The accessibility of spatial channels for stereo and motion.
Using fractal noise images, we measured the dependence of D(min) on the spatial passband (spatial frequency and orientation) over which information was correlated either between the eyes for stereo or between sequential frames for motion. Without affecting the amplitude spectrum of the noise stimulus we used idealized filters to scramble the phase of components outside a pre-defined passband. Using a simple Gaussian model in which performance depends on the signal/noise within a restricted spatial region, we obtained estimates of the bandwidth of the narrowest underlying spatial frequency and orientation spectral region subserving these two comparable tasks. Spatial bandwidths varied with peak spatial frequency but were very broad approximating the spectrum of the stimulus itself. Orientation properties of the underlying mechanisms were isotropic. These results suggest that the independent activity of individual narrowband spatial channels is not perceptually accessible for these tasks.
Hess
Robert F
RF
McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Canada. robert.hess@mcgill.ca
Wang
Yi-Zhong
YZ
Liu
Chang Hong
CH
D003867:Depth Perception / Q000502:physiology; D004192:Discrimination, Psychological; D005074:Evoked Potentials, Visual; D017709:Fractals; D006801:Humans; D009039:Motion Perception / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D010775:Photic Stimulation; D011581:Psychological Tests; D011601:Psychophysics; D014796:Visual Perception / Q000502:physiology*