P300 amplitudes and latencies within anterior (F3, F4, F7, F8, Fz, C3, C4, and Cz) and posterior (P3, P4, Pz, P7, P8, O1, and O2) regions. These regional values were incorporated into the MANCOVA as separate variates and individually tested with univariate ANCOVAs. Age and the total lifetime number of alcohol, cocaine, and opiate dependence were included as covariates in all analyses because they are known to affect P300.
