In contrast, the analysis of N2 sink at posterior sites did not reveal any significant effects involving group. Apart from another highly significant task main effect, confirming the presence of N2 sink for syllables but not tones, significant effects of hemisphere and task x hemisphere originated from a left-greater-than-right N2 asymmetry for the phonetic task (LH vs. RH; for syllables, −0.63 ±1.03 vs. −0.25 ±0.93) but not for tones (0.26 ±1.17 vs. 0.41 ±1.10). However, a highly significant task x hemisphere x site x group interaction, F[2,88] = 5.96, p = .005, ε = 0.91, could be traced to a greater phonetic N2 sink for patients compared to controls at site P7 (−0.89 ±0.92 vs. −0.27 ±1.09; simple group main effect, F[1,44] = 6.13, p = .02; Figure 4). A response mode main effect resulted from a greater N2 sink for silent count compared to left press (−0.14 ±1.10 vs. 0.03 ±1.18; F[1,44] = 5.94, p = .02), while the contrasts of these response modes to right press (−0.05 ±1.12) were not significantly different.
