Brain source connectivity reveals the visceral pain network

Introduction: Several brain structures have been consistently found to be involved in visceral pain processing. However, recent research questions the specificity of these regions and it has been suggested that it is not singular activations of brain areas, but their cross-communication that results in perception of pain. Moreover, frequency at which neurons are firing could be what separates pain from other sensory modalities which otherwise involve the same anatomical locations. In this test/retest study, we identified the network of sources and their frequencies following visceral pain. Methods: 62-channel evoked potentials following electrical stimulation in oesophagus were recorded in twelve healthy volunteers on two separate days. Multichannel matching pursuit (MMP) and dipolar source localisation were used. Multiple sources responsible for one MMP component were considered to act synchronously as each MMP component is mono-frequency and has a single topography. We first identified components that were reproducible within subjects over recording sessions. These components were then analysed across subjects. Results: MMP and source localisation showed three main brain networks; an early network at ~ 8.3. Hz and ~ 3.5. Hz involving brainstem, operculum, and pre-frontal cortex peaking at ~ 77. ms. This was followed by an operculum, amygdale, mid-cingulate, and anterior-cingulate network at ~ 4.5. Hz. Finally, there was an operculum and mid-cingulate network that persisted over the entire time interval, peaking at 245.5 ± 51.4 ms at ~ 2.1. Hz. Conclusion: This study gives evidence of operculum's central integrative role for perception of pain and shows that MMP is a reliable method to study upstream brain activity.