The amplitude of the P1 component has been associated with increased arousal and attention (Coull, 1998). Studies in high-alcohol-drinking (HAD) and low-alcohol-drinking (LAD) rats from replicate line 2 (HAD-2 and LAD-2) have also shown that HAD-2 rats have increased P1 amplitude compared to LAD-2 rats (Katner et al., 2002). We previously speculated that increased P1 amplitude in HAP-1 mice, compared to LAP-1 mice, could indicate an increased level of arousal or attention in HAP-1 mice (Slawecki et al., 2003). However, this hypothesis is not supported by the fact that alpha/beta EROs, which have been shown to reflect attentional demands (Klimesch et al., 1998), were not different between HAP-1 and LAP-1 mice in the present study. Interestingly, findings from our previous study also suggested that HAP-1 mice showed a significantly higher frontal EEG peak alpha frequency than LAP-1 and HS/Ibg mice (Slawecki et al., 2003). Consistent with the increase in P1 amplitude, these findings were not observed in the parietal cortex. Whether the higher frontal EEG peak alpha frequency played a role in the increase in P1 amplitude in HAP-1 mice remains unclear.
