Psychophysiological Modeling of Spatial Color Vision in Man

A psychophysiological model of the elementary color sensations red, green, blue, yellow, black and white, which constitute our color sensations, is presented. The model takes spectral sensitivity functions of human cones into account. The well approved neuronal color opponent coding (COC) model, originally developed for insect vision is incorporated and adapted to light discrimination judgments in humans [1]. In the case of human color vision, the parameters of the COC model could yet only be determined from the data of light discrimination experiments up to arbitrary rotations of the basis of the subjective light discrimination space [2], because of the rotational invariance of the Euclidean metric. In addition to spanning the light-discrimination space, the COC neurons are assumed to steer the amounts of the elementary color sensations piece by piece linearly. A hypothesized interaction-mechanism of the elementary colors normalizes the total amounts to 100%. An advantage is that all the parameters of this model have definite values, i.e. no rotational degrees of freedom. Classical psychophysical measurements of the amounts of the chromatic elementary color sensations stimulated by monochromatic light are simulated with the model. Best fits of the predicted data to the measured data of two observers determined the parameters uniquely. The model precisely describes the common characteristics as well as the measured individual differences by respectively deviating values of the physiological parameters.

Furthermore, the model has been extended by spatial aspects of color vision [3], explaining 1) hyperacuity, 2) the virtual projection of the color sensations to the outside of our head and 3) the visual "enlargement with depth" effect [4] and related 4) size distortion and constancy phenomena caused by 3D drawings.

[1] Backhaus, W., 2004. A physiological model of human color discrimination. In: Proceedings of the 4th Forum of European Neuroscience (FENS), July 10–14, 2004, Lisbon, Portugal, Abstracts, Vol. 2, A, p. 194.5. FENS, Lisbon.
[2] Backhaus, W., 2006. Psychophysical simulations of spatial color vision. In: Fünftes Symposium Licht und Gesundheit, 23.-24.2.2006. Eine Sondertagung der TU Berlin und der DGP mit DAfP und LiTG, Hrsg. H. Kaase & F. Serick, Tagungsband, Hauptvorträge, pp. 8-21. Technische Universtät, Berlin (ISBN 3-9807635-0-2).
[3] Backhaus, W., 2001. Measurement and simulation of colour sensations. In: Neuronal Coding of Perceptual Systems, ed. W. Backhaus. World Scientific, London , pp. 445-474.

[4] Backhaus, W. 2003. Evidence for a spherical geometry of color perception. In: Proceedings of the 29th Göttingen Neurobiology Conference and the 5th Meeting of the German Neuroscience Society 2003. From Basic Research to Therapy, pp.1007-1009. Thieme, Stuttgart - New York.