GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Central adaptation models of the vestibulo-ocular and optokinetic systems (1989)
    Springer
    Biological cybernetics 61 (1989), S. 255-264 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A theoretical analysis of two models of the vestibulo-ocular and optokinetic systems was performed. Each model contains a filter element in the vestibular periphery to account for peripheral adaptation, and a filter element in the central vestibulooptokinetic circuit to account for central adaptation. Both models account for1 adaptation, i.e. a response decay to a constant angular acceleration input, in both peripheral vestibular afferent and vestibulo-ocular reflex (VOR) responses and2 the reversal phases of optokinetic after-nystagmus (OKAN) and the VOR and3 oscillatory behavior such as periodic alternating nystagmus. The two models differ regarding the order of their VOR transfer function. Also, they predict different OKAN patterns following a prolonged optokinetic stimulus. These models have behavioral implications and suggest future experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203172
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A model of the nystagmus induced by off vertical axis rotation (1986)
    Springer
    Biological cybernetics 54 (1986), S. 337-350 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract A three-dimensional model is proposed that accounts for a number of phenomena attributed to the otoliths. It is constructed by extending and modifying a model of vestibular velocity storage. It is proposed that the otolith information about the orientation of the head to gravity changes the time constant of vestibular responses by modulating the gain of the velocity storage feedback loop. It is further proposed that the otolith signals, such as those that generate L-nystagmus (linear acceleration induced nystagmus), are partially coupled to the vestibular system via the velocity storage integrator. The combination of these two hypotheses suggests that a vestibular neural mechanism exists that performs correlation in the mathematical sense which is multiplication followed by integration. The multiplication is performed by the otolith modulation of the velocity storage feedback loop gain and the integration is performed by the velocity storage mechanism itself. Correlation allows calculation of the degree to which two signals are related and in this context provides a simple method of determining head angular velocity from the components of linear acceleration induced by off-vertical axis rotation. Correlation accounts for the otolith supplementation of the VOR and the sustained nystagmus generated by off-vertical axis rotation. The model also predicts the cross-coupling of horizontal and vertical optokinetic afternystagmus that occurs in head-lateral positions and the reported effects of tilt on vestibular responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318429
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    A dynamical model for reflex activated head movements in the horizontal plane (1996)
    Springer
    Biological cybernetics 75 (1996), S. 309-319 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract.  We present a controls systems model of horizontal-plane head movements during perturbations of the trunk, which for the first time interfaces a model of the human head with neural feedback controllers representing the vestibulocollic (VCR) and the cervicocollic (CCR) reflexes. This model is homeomorphic such that model structure and parameters are drawn directly from anthropomorphic, biomechanical and physiological studies. Using control theory we analyzed the system model in the time and frequency domains, simulating neck movement responses to input perturbations of the trunk. Without reflex control, the head and neck system produced a second-order underdamped response with a 5.2 dB resonant peak at 2.1 Hz. Adding the CCR component to the system dampened the response by approximately 7%. Adding the VCR component dampened head oscillations by 75%. The VCR also improved low-frequency compensation by increasing the gain and phase lag, creating a phase minimum at 0.1 Hz and a phase peak at 1.1 Hz. Combining all three components (mechanics, VCR and CCR) linearly in the head and neck system reduced the amplitude of the resonant peak to 1.1 dB and increased the resonant frequency to 2.9 Hz. The closed loop results closely fit human data, and explain quantitatively the characteristic phase peak often observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004220050297
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Motion of the eye immediately after a saccade (1986)
    Springer
    Experimental brain research 61 (1986), S. 386-394 
    Details
    ISSN: 1432-1106
    Keywords: Eye movement ; Saccades ; Dynamic overshoot ; Post-saccadic drift ; Active braking pulse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Dynamic overshoot is a small saccade that follows a main saccade, in the opposite direction, with no delay. To re-examine prior reports of dynamic overshoot, the properties of dynamic overshoot were studied in six normal subjects. The postsaccadic drift of eye movements was studied as well. Horizontal eye movements were recorded with the magnetic-field/search-coil method. System noise level was 0.05 deg. Dynamic overshoot occurred with a frequency of about 13% and was more frequent for saccades 10 deg or less. Its mean size was 0.15 deg and its peak velocity showed it to be saccadic in nature. Binocular recordings for three subjects showed that when dynamic overshoot occurred it was almost always in the abducting eye which also had the least post-saccadic drift. The adducting eye seldom had dynamic overshoot and consistently had a more pronounced post-saccadic drift, almost always in the onward direction. We suggest that, at the end of a saccade, the eye normally is brought to rest by a braking pulse and dynamic overshoot occurs when the braking pulse is accidentally too large. It would appear to serve no useful purpose. Why dynamic overshoot is monocular and coincides with the eye having less post-saccadic drift is unclear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239527
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Static roll and the vestibulo-ocular reflex (VOR) (1990)
    Springer
    Experimental brain research 82 (1990), S. 463-471 
    Details
    ISSN: 1432-1106
    Keywords: Vestibular ; VOR ; Semicircular canal ; Otolith ; Tilt ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We measured the effect of static lateral tilt (roll) on the gain and time constant of the vestibulo-ocular reflex (VOR) in five normal subjects by recording both the horizontal and vertical components of eye velocity in space for rotation about an earth vertical axis with the head either upright or rolled to either side. The time constant of the VOR in the upright position was 19.6 ±3.2s (mean ± standard deviation). The time constant of the horizontal component with respect to the head decreased to 15.7±4.0s for 30° roll and to 12.7±2.7s for 60° roll. The time constant of the vertical component with respect to the head was 11.0±1.4 s for 30° roll and 7.5±1.6 s for 60° roll. The gain of the horizontal VOR with respect to space did not vary significantly with roll angle but a small space-vertical component to the VOR appeared during all rotations when the head was rolled away from upright. This non-compensatory nystagmus built up to a maximum of 2–3°/s at 17.0±4.7s after the onset of rotation and then decayed. These data suggest that static otolith input modulates the central storage of semicircular canal signals, and that head-horizontal and head-vertical components of the VOR can decay at different rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228788
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Influence of eye and head position on the vestibulo-ocular reflex (1986)
    Springer
    Experimental brain research 64 (1986), S. 208-216 
    Details
    ISSN: 1432-1106
    Keywords: Eye movement ; Vestibulo-ocular reflex ; Semicircular canals ; Otolith organs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary For the vestibulo-ocular reflex (VOR) to function properly, namely to ensure a stable retinal image under all circumstances, it should be able to take into account varying eye positions in the orbit and varying orientations of the head with respect to the axis about which it is rotating. We tested this capability by quantifying the gain and the time constant of the horizontal component of the VOR during rotation about an earth vertical axis when the line of sight (optical axis) was moved out of the plane of head rotation — either by rotating the eyes up or down in the orbit or by pitching the head up or down with respect to earth-horizontal. In either case the gain of the horizontal component of the VOR was attenuated precisely by the cosine of the angle made between the optical axis and the plane of head rotation. Furthermore, if the head was pitched up or down but the eye rotated oppositely in the orbit so as to keep the line of sight in the plane of head rotation the gain of the horizontal component of the VOR was the same value as with the head and eyes both straight ahead. In contrast, the time constant of the VOR varied only as a function of the orientation of the head and not as a function of eye position in the orbit. During rotation about an earth vertical axis, the time constant was longest (about 18 s) when the head was pitched forward to place the lateral canals near earth-horizontal and shortest (about 11 s) when the head was pitched backward to place the vertical canals near earth-horizontal. Finally, since during rotation in yaw the pattern of stimulation of the lateral and vertical semicircular canals varies with different head orientations one can use measurements of the horizontal component of the VOR, under varying degrees of pitch of the head, to calculate the relative ability of the lateral and vertical semicircular canals to transduce head velocity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238215
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Optokinetic nystagmus and afternystagmus in human beings: relationship to nonlinear processing of information about retinal slip (1990)
    Springer
    Experimental brain research 81 (1990), S. 46-52 
    Details
    ISSN: 1432-1106
    Keywords: Optokinetic nystagmus ; Velocity storage ; Accessory optic system ; Retinal slip ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In four normal human subjects we measured eye movements during full-field optokinetic stimulation (10–220 deg/s) and determined the relationship among retinal-slip velocity (drum velocity minus slow-phase eye velocity), the slow-phase velocity of optokinetic nystagmus (OKN) and the initial value of the slow-phase velocity of optokinetic afternystagmus (OKAN) measured in darkness. OKN and OKAN were maximum (63–84 and 11–19 deg/s, respectively) when retinal slip ranged from 30–100 deg/s. For higher values of retinal slip, OKN and OKAN fell (in 3 subjects) or reached a plateau (in the fourth). The amplitude of OKAN in human beings was much less than that reported in monkeys. The shape, however, of the curve relating retinal slip to the amplitude of OKAN was similar to that of monkeys. Furthermore, in both cases the curve resembles that obtained by plotting the results of experimental recordings of neural discharge in the nucleus of the optic tract as a function of retinal slip. These results imply that the processing of visual information for generation of OKAN is similar in monkeys and human beings but that the gain of the system is much less in human beings. We also found that fixation of a small target during optokinetic stimulation nearly completely prevented the development of OKAN while fixation of a small target for short periods after optokinetic stimulation did not alter the pattern of decay of OKAN. Thus, fixation may actively prevent the coupling of visual information into the velocity-storage mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230099
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...