Figure 1.

Identification of the elements with spike-triggered analysis. A, The elements of the model have a linear filter in each eye followed by an output nonlinearity. The outputs of the elements are combined linearly, with some of their coefficients being negative. After a rectified nonlinearity, the signal intensity determines the firing rate. B, Sequences of noise patterns were presented to both eyes. The patterns were uncorrelated between the eyes. One noise frame preceding each spike was extracted. The spike-triggered stimulus ensemble consists of all such frames preceding a spike. L, Left; R, right.