A Time-Warping method for not-so-steady-state evoked-potentials

Electroencephalographic (EEG) responses that are locked to periodic events can be identified in the frequency spectrum of the EEG signal as Steady-State Evoked-Potentials (SS-EPs). By doing so, it is easy to measure the amplitude of the response and to differentiate it from other neural processes occurring at distinct frequencies. However, many repetitive ecological activities such as the synchronization of finger tapping to a musical beat are not strictly isochronous. Actually, the period of those activities fluctuates along time. This results in a spectral leakage of the SS-EPs, rendering it difficult to isolate and measure in the EEG spectrum. Here, we introduce a new method to concentrate the EEG responses of nearly isochronous activities in the frequency domain