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Martin Giesel, Julie Harris, Alexandra Yakovleva, Alex Wade, Marina Bloj, Anthony Norcia; Comparison of horizontal vergence responses to changing disparity and inter-ocular velocity differences. Journal of Vision 2017;17(10):412. doi: https://doi.org/10.1167/17.10.412.
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© ARVO (1962-2015); The Authors (2016-present)
A percept of motion in depth (MID) can be generated from two types of binocular cues: changes of disparity over time (CD) or inter-ocular velocity differences (IOVD). The relative contribution of these two cues to another important binocular function—vergence eye movements—is poorly understood. Stevenson et al. (1994) reported vergence responses to dynamic random-dot stereograms (RDS) containing only CD information. More recently Sheliga et al. (2016) showed that IOVD stimuli also drive the vergence system, albeit weakly. Here we compare the relative potency of IOVD and CD cues as inputs to the vergence system in the same participants. We used RDS stimuli portraying MID either towards or away from the observer with either a ramp or step motion profile. In the 'ramp' condition, the dots moved for 2s at 1deg/s, for 'step' the dots made an instantaneous 1deg step. Vergence eye movements were recorded in response to four types of MID stimuli: RDS that isolate IOVD (both anti-correlated, aIOVD, and de-correlated, dIOVD), isolate CD (dynamic RDS) or that contained both cue types (FULL). Stimuli were presented on a LG OLED TV passive 3D display. Vergence eye movements were measured using an EyeLink II. We measured the slopes of vergence, once underway, to provide an estimate of the velocity of the vergence response. We found high vergence velocities for both FULL and CD conditions. We also found responses to aIOVD and dIOVD cues, but they were clearly weaker than the responses to FULL and CD. No systematic differences were found between aIOVD and dIOVD. IOVD thus provides an input to vergence, but under our conditions of measurement, it is a weak one. Additionally, for FULL and CD we found evidence for gain differences in the vergence response depending on the direction of the movement in depth.
Meeting abstract presented at VSS 2017
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