Electroretinogram and OP component modelling.

<p>(A) Schematic representation of a trace ERG elicited by a control dark-adapted mouse retina in response to a light stimulus of 25 cd˖s/m² showing major characteristic components of the scotopic ERG. The ERG has 3 components, the a-wave, b-wave, and the oscillatory potentials (OPs). The OPs are the ascending waves between the a- and b-wave. Signal conditioning of OPs from the ERG trace waveform. (B) A digital subtraction of photoreceptor contribution (dashed line) was performed by a mathematical fitting and subtraction of the a-wave from the initial ERG (solid line). (C) The ERG waveform following complete a-wave digital subtraction. (D) The final waveform was passed through a fifth order Butterworth transformation (65–300 Hz) to remove any low or high frequency noise resulting in the final “OP extracted waveform” (solid line). Following waveform extraction, measurements of OP implicit time (ms) and amplitude (μV) were taken for OP2-5. Amplitude of each OP was defined as the difference between the trough and the peak immediately preceding it. Initial implicit time was defined as the time from stimulus to the onset of the OP2 peak. Interpeak distance was the measurement of time (ms) between adjacent peaks (E) Measurement of individual OP features in the frequency-domain. A fast Fourier transform (FFT) was applied to the extracted OP waveform and gave a single-sided smoothed frequency power spectrum (dotted line). The single-sided smoothed frequency power spectrum was fitted to a two-term Gaussian envelope (solid line) and measurements of peak power (P_peak), peak frequency (F_peak) and total energy (waveform integration) were taken.