Human Gamma Oscillations during Slow Wave Sleep Figure 7. Synchronization of gamma events occurring at different intracranial contacts during slow waves. (A) Distribution of co- detection probability for all analyzed contacts (n = 20 subjects). (B) Distribution of the co-detection probability vs. the distance between pairs of contacts and the corresponding regression curve (red line, n = 11 subjects). (C) Percentages of contact pairs presenting a co-detection probability $50% and located in frontal, temporal and cingulate cortex (wide blue bars in background), and corresponding percentages having significant PLV and CC values (yellow and red bars in foreground respectively, n = 20 subjects). (D) Histogram of the distance between pairs of contacts for all cases presenting co-detection probability $50% and statistically significant PLV (n = 11 subjects). (E) Plot of the distance between contact pairs vs. the PLV level with the corresponding regression curve (red line) (n = 11 subjects). (F) Examples of contact pairs presenting statistically significant phase synchronization modulated by IN-phase and ANTI-phase patterns. From top to bottom: superimposed scalp slow-waves associated with the first contact in the pair (see below), aligned around the central peak; Average time-frequency representations of the power for the first and second contacts; Phase-locking value for the phase difference between both contacts along all slow waves. Pairs of contacts (first and second) were implanted for subjects P7 and P13 respectively in the following locations: orbital sulcus and olfactory sulcus (left), frontal superior sulcus and frontal inferior sulcus (right). The distance between pairs of contacts shown in both examples was 10 mm. (G) Histograms presenting the distribution of the PLoS ONE | www.plosone.org 9 April 2012 | Volume 7 | Issue 4 | e33477