The binocular organization of complex cells
Izumi Ohzawa, and Ralph D. Freeman (1986)
The binocular organization of complex cells in the cat's visual cortex.
J. Neurophysiol. 56: 243-259.
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We have studied the manner by which inputs from the two eyes are
combined in complex cells of the cat's visual cortex. The stimuli are
drifting sinusoidal gratings presented dichoptically at optimal spatial
frequency and orientation. The relative phase between the gratings for left
and right eyes is varied over 360 degrees. Approximately 40% of complex
cells show phase-specific binocular interaction where response amplitudes
vary depending on the relative phase of the gratings shown to the two eyes.
This interaction is similar to that observed for most simple cells. We
devised a test to examine whether the phase-specific interaction in complex
cells results from linear convergence of neural signals at subunits of the
receptive fields. The data from this test are consistent with a linear
combination model. The phase-specific binocular interaction data from
complex cells imply that the optimal relative phase of the receptive field
subunits is closely matched. Another type of complex cell, approximately
40% of the total, could be driven through either eye, but exhibited
non-phase-specific responses to dichoptically presented gratings. This type
of interaction is found only in complex cells. Binocularly
non-phase-specific complex cells may have subunits whose optimal relative
phases are random or monocular. The division of complex cells into these
two major groups (binocularly phase specific and non-phase specific) is
independent of whether they are standard or special complex-cell types. A
small proportion (8%) of complex cells that appear monocular by alternate
tests of each eye show a purely inhibitory influence from the silent eye.
This inhibition is not generally dependent on the relative phase of the
gratings. Unlike simple cells, complex cells are not a homogeneous group.
However, nearly half of complex cells show phase-specific binocular
interaction that is probably the result of linear convergence. Combined
with the results from simple cells, the majority of binocular interaction
in the striate cortex may be accounted for by linear summation of neural
signals from each eye. This provides a simplified view of the nature of
binocular interaction in the visual cortex.