Purchase this article with an account.
J Jason McAnany, Jason C Park, Dingcai Cao; Rod- and cone-isolated flicker electroretinograms and their response summation characteristics. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3509.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To define the amplitude and phase characteristics of rod- and cone-isolated flicker electroretinograms (ERGs) and to determine how rod and cone responses summate to generate the non-receptor-isolated flicker ERG.
Following 30 minutes of dark-adaptation, full-field ERGs were obtained from four normally-sighted subjects (ages 25 to 36 years) using a 4-primary LED-based ganzfeld photostimulator and standard ERG recording techniques. The 4 primaries were either modulated sinusoidally in phase to achieve simultaneous rod and cone activation (ERGROD+CONE; non-receptor-isolated) or in different phases to achieve rod-isolated (ERGROD) and cone-isolated (ERGCONE) responses by means of triple silent substitution. ERGs were measured at two mean luminance levels (2.4 cd/m2 and 24 cd/m2) and four temporal frequencies (2, 4, 8, and 15 Hz). The amplitude and phase of the fundamental response component for each condition were derived by Fourier analysis.
At both luminance levels, response phase decreased approximately linearly as stimulus temporal frequency increased for all three paradigms, with the ERGROD and ERGCONE phases differing by approximately 180 deg at all frequencies. The relationship between response amplitude and stimulus frequency was complex and depended on the paradigm and mean luminance level. Specifically, ERGROD amplitude decreased as stimulus frequency increased for both luminance levels, whereas ERGCONE amplitude depended on mean luminance: at 2.4 cd/m2, ERGCONE amplitude decreased as stimulus frequency increased; at 24 cd/m2, ERGCONE amplitude decreased from 2 to 8 Hz and increased from 8 to 15 Hz. There were substantial differences under the ERGROD+CONE paradigm at the two luminance levels: the relationship between response amplitude and stimulus frequency was weakly band-pass at 2.4 cd/m2 and was U shaped at 24 cd/m2, due to ERGROD and ERGCONE responses having similar amplitudes and opposite phases at 4 and 8 Hz.
The pattern of responses for the combined rod and cone paradigm at both luminance levels can be accounted for by the summation of signals arising from the rod and cone pathways that have opposite response phase. Destructive interference between the rod and cone pathway signals was greatest for conditions that generated similar rod and cone ERG amplitudes, resulting in decreased amplitude under the combined rod and cone condition.
This PDF is available to Subscribers Only