MECHANISMS OF CHROMATIC-ROD VISION IN SCOTOPIC ILLUMINATION

After viewing a coloured patch for 30 sec, successive contrast colours were triggered by stimulating either rods or cones. The conditions we re arranged so that the rod and cone stimuli matched both with respect to chromaticness and brightness in a chromatically neutral state of a daptation. The results showed that the contrast colours triggered by r ods were strikingly similar to those triggered by cones. Yet, the scot opic contrast colours, as compared with the photopic ones, were genera lly found to be somewhat displaced toward blue. This displacement was attributed to the difference in test conditions. Thus, it was suggeste d that, although rods may excite all the different types of spectrally opponent cells, they generally tend to prefer the short-wave cells. M oreover, it was concluded that the scotopic successive contrast colour s are triggered by rod signals feeding into the primary rod pathway an d therefore must originate centrally to the receptor level.