MEP amplitudes during 2-D pattern vs. roughness discrimination. A. Examples of task-related differential modulation in MEP amplitude under the two task conditions (left-handed male, aged 26 years, 50% MEP facilitation pattern/roughness). Each trace is an average of 16 responses. B. Scatter plot showing the relative distribution of MEP amplitudes in the two tasks for all participants. Note the tendency for MEP responses to be larger in the pattern discrimination task. C. Comparison of mean MEP amplitudes in the two task conditions (pattern and roughness discrimination). Each bar represents the mean of individual values computed under each task condition for all participants (n = 18). Note that the main effect of task condition was significant for the overall variations in MEP amplitude (p < 0.05). D. Scatter plot showing the distribution of individual MEP amplitude task ratios (% MEPpattern/MEProughnes) against corresponding performance task ratios. Note that the two variables are not significantly related to one another.