Dysesthesia symptoms produced by sensorimotor incongruence in healthy volunteers: an electroencephalogram study

Abstract

Objectives: Pathological pain such as phantom limb pain is caused by sensorimotor incongruence. Several studies with healthy participants have clearly indicated that dysesthesia, which is similar to pathological pain, is caused by incongruence between proprioception and/or motor intention and visual feedback. It is not clear to what extent dysesthesia may be caused by incongruence between motor intention and visual feedback or by incongruence between proprioception and visual feedback. The aim of this study was to clarify the neurophysiology of these factors by analyzing electroencephalograms (EEGs).

Methods: In total, 18 healthy participants were recruited for this study. Participants were asked to perform repetitive flexion/extension exercises with their elbows in a congruent/incongruent position while viewing the activity in a mirror. EEGs were performed to determine cortical activation during sensorimotor congruence and incongruence.

Results: In the high-frequency alpha band (10-12 Hz), numeric rating scale scores of a feeling of peculiarity were significantly correlated with event-related desynchronization/synchronization under the incongruence and proprioception conditions associated with motor intention and visual feedback (right inferior parietal region; r=-0.63, P<0.01) and between proprioception and visual feedback (right temporoparietal region; r=-0.49 and r=-0.50, P<0.05). In these brain regions, there was a region in which incongruence between proprioception and visual feedback and between motor intention and visual feedback caused an increase in activity.

Conclusion: The present findings suggest that neural mechanisms of dysesthesia are caused by incongruence between proprioception associated with motor intention and visual feedback and, in particular, are a result of incongruence between proprioception only and visual feedback.

Keywords: dysesthesia; electroencephalogram; event-related desynchronization/synchronization; high-frequency alpha band; sensorimotor incongruence.

Figure 1

Photographs of the experimental setup. Notes: A mirror was placed between the participant’s right and left arms. The photographs depict the four study conditions: congruence (A), incongruence (B), intention (C), and proprioception (D).

Figure 2

A bar chart showing the degree of dysesthesia detected under the four conditions. Notes: Bars (mean [standard deviation]) represent the NRS scores for dysesthesia symptoms under the four conditions. The mean NRS scores for peculiarity and nausea were significantly higher under the incongruence, intention, and proprioception conditions than under the congruence condition. Abbreviation: NRS, numeric rating scale.

Figure 3

Correlation analysis of NRS scores for peculiarity (A and B) and nausea (C and D) with each condition. Notes: NRS scores for peculiarity under the incongruence condition were significantly correlated with scores under the intention and proprioception conditions (A and B). In addition, a significant positive correlation was found between NRS scores for nausea under the incongruence and intention conditions (C) and under the incongruence and proprioception conditions (D). Abbreviation: NRS, numeric rating scale.

Figure 4

Topographic maps of ERD/ERS% of the high-frequency alpha rhythm band in the congruence (A), incongruence (B), intention (C), and proprioception (D) conditions. Abbreviations: ERD, event-related desynchronization; ERS, event-related synchronization.

Figure 5

Correlation analysis of NRS scores for peculiarity and ERD/ERS% in the P8 channel (right inferior parietal region [A]) under the incongruence condition and the TP8 and P10 channels (right temporoparietal region [B and C]) under the proprioception condition. Abbreviations: ERD, event-related desynchronization; ERS, event-related synchronization; NRS, numeric rating scale.