Edwards M, Badcock D R
Department of Psychology, School of Behavioural Science, University of Melbourne, Parkville, Victoria, Australia.
Perception. 1993;22(9):1013-23. doi: 10.1068/p221013.
It is reasonable to ask whether observers are more sensitive to the pattern of image motion caused by forward locomotion through the environment than to the pattern caused by backward locomotion. The distribution of sensitivities of cells in MT does show such a bias, although this bias is minimal at small eccentricities. Additionally, both locomotion-induced stimulation and the sensitivities of MT cells suggest greater sensitivity should be obtained in the lower visual field. Previous research on this issue has usually employed frontoparallel motion in patterns presented to one side of the fixation point. Both centrifugal and centripetal biases have been obtained. In this study the stimuli present motion signals that travel radially from (or towards) the fixation point. These stimuli, which produce a strong percept of motion in depth, are an adaptation of the global-dot-motion stimulus employed by Newsome and Pare. With these stimuli we find that sensitivity to motion in depth is greater in the lower visual field than in the upper visual field, and that sensitivity is greater to centripetal motion than to either centrifugal or frontoparallel motion. This centrifugal bias in sensitivity decreases with eccentricity. The last two findings contradict the notion that the bias is produced by the visual experience induced by normal forward locomotion and also that the detection of motion in depth is subserved by MT.
观察者对于由在环境中向前移动所引起的图像运动模式，是否比对于向后移动所引起的模式更为敏感，这是一个合理的问题。MT区细胞的敏感性分布确实显示出这样一种偏向，尽管这种偏向在小偏心率时最小。此外，由移动引起的刺激以及MT细胞的敏感性都表明，在下视野中应能获得更高的敏感性。以往关于这个问题的研究通常采用在呈现于注视点一侧的模式中的额平行运动。已获得了离心偏向和向心偏向。在本研究中，刺激呈现从注视点径向向外（或向内）传播的运动信号。这些刺激能产生强烈的深度运动感知，是对纽瑟姆和帕尔所采用的全局点运动刺激的一种改编。利用这些刺激，我们发现对深度运动的敏感性在下视野中比在上视野中更高，并且对向心运动的敏感性高于对离心运动或额平行运动的敏感性。这种敏感性的离心偏向随偏心率降低。最后这两个发现与以下观点相矛盾：这种偏向是由正常向前移动所诱导的视觉经验产生的，以及深度运动的检测是由MT区负责的。
