Figure 9.

A physiological stimulation system is depicted which provides a determination of whether signals from left and right eyes are combined in a linear manner at the first stage of processing in the visual cortex. On the left, the right eye is occluded while the left is stimulated with the sinusoidal grating that is counter- phasing in position. Pathways from the left eye activate receptive field subunits in the visual cortex followed by nonlinear processing and convergence to form a frequency doubled response. On the right, both eyes are activated by drifting sinusoidal gratings moving in opposite directions in front of the two eyes. If there is a linear combination of signals from these patterns, a counter phased stimulus will be activated at the subunit level to produce a frequency doubled response as in the case on the left.