认知与发展心理学研究室知识库

判断自身运动方向是绝大部分能自主运动的生物的一项重要能力，这点在生物体趋利避害行为中体现尤为明显。包括人类在内的灵长类生物体，其主要信息来源的获取依赖视觉途径。通常我们把观察者自身运动引起的视网膜图像变化称为光流（optic flow），它是判断自身运动方向的重要视觉线索。由于自然情境下个体进行自身运动的同时往往伴随有眼球或头部的转动，虽然这会严重扭曲视网膜上光流的放射状图样，但往往对个体正确判断自身运动方向影响很小。因此视觉系统必然存在眼动补偿机制，以还原真实的自身运动方向，然而我们对自身运动方向判别中影响眼动补偿的各种因素及其神经机制都知之甚少。
判断自身运动方向是绝大部分能自主运动的生物的一项重要能力，这点在生物体趋利避害行为中体现尤为明显。包括人类在内的灵长类生物体，其主要信息来源的获取依赖视觉途径。通常我们把观察者自身运动引起的视网膜图像变化称为光流（optic flow），它是判断自身运动方向的重要视觉线索。由于自然情境下个体进行自身运动的同时往往伴随有眼球或头部的转动，虽然这会严重扭曲视网膜上光流的放射状图样，但往往对个体正确判断自身运动方向影响很小。因此视觉系统必然存在眼动补偿机制，以还原真实的自身运动方向，然而我们对自身运动方向判别中影响眼动补偿的各种因素及其神经机制都知之甚少。
然后我们用相同的实验范式，在猕猴完成实验任务的同时记录了自身运动判别关键脑区-VIP-中单个神经元的电活动，以考察眼动补偿中非视网膜信息的必要性和它与视网膜信息整合的神经机制。真实眼动条件下神经元反应是视网膜信息与非视网膜信息（眼动）整合的结果，模拟眼动条件下神经元反应只依赖于视网膜信息输入，而无视觉刺激条件下神经元活动反映的是投射到 VIP 脑区的眼动信息。我们发现 VIP 神经元反应性质在真实眼动和模拟眼动条件下并无显著的统计差异（N=27，Bootstrap, CI=95%），说明即使没有非视网膜信息的参与，VIP 脑区也能仅依靠光流结构的视觉线索完成眼动补偿，然而并不能排除自然状
态下非视网膜信号参与眼动补偿的可能性。

It is  critical  to correctly  judge  their  self-motion direction for most of  free moving animals, especially when they  are hunting or being hunted. The primates,  including human being, largely depend on the visual system to attain the information from outside world. Normally we define the retinal flow changes caused by self-motion as optic flow, which  is  an  important cue for  heading judgements.  In natural conditions,  eye/head rotations are common during self-motion. This will severely distort the radical image pattern of the retinal optic flow. However, we can still estimate the heading direction correctly. Therefore, the visual system must have a mechanism to compensate the eye movements and recover the real direction of self-motion. Unfortunately, the neuronal mechanism of eye movements compensation during self-motion are still unclear. We first conducted a series of behavioral experiments to test how eye movement speed, self-motion speed and visual signal reliability affect heading perception and eye movements compensation. The visual stimuli were generated by computer to simulate the retinal flow when the observer was moving towards a 3D cloud of points. Heading direction was varied along horizontal line. The participants were asked to report the perceived heading direction, either left or right. In real eye movements condition, the subject  was  required  to  pursuit moving target  with their eyes.  In simulated eye movements condition, subjects had to hold their gaze at fixation point but was presented with visual stimuli combined the effects of pursuit eye movements. In another word, the distortion on retinal flow cause by pursuit eye movement was superimposed on each heading stimulus to keep the retinal image equal, frame by frame, but no presence of extra-retinal signals. The error rate was used to evaluate the behavioral performance. We found that the levels of extra-retinal contributions increased with increasing pursuit speed (stronger extra-retinal signal), and with decreasing heading speed (weaker retinal signal). In addition, extra-retinal contributions also increased as we corrupted retinal signals with noise. Our results  suggest that neural system can flexible integrate the retinal and non-retinal signal based on the reliability of the information and optimally percept the direction of self-motion.
To further investigate the necessity of extra-retinal signals in eye movements compensation and how it was integrated with retinal signals to recover real heading direction, we recorded single neuron activities in primate VIP while we asked themonkey to perform the same 2AFC (two-alternative forced choice) task. We found that the neuronal responses had no significant difference between real pursuit and simulated pursuit condition (N=27, Bootstrap, CI=95%). As we known, the neuronal responses during real pursuit condition should be the result of both retinal and extra-retinal contribution, but only retinal signals were available during simulated pursuit condition. This result indicate that VIP area can compensate the eye movements merely depend on the optic flow pattern. However, we can’t rule out the possibility of non-retinal signal engaged in the eye movements compensation in natural condition.