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  • 1
    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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  • 2
    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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