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Jan J Kremers, Deepak Bhatt; ERG responses to heterochromatic stimuli that reflect L- and M-cone inputs and their additive or opponent interactions. Invest. Ophthalmol. Vis. Sci. 2016;57(12):No Pagination Specified. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
ERG responses to combined luminance and chromatic modulation can reveal the input strengths from the different cone types and can reflect the activities of post-receptoral luminance and chromatic channels. In the present studies the ERG responses to counterphase modulation of red and green stimuli were measured to quantify the receptoral and post-receptoral signals in normal trichromats and in subjects with color vision deficiencies.
98 subjects participated in this study. Their color vision was established with the Nagel anomaloscope: 38 were deuteranopes (D), 16 deuteranomalous trichromats (DA), 13 protanopes (P), 19 protanomalous trichromats and 22 normal trichromats. ERG responses were measured to counterphase modulation of the output of red and green LEDs. Different conditions were used varying from 100% red 0% green, via 50% red and 50% green, to 0% red, 100% green modulation. The sum of red and green contrasts always amounted to 100%. The measurements were performed at 12 Hz and 36 Hz temporal frequencies. Fourier transforms were used to extract response amplitudes and phases.
The 1st harmonic responses to 36 Hz stimuli and the 2nd harmonic responses to 12 Hz stimuli were mainly determined by an additive interaction between L- and M-cone driven signals, suggesting the reflection of a luminance signal. The ratio of L- to M-cone input strengths were largest in D and smallest in P, with a large overlap between D, DA and T. The mean ratios in PA were slightly larger than for P but with much larger inter-individual variability. The 1st harmonic responses to 12 Hz stimuli reflect mixtures of luminance and cone L-M-cone opponent (chromatic) signals. The chromatic signals were larger in T compared to the color deficient subjects.
It is possible to quantify the strengths of cone inputs and of signals of the luminance and chromatic channels, using objective ERG methods.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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