Figure 2.

Identified elements of two example cells. A, The STC matrix has four quadrants. The top left and the bottom right quadrants show correlations between pixels shown to the left eye (L-eye) or to the right eye (R-eye). Structures in the top right and bottom left quadrants show binocular interaction. The diagonal was replaced with zeros in this figure to show the important structures in the matrix. The diagonal contained large values in the actual calculations (corresponding to the variance of each pixel). The color bar shows the scale of covariance values. B, After projecting out the STA from the ensemble, the eigenvalues of the STC matrix reveal the significant elements (filled symbols). The eigenvalues are normalized to a sum of one. The last eigenvalue was always zero, corresponding to the axis that had been projected out (data not shown). C, Four elements were identified as excitatory (Exc) elements. The left column shows the eigenvectors (receptive field elements). The blue and red segments show the filters of the left and right eyes. The ordinate is in arbitrary units. D, Three elements were identified as suppressive (Sup) elements. The STA is shown on the bottom row. E–H, Another example cell. The plotting conventions are the same as in A–D. This cell revealed two suppressive elements.