Source localization of S-cone and L/M-cone driven signals using silent substitution flash stimulation

This study aimed to analyze the neuronal sources of the visual evoked potentials after flash stimulation of the S- and the L/M-cone driven channels of the visual system. For 11 volunteers a 64-channel electroencephalography (EEG) was recorded during selective excitation of both color opponent channels. Individual and grand average data were analyzed topographically. Source localization was carried out using a realistically shaped three compartment boundary element model (BEM) and a mirrored moving dipole model. We found two main components (N1, P1) in all subjects, as well as a third late component in most subjects. For these components significant latency differences (N1=33 ms, P1=22 ms; p<0.05) between both color opponent channels were found. The results showed no differences in the topography and no differences in dipole localization between both color channels. Talairach coordinates of grand averages indicated activation in area 18. Comparison of results of separately stimulated eyes revealed no differences. Our findings showed that neural processing occurs in the same areas of the visual cortex for stimuli with different spectral properties. The signals of S- and L/M-cone driven channels are transmitted in distinct pathways to the cortex. Thus, the observed latency differences might be caused by different anatomical and functional properties of these pathways.