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Andre Kaminiarz, Kathrin Bartelheimer, Frank Bremmer; Systematic deviation of eye-movement direction from stimulus-direction during Optokinetic Nystagmus. Journal of Vision 2013;13(9):386. doi: 10.1167/13.9.386.
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© ARVO (1962-2015); The Authors (2016-present)
Optokinetic nystagmus (OKN) is a reflexive eye movement, which serves to stabilize the retinal image. It consists of two alternating phases: a slow phase in the direction of stimulus motion and a fast phase in the opposite direction. It is well known that eye-movement characteristics are affected by stimulus direction. During smooth pursuit the eye-movement direction systematically deviates from target direction [oblique effect: Krukowski & Stone, 2005] in a way that can be interpreted as a perceptual expansion of space around the cardinal axes. Based on neurophysiological recordings in macaque monkeys, it had been suggested that the neural basis of this phenomenon is located in area MST or further downstream of the cortical visuo-motor system. Here we investigated in psychophysical experiments in humans whether also slow-phases of stare OKN show an oblique effect. We recorded eye movements from human subjects performing OKN while looking at large random dot patterns moving at 20°/s in 24 directions (0, 15, …, 345°) . Subjects were instructed to watch the stimulus without intentionally following individual dots. All subjects showed a periodic deviation of eye-movement direction from stimulus-direction. Eye-movement patterns revealed three different periodicities: 90°, 180°, and 360°. A 90° period with a phase-shift of 0° resulted in a shift of eye-movement direction away from both cardinal axes as described for smooth pursuit. The 180° error pattern in combination with the observed phase-shifts resulted in a shift away from one of the cardinal axes. The 360° error-pattern induced a shift in a single direction, which was upward for most subjects. Taken together we showed that during voluntary and reflexive eye-movements similar deviations of eye-movement direction from stimulus-direction can be observed. We conclude that the neuronal basis of the effect is located rather early within the cortical visuo-motor system (area MST or upstream).
Meeting abstract presented at VSS 2013
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