Elevated Resting State Gamma Oscillatory Activities in Electroencephalogram of Patients With Post-herpetic Neuralgia

FIGURE 1. Power spectrum at high frequency increased in PHN patients. (A) Averaged power spectrum across all channels from 1 to 70 Hz in PHN patients and healthy controls. (B) Gamma power (40–70 Hz marked as gray area in panel A) was significantly higher in PHN patients. Power scale is μV2. ∗p < 0.05.

FIGURE 2. Spatial distribution of increased gamma power at channels on parietal and temporal areas. (A) Topography of gamma power for Patient and Control groups. Gamma power (μV2) is color-coded. (B) Significantly different distribution of gamma power between Patient group and Control group. Z-values representing the statistical comparison between two groups are color-coded. “×” marks the cluster that significantly higher in Patient group.

FIGURE 3. Source distribution of gamma power. Sources with enhanced gamma power in PHN patients were shown in slice (A) and brain cortex (B). Sources locate in the prefrontal cortex including dorsolateral and medial prefrontal cortices as well as cerebellum area. The t-values are color-coded and only significant changes are displayed.

FIGURE 4. Positive correlation between gamma power and pain ratings. Gamma power was positively correlated with VAS rating (A), BAI score (B), and BDI score (C).

FIGURE 5. Reduction of increased power spectrum in one patient after pain relief in patient No. 10. Averaged power spectrum across all channels from 1 to 70 Hz before and after pain relief (A). Power scale is μV2. The difference of topography of gamma power under pain condition vs. pain relief condition (B). Difference of gamma power between pain and relief condition are color-coded.

FIGURE 6. Modulation of gamma amplitude by phase at low frequencies. Gamma amplitude was modulated by phase at 2–8 Hz in PHN patients (A) and in healthy controls (B). Modulation index are color-coded.