Sensitivity to horizontal and vertical corrugations defined by binocular disparity

Sensitivity to corrugations defined by binocular disparity differs as a fun ction of the modulation frequency. Such functions have proved to be useful descriptive and analytical tools in the study of the mechanisms involved in disparity processing. Indeed, given certain assumptions, these sensitivity functions can be used to predict certain perceptual outcomes. Given their importance, it is surprising that there is no comprehensive data set of dis parity sensitivity functions (DSF) for a range of observers over a broad ra nge of spatial frequencies and orientations. Here we report DSFs for six ob servers over an eight octave range of sinusoidal corrugations in disparity (0.0125-3.2 cpd). Multi-cycle, low frequency surfaces were used to assess t he degree to which the fall-off in sensitivity at low corrugation frequenci es is attributable to the decreasing number of cycles displayed. The data w as found to form a continuous function despite the different number of cycl es displayed. We conclude that the fall off in sensitivity is due to the sp atial interactions in disparity processing. We also determined DSFs for the same observers to both vertically and horizontally oriented sinusoidal dis parity corrugations in order to characterise the extent of the stereoscopic anisotropy In general, the best thresholds for detecting vertically orient ed disparity corrugations were higher (similar to 4 arc sec) than for horiz ontally oriented corrugations (similar to 2 arc sec). Moreover, the functio ns were shifted toward the high spatial frequency end of the spectrum. (C) 1999 Elsevier Science Ltd. (C) All rights reserved.