Abstract
Conscious perception is modulated with eccentricity. The main explanation of this phenomenon is the progressive decrease in photoreceptor's density. Actually, cortical magnification factor is often used to equalize central and peripheral performance, but size is not enough to explain perceptual differences at large eccentricities. Here we used binocular rivalry in order to investigate how the information driven by magnocellular (M) and parvocellular (P) pathways is differentially modulated with eccentricity (until 24°), and which are the implications for conscious perception. We made two rivalry experiments in order to stimulate preferentially M or P pathways. In the first experiment, two kinds of achromatic gabor patches were used with different physical properties (contrast, spatial and temporal frequency). In the second, we used red/green gabors in two different conditions: isoluminant (activating preferentially P pathway) and 4% contrast (activating preferentially M pathway). In both experiments, when two stimuli activating preferentially the M pathway were presented in central vision, fusion of both predominated significantly over rivalry. On the other hand, when two stimuli activating preferentially the P pathway were presented, rivalry was significantly higher than fusion. This supports the idea that M pathway is related with fusion and P pathway with rivalry. Moreover, in the M condition fusion decreased significantly with eccentricity, whilst no changes were observed in the P condition. Finally in a P versus M condition, rivalry predominated at all eccentricities, with ocular dominance of M over P stimulus, but fusion decreased significantly with eccentricity. Altogether, these results demonstrate that the information driven by M pathway is modified with eccentricity whilst it is not the case for P pathway. This suggests that the difference in conscious perception between central and peripheral vision is mainly due to a change in M pathway, giving new cues about why conscious perception is modified with eccentricity.