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Arthur Portron, Jean Lorenceau; Maintaining smooth pursuit after target disappearance with eye-induced reverse-phi motion . Journal of Vision 2016;16(12):1350. doi: 10.1167/16.12.1350.
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© ARVO (1962-2015); The Authors (2016-present)
The gain and speed of smooth pursuit eye movements quickly drop whenever a moving tracked target disappears behind an occluder  . In 3 experiments, we test whether, and to what extent, pursuit maintenance after target disappearance depends on occluder's characteristics. In all experiments, a target moving for 900 (or 450 ) ms at 13.3 (or 26.6) °/s., disappears behind an occluder for 700 (350 or 1350) ms. Participants are asked to maintain their pursuit eye movements, recorded with an Eye-Link 1000, as long as possible. Experiment 1 uses 4 occluders: visible/invisible uniform occluders, random texture of disks, static/flickering (darker of brighter than background, 10 Hz). Experiment 2 uses varying flickering frequencies of texture of disks (6-10-20-40-60 Hz). Experiment 3, uses flickering textures of disks with different contrast reversals (LIGHT/light, DARK/dark, light/dark, relative to background (31.49 cd/m²). The results of Experiment 1 show that pursuit after target disappearance is maintained for longer durations (~700 ms) for a flickering texture as compared to the other occluders. Experiment 2, reveals a band pass effect of the frequency of the flickering texture, with longer pursuit maintenance for 20 and 40 Hz, relative to other flickering frequencies (6 and 60 Hz). The results of Experiment 3 show that pursuit maintenance is better with a balanced -dark/light- flickering contrast, than for the other contrasts conditions. Altogether, the results suggest that a flickering occluding texture with balanced contrast elicits eye-induced reverse-phi motion responses in V1  and MT neurons  that contribute on-line to the maintenance of smooth pursuit for a long duration, in the absence of any explicitly moving target. The implications of these findings for modeling of smooth pursuit will be discussed.
Meeting abstract presented at VSS 2016
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