Altered neural oscillations within and between sensorimotor cortex and parietal cortex in chronic jaw pain

Figures

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  Fig. 1. Setup and trial timeline. The experiment was comprised of two conditions: low pain and moderate pain-eliciting stimuli, delivered to the right forearm. A. Participant's view of the screen during a low pain trial. The trial started with a 4-s rest period and was followed by a 4-s anticipation period (Ant.). During the anticipation period, the white bar was separated from the baseline red bar. Thereafter, the thermode was heated to a participant-specific and condition-specific temperature and stayed on for 5-s. As the white bar returned to the baseline position, the temperature of the thermode dropped to baseline and a 3-s period of rest began. A rating bar then appeared on the screen for 8-s and participant gave ratings using the VAS shown in Figure C. B. The participant's view of the screen during a pain trial. Stimulus intensity and the relative position of the white bar were the only differences between trials. Each block of trials included 24 trials – 12 low pain trials and 12 moderate pain trials, which were delivered in a pseudorandomized order. A total of four blocks were performed. C. The visual analog scale (VAS) for pain rating. Extreme left indicates no pain whereas…

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  Fig. 2. Overview of the EEG analysis. A. Applying filter and within-trial assessment. B. Across-trial assessment. C. Independent component analysis (ICA). D. Automated artifact rejection using the Multiple Artifact Rejection Algorithm (MARA) Toolbox. E. Second implementation of ICA. F. Source localization of each independent component using the DIPFIT Toolbox. G. Comparison and inferences of multi-subject EEG independent components using the measure projection toolbox (MPA).

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  Fig. 3. Pain rating and stimulus Intensity. Mean subjective pain rating for the chronic jaw pain group (green bars) and the control group (black bars) for the low pain condition (A) and the moderate pain condition (B) across blocks. No block effect was found in either condition. In the low pain condition, the chronic jaw pain group had higher pain ratings compared to the control group (p < .05). In the moderate pain condition, there was no significant difference between groups (p > .05). Mean temperatures (i.e., stimulus intensity) for the low pain condition and the moderate pain condition for the chronic jaw pain group and the control group (C). Stimulus intensity was not significantly different between groups. VAS = Visual analog scale, B = Block, Mod = moderate.

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  Fig. 4. Time-frequency representations from the contralateral sensorimotor domain in the chronic jaw pain group and control group. A. The sensorimotor domain revealed by the MPA analysis across participants. B. The anatomical areas identified in the domain and the fraction of the domain in each anatomical region. Anatomical localization of the domain was based on the brain atlas provided by LONI project. C. ERSP measure for the control group in the low pain condition. The two solid black lines demarcate the onset of the anticipation period (Anti. time = 0 s) and the onset of the heat stimulation (Heat. time = 4 s). Sinusoidal wavelet transform, which was used to convert the EEG data to time-frequency space, led to truncation of 740 ms from each end of the ERSP plot. The color scale represents the average increase or decrease of oscillation magnitude, relative to a pre-stimulus baseline (−2-s to 0-s before the onset of anticipation period). D. ERSP measure for the chronic jaw pain group in the low pain condition. E. The contrast plot (jaw pain – controls) in the low pain condition. F. ERSP measure for the control group in the moderate pain condition. G. ERSP measure for the chronic jaw…

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  Fig. 5. Time-frequency representations from the ipsilateral sensorimotor domain in the chronic jaw pain and control groups. A & B. The ipsilateral sensorimotor domain and the anatomical areas revealed by the MPA. C. ERSP measure for the controls in the low pain condition. D. ERSP measure for the chronic jaw pain group in the low pain condition. E. Between group contrast plot (jaw pain – controls). F. ERSP measure for the control group in the moderate pain condition. G. ERSP measure for the chronic jaw pain group in the moderate pain condition. H. Between group contrast plot (jaw pain – controls). Mod = moderate.

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  Fig. 6. Time-frequency representations from the contralateral parietal domain in the chronic jaw pain and control groups. A & B. The contralateral parietal domain and the anatomical areas revealed by the MPA. C. ERSP measure for the controls in the low pain condition. D. ERSP measure for the chronic jaw pain group in the low pain condition. E. Between group contrast plot (jaw pain – controls). F. ERSP measure for the control group in the moderate pain condition. G. ERSP measure for the chronic jaw pain group in the moderate pain condition. H. Between group contrast plot (jaw pain – controls). Mod = moderate.

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  Fig. 7. Effective connectivity (dDTF). A. A significant Group x Time interaction was found between the contralateral parietal lobe domain (PLc) and the ipsilateral sensorimotor domain (SMi). Connectivity strength is shown in the theta (B), alpha (C), beta (D), and gamma (E) bands during the baseline, anticipation period, and heat stimulation period. The three time periods (i.e. baseline, anticipation, and heat stimulation) are on the x-axis. Connectivity strength is on the y-axis. Compared to the control group, the chronic jaw pain group showed significantly lower connectivity strength in the beta and gamma bands (FDR corrected at p < .05*) within each time period.