The interaction of emotion and pain in the insula and secondary somatosensory cortex

Pain is processed in a large neural network that partially overlaps structures involved in emotion processing. Despite the fact that pain and emotion are known to share neural regions and interact in numerous clinical conditions, relatively little is known about the interaction of pain and emotion at the neural level. This study on healthy adults aimed to investigate the interaction between negative and positive emotional stimuli and experimental pain in an essential pain processing network. Sixteen healthy young adult subjects were exposed to pictures from the International Affective Picture System (IAPS) with negative, neutral or positive valence, along with laser pain stimuli. The stimuli were pseudo-randomly arranged in three 15-min experiment series comprising 49 stimuli each (picture, laser or simultaneous picture and laser stimuli). The whole-brain blood-oxygen-level-dependent (BOLD) signal was acquired using 3T functional magnetic resonance imaging (fMRI). As expected, the pain stimulus elicited activation in the secondary somatosensory cortex (SII), insula and anterior cingulate cortex (ACC) when compared to the baseline. The interaction of negative emotion and laser stimuli related to the activation of the left SII. The interaction of positive emotion and pain stimuli led to bilateral activation of the SII and left insula. These findings reveal interaction in parts of the pain processing network during simultaneous emotion and physical pain. We demonstrated a valence-independent interaction of emotion and pain in SII.