Our previous studies in B6 and D2 mice showed that the mouse P3 and N1 amplitudes were significantly larger in response to the rare tones, compared to the standard tones (Ehlers and Somes, 2002). Our present findings showed that ERO energy was not significantly greater in response to the rare tones, compared to the standard tones. However, PLI values in the 0–50 ms and 50–350 ms time window were significantly higher in rare tones, compared to standard tones. These findings suggest that an increase in phase locking and reduction in phase variability could be responsible for the larger P3 and N1 ERP amplitudes in response to the rare tones.
