Georges Sébastien, Seriès Peggy, Frégnac Yves, Lorenceau Jean
Unité de Neurosciences Intégratives et Computationnelles, Institut de Neurobiologie, UPR 2191 CNRS, INAF, 1 Av. de la terrasse, Cedex 91198, Gif sur Yvette, France.
Vision Res. 2002 Nov;42(25):2757-72. doi: 10.1016/s0042-6989(02)00303-6.
We report several experiments showing that a Gabor patch moving in apparent motion sequences appears much faster when its orientation is aligned with the motion path than when it is at an angle to it. This effect is very large and peaks at high speeds (64 degrees /s), decreases for higher and lower speeds and disappears at low speeds (4 degrees /s). This speed bias decreases as the angle between the motion axis and the orientation of the Gabor patch increases, but remains high for curvilinear paths, provided that element orientation is kept tangential to the motion trajectory. It is not accounted for by decision strategies relying on the overall length and duration of the motion sequence or the gap size (or spatial jump) between successive frames. We propose a simple explanation, thoroughly developed as a computational model in a companion paper (Seriès, Georges, Lorenceau & Frégnac: "Orientation dependent modulation of apparent speed: a model based on the dynamics of feedforward and horizontal connectivity in V1 cortex", this issue), according to which long-range horizontal connections in V1 elicit differential latency modulations in response to apparent motion sequences, whose read-out at an MT stage results in a perceptual speed bias. The consequences of these findings are discussed.
我们报告了几项实验，这些实验表明，在视动序列中移动的Gabor斑块，当其方向与运动路径对齐时，看起来比与运动路径成一定角度时要快得多。这种效应非常大，在高速（64度/秒）时达到峰值，在更高和更低速度时减小，在低速（4度/秒）时消失。随着运动轴与Gabor斑块方向之间的角度增加，这种速度偏差会减小，但对于曲线路径，只要元素方向与运动轨迹保持相切，速度偏差就会保持较高。它不能用依赖于运动序列的总长度和持续时间或连续帧之间的间隙大小（或空间跳跃）的决策策略来解释。我们提出了一个简单的解释，并在一篇配套论文（Seriès, Georges, Lorenceau & Frégnac: “视速度的方向依赖性调制：基于V1皮层前馈和水平连接动力学的模型”，本期）中作为一个计算模型进行了全面阐述，根据该解释，V1中的长程水平连接会响应视动序列引发不同的潜伏期调制，其在MT阶段的读出会导致感知速度偏差。我们讨论了这些发现的后果。
