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.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
30
A bolus injection of hypertonic saline (7% NaCl) will be administered to the FDI muscle using a 1 mL syringe with a disposable needle (27G), and the volume of the bolus will be 0.1 mL
A small drop of histamine dihydrochloride will be applied to a previously determined area on the volar forearm, followed by a prick through the drop
This insertion is conducted by forceps using a stereomicroscope, and 30-35 spicules are gently rubbed into a 1 cm diameter skin area.
Transcranial magnetic stimulation (TMS) will be used to evoke motor-evoked potentials (MEPs) in the muscle of interest and cortical responses (TMSevoked potentials - TEPs) in the motor cortex with a figure-eight-shaped cone coil.
Aalborg University
Gistrup, Denmark
RECRUITINGAalborg University
Gistrup, Denmark
RECRUITINGNumeric rating scales (NRS)
NRS are essentially VAS but have tick marks spaced every centimeter so as to create 11-point scale (from 0 to 10). Subject can use these tick marks as a guide when they mark their severity on the scale.
Time frame: 1 minute after every itch/pain induction
Measuring cortical excitability (TEPs)
Transcranial magnetic stimulation (TMS) with a figure-eight-shaped cone coil will be used to evoke cortical responses in the motor cortex. The resulting TMS-evoked potentials (TEPs) will be collected using an electroencephalogram (EEG). This assessment will last for 7 minutes before inducing itch or pain.
Time frame: Baseline
Measuring cortical excitability (TEPs)
Transcranial magnetic stimulation (TMS) with a figure-eight-shaped cone coil will be used to evoke cortical responses in the motor cortex. The resulting TMS-evoked potentials (TEPs) will be collected using an electroencephalogram (EEG). This assessment will last for 7 minutes during itch or pain. The pain or itch sensation will last 10 minutes.
Time frame: During Itch/pain stimulation for 10 minutes
Measuring cortical excitability (TEPs)
Transcranial magnetic stimulation (TMS) with a figure-eight-shaped cone coil will be used to evoke cortical responses in the motor cortex. The resulting TMS-evoked potentials (TEPs) will be collected using an electroencephalogram (EEG). This assessment will last for 7 minutes during motor imagery task.
Time frame: During motor imagery task for 7 minutes
Measuring cortical excitability (TEPs)
Transcranial magnetic stimulation (TMS) with a figure-eight-shaped cone coil will be used to evoke cortical responses in the motor cortex. The resulting TMS-evoked potentials (TEPs) will be collected using an electroencephalogram (EEG). Similar to the baseline, this assessment will last for 7 minutes after itch or pain.
Time frame: Post induction of itch or pain
Pain Catastrophizing Scale (PCS).
The PCS assesses negative and exaggerated coping concerning anticipated or experienced painful stimuli. Thirteen items have to be answered on a 5-point Likert-type scale.
Time frame: Baseline
Itch Catastrophizing Scale (ICS).
The ICS assesses negative and exaggerated coping concerning anticipated or experienced itchy stimuli. Thirteen items have to be answered on a 5-point Likert-type scale.
Time frame: Baseline
Reinforcement Sensitivity Theory - Personality Questionnaire (RST-PQ).
The RST-PQ contains the following subscales: the Fight-Flight-Freeze System (FFFS, 10 items), which represents a defensive factor related to active avoidance of adverse stimuli; the Behavioral Inhibition System (BIS, 23 items), which represents a defensive factor related to anxiety and passive avoidance of adverse stimuli; and the Behavioral Approach System (BAS, 32 items), which reflects reward interest, goal-drive persistence, reward reactivity, and impulsivity. In total, 65 items have to be answered on a 4-point Likert-type scale
Time frame: Baseline
The Pittsburg Sleep Quality Index (PSQI)
The PSQI consists of 19 items generating seven component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. The seven component scores can be summarized in a global score ranging from zero to 21 with higher scores reflecting a worse overall quality of sleep
Time frame: Baseline
Depression, Anxiety, Stress Scale (DASS-21)
The questionnaire measures the magnitude of depression, anxiety, and stress. Each of these three subscales consists of 7 questions answered using a 0-3 Likert scale, with 0 meaning "it did not apply to me", and 3 meaning "it applied to me very much".
Time frame: Baseline
Learned Helplessness Scale (LHS)
The questionnaire consists of 20 items, and the participant's response to each item is rated on a 4-point Likert scale ranging from strongly agree (1) to strongly disagree (4).
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Time frame: Baseline
Positive And Negative Affect Schedule (PANAS)
PANAS measures positive and negative affect dimensions. Twenty words are associated with the subject's current feelings and have to be rated on a 5-points Likert-type scale.
Time frame: Baseline