Abstract
Purpose:
To better understand the mechanisms underlying global stereopsis we examined the relationship between carrier luminance spatial frequency and modulator disparity spatial frequency.
Methods:
Thresholds for detecting global sinusoidal disparity corrugations of equi-detectable spatially band-pass noise were measured as a function of modulator disparity spatial frequency for both centrally and peripherally located stimuli using a standard 2-IFC task.
Results:
We found a characteristic relationship that depended on modulator disparity spatial frequency. At high modulator disparity spatial frequencies (>1 c/d), there is an optimal ratio of around 2.6, whereas at low modulator disparity spatial frequencies, there is an optimal absolute carrier luminance spatial frequency (i.e., 3 c/d). In the periphery, vision is restricted to modulator disparity spatial frequencies below 1 c/d and, as a consequence, follows the above rule, there is an optimum absolute carrier luminance spatial frequency that reduces in spatial frequency with increasing eccentricity.
Conclusions:
This finding is consistent with there being more than one channel processing global stereo. This is subsequently confirmed using a 2x2 AFC detection/discrimination paradigm. Furthermore, because of the different carrier/modulator relationships in central and peripheral vision, peripheral global stereo cannot be simply related to central global stereo by a scaling factor and thus cannot be simply due to cortical magnification as previously proposed.
Keywords: 434 binocular vision/stereopsis •
640 pattern vision