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David H. Brainard, Jack B. Calderone, Alexander K. Nugent, Gerald H. Jacobs; Flicker ERG Responses to Stimuli Parametrically Modulated in Color Space. Invest. Ophthalmol. Vis. Sci. 1999;40(12):2840-2847.
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purpose. To develop methods for recording human electroretinogram (ERG)
responses to stimuli that modulate different classes of cones in
various ratios, to draw inferences about the combination of cone
signals in early retinal processing.
methods. Subjects viewed large-field temporal modulations presented on a
computer-controlled color monitor. A flicker photometric paradigm was
used to equate the ERG response elicited by interleaved reference and
test modulations. Test modulations were chosen to stimulate the L- and
M-cones in various ratios. Results were obtained from color-normal
subjects, dichromats, and an anomalous trichromat.
results. Reliable signals were obtained from all subjects to both L- and
M-cone–isolating modulations and to intermediate modulations. Signals
from color-defective subjects were predominantly determined by the
modulation seen by only one cone type, whereas signals from
color-normal subjects were sensitive to both L- and M-cone modulations.
For most color-normal subjects, the recorded signal was a linear
function of the contrasts seen by the L- and M-cones. There was
individual variability in how strongly each cone type contributed to
the overall signal.
conclusions. It is straightforward to record signals to color modulations presented
on a CRT by using the flicker photometric ERG. For most observers,
signals from L- and M-cones combine linearly. The relative contribution
of the two cone classes varies across observers, probably because of
individual differences in the relative numbers of L- and
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