Current source density analysis of linear and non‐linear components of the primate electroretinogram.

Abstract

SUMMARY1. Wte have used the method of current source density analysis to locate the generators of harmonic electroretinogram (ERG) responses to contrast-modulated pattern and uniform-field stimuli in the primate retina.2. Sinusoidal steady-state analysis was used, with a stimulus temporal frequency of 8 Hz. Fundamental and second-harmonic response components were measured for the uniform-field response. The second harmonic of the average of contrast-reversal pattern responses obtained at a series of spatial phases was also determined in the same experiments. In addition, retinal tissue resistance was measured. All of these measurements were obtained at a series of equally spaced depths in the retina.3. Retinal resistivity was not observed to vary systematically with depth. In addition, any plausible undetected inhomogeneities of resistivity with depth were found to slightly affect the relative magnitudes of estimated current sources and sinks, but to have little effect on their localization.4. In a given penetration, the phase lag of each harmonic component was relatively constant with depth in most cases; however the magnitude of this phase lag sometimes varied in different penetrations. To compare data from different penetrations, the constant phase lag for each harmonic was estimated, and the response data phase-shifted so as to bring all data into a standard (cosine) phase.5. The resulting current source density analyses were found to be quite consistent in overall form for different penetrations and in different animals. These data were averaged to obtain a final estimate of the depth profiles for generators of different ERG components.6. The uniform-field fundamental response was found to have a predominant source-sink pair in the distal half of the retina (receptor layer to outer plexiform layer). The pattern (second-harmonic) response generators had a quite different depth profile, consisting mainly of a source-sink pair in the proximal 20% of the retina (encompassing the nerve fibre layer to the middle of the inner plexiform layer).

Pattern electroretinogram association with spectral domain-OCT structural measurements in glaucoma

“…[1][2][3][4][5] The PERG stimulus isolates the ganglion cell response by using a reversing (ie, contrast modulated) checkerboard or grating pattern that carries no change in overall luminance over time (space-averaged luminance). If the PERG response is measuring retinal ganglion cell activity, it should be associated with the number of retinal ganglion cells.…”

Presence and further development of retinal dysfunction after 3-year follow up in IDDM patients without angiographically documented vasculopathy

“…This consists mainly of neural tissue, the activity of which is revealed by ERG techniques. With focal ERG, it is possible to provide information from the central retina, i.e., the macula, which has higher neuronal density than peripheral retina [32][33][34]. Some papers have shown that the pattern and focal ERG can become abnormal in diabetes before the onset of any visible vasculopathy [ [23][24][25][26][27].…”

“…Some papers have shown that the pattern and focal ERG can become abnormal in diabetes before the onset of any visible vasculopathy [ [23][24][25][26][27]. Experimental [32,42] and clinical [32][33][34] studies showed that 1F, 2F, and 2P components of a steady-state focal ERG arise from different retinal neurons. Using this technique, which was first performed in different retinal disorders [35], we have found a gradual loss of postreceptor neuronal function as a result of diabetes, despite intensive insulin therapy and good metabolic control as reported by mean HbAlc levels during the 3-year follow-up.…”

“…FERG analysis yields a first (1F) and second (2F) component; PERG only has a second component (2P) [31][32][33][34]. 1F originates in the photoreceptor layer, whereas 2F and 2P represent subsets of generators in the inner retina.…”

“…1F originates in the photoreceptor layer, whereas 2F and 2P represent subsets of generators in the inner retina. 2P, but not 2F, is correlated to ganglioncell function [34,35]. A recent study has provided evidence that the 2F component, unlike 2R has multiple generators in the middle-to-inner retina and that 2F and 2P may originate, at least in part, from the same retinal layer(s) [36].…”