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T. Eysteinsson, G. A. Olafsdottir, R. R. Noadottir, Á. Kristjansson; Interocular Luminance Differences and the Magnocellular and Parvocellular Pathways. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3316. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the relative contribution of the magnocellular (MC) and parvocellular (PC) visual pathways to the effect of intraocular luminance difference (ILD, ,,Fechner‘s Paradox") on the binocular pattern reversal visual evoked potential (VEP).
Pattern reversal visual evoked potentials were recorded with a UTAS E-3000 system from 6 volunteers, with an active skin electrode over the occiput at the midline. Interocular luminance differences were established by placing neutral density filters in front one eye during binocular viewing. Each VEP response was the average of 100 reversals. Stimuli were presented on a high resolution monitor viewed at 1 m distance. The stimuli were checkerboard patterns with an average luminance of 50 cd/m2. A low contrast (20%), achromatic pattern with 4x4 checks, with a reversal rate of 10 Hz was used to evoke MC-dominated VEP. A high contrast (100%), chromatic (red/green) pattern with 16x16 checks, and a reversal rate of 2 Hz was used to evoke a PC-dominated VEP. Neutral density filters placed in front of one eye were used to establish an ILD, with attenuation between 0,5-3,0 log.
Interocular luminance difference (ILD) had a significant effect on the binocular/monocular summation ratio of the VEP primarily driven by the PC pathway (repeated measures ANOVA, F(6,30)= 5,28; p=.016), but not on the MC-dominated ratio. ILD had a significant effect on the amplitude of the PC-dominated VEP (F(6,30)= 5,45; p=.010), but not on the amplitude of the MC-dominated VEP.
The results suggest that the effect of intraocular luminance difference (,,Fechner's paradox") on the binocular visual evoked potential is primarily mediated by the parvocellular visual pathway, with no significant contribution from the magnocellular pathway.
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