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Andre Kaminiarz, Marc Rohe, Bart Krekelberg, Frank Bremmer; Localization of visual targets during optokinetic eye movements. Journal of Vision 2006;6(6):81. doi: 10.1167/6.6.81.
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© ARVO (1962-2015); The Authors (2016-present)
Previous psychophysical studies demonstrated a perceptual distortion of space during smooth and saccadic eye movements. Both types of eye movements are voluntarily controlled. In this study we asked how accurately human subjects can localize flashed visual targets during reflexive eye movements namely optokinetic nystagmus (OKN).
Nine subjects participated in the experiments, which were performed in complete darkness. Eye movements were sampled at 500 Hz. In blocks of trials subjects performed either baseline or eye movement tasks. In baseline trials subjects freely viewed a homogeneous gray monitor for 4000 ms. After 3500 ms a visual target was flashed for 10 ms at one of five possible locations. During eye movement trials a random dot pattern was moving to the right or left for 6000 ms and reliably elicited an OKN. After 5500 ms the target was presented. At the end of each trial subjects indicated the perceived horizontal or vertical target location with respect to a ruler.
Localization during baseline trials was biased towards a location centered on the vertical meridian in head centered space. During OKN we observed an additional shift in direction of the slow eye movement. This bias decreased shortly before a saccade and temporaryly increased afterwards. Mean error as well as modulation of localization error around the time of saccades increased with rising background motion speed. Control experiments showed that localization errors were mainly due to eye movements. Our results therefore indicate that localization of visual targets is influenced during reflexive eye movements.
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