Purchase this article with an account.
M Fresina, B Falsini, C Bellusci, A Duca, F Quagliano, S Fabbri, EC Campos; >Photopic Negative Response of the Human Focal ERG: Luminance versus Chromatic Modulation . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1799.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the characteristics of human photopic negative response (PhNR), an ERG component originating from inner retina, elicited by luminance (L) and chromatic equiluminant (C-Eq) modulation. Methods: In eleven normal volunteers (mean age: 28, range: 26-32 years), focal ERGs were recorded in response to square-wave, counterphase modulation (2 Hz) of two large (5° x 15°) bars (mean luminance: 50 cd/m2) presented to the macular region (10° x 15°) on a light-adapting background. Stimuli were modulated either in pure L (yellow-black) or C-Eq (red-green) condition. Equiluminance was established psychophysically for every subject from the minimum flicker perception when the red-green stimuli were modulated at 15 Hz. Results: Both L and C-Eq stimuli elicited a focal ERG waveform consisting of a positive component (PC) followed by a slower negative potential (PhNR). Mean (± SE) implicit times of PC and PhNR evoked by C-Eq stimuli were 70 (± 2) and 119 (± 3) ms, slower (p < 0.01) than those (60 ± 1 and 106 ± 2 ms, respectively) evoked by L stimuli. Mean amplitude of PC evoked by C-Eq stimuli (0.7 ± 0.1 µV) was smaller (p < 0.05) than that evoked L stimuli (1.2 ± 0.2 µV). Mean PhNR amplitudes evoked by L (0.7 ± 0.1) and C-Eq (0.9 ± 0.1) stimuli a did not differ significantly. Mean PhNR/PC amplitude ratio was greater (p < 0.01) for the responses to C-Eq (1.4 ± 0.2) than for those to L stimuli (0.6 ± 0.1). Conclusion: The properties of the PhNR to C-Eq stimuli, compared to that elicited by L stimuli, are consistent with a contribution of retinal generators sensitive to chromatic modulation (i.e. parvo-cellular ganglion cells), and support the clinical use of both responses as functional probes of magno- and parvo-cellular retinal subpopulations.
This PDF is available to Subscribers Only