Advance in ERG Analysis: From Peak Time and Amplitude to Frequency, Power, and Energy
Figure 2
Continuous wavelet transform (CWT) analysis of the ERGs that were shown at Figure 1. All scalograms were normalized to their maximal energy values, and the color-coding (see colorbar) indicates low (blue), moderate (green), and high (red) energy values. The associated ERGs are shown at the bottom of each scalogram. The a-wave, b-wave, and oscillatory potentials are indicated as “a,” “b,” and “OPs,” respectively. (a) CWT of the composite ERG showing the energy (as per colorbar) and the temporal location of the 3 typical frequency components that were previously identified in the Fourier domain (~30 Hz: a- and b-waves contribution, white arrow; ~75 Hz and ~150 Hz: oscillatory potentials (OPs) contribution, gray arrows). (b) CWT of the ERG that had enhanced OPs [increased ~75 Hz and ~150 Hz energy; thick gray arrows]. (c) CWT of the contaminated ERG showing the 3 standard components (see arrows, same color-coding as previous panels) and a strip of moderate energy localized at 60 Hz for the whole duration of the signal (60-cycle interference contribution). (d) CWT of the second contaminated ERG also evidencing the 3 characteristic frequency components of the ERG and several transient, interference-related, patches of energy (60-cycle harmonics contribution).
