To access the data, click or select the words “Appendix 3.” A-wave amplitude was measured from baseline at 3, 8 and 15 msec of the end of the stimulus. The reduction in amplitude is similar at 3 and 8 msec, when no b-wave contribution is present and at 15 msec, which is near the trough. Data are mean± standard error of the mean (SEM), *** p<0.01 (ANOVA followed by Bonferroni’s test).