Harris R A, O'Carroll D C, Laughlin S B
Department of Zoology, University of Cambridge, United Kingdom.
Neuron. 2000 Nov;28(2):595-606. doi: 10.1016/s0896-6273(00)00136-7.
In many species, including humans, exposure to high image velocities induces motion adaptation, but the neural mechanisms are unclear. We have isolated two mechanisms that act on directionally selective motion-sensitive neurons in the fly's visual system. Both are driven strongly by movement and weakly, if at all, by flicker. The first mechanism, a subtractive process, is directional and is only activated by stimuli that excite the neuron. The second, a reduction in contrast gain, is strongly recruited by motion in any direction, even if the adapting stimulus does not excite the cell. These mechanisms are well designed to operate effectively within the context of motion coding. They can prevent saturation at susceptible nonlinear stages in processing, cope with rapid changes in direction, and preserve fine structure within receptive fields.
在包括人类在内的许多物种中，暴露于高图像速度会引发运动适应，但其中的神经机制尚不清楚。我们已经分离出两种作用于果蝇视觉系统中方向选择性运动敏感神经元的机制。这两种机制都受到运动的强烈驱动，而受闪烁的驱动则很微弱（如果有影响的话）。第一种机制是一个减法过程，具有方向性，且仅由激发神经元的刺激激活。第二种机制是对比度增益降低，它会被任何方向的运动强烈激活，即使适应刺激并未激发该细胞。这些机制经过精心设计，能够在运动编码的背景下有效运作。它们可以防止处理过程中敏感的非线性阶段出现饱和，应对方向的快速变化，并保留感受野内的精细结构。
