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A. Rezec, K. R. Dobkins; Sensory- and attention- based visual field asymmetries for motion and orientation discrimination. Journal of Vision 2001;1(3):89. doi: https://doi.org/10.1167/1.3.89.
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Previous studies have reported better performance on visual tasks in the inferior visual field (IVF) as compared to the superior visual field (SVF), which may be attributed to attentional differences between the vertical hemifields (e.g., He et al., 1996). To investigate directly whether vertical visual field asymmetries for motion and orientation processing are sensory or attentional in nature, we obtained thresholds on a direction-of-motion task and an orientation discrimination task. In exp. 1, a stochastic motion stimulus (coherently moving dots presented amongst randomly moving dots) was presented in one of the four quadrants of visual space, randomly across trials. In exp. 2, a stochastic oriented line stimulus (tilted lines amongst vertical lines) was employed. Two display types were employed: “single”, in which the target was presented alone, and “multiple”, in which the target was presented in one quadrant while the other three quadrants contained noise distractors; randomly moving dots (motion task) or vertically oriented lines (orientation task). For the single condition, a small IVF advantage was found only for the motion task, suggesting enhanced motion processing in this region of space. In the multiple condition, however, a large IVF advantage emerged in both the motion and the orientation task. These results thus suggest the existence of an attentional bias in the IVF under conditions in which target location is uncertain.
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