Skottun B C, Zhang J, Grosof D H
Department of Psychology, University of California, Berkley.
Vis Neurosci. 1994 Sep-Oct;11(5):885-97. doi: 10.1017/s0952523800003849.
It is well established that cortical neurons frequently show different preferred drift directions for random dots and gratings. Dot stimuli often produce two preferred directions which are arranged symmetrically on either side of the preferred directions for gratings. Based on their filter properties in three-dimensional (3-D) Fourier space and on the 3-D power spectra of drifting dot patterns, we estimated the optimal direction to drifting dots for ten neurons in the striate cortex of five adult cats. These estimates frequently gave two optimal directions, one on either side of the optimal direction to gratings. The angle between the two estimated peaks increases with drift speed. Predicted and actual angles were in reasonably good agreement. We conclude, therefore, that the directional selectivity of cortical neurons to drifting random dot patterns can be understood from linear filtering properties. For this reason, the directional tuning to drifting dot patterns seems to reflect the same mechanisms that mediate the responses to sinusoidal gratings and do not require a separate directional mechanism.
皮质神经元对随机点和光栅常常表现出不同的偏好漂移方向，这一点已得到充分证实。点刺激通常会产生两个偏好方向，它们在光栅偏好方向的两侧对称排列。基于它们在三维（3-D）傅里叶空间中的滤波特性以及漂移点图案的三维功率谱，我们估计了五只成年猫视皮层中十个神经元对漂移点的最佳方向。这些估计值常常给出两个最佳方向，一个在光栅最佳方向的一侧，另一个在另一侧。两个估计峰值之间的角度随漂移速度增加。预测角度和实际角度相当吻合。因此，我们得出结论，皮质神经元对漂移随机点图案的方向选择性可以从线性滤波特性来理解。出于这个原因，对漂移点图案的方向调谐似乎反映了介导对正弦光栅反应的相同机制，不需要单独的方向机制。
