The perceptual circularity demonstrated by R. Shepard with respect to hue turns out to be a sphericity of color perception based on color excitation vectors of neuronal level. The spherical color model implicitly contains information concerning generalization under color learning. Subjective color differences are “computed” in neuronal nets being represented by amplitudes of evoked potentials triggered by color change. [Shepard].

Vector encoding in perception -- From detector map to maps of memory and semantic units -- Vector encoding in response conditioning -- The neural screen of consciousness -- The modular organization of the brain -- The mosaic nature of consciousness -- Varieties of consciousness -- The neurophysiology of consciousness -- Conclusion: the spherical model of consciousness.