Geisler W S
Department of Psychology, University of Texas at Austin, 78712, USA.
Nature. 1999 Jul 1;400(6739):65-9. doi: 10.1038/21886.
Although many neurons in the primary visual cortex (V1) of primates are direction selective, they provide ambiguous information about the direction of motion of a stimulus. There is evidence that one of the ways in which the visual system resolves this ambiguity is by computing, from the responses of V1 neurons, velocity components in two or more spatial orientations and then combining these velocity components. Here I consider another potential neural mechanism for determining motion direction. When a localized image feature moves fast enough, it should become smeared in space owing to temporal integration in the visual system, creating a spatial signal-a 'motion streak'-oriented in the direction of the motion. The orientation masking and adaptation experiments reported here show that these spatial signals for motion direction exist in the human visual system for feature speeds above about 1 feature width per 100 ms. Computer simulations show that this psychophysical finding is consistent with the known response properties of V1 neurons, and that these spatial signals, when appropriately processed, are sufficient to determine motion direction in natural images.
虽然灵长类动物初级视觉皮层（V1）中的许多神经元具有方向选择性，但它们提供的关于刺激运动方向的信息并不明确。有证据表明，视觉系统解决这种模糊性的一种方式是根据V1神经元的反应计算两个或更多空间方向上的速度分量，然后将这些速度分量组合起来。在这里，我考虑另一种确定运动方向的潜在神经机制。当一个局部图像特征移动得足够快时，由于视觉系统中的时间整合，它应该在空间中变得模糊，从而产生一个沿运动方向定向的空间信号——“运动条纹”。此处报告的方向掩蔽和适应实验表明，对于速度高于每100毫秒约1个特征宽度的特征，人类视觉系统中存在这些用于运动方向的空间信号。计算机模拟表明，这一心理物理学发现与V1神经元的已知反应特性一致，并且这些空间信号经过适当处理后足以确定自然图像中的运动方向。
