Pupillary response induced by dynamic random-dot stereogram
Pupillary control system is a typical biological control system. Investigation of pupillary response provides a non-invasive approach to explore the mechanism of the central neural information processing. In the present study, with dynamic random-dot stereogram (dRDS), we investigated whether the pupillary response can be induced by pure stereo stimuli. We found that transient pupillary response can be evoked by dichoptically viewing the emergence of a stereoscopic sinusoidal grating composed of dynamic random-dot stereograms. Contrarily, no pupillary response was elicited when viewed the same stimuli monocularly. Thus, it clearly indicates that pupillary response can be induced by pure stereo information. We further studied the properties of this stereo pupillary response. It is shown that the amplitude of the stereo pupillary response varied obviously and regularly as the spatial frequency or disparity amplitude of the stereo grating shifted. This implies that the pupillary response might provide an objective approach for investigation of stereo perception. Moreover, we also examined preliminarily the stereo pupillary response in subjects with mild stereo deficiency. Results showed that their threshold of stereo perception were higher than the normals, and when the stereo deficient subjects were tested by stereo gratings above their thresholds, pupillary response can be elicited, but latency of this response was about 200 ms longer than that of the normals. This indicates that the stereo pupillary response could be applied in the clinical stereopsis tests.
Saccadic-like analysis for rapid eye movement (REM)
The rapid eye movement (REM) occurred periodically during sleep in normal subjects. The REM reflects the information processing of central nervous system. In the present study, eye movements of normal subjects were recorded for whole duration of sleep. The saccadic-like analysis was processed for these REMs, including the analysis of REM duration, amplitude, peak velocity, main sequence, periodicity, and direction preference. Results showed that the REM is similar to the normal saccade: the waveform of both REM and saccadic eye movements are quite similar, and more than 90% REM amplitudes are limited within 15 deg, which is similar to the saccadic amplitude during normal vision. The difference is that the peak velocity of the REM is 10%~30% slower than that of the saccade with the same amplitude. These results provide valuable data for the further understanding of mechanism in the central nervous system for REM control. It might also useful in the clinical application for psychosis diseases.