Purpose. Two binocular mechanisms to see motion in depth are known. One is that based on disparity change in time and the other is that based on inter-ocular velocity differences (IOVDs). To investigate the spatial frequency properties of the IOVD mechanism, we developed a technique to isolate the mechanism from the other. Experiment. In the technique developed, one eye is exposed to horizontal motion (adaptation phase), following which a static stimulus is presented binocularly (test phase). Monocular MAE in the adapted eye should generate IOVDs in the static stimulus presented binocularly. If the observer perceives motion in depth there, the perception should be attributed to a motion sensitive mechanism. After confirming that motion in depth was seen in this procedure, we measured MAE duration to investigate spatial frequency properties of the IOVD mechanism. The MAE contained horizontal motion (2D MAE) and depth motion (3D MAE) components and the duration of 3D MAE as well as that of 2D MAE was measured using sinusoidal gratings with various spatial frequencies both in adaptation and test phases. Results and Discussions. The results showed that 3D MAE duration was about a half of 2D MAE duration. Dependently on which eye had been adapted, either approaching or receding motion was seen with leftward (or rightward) motion at the beginning, while the depth motion component disappeared earlier than the horizontal motion component. The longest 2D MAE duration was found when the spatial frequency was the same for the adaptation and test gratings, as predicted from spatial frequency channels in the motion analysis. In contrast, 3D MAE duration was approximately constant for all test spatial frequencies, suggesting the broad spatial frequency tuning of the IOVD mechanism. These results can be explained as signals from monocular motion detectors with different spatial frequency tunings are combined before comparing the motion signals between the two eyes.
ASJC Scopus subject areas
- Sensory Systems