Figure 4.

The mean global-signal-regressed (GSR) signal decreases with sleep depth in midline and subcortical regions and increases in extrastriate regions. Direct statistical comparison of the mean GSR signal over the four non-REM sleep stages. The main effect of sleep stage from a group-level linear mixed effects analysis of 71 subjects is shown. Displayed regions exhibit significant mean GSR signal changes across W, N1, N2, and N3 sleep. Color bar reflects the value of gaussianized F statistics corrected for multiple comparisons (P < 0.05). Highlighted regions include the anterior cingulate (first row), posterior cingulate, caudate, mediodorsal thalamus, MT and fusiform gyrus (last row). Plotted are mean GSR, global and minimally processed (last column) signals reflecting group averages of 71 subjects (W), 58 subjects (N1), 42 subjects (N2) and 19 subjects (N3). Note different ordinate scales between GSR and global/minimally processed signals. Percent BOLD signal was computed for each subject by normalizing to the value of the constant term, then multiplying by 100. Error bars reflect the 95% confidence interval of the means. Included in the plots are three regional post hoc, group-level linear mixed effects analyses: W vs. N1 (71 subjects), N1 vs. N2 (58 subjects) and N2 vs. N3 (42 subjects), with * indicating P < 0.05 for the two stages it is placed between. ns: main effect of sleep stage not significant (P > 0.05).