动态歧义图知觉中的瞳孔反射和眼动扫视行为

歧义图的双稳态知觉是一种非常有趣的视觉现象,但对其机制还不十分清楚.采用"运动产生的结构"(structurefrom-motion)的歧义图和无歧义的对照图,我们研究了这一问题.被试者在报告对歧义图和无歧义图的知觉发生翻转时,其瞳孔都扩张,而且在翻转之后都达到峰值;与无歧义图条件下不同,在报告知觉翻转前,歧义图条件下的瞳孔要明显小于均值,而在瞳孔扩张达到峰值之后,瞳孔仍然明显大于均值.这些结果说明知觉翻转后的瞳孔扩张是一个表达被试知觉状态已改变的指标.而对歧义图和无歧义图刺激的瞳孔反射的差异,可能反映了由歧义图所产生知觉翻转的神经信号和知觉状态的内源性.另外,被试眼动扫视的方向会随着运动轴的变化呈现不同的扫视分布模式,但在歧义图与无歧义图之间分布模式是一致的,这不仅表明被试从歧义图中感知到了与无歧义图同样的信息,也表明瞳孔反射变化与双稳态知觉变化相关的结论具有可靠性.本文对歧义图双稳态知觉的视觉机制提供了新的认识.

Pupillary Reflex and Saccade in Bistable Perception to Ambiguous Figure of Stucture-from-Motion

Bistable perception to ambiguous figure is an intriguing visual phenomenon. The underlying mechanisms, however, remain largely unclear. We addressed the issue by recording eye saccade and pupillary reflex in the perceptual responses of human subjects to the ambiguous figure and disambiguous figure (control) generated from the structure-from-motion stimuli. Their pupils dilated when the subjects reported the perceptual reversal between the two mutually exclusive states to both the ambiguous figure and disambiguous figure. The pupillary dilation reached the peak after the perceptual reversal. In contrast to the disambiguous figure, before reported the reversal to the ambiguous figure, the pupils were smaller than the mean size, while after the peak of pupillary dilation occurred, the pupils were still larger than the mean size. These results illustrate that the pupillary dilation posterior to the perceptual report can be regarded as an indication of the perceptual reversal that had occurred, while the differences in pupillary reflex to the ambiguous figure and disambiguous figure prior to the perceptual report probably reflects the intrinsic neural trace of the perceptual reversal and of the perceptual states. Additionally, in the process of perceiving structure-from-motion stimuli, the distribution in directions of eye saccades of subjects changed with the change in the motion axis of the stimuli. The change fashions were accordant between the ambiguous figure and disambiguous figure. This suggests that subjects have the same perception to the ambiguous figure and disambiuous figure and that the correlation of the pupillary reflex changes with the perceptual reversals to the bistable figure of structure-from-motion is reliable. The study casts new light on the visual mechanisms for bistable perception to ambiguous figure.