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Matteo Valsecchi, Karl R. Gegenfurtner; High-precision control of binocular gaze. Journal of Vision 2014;14(10):200. doi: 10.1167/14.10.200.
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© ARVO (1962-2015); The Authors (2016-present)
Humans can orient gaze extremely precisely on the fronto-parallel plane when high visual acuity is required. Yet, it is not known whether this extends to high-acuity natural tasks requiring an adjustment of vergence. We investigated the precision of binocular gaze control while observers performed a high-precision manual movement. The task involved hitting a target hole (1 mm diameter) in a plate with a hand-held needle (0.5 mm diameter) at 200 mm viewing distance. Binocular eye movements and the 3D-position of the needle tip were tracked. The six observers consistently set their point of gaze at the target height first, while the horizontal and depth adjustments took place more slowly as the needle approached the target. Microsaccade rate and amplitude decreased as the distance between needle and plate dropped below 3 mm. Microsaccades contributed to displace gaze between the needle and the target, since the horizontal point of gaze was located on average in between these two positions. This was not the case for depth, where the average point of gaze was centered on the needle tip. Moreover, changes in version and vergence were not coordinated during microsaccades. In a control experiment five observers moved gaze between marks on a slanted plane. Even when the inter-mark distance was 1 mm, instructing a saccade as small as the microsaccades in the needle experiment, we observed a coordinated displacement of the point of gaze on the horizontal and depth axis, although the vergence gain was relatively small (47.1%). Our results show that observers can control the position of binocular gaze very precisely in a high-acuity visual task, and that microsaccades contribute to displacing gaze between relevant objects. However, a coordinated control of version and vergence in small saccades is only observed if a movement of gaze along a slanted trajectory is explicitly instructed.
Meeting abstract presented at VSS 2014
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