Mechanisms for dynamic stereomotion respond selectively to horizontal velocity components.

When dynamic visual noise such as the 'snow' on a detuned television receiver is inspected with a delay between the signals in the two eyes, the noise appears to rotate in depth around a vertical axis. We propose that this dynamic noise stereophenomenon arises because channels tuned jointly to depth and motion respond selectively to horizontal motion components in the noise. We used spatially filtered stimuli to reduce the strength of vertically oriented Fourier components in the noise, and found that this reduced the strength of the stereophenomenon. Reducing the strength of horizontally oriented components had a lesser effect. Our evidence is consistent with the conclusion that stereo-motion is predominantly detected by oriented receptive fields with an aspect ratio similar to those of cortical simple cells.