Article Figures & Data
Figures
- Figure 1.
Spectral coherence in ECoG recordings reveals evidence of spatially extended, temporally coherent oscillations in the DMN. A, DMN fMRI and electrode localization for a single subject. Electrodes overlying DMN are marked in green. Exemplar electrodes over DMN (D1, D2) and one distant electrode (ND) are indicated. Orange regions indicate cortex from which fMRI BOLD signal is derived. B, Gamma-band (70–120 Hz) second spectral power in D1, D2, and ND electrodes, showing 1/f-like power distribution. Significant peaks in second spectral power at 0.015 Hz would be difficult to identify. C, Gamma-band spectral coherence between DMN (D1–D2) electrodes exhibits a peak around 0.015 Hz, a frequency similar to that seen in the BOLD PSD. Other interactions (D1–ND, D2–ND) do not. The 0.015 Hz peak is clearly seen for this electrode pair. Analyses of grouped electrodes, with statistical confirmation of significance, show similar results (see Fig. 2 and Results).
- Figure 2.
Spectral coherence in ECoG shows significant gamma-band coherence in the DMN and not in non-DMN control electrodes in a single subject: S3. A, DMN fMRI and electrode localization. Electrodes overlying DMN are green. A control group of electrodes (blue) does not overlie DMN cortex. B, BOLD time series derived from DMN cortex marked in orange in A. C, Top, Control group electrodes do not exhibit a clear peak in gamma-band coherence (p = 0.002, q = 0.0076). C, Middle, DMN electrodes show a significant peak in coherence near 0.015 Hz (p = 0.0005, q = 0.0277), which is commensurate with the highest peak (C, bottom) in the BOLD PSD derived from DMN cortex in this subject. Both control and DMN electrodes exhibit spectral coherence throughout the f2 range in the alpha band (f1 = 4–15 Hz). Black contour lines outline areas of significant spectral coherence.
- Figure 3.
Histograms of significant coherence values across subjects. A, DMN electrodes show significant coherence in the gamma band at an f2 range near 0.017 Hz. Across subjects, this happens more often (h = 4, p = 0.007) than one would expect if significant values were distributed across all (f1, f2) uniformly. Importantly, the frequency range where gamma-band coherence appears is consistent across different individuals. In the alpha band, the pattern of significant coherence is not limited to a narrow f2 range. B, Control electrodes do not show a consistent pattern of significant gamma-band coherence across subjects. However, significant coherence in the alpha-band range is seen throughout the f2 range (h = 4, p = 0.007). Significant gamma-band coherence therefore seems specific to the DMN, whereas the broadband coherence in the alpha band is consistent with correlated 1/f-like fluctuations in power.
Tables
Subject (age/sex) ICA Sampling rate (Hz) Default network electrodes Electrode locations Max. gamma-band coherence (Hz) S1 23 500 14 Posterior cingulate 0.018 (11/F) (3) Precuneus Cingulate gyrus S2 29 500 1 Cingulate gyrus n/a (14/M) (28) S3 38 500 4 Middle temporal gyrus 0.018 (11/F) (7) Inferior frontal gyrus S4 28 500 3 Inferior frontal gyrus 0.015 (7/F) (24) Superior frontal gyrus S5 n/a 250 11 Precuneus 0.012 (24/M) Posterior cingulate Cingulate gyrus S6 n/a 2000 5 Medial frontal gyrus — (43/F) Cingulate gyrus S7 n/a 250 6 Posterior cingulate 0.018 (38/M) Cingulate gyrus Precuneus S8 n/a 500 10 Anterior cingulate — (20/F) Medial frontal gyrus Superior frontal gyrus Precuneus Cingulate gyrus If applicable, the number of components identified using independent components analysis is indicated (ICA) with the component corresponding to the Default Mode Network indicated in parentheses. The frequency at which maximum gamma-band coherence appears, if seen, is presented in the final column.
Supplemental Material
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