The first component clearly discernible in Fig. 13.4 is the small negative blip that occurs between 150 and 200 msec poststimulus onset at the Cz site. This activity probably represents the occurrence of the frequently reported N1 component (Hillyard, Hink, Schwent, & Picton, 1973). N I is followed immediately by a large positive complex, P2, which peaks at about 270 msec at Cz and Pz, but not Oz. A negative going (although negative going, this component does not in many cases cross the baseline into the negative region) component, N2, which is visible at the same sites as P2, peaks at between 350 and 450 msec. (Note that N2 is quite attenuated at Pz-possibly by the large ensuing positive component.) P3 can be seen as the large and broad positive component, which follows N2 at the Cz and Pz sites. P3 can also be seen in the Oz record where, as with Pz, it is the largest ERP component. P3 spans the epoch between 400 and 800 msec at all sites.