MEP amplitudes during the smooth vs. grating trials in Experiment II. A. Examples of task-related differential modulation in MEP amplitude under the two trial types in the left and right resting hands in typical young (right-handed female, aged 25 years) and older (right-handed female, aged 77 years) participants. Each trace is an average of 12 responses. B. Comparison of mean MEP log-amplitudes in the resting hand when the task hand was performing the two trial types (grating/smooth). The gray area represents the mean and standard error of the baseline resting MEP log-amplitudes in the young adult and senior age groups. Each bar represents the mean of individual values computed for the resting hand when the task hand performed each trial type (grating/smooth) for all young adult (N = 16) and senior participants (N = 16). Note the main effect of trial type in the task hand was significant for the overall variations in MEP log-amplitude in the resting hand (F1,30 = 16.98, p < 0.001, partial eta squared = 0.36), reflecting enhanced MEP amplitudes in the resting hand when the other hand was doing the grating trials vs. the smooth trials (Bonferroni's p = 0.001) or resting baseline values (Bonferroni's p < 0.001), which were not different from one another (Bonferroni's p = 1.0).