Contrast dependence of response normalization in area MT of the rhesus macaque
Contrast dependence of response normalization in area MT of the rhesus macaque
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DOI：
10.1152/jn.00255.2002
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发表时间：
2002-12-01
影响因子：
2.5
通讯作者：
Britten, KH
中科院分区：
文献类型：
--
作者：
Heuer, HW;Britten, KH
对比度归一化是根据神经元感受野附近图像区域中的对比度总量来缩放神经元响应的过程。这个过程允许神经元以不受照明变化影响的方式编码信息丰富的场景或对象属性。从实验中可以在纹状皮层和纹状外皮层中看到归一化的证据，其中多个刺激通过单个感受野（RF）呈现。此类实验中的神经元反应小于线性求和预测的神经元反应，揭示了标准化的存在。虽然正常化的存在通常很明显，但其机制却不太清楚。为了研究归一化机制，我们测量了猴子中颞区（MT 或 V5）区域细胞 RF 内的成对短暂局部刺激（空间 Gabor 函数）之间的相互作用，并改变了刺激的位置和对比度。我们发现，当对比度较低时，响应近似呈线性求和，但随着刺激对比度增加，响应会迅速归一化。在低对比度下快速过渡到有效标准化表明标准化中的协作性，并且体现这种协作步骤的模型很好地说明了我们的数据。
Contrast normalization is a process whereby responses of neurons are scaled according to the total amount of contrast in a region of the image nearby the receptive field of a neuron. This process allows neurons to code for informative scene or object attributes in a manner unaffected by changes in illumination. Evidence for normalization is seen in striate and extrastriate cortex from experiments where multiple stimuli are presented with a single receptive field (RF). Neuronal responses in such experiments are smaller than that predicted by linear summation, revealing the presence of normalization. While the presence of normalization is often clear, its mechanism is less so. To study the mechanism of normalization, we measured the interaction between pairs of brief local stimuli (spatial Gabor functions) within the RFs of cells in the middle temporal (MT or V5) area of monkeys and varied both the location and contrast of the stimuli. We found response summed approximately linearly when contrast was low but rapidly became normalized as stimulus contrast increased. The rapid transition to effective normalization at low contrasts suggested cooperativity in the normalization, and a model embodying such a cooperative step provided a good account of our data.