Event-related oscillations (EROs) are embedded in continuous scalp-recorded EEG activity acquired during cognitive tasks. A substantial literature indicates that some ERP features arise from changes in dynamics of ongoing EEG rhythms/oscillations of different frequency bands that reflect ongoing sensory and/or cognitive processes (see Figure 23.1 (bottom) for illustration of EROs during P3 response to targets in oddball task). While EROs may be partitioned into the same frequency bands as spontaneous resting EEG (e.g., delta, theta, alpha, beta, gamma), they are functionally different from spontaneous rhythms (Klimesch et al., 2007). Specific frequency oscillatory responses have been attributed to underlie various cognitive processes, as follows: delta: signal detection and decision making; theta: conscious awareness, recognition memory, and episodic retrieval; slow alpha: attribution of attentional resources; fast alpha: semantic memory and stimulus processing; beta and gamma: sensory integrative processes (Basar, 1999). Newer time by frequency transformations such as S-transform (Stockwell et al., 1996) or other wavelet-type analyses provide a time-based decomposition of the EEG signal associated with an event (van Vugt et al., 2007), and generate amplitude/power measures and phase information. EROs influence
