tendency for the eyes to deviate downward during near vergence. The results may be useful in experiments in which one wishes to control vergence without providing a visual reference which might inhibit conjugate eye movements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243228
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  • 7
    Electronic Resource
    Electronic Resource
    Modeling the vestibulo-ocular reflex of the squirrel monkey during eccentric rotation and roll tilt (1995)
    Springer
    Experimental brain research 106 (1995), S. 123-134 
    Details
    ISSN: 1432-1106
    Keywords: Model ; Nystagmus ; Vestibular ; VOR ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Model simulations of the squirrel monkey vestibulo-ocular reflex (VOR) are presented for two motion paradigms: constant velocity eccentric rotation and roll tilt about a naso-occipital axis. The model represents the implementation of three hypotheses: the “internal model” hypothesis, the “gravito-inertial force (GIF) resolution” hypothesis, and the “compensatory VOR” hypothesis. The internal model hypothesis is based on the idea that the nervous system knows the dynamics of the sensory systems and implements this knowledge as an internal dynamic model. The GIF resolution hypothesis is based on the idea that the nervous system knows that gravity minus linear acceleration equals GIF and implements this knowledge by resolving the otolith measurement of GIF into central estimates of gravity and linear acceleration, such that the central estimate of gravity minus the central estimate of acceleration equals the otolith measurement of GIF. The compensatory VOR hypothesis is based on the idea that the VOR compensates for the central estimates of angular velocity and linear velocity, which sum in a near-linear manner. During constant velocity eccentric rotation, the model correctly predicts that: (1) the peak horizontal response is greater while “facing-motion” than with “back-to-motion”; (2) the axis of eye rotation shifts toward alignment with GIF; and (3) a continuous vertical response, slow phase downward, exists prior to deceleration. The model also correctly predicts that a torsional response during the roll rotation is the only velocity response observed during roll rotations about a nasooccipital axis. The success of this model in predicting the observed experimental responses suggests that the model captures the essence of the complex sensory interactions engendered by eccentric rotation and roll tilt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241362
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  • 8
    Electronic Resource
    Electronic Resource
    Spatial orientation in the squirrel monkey: An experimental and theoretical investigation (1993)
    Springer
    Annals of biomedical engineering 21 (1993), S. 186-186 
    Details
    ISSN: 1573-9686
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02367617
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  • 9
    Electronic Resource
    Electronic Resource
    Prototype Neural Semicircular Canal Prosthesis using Patterned Electrical Stimulation (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 572-581 
    Details
    ISSN: 1573-9686
    Keywords: Vestibular ; Prosthesis ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The design of a prototype semicircular canal prosthesis is presented along with preliminary results. This device measures angular velocity of the head (±500°/s) using a piezoelectric vibrating gyroscope. With a digital filter this velocity is filtered to match the dynamic characteristics of the semicircular canals, which are the physiological rotation sensors of the vestibular system. This digitally filtered signal is used to modulate the pulse rate of electrical stimulation. The pulse rate is varied between 50 and 250 Hz via a sigmoidal lookup table relating pulse rate to angular velocity; the steady-state rate is 150 Hz. A current source utilizes these timing pulses to deliver charge balanced, cathodic-first, biphasic, current pulses to the nerves innervating the semicircular canal via platinum electrodes. Power is supplied via lithium batteries. dc/dc converters are used to generate regulated ±5 V supplies from the batteries. All of the components are contained in a small, lightweight, Nylon box measuring roughly 43 mm×31 mm×25 mm, which can be mounted on the top of an animal's head. This device has been tested in guinea pigs having surgically implanted platinum electrodes, and the results show that the prosthesis can provide a rotational cue to the nervous system. © 2000 Biomedical Engineering Society. PAC00: 4366Ts, 8719Nn, 8719La, 8780Xa
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.293
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