Smith E L, Chino Y, Ni J, Cheng H
College of Optometry, University of Houston, Texas 77204-6052, USA.
J Neurophysiol. 1997 Jul;78(1):366-82. doi: 10.1152/jn.1997.78.1.366.
With the use of microelectrode recording techniques, we investigated how the contrast signals from the two eyes are combined in individual cortical neurons in the striate cortex of anesthetized and paralyzed macaque monkeys. For a given neuron, the optimal spatial frequency, orientation, and direction of drift for sine wave grating stimuli were determined for each eye. The cell's disparity tuning characteristics were determined by measuring responses as a function of the relative interocular spatial phase of dichoptic stimuli that consisted of the optimal monocular gratings. Binocular contrast summation was then investigated by measuring contrast response functions for optimal dichoptic grating pairs that had left- to right-eye interocular contrast ratios that varied from 0.1 to 10. The goal was to determine the left- and right-eye contrast components required to produce a criterion threshold response. For all functional classes of cortical neurons and for both cooperative and antagonistic binocular interactions, there was a linear relationship between the left- and right-eye contrast components required to produce a threshold response. Thus, for example for cooperative binocular interactions, a reduction in contrast to one eye was counterbalanced by an equivalent increase in contrast to the other eye. These results showed that in simple cells and phase-specific complex cells, the contrast signals from the two eyes were linearly combined at the subunit level before nonlinear rectification. In non-phase-specific complex cells, the linear binocular convergence of contrast signals could have taken place either before or after the rectification process, but before spike generation. In addition, for simple cells, vector analysis of spatial summation showed that the inputs from the two eyes were also combined in a linear manner before nonlinear spike-generating mechanisms. Thus simple cells showed linear spatial summation not only within and between subregions in a given receptive field, but also between the left- and right-eye receptive fields. Overall, the results show that the effectiveness of a stimulus in producing a response reflects interocular differences in the relative balance of inputs to a given cell, however, the eye of origin of a light-evoked signal has no specific consequence.
利用微电极记录技术，我们研究了在麻醉和瘫痪的猕猴纹状皮层中，来自两只眼睛的对比度信号如何在单个皮层神经元中进行整合。对于给定的神经元，分别确定了每只眼睛对正弦波光栅刺激的最佳空间频率、方向和漂移方向。通过测量由最佳单眼光栅组成的双眼视差刺激的相对眼间空间相位的函数响应，来确定细胞的视差调谐特性。然后，通过测量最佳双眼视差光栅对的对比度响应函数来研究双眼对比度总和，这些光栅对的左眼与右眼眼间对比度比值在0.1到10之间变化。目的是确定产生标准阈值响应所需的左眼和右眼对比度分量。对于所有皮层神经元功能类别以及协同和拮抗的双眼相互作用，产生阈值响应所需的左眼和右眼对比度分量之间存在线性关系。因此，例如对于协同双眼相互作用，一只眼睛对比度的降低会被另一只眼睛对比度的同等增加所抵消。这些结果表明，在简单细胞和相位特异性复杂细胞中，来自两只眼睛的对比度信号在非线性整流之前在亚单位水平上进行线性组合。在非相位特异性复杂细胞中，对比度信号的线性双眼汇聚可能在整流过程之前或之后发生，但在产生动作电位之前。此外，对于简单细胞，空间总和的矢量分析表明，来自两只眼睛的输入在非线性产生动作电位机制之前也以线性方式进行组合。因此，简单细胞不仅在给定感受野内和子区域之间表现出线性空间总和，而且在左眼和右眼感受野之间也表现出线性空间总和。总体而言,结果表明，刺激产生反应的有效性反映了给定细胞输入相对平衡中的眼间差异，然而，光诱发信号的起源眼没有特定影响。
