THE USE OF PHANTOM CONTOURS TO ISOLATE MAGNOCELLULAR AND PARVOCELLULAR RESPONSES

In some "flickering" spot stimuli, two kinds of percepts can be seen at different frequencies: phantom contours and "surface characteristics." It has been proposed that their perception may be used to evaluate the magnocellular and parvocellular systems. This, however, is problematic. First, the difference in temporal frequencies associated with the two percepts is large compared to that between the temporal tuning of magno- and parvocellular neurons. Second, the lack of absolute temporal phase information in the case of surface characteristics does not fit with parvocellular neuron behavior. Third, the low temporal threshold of surface characteristics suggests cortical mechanisms rather than parvocellular ones. And fourth, the relationship between the two percepts and color may reflect parvocellular responses not magno- and parvocellular ones.