Topographic distribution of EEG power during REM sleep.

<p>Average values were normalized by total power, colour coded, plotted at the corresponding position on the planar projection of the scalp surface, and interpolated (biharmonic spline) between electrodes. The maps are based on the 19 unipolar EEG derivations of the international 10–20 system with averaged mastoid reference, and on 10 additional derivations, positioned in both hemispheres over the left <i>individual</i> optimal site of transcranial magnetic stimulation stimulation and in each orthogonal direction at a distance of 1.5 cm from the hotspot (electrode positions indicated by dots). From the left, the first three columns show the absolute EEG power during REM sleep of the baseline night (BSL), of the night preceded by the protocol of paired associative stimulation paradigm with a 25-ms interval (PAS-25) and of the night preceded by the protocol with a 50-ms interval (PAS-50). Each row reports maps of EEG power in the delta, theta, alpha and sigma frequency ranges. To optimize contrast, each map was scaled separately between minimal (min) and maximal (max) power values. In the other three columns, the statistical maps (<i>t-values</i> maps) of the comparisons between PAS-25 vs. BSL, PAS-50 vs. BSL, PAS-25 vs. PAS-50 are illustrated for each frequency band (positive t-values indicate a prevalence of the first over the second term). Please note that, for the three columns on the right side, the colour code reports the actual <i>t-values</i> (the two-tailed level of significance of <i>p</i> = 0.02, after the Bonferroni correction, corresponds to a <i>t</i> = 2.82).