Linearity and Normalization in Simple Cells of the Macaque Primary Visual Cortex
Linearity and Normalization in Simple Cells of the Macaque Primary Visual Cortex
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DOI：
10.1523/jneurosci.17-21-08621.1997
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发表时间：
1997-11
期刊：
影响因子：
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通讯作者：
M. Carandini;D. Heeger;J. Movshon
中科院分区：
文献类型：
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作者：
M. Carandini;D. Heeger;J. Movshon
初级视觉皮层中的简单细胞通常会计算落在其感受野上的视觉刺激的光强度分布的加权和。这些细胞的线性模型具有简单的优点，并且捕获了细胞功能的许多基本方面。然而，它未能解释重要的响应非线性，例如在高对比度下观察到的响应增益和延迟的减少，以及单独呈现时无法引起响应的刺激的掩蔽效应。为了解释这些非线性，我们提出了一个归一化模型，它将线性模型扩展到包括大量皮质细胞之间的相互分流抑制。分流抑制是有争议的，它在模型中的作用是通过刺激能量的测量来标准化线性响应。为了测试这个模型，我们对麻醉猕猴的初级视觉皮层中的简单细胞进行了细胞外记录。我们提出了大型刺激集，其中包括（1）各种方向和时空频率的漂移光栅； (2)由两个漂移光栅组成的格子； (3)全屏时空白噪声掩盖的光栅。我们导出了模型预测的表达式，并将其拟合到生理数据中。我们的结果支持归一化模型，该模型解释了细胞的线性和非线性特性。另一种模型的线性响应受到压缩非线性的影响，但其表现却差强人意。
Simple cells in the primary visual cortex often appear to compute a weighted sum of the light intensity distribution of the visual stimuli that fall on their receptive fields. A linear model of these cells has the advantage of simplicity and captures a number of basic aspects of cell function. It, however, fails to account for important response nonlinearities, such as the decrease in response gain and latency observed at high contrasts and the effects of masking by stimuli that fail to elicit responses when presented alone. To account for these nonlinearities we have proposed a normalization model, which extends the linear model to include mutual shunting inhibition among a large number of cortical cells. Shunting inhibition is divisive, and its effect in the model is to normalize the linear responses by a measure of stimulus energy. To test this model we performed extracellular recordings of simple cells in the primary visual cortex of anesthetized macaques. We presented large stimulus sets consisting of (1) drifting gratings of various orientations and spatiotemporal frequencies; (2) plaids composed of two drifting gratings; and (3) gratings masked by full-screen spatiotemporal white noise. We derived expressions for the model predictions and fitted them to the physiological data. Our results support the normalization model, which accounts for both the linear and the nonlinear properties of the cells. An alternative model, in which the linear responses are subject to a compressive nonlinearity, did not perform nearly as well.