Temporal frequency limits for stereoscopic apparent motion processes

Temporal processing limits were determined for two types of stereoscopic percept associated with square wave disparity alternation: apparent depth motion and depth pulsation. The stimuli were dynamic random dot stereograms containing no monocular cues for either target motion or disparity change. The percept of a single noise plane undergoing apparent depth motion coincided with the extent of a large peak in the low frequency portion of the evoked potential amplitude spectrum. The limit for apparent depth motion was approximately 6 Hz. Above this frequency two pulsating depth planes were seen simultaneously. Depth pulsations wer visible up to 14 Hz and an evoked potential occurred in synchrony with each disparity change (up to 28 depth reversals/sec). Above 14 Hz two transparent planes were perceived without depth pulsation and no stereoscopic evoked potential could be recorded. The results indicate a higher temporal resolution for stereoscopic position change than has been reported in previous studies of apparent depth motion.