Figure 1.
Automatic detection of slow waves and gamma events.
(A) Examples of scalp (blue line) and intracranial (red line) detected slow waves, inside a 2-seconds window around the central peaks. Scalp slow wave were detected according to defined duration and amplitude criteria (top right). (B) Raw intracranial LFP (gray line) and the corresponding gamma event detected in the filtered LFP (bottom) when the amplitude of the envelope signal was over 3σ. Presented times and duration correspond to: τo→first detection time, τl→last detection time, τm→maximal amplitude time, Δτw = τl−τo→total event duration.
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).
Figure 3.
Two patterns of phasic modulation of gamma oscillations by the slow waves.
(A–B) Examples of IN-phase and the ANTI-phase modulation patterns of gamma oscillations recorded in intracranial contacts in the cingulate gyrus (subject P15) (A) and the superior temporal sulcus (subject P18) (B), respectively. From Top to Bottom: Superimposed scalp slow waves aligned around their central peak; Simultaneously recorded intracranial LFPs, also showing slow components; Intracranial filtered (30–120 Hz) signals with the average RMS activity (orange line); Average of their time-frequency representations. (C–D) Total number of gamma events, associated with IN-phase and ANTI-phase patterns respectively, detected along frequency (30–120 Hz) and time (2-seconds window around the scalp negative peak) for all patients (n = 19) and all analyzed contacts (n = 233). For IN-phase and ANTI-phase patterns, the cumulative histograms of their frequency distributions were illustrated (Top-Right and Top-Left) with the corresponding regression curves (red lines). Several dominant peaks were identified at fa≈41, fb≈67, fc≈87, fd≈105 Hz and f′a≈70, f′b≈97 Hz. The cumulative histograms of their first detection times (relatives to the intracranial central peak of the slow waves) are also illustrated (Bottom).
Figure 4.
Percentage of intracranial contacts presenting depth-positive (blue bars) or depth-negative components (red bars) during the IN-phase (left) and ANTI-phase (right) patterns for 15/19 and 7/19 subjects respectively, see the text.
This analysis was performed by taken into account all contacts ( “ALL”) or only contacts located in the frontal (Fro) and temporal (Tem) cortex.
Figure 5.
Histograms presenting the distribution of the preferred phases for all contacts associated with IN-phase (122 from 15 subjects, top histogram) and ANTI-phase (21 from 7 subjects, bottom histogram) patterns, for the first detection time (left) and the maximal amplitude time (right).
Phases of the corresponding SW are given for reference (blue lines on top).
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.
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 preferred phases for all cases presenting statistically significant phase-sycnhronization across all slow waves and associated with IN-phase (top histogram) and ANTI-phase (bottom histogram) patterns. Phases of the corresponding SW are given for reference (blue line on top) (n = 8 subjects).