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Retinal and cortical nonlinearities combine to produce masking in V1 responses to plaids.
Journal of Computational Neuroscience ( IF 1.2 ) Pub Date : 2008-06-24 , DOI: 10.1007/s10827-008-0086-6
Melinda Koelling 1 , Robert Shapley , Michael Shelley
Affiliation  

The visual response of a cell in the primary visual cortex (V1) to a drifting grating stimulus at the cell's preferred orientation decreases when a second, perpendicular, grating is superimposed. This effect is called masking. To understand the nonlinear masking effect, we model the response of Macaque V1 simple cells in layer 4Calpha to input from magnocellular Lateral Geniculate Nucleus (LGN) cells. The cortical model network is a coarse-grained reduction of an integrate-and-fire network with excitation from LGN input and inhibition from other cortical neurons. The input is modeled as a sum of LGN cell responses. Each LGN cell is modeled as the convolution of a spatio-temporal filter with the visual stimulus, normalized by a retinal contrast gain control, and followed by rectification representing the LGN spike threshold. In our model, the experimentally observed masking arises at the level of LGN input to the cortex. The cortical network effectively induces a dynamic threshold that forces the test grating to have high contrast before it can overcome the masking provided by the perpendicular grating. The subcortical nonlinearities and the cortical network together account for the masking effect.

中文翻译:

视网膜和皮质非线性相结合,在 V1 对格子的响应中产生掩蔽。

当叠加第二个垂直光栅时,初级视觉皮层 (V1) 中的细胞对细胞首选方向的漂移光栅刺激的视觉反应会降低。这种效果称为掩蔽。要了解非线性掩蔽效应,我们模拟了 4Calpha 层中猕猴 V1 简单细胞对来自大细胞横向膝状核 (LGN) 细胞的输入的响应。皮层模型网络是一个由 LGN 输入激发和来自其他皮层神经元抑制的集成和发射网络的粗粒度减少。输入被建模为 LGN 细胞反应的总和。每个 LGN 细胞都被建模为时空滤波器与视觉刺激的卷积,通过视网膜对比度增益控制进行归一化,然后是代表 LGN 尖峰阈值的整流。在我们的模型中,实验观察到的掩蔽出现在 LGN 输入到皮层的水平。皮层网络有效地诱导了一个动态阈值,迫使测试光栅在克服垂直光栅提供的掩蔽之前具有高对比度。皮层下非线性和皮层网络共同解释了掩蔽效应。
更新日期:2019-11-01
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