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Jan Kremers, Maciej W. Stepien, Hendrik P. N. Scholl, Cézar Saito; Cone selective adaptation influences L- and M-cone driven signals in electroretinography and psychophysics, by Kremers, Stepien, Scholl & Saito. Journal of Vision 2003;3(2):3. doi: 10.1167/3.2.3.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the influence of selective adaptation of long (L) and middle (M) wavelength sensitive cones with electroretinography (ERG) and psychophysics, a novel adaptation procedure was developed, which comprises a selective and quantifiable change in the state of adaptation in the different cone types. One adaptation condition was used as a reference. In four additional conditions, the M-cones or the L-cones were selectively adapted, so that they absorbed either more or less photons. At each of these five states of adaptation, the ERG response amplitudes to 30Hz L- and to M-cone selective stimuli were measured. Furthermore, the psychophysical sensitivities to L- and M-cone selective stimuli were measured at different temporal frequencies. In subjects with normal color vision, adaptation can have a strong influence on the L- and M-cone driven response amplitudes in the ERG and on both the L- and the M-cone sensitivities in the psychophysical luminance channel. As a result, the L- to M-cone ERG and psychophysical ratios can change dramatically at the different states of adaptation. The cone sensitivity thresholds and the L- to M-cone sensitivity ratio in the psychophysical chromatic channel are about unity at all states of adaptation, suggesting the presence of a compensatory mechanism. In dichromats, the responses and sensitivities to stimulation of the absent cone type were generally small at all states of adaptation. But, with reddish backgrounds residual ERG responses and residual psychophysical sensitivities were observed, indicating the presence of either a robust rod driven signal or an additional adaptation mechanisms that are not cone driven and that have not been described before.
The outputs of the red, green and blue phosphors of the monitor, the total output of the monitor, total retinal illuminance during electroretinography and the psychophysical experiments, the large field (10°) CIE coordinates and the excitations in the four photoreceptor types during the ERG measurements at all adaptation conditions. The total excitations in the photoreceptors during the psychophysical measurements were approximately 7 times smaller than those in the ERG recordings.
The rod contrasts during ERG recordings at L- and M-cone selective stimulation and at different states of adaptation. The rod contrast is substantially larger at M-cone selective stimulation than at L-cone selective stimulation. L-cones were modulated in phase and M-cones in counter phase (indicated by a negative sign of the M-cone contrast) relative to the modulation of the red phosphor. The rods were modulated in counter phase with L-cones and in phase with M-cones.
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