Generally, EROs have been analyzed using traditional EEG frequency band limits: delta (1-3 Hz); theta (4-7 Hz); alpha (8-12 Hz); beta (13-28 Hz); and gamma (>29 Hz). EROs have been increasingly used to study the neural components of brain function [Klimesch et al., 1997b, 2001; Schurmann et al., 1997; Basar et al., 2000, 2001a]. Different frequency rhythms of oscillatory responses are attributed to particular cognitive processes. For instance, delta EROs are attributed to signal evaluation and decision-making [Basar et al., 1999; Schurmann et al., 2001], whereas theta rhythms appear to mediate conscious awareness, attention, recognition memory, frontal inhibitory control, and episodic retrieval [Klimesch et al., 1994, 2001; Doppelmayr et al., 1998; Gevins et al., 1998; Karakas et al., 2000a,b; Basar et al., 2001b]. The P300 component is composed of a superposition of different frequency bands, predominantly theta and delta, with the theta having a more frontal topography, while the delta maximum has a more parietal location.
