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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 656 (1992), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 656 (1992), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 374 (1981), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 49 (1983), S. 257-268 
    ISSN: 1432-1106
    Keywords: Vestibulo-ocular reflex ; Visual suppression ; Fovea ; Peripheral retina ; Head-fixed display
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experiments on human subjects exposed to angular oscillation whilst viewing a head-fixed display have indicated that the degree of suppression of the vestibulo-ocular reflex is dependent upon the peripheral location of the visual target. Suppression is greatest when fixating a central target and decreases in a graded manner for targets placed more peripherally. During central fixation a low-velocity nystagmus is still evident and there is no indication of any complete cancellation of the vestibulo-ocular reflex.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 52 (1983), S. 9-19 
    ISSN: 1432-1106
    Keywords: Vestibulo-ocular reflex ; Visual suppression ; Head-fixed display ; Fovea ; Peripheral retina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Visual-vestibular interaction in the control of eye movement was investigated in six subjects during exposure to a low frequency (0.05 Hz) angular oscillation about the longitudinal axis of the body at four levels of peak head velocity: 30, 60, 90 and 120°/s. Eye movements were recorded whilst the subject was presented with a head-fixed visual display consisting of either a single central target or a pair of targets placed at ±20° in the periphery. For the lower stimulus levels (30 and 60°/s) the degree of suppression was reasonably constant and the vestibular nystagmus was never completely suppressed. However, during oscillation at higher velocity levels (90 and 120°/s) the relationship between eye velocity and head velocity became non-linear, the degree of suppression being much less during the high velocity periods of the waveform than when the head velocity was low. The changes in suppression may be interpreted as a decrease in gain of visual feedback as a function of increasing image velocity error on the retina.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 56 (1984), S. 438-447 
    ISSN: 1432-1106
    Keywords: Pursuit eye movements ; Velocity feed-back ; Fovea ; Peripheral retina ; Vestibulo-ocular suppression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A series of experiments has been conducted on human subjects to examine the effect of the movement of small targets located in the peripheral visual field on oculomotor response. Subjects were presented with either a single centrally positioned target or a pair of targets displaced at angles of ±5°, ±10° and ±20° from centre. Target movement was in the horizontal plane, the paired targets always moving in unison. The stimulus waveform consisted of either a sinusoidal or random target motion encompassing a frequency range from 0.1 to 4 Hz with an angular displacement of ±3.5°. Subjects made two types of response. First they were instructed to follow the single target or the centre point of the paired targets. In this ‘active’ pursuit condition the gain of slow-phase eye velocity progressively decreased as the moving targets were moved from the central position to the most peripheral location (±20°). Secondly, subjects were required passively to ignore the target movement by staring blankly ahead. During this ‘passive’ response nystagmic eye movements were induced for which the slowphase eye velocity also decreased with increasing target eccentricity, but the gains were always less than those induced during ‘active’ pursuit. The frequency characteristics of the ‘passive’ response were very similar to those of the ‘active’ response, breaking down at frequencies beyond 1 Hz. The ability to suppress the ‘passive’ response was also investigated by the presentation of a tachistoscopically illuminated earth-fixed target. The response was found to decline as the interval between presentations of the fixation target was decreased from 3000 ms to 100 ms. It is suggested that the ‘passive’ response originates from a basic velocity drive to the oculomotor system resulting from image movement across the retina. This velocity drive may be cancelled with adequate fixation but must be enhanced to accomplish desired eye velocity during active pursuit.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 59 (1985), S. 548-558 
    ISSN: 1432-1106
    Keywords: Oculomotor control ; Nystagmus ; Pursuit ; Retinal conflict ; Visual feedback
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Oculomotor response has been assessed in humans during the presentation of conflicting retinal motion stimuli. In the majority of experiments a background stimulus was made to move with a constant velocity ramp in one direction followed by rapid resets at regular intervals. In the absence of an adequate fixation target this ramp-reset stimulus induced a nystagmus with a slow-phase velocity and saccadic frequency which remained almost constant as reset frequency was increased from 2 to 5 Hz. Moreover, the induced eye velocity could be considerably increased if the subject attempted ‘active’ matching of display velocity. During both ‘active’ and ‘passive’ responses eye velocity gain reached a peak when display velocity was between 2°/s and 5°/s. The presence of small stationary targets induced a suppression of the passive ramp-reset response which was modified by target eccentricity and by tachistoscopic target illumination. When subjects pursued a sinusoidally oscillating target against a stationary structured background, eye velocity gain was significantly less than for pursuit against a blank background. The degree of interaction between conflicting stimuli was found to be dependent on their relative size, peripheral location and velocity. However, it appears that the human observer is able selectively to enhance feedback gain from one particular source in order to dominate stimuli from other unwanted sources.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 120 (1998), S. 325-334 
    ISSN: 1432-1106
    Keywords: Key words Eye movements ; Timing ; Saccades ; Human ; Wing and Kristofferson model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We assessed the suitability of using the Wing and Kristofferson model for timing repetitive motor responses to analyse timing variability during repetitive saccadic eye movements. The model decomposes total timing variability (TV) into a central timing component (CV) and a peripheral motor delay component (MV). Eight normal subjects made voluntary horizontal saccades, in darkness, in synchrony with a regular auditory metronome. After 20 saccades had been produced, the metronome was switched off and subjects continued responding at the same frequency until 31 further saccades had been made. Inter-saccade intervals (ISIs) from the unpaced phase were used to calculate TV, CV and MV. Three different target intervals, paced by auditory cues, were used – 496 ms, 752 ms and 1000 ms. In the paced phase, subjects’ ISIs closely matched the auditory cue intervals. In the unpaced phase, subjects were clearly able to respond at three different frequencies. As predicted by the Wing and Kristofferson model, the durations of successive ISIs tended to be negatively correlated. As expected, TV and CV increased with increasing ISI. Contrary to the expectation of the model that MV would remain constant, we found that it increased with increasing interval. Our results do not conclusively demonstrate the validity of applying the Wing and Kristofferson model to the analysis of timing variability during repetitive saccadic eye movements. However, comparison with previous studies shows that, at least in normal subjects, it is equally valid to apply the model to the analysis of repetitive saccadic eye movements as it is to apply it to the analysis of data from other effectors.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 129 (1999), S. 57-67 
    ISSN: 1432-1106
    Keywords: Key words Ocular pursuit ; Eye movements ; Timing ; Prediction ; Anticipation ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Regular, repeated presentation of identical constant-velocity target motion stimuli (ramps) appears to allow build up of an internal store, release of which can be used to generate anticipatory smooth pursuit prior to subsequent target onset. Here, we examine whether release of the anticipatory response can be controlled by timing cues unrelated to the motion stimulus itself. In experiment 1, the target moved in alternate directions and was exposed for 480 ms as it passed through centre; otherwise subjects were in darkness. Inter-stimulus interval (ISI) was either regular (3.6 s) or randomized (2.7–4.3 s). Presentations were given with or without audio cues that occurred at a constant cue time (CT) prior to target appearance. Even when ISI was randomized, cues could be used to generate anticipatory smooth pursuit. Eye velocity (V100) measured 100 ms after target onset (just prior to visual feedback influence) was greater with cues than without and decreased significantly as CT increased from 240–960 ms. In experiment 2, we assessed the effects of fixation between presentations and eccentricity of target starting position, using unidirectional ramps. The target was visible for 400 ms and started on, ended on or straddled the midline. Subjects held fixation on the midline until an audio cue signalled that preparation for ensuing target appearance could begin. There was no difference in V100 between starting positions or between presence/absence of fixation. In experiment 3, we compared the effects of using audio, visual or tactile cues. All types of cue evoked anticipatory smooth pursuit, but the response to the visual cue was significantly delayed compared with the others. However, V100 was not significantly different between cues. In all experiments, V100 was scaled in proportion to target velocity over the range 12.5–50°/s, showing that this was a truly predictive response. The results provide evidence that timing and velocity storage can be independently controlled through different sensory channels and suggest that the two functions are probably carried out by separate neural mechanisms.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 50 (1983), S. 228-236 
    ISSN: 1432-1106
    Keywords: Vestibulo-ocular reflex ; Visual suppression ; Tachistoscopic presentation ; Head-fixed display ; Fovea ; Peripheral retina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of degrading retinal image velocity information on suppression of the vestibulo-ocular reflex have been assessed through tachistoscopic presentation of target sources in man. Subjects were required to fixate a head-fixed display during exposure to a 0.5 Hz sinusoidal angular oscillation of the head at ±60 °/s. In the first experiment it was found that the degree of suppression was progressively degraded as the interval between successive target presentations was increased from 10 to 3,000 ms. In the second experiment no effect of changing the duration of the target pulse was observed over a range from 20 to 1,000 μs. The results appear consistent with a model of visual motion sensitivity in which relative velocity information is obtained by the temporal integration of responses from spatially separated retinal cells.
    Type of Medium: Electronic Resource
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