Figure 8.

Topographic distribution of spectral power in the alpha band (8–12 Hz, upper panel) and in the beta band (20–30 Hz, lower panel). In the upper panel, the distributions of the alpha (8–12 Hz) power changes during an active period between 0.2 and 0.4 s after stimulus relative to the baseline period (−0.4 to −0.2 s) are plotted for the left (first column) and right (second column) index finger stimulation conditions. For each stimulation condition, statistical significance of the power change relative to baseline was evaluated by using a cluster-based permutation test (N = 29, 1,000 permutations, cluster-defining threshold p < 0.05, α = 0.05). In addition, the difference in the alpha power for the active period between left and right stimulation conditions, as well as the difference in baseline alpha activity between conditions, was also statistically tested for significance (N = 29, cluster-based permutation test, 1,000 runs, cluster-defining threshold p < 0.05, α = 0.05). Channels associated with significant clusters are indicated by asterisks. In the lower panel, the same analyses were applied as the upper panel but for oscillatory powers in the beta band (20–30 Hz). All plots are obtained for planar gradiometers.