2-D representation of the overall COG movement (cm) across three sessions for each participant and both hemispheres. First session is demarcated by a larger symbol. The COG was calculated using mean MEP amplitudes shown for active sites only. Larger numbers on the x-coordinate and y-coordinates represent lateral and anterior scalp stimulus locations, respectively. Note that locations are unadjusted for the repeated measures on hemisphere and session. Each grid location represents one centimeter. The hatched circle represents the COG centroid location for a single subject in one hemisphere. All centroids are displayed in Figure 4.