right temporal lobe sites (T7/8) in either silent-counting or button-pressing tasks. In contrast, Salisbury et al.27 found that overall P3 amplitude was smaller and P3 asymmetry was reduced when healthy controls (n = 46) responded with the right finger as compared to silent counting of oddball tones. Using a reaction-time procedure to correct for contamination by MRPs restored the P3 asymmetry in the button-pressing task to the normal level, and the MRP-corrected data for 36 healthy men in this study differed significantly in P3 asymmetry when compared to schizophrenic patients in their prior study. Moreover, while a frontal P3 asymmetry was observed for right button presses to targets (Go-P3) in a follow-up study,28 this asymmetry was absent in healthy adults (n = 34) when response requirements were reversed (i.e., button press to nontargets; NoGo-P3). The authors also observed a frontally reduced P3 amplitude in the Go condition when compared to NoGo and silent-counting conditions, resulting in an anterior shift of the P3 topography (i.e., NoGo-anteriorization), which can be interpreted as a superposition of an anterior negativity associated with a motor response. However, no comparison was made of ERPs for right versus left hand responses in healthy adults, or for silent-counting
