The phase-locking index, or PLI, reflects the degree of phase variation over trials and may have a significant effect on the amplitudes and latencies of ERP components (Gruber et al., 2005; Sauseng et al., 2007; Schack and Klimesch, 2002). PLI is similar to other measures of phase variation including ‘inter-trial coherence’ (Makeig et al., 2002), ‘phase-locking factor’ (Tallon-Baudry et al., 1996), and ‘phase-locking value’ (Rodriguez et al., 1999). Findings from the present study suggest that the decrease in P3 amplitudes in P rats is associated with a decrease in delta and alpha/beta band PLI. The mechanisms mediating the lower evoked delta and alpha/beta phase locking in adult P rats and their potential role increasing the risk for ethanol dependence are not clearly understood. Studies in humans have demonstrated that delta and theta EROs are the primary contributors to the human P3 ERP component (Basar et al., 1999; Basar-Eroglu et al., 1992; Demiralp et al., 2001; Karakas et al., 2000; Schurmann et al., 2001; Stampfer and Basar, 1985; Yordanova and Kolev, 1996). However, the primary contributors to the P3 ERP component
