Ilg U J, Thier P
Sektion für Visuelle Sensomotorik, Neurologische Universitätsklinik, Hoppe-Seyler-Strasse 3, D-72076 Tübingen, Germany.
Eur J Neurosci. 1996 Jun;8(6):1156-66. doi: 10.1111/j.1460-9568.1996.tb01283.x.
Retinal image slip can result from an eye movement across a stationary object or alternatively from motion of the object while the eyes are stationary. The ability to discriminate between these two kinds of retinal image slip is necessary for the perception of a stable visual world. In order to determine if this ability is already present in monkey visual area V1, we asked if single V1 units are able to differentiate between externally and self-induced retinal image slip. Externally induced retinal image slip was realized in the 'object motion' condition (OMC) by moving a behaviourally irrelevant visual stimulus ('object': a bar or a large random dot pattern) across the receptive field while the monkey fixated a small, stationary target. Conversely, self-induced retinal image slip of comparable size was evoked in the 'ego motion' condition (EMC) by asking the monkey to pursue the target, moving at the speed of the object in the OMC, while the object was kept stationary. We recorded 221 units from visual area V1, 51, (23%) of them directionally selective, and compared their responses to self-induced and externally induced retinal image slip. Many of them seemed to give some preference to externally induced retinal image slip. However, on closer examination it became clear that this seeming preference could be attributed to the fact that oculomotor performance was less precise in the EMC than in the OMC, causing a larger deviation from the optimal retinal image trajectory in the EMC. We show that the impact of eye position errors can be eliminated by the use of a position-invariant stimulus, such as large-field random dot patterns. We then show that the impact of both eye position errors and deviation of eye velocity from target velocity in the EMC can be eliminated by moving the stimulus in a given OMC trial according to an inverted replica of the eye movement trajectory in the preceding EMC trial, guaranteeing identical retinal stimulation in the OMC and the EMC. If identical retinal stimulation was ensured, none of the V1 units tested was able to differentiate between externally and self-induced retinal image slip. We conclude that V1 does not contribute to the perception of a world which is stable despite eye movements.
视网膜图像滑动可能源于眼睛在静止物体上的移动，或者源于眼睛静止时物体的运动。区分这两种视网膜图像滑动的能力对于感知稳定的视觉世界至关重要。为了确定这种能力在猴子视觉区域V1中是否已经存在，我们研究了单个V1神经元是否能够区分外部诱导和自我诱导的视网膜图像滑动。在“物体运动”条件（OMC）下，通过在猴子注视一个小的静止目标时，将一个行为上无关的视觉刺激（“物体”：一条线或一个大的随机点图案）在其感受野上移动，来实现外部诱导的视网膜图像滑动。相反，在“自我运动”条件（EMC）下，通过要求猴子追踪以OMC中物体的速度移动的目标，同时物体保持静止，来诱发大小相当的自我诱导视网膜图像滑动。我们从视觉区域V1记录了221个神经元，其中51个（23%）具有方向选择性，并比较了它们对自我诱导和外部诱导视网膜图像滑动的反应。它们中的许多似乎对外部诱导的视网膜图像滑动有一定的偏好。然而，经过更仔细的检查发现，这种看似的偏好可能是由于在EMC中眼球运动的表现不如在OMC中精确，导致在EMC中与最佳视网膜图像轨迹的偏差更大。我们表明，通过使用位置不变的刺激，如大视野随机点图案，可以消除眼位误差的影响。然后我们表明，通过在给定的OMC试验中根据前一个EMC试验中的眼球运动轨迹的反向复制品移动刺激，可以消除EMC中眼位误差和眼速度与目标速度偏差的影响，从而保证在OMC和EMC中视网膜刺激相同。如果确保视网膜刺激相同，所测试的V1神经元中没有一个能够区分外部诱导和自我诱导的视网膜图像滑动。我们得出结论，V1对尽管有眼球运动但仍稳定的世界的感知没有贡献。
