关键词: 眼跳, 眼跳遗漏, 眼跳抑制, 后向掩蔽, 双相调节理论

Abstract: Purposes: People shift their gaze between objects of interest using rapid pre-planned eye movements known as saccade. Humans make 2–8 saccadic eye movements per second. Saccades are very important for pointing the eye at targets in the scene, but these rapid scenes shifts are not perceived. The visual stimulus generated by the saccade is omitted from our subjective awareness known as saccadic omission. Saccadic omission is important for visual system: without it, the motion on the retina would prevent us from seeing anything at all. Based on evidences coming from numerous physiological studies in behaving primates, investigators propose the biphasic modulation theory to explain the neural mechanism of saccadic omission. However, no studies have reported whether the biphasic modulation theory of saccadic omission exists in the human visual system. Thus, the study examined whether the biphasic modulation theory was applicable to the human visual system (experiment 1). Moreover, the study explored stimulus selectivity of the theory (experiment 2). Procedures: So, the study included two experiments. The stimuli in both experiments were circular patches of sinusoidal gratings with a randomized phase (diameter: 2.5°; orientation: -3° or +3°, ‘-’ and ‘+’ indicate that a grating was left- or right-tilted). Spatial frequencies of gratings in experiments 1 and 2 were difference: that in experiment 1 (1.5 cycles/°) and in experiment 2 (0.1 cycles/°, 3 cycles/° and 6 cycles/°). In the experiment 1, the study measured the orientation discrimination accuracies of gratings for human subjects in three time periods of saccade: baseline period (over 700 ms before the onset of saccade), suppression period (100 ms before the onset of saccade – 25 ms after the saccade) and enhancement period (25 ms after the saccade – 150 ms after the saccade)). In the experiment 2, using three different spatial frequencies of gratings, the study measured the orientation discrimination accuracies of each grating for human subjects in three time periods of saccade, respectively. Results: In the experiment 1, the orientation discrimination accuracy of gratings in the suppression period was significantly lower than that in the baseline period. Meanwhile, the orientation discrimination accuracy of gratings in the enhancement period was significantly higher than that in the baseline period. In the experiment 2, when the low spatial frequency (0.1 cycles/°) grating as the test stimulus, the orientation discrimination accuracy of gratings in the suppression (or enhancement) period was significantly lower (or higher) than that in the baseline period; when the middle spatial frequency (3 cycles/°) grating as the test stimulus, the result is same with that using the low spatial frequency grating; However, when the high spatial frequency (6 cycles/°) grating as the test stimulus, There was no significant difference between any two of the three conditions. Conclusions: These results indicate that the human visual system also has the biphasic modulation mechanism across saccadic eye movement. Moreover, the biphasic modulation mechanism has stimulus selectivity: visual system selectively suppresses (in suppression period) or enhances (in enhancement period) the response to low spatial frequency gratings, but not high spatial frequency gratings.

Key words: saccade, saccadic omission, saccadic suppression, backward masking, biphasic modulation theory