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Camille Morvan, Mark Wexler; The timing of space constancy during smooth pursuit eye movements. Journal of Vision 2005;5(8):132. doi: 10.1167/5.8.132.
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© ARVO (1962-2015); The Authors (2016-present)
The present study is concerned with the problem of compensation for smooth pursuit eye movements, especially with the timing of this compensation. When the eyes are engaged in a pursuit movement, a stationary background moves on the retina on the opposite direction. The visual system compensates for this retinocentric motion, recovering the stability of the visual environment. The compensation is incomplete, giving rise to the Filehne illusion, in which a stationary background is perceived as moving slightly in the direction opposite to the pursuit.
How long does it take to the visual system to compensate for those eye movements? Although this issue has received some attention in psychophysics (Stoper, 1967, Mack and Herman, 1978) and in neurophysiology (Haarmeier and Thier, 1998, Hoffmann and Bach, 2002, Tikhonov et al., 2004), little evidence of time evolution of compensation has been presented.
Recently, we have introduced a new technique to study the time evolution of compensation in the case of motion detection (VSS 2004). We found that in as little as 150 ms following stimulus appearance, motion is detected with respect to an allocentric reference frame; earlier, only motion in a retinocentric frame is detected. Thus, in the case of motion detection, compensation is in place by 150 ms.
Here, we ask whether the time evolution of compensation is specific to motion detection or whether it generalizes to other visual tasks. In the first experiment, we measured the time course of the Filehne illusion for extremely brief durations. In the second experiment, we study whether manually displacing the pursuit target—which reduces the time lag between target and eye movements—has an effect on the time course of compensation.
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