September 2015
Volume 15, Issue 12
Free
Vision Sciences Society Annual Meeting Abstract  |   September 2015
On saccade programming as a function of stimulus complexity: Estimating the population-averaging window for simple shapes, textured discs and natural objects
Author Affiliations
  • Lotje Linden
    Aix-Marseille University, CNRS, LPC UMR 7290, Marseille, France
  • Gregory Zelinsky
    Department of Psychology, Stony Brook University, New York, United States
  • Françoise Vitu
    Aix-Marseille University, CNRS, LPC UMR 7290, Marseille, France
Journal of Vision September 2015, Vol.15, 605. doi:10.1167/15.12.605
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      Lotje Linden, Gregory Zelinsky, Françoise Vitu; On saccade programming as a function of stimulus complexity: Estimating the population-averaging window for simple shapes, textured discs and natural objects. Journal of Vision 2015;15(12):605. doi: 10.1167/15.12.605.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

In visual displays containing two stimuli, saccades reveal a global effect (GE): Even though participants aim for one of the stimuli, their eyes land in between the two. The GE presumably results from population averaging in the superior colliculus (SC): As neurons in the retinotopic sensory and motor maps have large and overlapping receptive/movement fields, overlap in the recruited populations causes activity to peak at the intermediate location. Consequently, the GE should diminish when the distance between the two recruited populations exceeds a threshold separation. However, while this threshold should remain invariant across the SC, due to nonhomogeneous afferent mapping to the SC, the corresponding inter-stimulus distance (i.e. averaging window) in visual space should increase as stimuli become more eccentric. Casteau and Vitu (ECEM, 2009) confirmed this prediction for simple shapes. To investigate whether the same mechanisms generalize to the programming of saccades towards more natural stimuli, we estimated the averaging window in a saccade-targeting task for distractor-target (TD) pairs of increasing complexity: (1) simple shapes (circles/ triangles, diameter = 0.24°), (2) images of objects normalized for pixel area (median diameter = 1.7°) and, (3) as an intermediate level, discs (diameter = 1.4°) whose texture was matched to the texture of the objects. We systematically varied distance (3-10°) and eccentricity (3 or 5°) of the TD arrangement along various axes (0, 45, 90°). As predicted, we found that for shapes and discs, the critical distance for a GE increased with eccentricity in visual space, but was relatively constant when converted to millimeters of collicular space (Ottes et al., 1986). For objects, the pattern appeared similar, although the variance of landing positions was larger. We will discuss which object properties modulated the averaging window, in the framework of models of saccade programming.

Meeting abstract presented at VSS 2015

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