The combined layer of simple and complex cells is practically identical to the model proposed in [42] for modeling responses of binocular cortical neurons. For simplicity, neurons in our simulation are allowed to code negative as well as positive signal values; in [42], a push-pull configuration of neurons was used instead.

The receptive fields of the simple cells are modeled by a generic Gabor function
of the form

Simple cells sample data from both left and right input streams, which we denote
here by and . As transfer function
for simple cells, a squaring nonlinearity is used. With the normalized filter
coefficients given by
, the output of a
simple cell can be written as

For quadrature filtering, the output of any simple cell having a phase-shift
has to be paired with another simple cell, having a phase-shift
of
. This means that for every simple cell
with a receptive field defined by (7) there exists another, paired
one, calculating