Grand average waveforms of CNV and EMG between S1 and S2. Means and standard deviations of mean amplitude for every 100-ms period were overlapped on the waveforms. Thin line: initial set; thick line: second set. The * and † indicate a significant increase from baseline in the initial set and second set, respectively. ***Indicates a significant difference in late CNV amplitude between the initial and second sets in the young.