Using common sense or introspection, we “know” that color is a visual property of
objects and surfaces that we perceive separately from shape or direction of motion or
depth order in the visual scene. Vision scientists often have studied color perception
under conditions where form is minimal. It is natural for us as scientists and also as
human beings to think of color as separate and apart. But on the contrary, color and
form are linked inextricably as properties of objects in visual perception and in the visual
cortex. The famous psychologist Gaetano Kanizsa was an eloquent advocate of this
viewpoint; he wrote:
“…space and color are not distinct elements but, rather, are
interdependent aspects of a unitary process of perceptual organization.”
(Kanizsa 1979)

The reason for the linkage of color and form is that the brain needs to construct a color
signal to recover, as well as it can, the reflective properties of a surface, independent of
illumination. So, neural mechanisms of color perception must make computations that
take into account the spatial layout of a scene as well as the reflectances of the surfaces
in the scene. Our work suggests that the primary visual cortex, V1, plays an important
role in neural computations for color and form perception, through the construction of
spatially-tuned double-opponent color cells.