Article Figures & Data
Figures
- Figure 1.
Phase coherence spectrum. A, The phase coherence spectrum shows how precisely the response is synchronized to the stimulus. The colored lines on top denote frequency bins in which the phase coherence is significantly higher than chance (p < 0.01, permutation test, FDR corrected). Stimulus-response phase synchronization is significantly reliable below ∼9 Hz. B, Topography of phase coherence. To better illustrate the spatial distribution, the phase coherence is separately normalized in each plot by dividing by the 95th percentile of phase coherence across electrodes, and the values of the 95th percentile is shown on top of each plot. The dark dots represent the 14 centro-frontal electrodes chosen for subsequent phase analysis.
- Figure 2.
Phase-frequency curve. The phase-frequency curve shows the stimulus-response phase lag as a function of frequency. The phase lag appears to linearly decrease over frequency in a frequency range between 3.5 and 8 Hz. The dotted lines are fitted based on the phase lag between 3.5 and 8 Hz.
- Figure 3.
Linearity of the phase-frequency curve. A, The second-order derivative of the phase-frequency curve is used to quantify the linearity of the phase-frequency curve. The second-order derivative is 0 if the stimulus-response phase lag changes linearly with frequency. The colored lines on top denote the frequency bins in which the absolute value of the second-order derivative is significantly closer to 0 than chance (p < 0.01, permutation test, FDR corrected). B, The relationship between phase coherence and absolute value of second-order derivative of the phase-frequency curve. The phase coherence and the absolute value of second-order derivative are both averaged between 3.5 and 8 Hz. Participants with higher phase coherence generally show lower absolute value of second order derivatives, i.e., better linearity.
- Figure 4.
Group delay of the speech response. A, Group delay for four populations. Each dot denotes a participant. Between 3.5 and 8 Hz, the group delay is consistent across healthy individuals, but less consistent for the DoC patients. B, The relationship between group delay and phase coherence for individuals. The x-axis is the phase coherence averaged between 3.5 and 8 Hz. The y-axis on the left is the mean phase difference between neighboring frequency bins, and the y-axis on the right shows the group delay. Participants with higher phase coherence generally show consistent group delay.
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