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Saumil S. Patel, Harold E. Bedell; Disparities in non-vertical spatial frequency components extend the range of accurate depth perception in humans. Journal of Vision 2006;6(6):651. doi: 10.1167/6.6.651.
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Purpose>> We tested how disparity information from non-vertical spatial-frequency components (SFCs) contribute to the range of the human stereovision system by comparing the perceived depth of stimuli that contained differing orientation bands . Methods>> Observers (N=3) adjusted the perceived depth of a small (4×4 arc-min) bright probe to match SF band-pass (2–4 cpd) and orientation low-pass filtered random-dot stimuli (mean luminance = 3 cd/sq. m, 24% RMS contrast) with crossed and uncrossed relative disparities up to 30 arc-min. The highest orientation present in the orientation band of the stimulus (cut-off orientation) ranged from 15 to 89 o[rientation]deg, where 0 odeg represents a vertically oriented SFC. From the data, we computed the range of stimulus disparities for which perceived depth (1) changed monotonically in the veridical direction (VDmax) and (2) was in the veridical direction with respect to the reference plane (Dmax). In addition, we assessed the discrepancy between the changes in perceived and veridical depth within the VDmax range (Quality). Results>> For all observers, VDmax increased by a factor of 2 as cut-off orientation increased from 15 to 89 odeg. Across observers, Dmax also increased by approximately a factor of 2 as the cut-off orientation increased and exceeded VDmax by at least a factor of 2. The Quality of perceived depth was within approximately 10% of veridical for all cut-off orientations. Conclusions>> Perception of accurate suprathreshold depth results from the pooling of disparity signals from vertically and non-vertically tuned neural mechanisms.
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