Human Gamma Oscillations during Slow Wave Sleep Figure 2. Gamma oscillations recorded with intracranial electrodes during SWS. (A) All-night hypnogram of a representative subject (P15) (Top), time-frequency evolution of the power for one scalp electrode (Middle), density of gamma events (30–120 Hz) detected on seven intracranial contacts located in the frontal and temporal cortex (Bottom). (B) 3D MRI reconstruction of the patient’s brain presenting one depth electrode and its corresponding 6 intracranial contacts in the left orbito-frontal gyrus (Left). Simultaneous recordings during deep sleep (S4 stage) showing raw and 30–120 Hz filtered activities (presented below each raw one) for one scalp (FP1) and three depth contacts in the same cortical region (Right). (C) Time-frequency representations of the three bursts of gamma activity shown in (B) illustrating examples of pure oscillations with a narrow frequency in the high gamma range (Left), the low gamma range (Right), and complex oscillations composed of a few mixed low and high frequencies (Middle), as also shown in the filtered signals (Bottom). doi:10.1371/journal.pone.0033477.g002 PLoS ONE | www.plosone.org 4 April 2012 | Volume 7 | Issue 4 | e33477