Modulatory Effects of Multichannel tDCS During Prolonged Experimental Pain

Effects of Non-invasive Brain Stimulation Methods in Experimentally Induced Pain

Corticomotor excitability, pain sensitivity, descending pain control and somatosensory evoked potentials (SEPs) is often altered in acute and chronic pain.

Topical capsaicin generates stable, long-lasting hyperalgesia and ongoing tonic pain in healthy participants, which significantly inhibits corticomotor excitability in the primary motor cortex (M1).

Recent studies (by Fischer et al 2017) indicated that multifocal Transcranial Direct Current Stimulation (tDCS) administered to brain regions linked to the resting state motor network (network-tDCS) could enhance corticomotor excitability in healthy participants compared to single site M1-tDCS.

It remains unknown whether network-tDCS has also the potential to modulate the inhibitory effects on motor cortex excitability, pain sensitivity, descending pain control and SEPs associated with prolonged pain

To date, pain modulation to M1 rs-network tDCS during 8% capsaicin induced pain has not been assessed (Mylius, Borckardt and Lefaucheur, 2012). Further, it is unknown how multichannel tDCS acts on tonic cutaneous pain for approximately 24 hours.

The main objective of these projects are to study and characterize quantitatively the effects of multichannel tDCS in the development of prolonged pain.

It is hypothesized that multichannel tDCS of left M1 resting-state network will reduce the severity of experimentally prolonged pain over the m. first dorsal interosseous (FDI), will increase descending pain control, might possibly increase pain thresholds and simultaneously will modulate the peak-to-peak amplitude of SEPs to electrical painful stimulation. Further, it is hypothesized that descending pain modulation of M1 tDCS will be related to interference with the suppression of cortical excitability

Inclusion Criteria:

-Right-handed healthy men and women in the age 21-50 years who speak and understand English

Exclusion Criteria:

• Lack of ability to cooperate
• History of chronic pain or current acute pain
• Pregnancy
• Drug addiction defined as the use of cannabis, opioids or other drugs
• Present and previous neurologic, musculoskeletal or mental illnesses
• Chili allergies (subproject 1 and 2)
• Current use of medications that may affect the trial
• Previous experience with rTMS and tDCS
• Contraindications to rTMS application (history of epilepsy, metal implants in head or jaw, etc.)
• Failure to pass the questionnaire for tDCS
• Failure to pass the "TASS questionnaire" (TASS = Transcranial Magnetic Stimulation Adult Safety Screen) (Rossi et al., 2001)