Purpose: Multiple channels with different spatial frequency tunings have been suggested to contribute to stereopsis. We investigated whether the different channels have different temporal frequency tunings. Method: We measured contrast threshold with various disparities and disparity threshold with various contrasts for depth discrimination, to characterize the sensitivity profile of the depth detection mechanism concerned at a given spatiotemporal frequency. The stimulus display consisted with four squares filled with sinusoidal gratings arranged in a 2×2 array with gaps to separate them. The gratings in the upper right and the lower left squares had the same disparity that was opposite of those in the other two squares. The observers responded which pair appeared to be closer in depth. All the gratings drifted in the same direction, either left or right, and the direction varied from trial to trial randomly. Contrast threshold as a function of disparity (CD curve) was obtained for each combination of six temporal frequencies (0.15 ∼ 20.0 Hz) and four spatial frequencies (0.23 ∼ 3.75 c/deg). Disparity thresholds provided portions of the curve at small disparities and contrast thresholds provided portions of the curve at large disparities. Results: DC curves were similar with the highest contrast sensitivity at about the same disparity for all temporal frequencies for a given spatial frequency. Changes in temporal frequency shifted the DC curve along the contrast axis. The relative shift of the curve, which corresponds to relative contrast sensitivity, showed a bandpass temporal frequency tuning for low spatial frequency and a lowpass temporal frequency tuning for high spatial frequency. These results suggest that the channel sensitive to high spatial frequency is sensitive to low temporal frequencies and the channel sensitive to low spatial frequency is sensitive to high temporal frequencies.
ASJC Scopus subject areas
- Sensory Systems