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Jonathan Gotzmann, Ioannis Dimopoulos, Yves Sauve; Contribution of oscillatory potentials to the ON- and OFF- photopic electroretinogram (ERG) in human. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3510.
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© ARVO (1962-2015); The Authors (2016-present)
To describe changes in the time, power and frequency domain of the ON (b-wave) and OFF (d-wave) oscillatory potential (OP) components of the human ERG.
Full-field ERG ON- and OFF- responses were recorded from the eyes of 9 healthy subjects (aged 20-49 years) with dilated pupils using DTL fiber electrodes and an Espion e2 system (Diagnosys LLC; 0.3-300Hz bandpass), with 30 cd.m-2 background adaptation and stimulus intensity of 2.75 log cd.m-2. Light stimulus duration was increased in a stepwise fashion from 10ms to 800ms in eight steps. A total of 20 traces were averaged at each step. Oscillatory potentials of the b- and d-waves were analyzed with trough-to-peak measurement and also Fast-Fourier-Transform (FFT) to determine the dominant power (µV2) and frequency (Hz).
Four distinct OP peaks were consistently phase-locked to the ON response (ON-OPs). Power of the ON-OPs peaked at shorter duration stimuli (<20ms) followed by an exponential decay with longer durations. The dominant frequency remained ~140Hz for all durations. The ON-OPs (OP1-4) timing also remained constant for all stimulus durations (peaks at t=19ms, t=25ms, t=32ms and t=40ms after stimulus onset) with amplitudes remaining constant after a stimuli durations >20ms. For the OFF phase, two distinct OPs were distinguished. The OFF-OPs (OP1-2) timing remained constant for stimuli durations >100ms (peaks at t=19ms and t=26ms after stimulus offset). The dominant power of the OFF-OPs increased with stimulus duration, reaching a plateau after a 500ms duration. The dominant frequency remained ~120Hz for all durations At a short duration stimulus of 10ms OFF-OP1 significantly contributed to ON-OP3, while with a stimulus duration of 20ms, OFF-OP1 contributed significantly to ON-OP4. The OP peaks measured from a filtered trace precede the peaks found in the raw trace by 1-2ms for both the ON and OFF response.
Our results imply that OPs to short duration stimuli, as used in the clinic, represent a mixed contribution from both the ON and OFF retina circuitry. Selective testing of these two distinct circuits would be optimally achieved using longer duration stimuli such as 200 msec, which allows a clear separation of both response types without the discomfort of subject exposure to longer duration stimuli.
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