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N. Tanimoto, M. W. Seeliger; From Flash to Flicker: Assessing Factors Determining the Steady-State Responses in Rod Flicker Electroretinograms. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1299.
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To investigate the factors leading to the attenuation of rod flicker responses during the transition from single flash to steady-state.
For this work, functionally normal wild-type mice (C57Bl/6) were examined with Ganzfeld electroretinography (ERG; Multiliner Vision, VIASYS, Germany). In a first experiment, a series of scotopic flicker ERGs with dim flashes of 10 mcd*s/m2, only visible to the rod system, and flash frequencies ranging from 0.5 to 30 Hz, was recorded under standard conditions. In a second experiment, traces of 1 s length with repetitive single flashes, mimicking the above rod flicker but having a defined onset, were obtained. This way, it was possible to assess the development of steady-state responses (towards the end of each trace) from the single flash response (at the beginning of stimulation). In addition, the previous experiments were repeated on a static background (during the standard recording) or with a light step (during the second experiment). The study was performed in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Visual Research.
The amplitudes of the standard flicker declined with increasing stimulus frequencies until they vanished at ~30 Hz. Static backgrounds further decreased response amplitudes. The second experiment allowed to assess the reason for this decline. Whenever either the stimulus frequency became so high that the amplitude was not back to the initial value at the onset of the subsequent response, or a background was turned on, the baseline became and remained elevated, reducing the dynamic range for the following response and resulting in a decreased amplitude. With increasing flicker frequencies, the dynamic range became smaller as the baseline became more and more elevated. At about 30 Hz, this led to a step response, i.e. a continuously high baseline directly after the first stimulus with no remaining dynamic range.
The factors leading to the attenuation of rod flicker responses during the transition from single flash to steady-state were described.
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