Decoding Mechanisms of Pain Modulation

The hypnosis will be conducted by clinical psychologists who have the formal competence and training in hypnosis. We will be using a tailored hypnosis script designed for this particular study, with a duration of 10-15 minutes. The script involves a hypnotic induction (relaxation-based), imagery (suggestions for pleasant visual imagery), a deepening procedure, and symptom-specific suggestions. The introduction begins by having the hypnotist debunk many of the common myths and misconceptions that patients may hold about hypnosis, and provide a description of hypnosis. Hypnosis is described as focused attention and concentration - like being so lost in a book or movie that it is easy to lose track of what is going on around you. Once the patient is deeply hypnotized, the therapist offers suggestions to reduce distress and improve pain tolerance.

A CE approved tVNS device will be used to stimulate the afferent auricular branch of the vagus nerve located medial of the tragus at the entry of the acoustic meatus \[36\]. A standardized intensity of 10 mA with a pulse width of 250 μs and a consistent stimulation frequency of 25 Hz will be used for optimal stimulation. The stimulation will constantly alternate between active stimulation for 30 seconds, followed by a break of 30 seconds \[37\], and will have a duration of 15 minutes. Active tVNS is performed in a relaxed position, sitting back in a chair no more than 30 degrees from the horizontal, with both feet flat on the floor, and hands on thighs with palms facing downward. The bipolar stimulation electrode is placed correctly within the concha of the left ear. Participants are instructed to breathe normally while not talking or making any movements during their session.

Sham tVNS is performed in a relaxed position, sitting back in a chair no more than 30 degrees from the horizontal, with both feet flat on the floor, and hands on thighs with palms facing upward. The bipolar stimulation electrode is placed correctly within the concha of the left ear, but no actual stimulation will be performed. The electrode will be left on for 15 minutes. Participants are instructed to breathe normally while not talking or making any movements during their session