Item no and Item | Description |
1.Brief name | HD-tIPNS |
2.Why | The HD technique uses arrays of multiple small electrodes whose configuration can be optimised for focally targeting specific brain regions.58 59 76–80 The HD-tIPNS technique is developed to specifically modulate the infraslow electrical activity (0–0.1 Hz) in the brain. The infraslow electrical activity, a fundamental frequency range of the brain, reorganises neurons and improves the electrical connectivity of the brain-wide functional networks.48–51 Optimising the infraslow frequency can normalise the electrical activity in the higher frequency bands known to be affected in individuals with chronic pain.48–51 Recent imaging studies have also demonstrated alterations in the infraslow oscillations in individuals with CLBP in descending (pgACC) and ascending (dACC, SSC) pain pathways.54 56 57 Research shows that pink noise stimulation can influence the infraslow electrical activity (0–0.1 Hz) in the brain.58 59 The pink noise frequency spectrum resembles the naturally occurring signals in the self-organisation of the brain, thus can be more effective than standard tDCS electrical parameters.58 59 We, therefore, hypothesise that specifically and simultaneously targeting the fundamental infraslow activity at the key nodes of pain processing networks, using a novel HD-tIPNS technique, could normalise brain-wide electrical activity and functional connectivity between areas of interest, promoting better pain modulation and producing more meaningful clinical benefits. |
3.What | A battery-driven wireless transcranial electrical stimulator (Starstim-Home TES, Neuroelectrics, Spain) will be used to deliver stimulation while participants are comfortably and quietly seated. Eight electrodes will be placed on a neoprene head cap following the International 10–20 EEG system to simultaneously target pgACC, dACC and SSC (figures 2 and 3). |
4.Procedures | At each session, participant’s scalp will be cleaned with alcohol wipes. The treating researcher will place the neoprene cap with the eight electrodes attached to it on the participant’s head while they are comfortably seated in a chair. The reference electrode will be placed on the right ear. Electrogel will be applied to the scalp at the locations of the electrodes for reducing the impedance. The NIC2 software uses a traffic light signal indicator (red, yellow, green) for impedance. All electrodes will be prepared to have the lowest impedance (green colour). All the cables will be attached to the stimulating electrodes and the neckbox. The stimulator will be connected to the NIC2 software using its wifi function. The participant will be comfortably positioned in a half-lying position with their eyes closed. The participant will be asked to relax, and the stimulation intervention will be delivered for 30 min. |
5.Who provided | Two independent researchers will be involved in the delivery of the intervention. A researcher (R1) with a health professional background (physiotherapist) will design and control the Starstim-Home device and set up the stimulation programmes in the NIC2 (neuroelectrics software), to allow blinding of the treating researcher (R2). The programme will be uploaded to the online portal and the treatment will be scheduled for each participant by R1. Another independent researcher (assistant research fellow, R2) with considerable experience in administering neuromodulation techniques will prepare the participants for treatment and administer the stimulation intervention using the iPad of the Starstim-Home TES system. During the stimulation period, the iPad screen presents only a green bar for indicating the duration of the stimulation session and no other stimulation parameters are presented. This allows for appropriate blinding of the treating researcher (R2). |
6. How | All participants will receive individual face-to-face sessions. |
7. Where | Interventions will be delivered at a clinical laboratory in the Otago Medical School, Department of Surgical Sciences, located in the Dunedin Hospital, Dunedin, New Zealand. |
8. When and how much | All participants will receive the intervention (based on their randomised group) for a total of 20 sessions, five times a week for four consecutive weeks. Each stimulation session will last for 30 min duration. |
9. Tailoring | The interventions will not be tailored to individual participant’s brain states. All participants in HD-tIPNS group will receive the same stimulation waveform, pink noise stimulation at a current strength of a maximum of 0.6 mA superimposed on the infraslow (0.1 Hz sinusoidal) waveform of a current intensity of 1 mA. |
10. Modifications | Not applicable. This is a protocol for a pilot trial. |
11. How well | Adherence to intervention will be one of the primary outcomes for the study and will be recorded by the treating researcher. Adherence rates will be calculated once the treatment phase is completed. The number of treatment sessions attended by each participant will be recorded and expressed as a percentage of the total no of sessions. |
12. Actual: describe the extent to which the intervention was delivered as planned. | Not applicable. This is a protocol for a pilot trial. |
ACC, anterior cingulate cortex; CLBP, chronic low back pain; dACC, dorsal region of ACC; EEG, electroencephalogram; HD-tIPNS, high-definition transcranial infraslow pink noise stimulation; pgACC, pregenual region ACC; SSC, somatosensory cortex; tDCS, transcranial direct current stimulation; TES, transcranial electrical stimulation.