Fig. 4.

Convolution with complex Morlet wavelet to measure amplitude and phase of oscillations across time for each frequency. The EEG signal is convolved with a complex Morlet wavelet using the dot product (element-by-element multiplication and summing the products), creating a complex number. This process is repeated across the signal by shifting the wavelet across the signal, yielding a time series of complex numbers. These complex numbers contain information about the amplitude (M) and phase ($\varphi$) of the oscillations for each time point. This process can be repeated with wavelets of different characteristics like different frequencies to capture the amplitude and phase information of the EEG signal across time and frequencies.