The visual system integrates information from the left and right eyes and c
onstructs a visual world that is perceived as single and three dimensional.
To understand neural mechanisms underlying this process, it is important t
o learn about how signals from the two eyes interact at the level of single
neurons. Using a sophisticated receptive field (RF) mapping technique that
employs binary m-sequences, we have determined the rules of binocular inte
ractions exhibited by simple cells in the cat's striate cortex in relation
to the structure of their monocular RFs. We find that binocular interaction
RFs of most simple cells are well described as the product of left and rig
ht eye RFs. Therefore the binocular interactions depend not only on binocul
ar disparity but also on monocular stimulus position or phase. The binocula
r interaction RF is consistent with that predicted by a model of a linear b
inocular filter followed by a static nonlinearity. The static nonlinearity
is shown to have a shape of a half-power function with an average exponent
of similar to 2. Although the initial binocular convergence of signals is l
inear, the static nonlinearity makes binocular interaction multiplicative a
t the output of simple cells. This multiplicative binocular interaction is
a key ingredient for the computation of interocular cross-correlation, an a
lgorithm for solving the stereo correspondence problem. Therefore simple ce
lls may perform initial computations necessary to solve this problem.