Therapeutic Drug Monitoring
R Goulding · Journal of Clinical Pathology · 1982
Abstract Negative colour afterimages are a fundamental phenomenon reflecting the adaptative mechanisms of colour processing. Despite its fundamental importance, the precise mechanisms underlying afterimages are very much controversial. What has been overlooked is that the adaptation of different mechanisms makes fundamentally different predictions about the hue and saturation of afterimages. We developed two experimental paradigms to measure the exact colours perceived in afterimages and test those predictions empirically. All results of these two different paradigms confirm that afterimages do not align with cone-opponency but instead tightly follow a well-founded, straight-forward model of cone adaptation (i.e., cone contrasts). This model implements cone adaptation according to Weber’s Law, which is a direct consequence of the proportional decrement of photon catches due to cone bleaching and results in a nonlinear, multiplicative inverse function of cone excitations. This nonlinear adaptation of the three cones predicts three peaks of afterimage intensity that correspond with the three peaks of saturation and the three clusters of hue in the measurements of afterimages. Our findings establish cone-adaptation as the sole origin of negative colour afterimages. The quantitative cone-contrast model resolves apparent contradictions and provides a comprehensive, straight-forward explanation of the adaptive mechanisms underlying colour afterimages.