The Effects of Performing a Motor Imagery Task on Cortical Excitability During Acute Experimental Muscle Pain and Acute Itch

Investigation of the Neurophysiological and Psychological Aspects of Itch

The aim of this project is to determine the effects of performing a motor imagery task on cortical excitability during acute experimental muscle pain (induced by hypertonic saline), acute histaminergic itch (induced by histamine), and non-histaminergic itch stimulation (triggered by Cowhage). We hypothesize that motor imagery will counteract the alterations in cortical excitability observed during experimental muscle pain and both itch models.

Itch and pain share many similarities and dissimilarities in terms of the mechanisms and molecules involved. Many studies have been conducted to explain all the neurophysiological aspects involved in the pain process, and cortical adaptations have been provoked in healthy individuals using experimental pain models. Unfortunately, all these aspects still need to be clarified regarding itch. Has been previously demonstrated that motor imagery can counteracted the pain-induced decrease in corticospinal excitability observed during acute pain, and it has also been proposed as a potential intervention for individuals with pain to restore maladaptive neuroplasticity. However, whether motor imagery can similarly counteract the itch-induced cortical changes remains unclear. Therefore, the aim of this project is to investigate whether motor imagery would counteract the reduction in cortical excitability during acute itch, similar to the effects observed in the context of acute pain.

Inclusion Criteria:

• Healthy men and women
• 18-60 years
• Speak and understand English

Exclusion Criteria:

• Pregnancy or lactation
• Drug addiction defined as any use of cannabis, opioids, or other addictive drugs
• Previous or current history of neurological (e.g. neuropathy), immunological (e.g. asthma, immune deficiencies, arthritis), musculoskeletal (e.g. muscular pain in the upper extremities,), cardiac disorder (e.g., heart stroke), or psychiatric diagnoses (e.g. depression) that may affect the results
• Current use of medications that may affect the trial, such as antihistamines, antipsychotics, and painkillers, as well as systemic or topical steroids
• Skin diseases (e.g., atopic dermatitis, pruritus nodularis, eczema, psoriasis)
• Moles, scars, or tattoos in the area to be treated or tested.
• Consumption of alcohol or painkillers 24 hours before the study days and between these
• Acute or chronic pain
• Unable to pass the "Transcranial Magnetic Stimulation Adult Safety Screen" (subproject 1 and 2)
• Contraindications to transcranial magnetic stimulation (TMS) application (history of epilepsy, metal implants in head or jaw, etc.)
• Presence of implanted hearing aids or metal implants on the face, including permanent makeup or tattoos
• Participation in other trials within one week of study entry (four weeks in the case of pharmaceutical trials)
• Lack of ability to cooperate