Wavelet Transform in the analysis of the frequency composition of evoked potentials

This technical paper deals with the application of the Wavelet Transform to the study of evoked potentials. In particular, Wavelet Transform gives an optimal time-dependent frequency decomposition of the evoked responses, something difficult to be achieved with previous methods such as the Fourier Transform. We describe in detail the protocol for implementing the decomposition based on the Wavelet Transform and apply it to two different types of evoked potentials. In the first case we study alpha responses in pattern visual evoked potentials and in the second case, we study gamma responses to bimodal (auditory and visual) stimulation. Although in this study we focus on methodological issues, we briefly discuss physiological implications of the present time-frequency analysis. Furthermore, we show examples of the better performance of the wavelet decomposition in comparison with Fourier-based methods.