Brain Network Stimulation for Chronic Low Back Pain.

HD-tIGNS will be administered three times a week (30 minutes/ session) for a total of 4 weeks (i.e., 12 sessions in total) using a 32-channel transcranial current stimulator. The HD-tIGNS will be used to alter the functional connectivity strength between the three cortical networks \[namely the salience network (SN), the default mode network (DMN) and the somatomotor network (SMN)\] in the infraslow frequency spectrum (0.1 Hz). A total of fifteen circular Ag/AgCl electrodes \[eleven stimulation electrodes (C1, C2, C3, C4, F7, F8, FC3, FT7, FPz, Fz, and O2) and four electrodes with zero current (FC1, FC2, FC4, and FCz)\] will be placed on a neoprene head cap following the International 10-10 EEG system. The optimal montages has been created using the Stimweaver optimization software by the Neuroelectrics company, to specifically decrease the functional connectivity i.e., phase synchronization of the brain regions of the SN with the SMN and the DMN.

The Actisham protocol (with FC2 as the itchy electrode) created by the Neuroelectrics will be used for the sham stimulation group. Similar to the active treatment group, the actisham will be administered three times a week (30 minutes/ session) for a total of 4 weeks (i.e., 12 sessions in total) using a 32-channel transcranial current stimulator.Similar to active group, a total of fifteen circular Ag/AgCl electrodes will be placed on a neoprene head cap following the International 10-10 EEG system to appropriately blind the participant. The electrodes would comprise of four stimulation electrodes (FC1, FC2, FC4, and FCz) and eleven electrodes (C1, C2, C3, C4, F7, F8, FC3, FT7, FPz, Fz, and O2) with zero current.