Human Gamma Oscillations during Slow Wave Sleep Figure 6. Spatial distribution of phase-modulated gamma patterns. Locations of all intracranial contacts associated with IN-phase (blue balls) and ANTI-phase (red balls) patterns for 11 subjects for which Talairach coordinates could be successfully estimated are superimposed on a cortical reconstruction of one subject. Yellow balls correspond to the locations of all analyzed contacts for the corresponding 11 subjects (418). From left to right and from top to bottom, views are presented from the following planes: frontal-coronal, back-coronal, top-axial, bottom-axial, left-sagital and right-sagital. doi:10.1371/journal.pone.0033477.g006 and 3.87 radians (,0.14 sec) for IN-phase and ANTI-phase patterns. Discussion The main observations of our study can be summarized as follows: 1) Gamma oscillations in the range 30–120 Hz were observed during SWS in the majority of investigated cortical LFPs. They were characterized by oscillations in narrow frequency bands in the low (,30–50 Hz) and high gamma (,60–120 Hz) ranges. 2) Different patterns of phasic activation of gamma oscillations could be identified: IN-phase gamma patterns tended to appear around the positive phase of the scalp SW. They were strongly expressed in the frontal and temporal cortical regions and were, in most of the cases, constituted by narrow band frequencies distributed over the whole gamma range from 30 to 120 Hz. In PLoS ONE | www.plosone.org 8 April 2012 | Volume 7 | Issue 4 | e33477