Purchase this article with an account.
E. V. Vukmanic, P. J. DeMarco; Analysis of Human ERG Responses to Equal Contrast Positive and Negative Flashes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2173.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The electroretinogram (ERG) is a retinal evoked potential which reflects interactions between photoreceptors, depolarizing and hyperpolarizing bipolar cells, and contributions from the inner-retina. The balance of activity from these various retinal networks reflected by the ERG in influenced both by background luminance and flash polarity. Previous studies have shown a response bias in the ERG for postive versus negative flashes. We further investigated this bias by analyzing the ERG response to equal contrast positive and negative flashes elicited from a standard adapting background.
ERG responses were recorded from human subjects using DTL fiber electrodes and standard recording procedures. Stimuli were positive and negative square-wave flashes, which elicit ERG b- and d-wave responses, respectively. Flashes were initiated from a standard background luminance of 175 cd/m2. Flash duration was 100 ms and flash contrast was varied +/- 600% for initial measurements. Mean contrast-response functions were derived for the b-wave and d-wave responses and fit with log-linear curves. In subsequent experiments, flash duration was varied from 5-250 ms to examine temporal interactions between networks that generate the b-wave and d-wave.
Analysis of the contrast response functions for the b- and d-wave revealed a steeper slope for the d-wave response, and the amplitude of the d-wave was slightly larger than the b-wave response to equal contrast flashes. The duration-response series revealed significant, and asymmetric, interactions between the b-wave and d-wave generators.
While previous studies have shown a bias in the ERG response toward positive flashes, here we find slightly higher sensitivity to negative flashes. Varying the duration of positive and negative flashes provides insight into the nonlinear summation of activity from ON- and OFF-retinal pathways at the level of the ERG. The use of opposite polarity stimuli expands the utility of the ERG as an analysis tool for the assessing the function, and integrity, of inner-retinal networks.
This PDF is available to Subscribers Only