Abstract
We studied the spatial arrangement of L- and M-cone driven electroretinograms (ERGs) reflecting the activity of magno- and parvocellular pathways. L- and M-cone isolating sine wave stimuli were created with a four primary LED stimulator using triple silent substitution paradigms. Temporal frequencies were 8 and 12 Hz, to reflect cone opponent activity, and 30, 36 and 48 Hz to reflect luminance activity. The responses were measured for full-field stimuli and for different circular and annular stimuli. The ERG data confirm the presence of two different mechanisms at intermediate and high temporal frequencies. The responses measured at high temporal frequencies strongly depended upon spatial stimulus configuration. In the full-field conditions, the L-cone driven responses were substantially larger than the full-field M-cone driven responses and also than the L-cone driven responses with smaller stimuli. The M-cone driven responses at full-field and with 70° diameter stimuli displayed similar amplitudes. The L- and M-cone driven responses measured at 8 and 12 Hz were of similar amplitude and approximately in counter-phase. The amplitudes were constant for most stimulus configurations. The results indicate that, when the ERG reflects luminance activity, it is positively correlated with stimulus size. Beyond 35° retinal eccentricity, the retina mainly contains L-cones. Small stimuli are sufficient to obtain maximal ERGs at low temporal frequencies where the ERGs are also sensitive to cone-opponent processing.
Highlights
There is increasing evidence that flicker electroretinograms (ERGs) to stimuli containing luminance and red-green chromatic information are governed by two mechanisms that probablyPLOS ONE | DOI:10.1371/journal.pone.0121218 March 18, 2015Spatial Distribution of L- and M-Cone ERGs and analysis, decision to publish, or preparation of the manuscript
In previous experiments [17], we found that the response amplitudes of S-cone- and rod-driven responses were substantially smaller than M-cone driven responses even if the S- cone- and rod-contrasts were substantially higher than the M-cone contrast
Experiment 1 In Experiment 1, the L- and M-cone driven ERGs were measured at five temporal frequencies with the 14 spatial stimulus configurations, from four subjects
Summary
The aim of the present study was to examine in detail the spatial distribution of L- and Mcone driven responses in ERGs reflecting activity of the two post-receptoral pathways while using the triple silent substitution paradigm and including conditions wherein far peripheral cones were stimulated so L- and M-cone driven ERG signals can be studied for the complete retina
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