Experimentally induced central sensitization is accompanied by alterations in electroencephalographical microstate parameters

Pain perception is a dynamic and time-varying phenomenon. The high temporal resolution of electroencephalography (EEG) can be leveraged to gain insight into its cortical dynamics. Electroencephalography microstate analysis is a novel technique that parses multichannel EEG signals into a limited number of quasi-stable topographies (microstates) that have a meaningful temporal structure and have been linked to the activity of resting state networks. In recent years, several studies have investigated alterations in EEG microstate parameters associated with acute and chronic pain states, with mixed results. In the present study, we used high-frequency stimulation (HFS), in healthy human volunteers, to induce mechanical hypersensitivity (a perceptual correlate of central sensitization) and investigated (1) changes in microstate parameters before vs after the induction of mechanical hypersensitivity and (2) whether microstate parameters before HFS were linked to the development of mechanical hypersensitivity. Results showed that the duration of microstate E, typically related to the activity of the salience/default mode network, was consistently decreased post-HFS. The global explained variance of microstates A (Auditory network) and E and coverage of microstate A were positively associated with mechanical hypersensitivity. Conversely, the transition probabilities from microstates B (Visual network) to A and the bidirectional transition probabilities between B and C (saliency and default mode networks) were negatively associated with mechanical hypersensitivity. We discuss these findings in the context of the functional significance of EEG microstates. Our results highlight the potential utility of microstate analysis in understanding pain processing and its potential link to changes in the nociceptive system.