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G. S. Gilmour, B. Dornstauder, D. Bartel, F. P. Gaillard, Y. Sauve; Analysis of the ERG Oscillatory Potentials in the Cone-Rich Nile Grass Rat. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1069.
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© ARVO (1962-2015); The Authors (2016-present)
The Nile rat (Arvicanthis niloticus) is a diurnal rodent with a cone-rich retina. As an expansion on our previous work in characterizing the visual system of the Nile rat, we have analyzed the electroretinogram (ERG) oscillatory potentials (OPs).
Nile rats were tested using dark- and light-adapted ERGs. Analysis of the data was done by direct measurement of peak-to-trough amplitude (using 60-300Hz bandpass). In addition, wavelet analysis was performed using a continuous wavelet transform with a complex Morlet wavelet over a frequency range of 50-300Hz (Forte et al., 2008, J Neurosci Methods 169:191-200). Peak OPs amplitude was determined with a peak-finding algorithm on the coefficients matrix of the wavelet transform, and the time and frequency positions of the maxima were recorded. These data were compared with OP data obtained from humans.
Both dark- and light-adapted OP peak to trough amplitudes were increased as a function of stimulus intensity, reaching maximal values that exceeded those recorded in humans. In both Nile rats and humans, OP maximal amplitudes were higher under dark- compared to light-adaptation. Wavelet analysis confirmed the increase in OP amplitude as a function of stimulus intensity for all species. Furthermore, wavelet analysis revealed that peak OP frequencies were higher under dark- than light-adaptation, in both Nile rats and humans. Another similarity between both species was the lack of any discernable relationship between OP peak frequency and stimulus intensity; this was in contrast with rat data (Forte et al., 2008). However, peak OP time varied with flash intensity. This relationship was species dependent: in human there was an increase in OP implicit time at intermediate intensities, while there was a monotonic decrease in both Nile rats and rats.
OP analysis in Nile rats reveals features that are in-between humans and rats. The larger OP amplitudes in Nile rats might provide a better experimental model to assess modulation of the inner retina due to experimental retinopathies.
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