Brain Asymmetry in Pain Affective Modulation

Objective The aim of this study was to characterize the dynamic brain networks underlying the affective modulation of pleasant, unpleasant, and neutral image perception due to painful stimulations in healthy subjects. Methods Forty volunteers, 20 men and 20 women, participated in this study. Brain activity was recorded by 64-channel electroencephalography. After data cleaning, brain functional networks were built through the use of the motif synchronization method. Results We found that increased cerebral connectivity in the left hemisphere under the pain condition broke the connection symmetry. Both women and men showed homophilic connections (intrahemispheric), but women were more homophilic than men. The pain condition increased homophily in the left hemisphere, and emotions could modulate pain. The frontal, central, and left temporal regions showed homophilic variation, depending on the emotional stimulus. Conclusions Pain and emotions altered brain activity. There was increased connectivity and homophily in the left brain hemisphere for the painful experience. The emotions modulated brain activity in the pain condition. Overall, the brain presented homophilic characteristics; homophily changed, depending on emotion or pain. The left brain hemisphere seems to be related to pain processing.