In this study, we want to investigate how pain processing and sensation are related to a certain part of the nervous system, the so-called autonomic nervous system.
For this purpose, we apply heat and pressure stimuli to the skin and test pain processing by means of ratings scales and sensory tests. Breathing, heart rate and sweat response are also measured. To assess the spinal cord level, we measure muscle response (measured by electromyography, EMG) to electrical stimulation. Additionally, sensory nerves will be stimulated at the ear and participants will also be given various questionnaires to complete.
Over 18 and below 40 years of age
Good general health
Able to give informed consent
Any major medical or psychiatric condition (e.g. heart disease, diabetes, autoimmune disorders, infectious diseases, major depressive disorder), any chronic pain condition, any respiratory problems, any acute pain at time of study
Inability to follow study instructions, e.g. due to language problems
Pregnancy (female participants will be asked if pregnancy could be possible)
Increased alcohol (>2 (for women)/4 (for men) standard glasses per day or >5 (for women)/4 (for men) glasses at least once a month within a few hours) or caffeine consumption (≥ 400mg per day)
Crossover
respiratory gated taVNS
Other interventionElectrical stimulation will be delivered in bursts during expiration
random burst stimulation
Other interventionElectrical stimulation will be delivered in bursts at random timepoints during the breathing cycle
continuous stimulation
Other interventionElectrical stimulation will be delivered continuously for 30sec followed by a 30sec break.
Sham stimulation
Other interventionElectrical stimulation will be identical to the taVNS, but the electrodes will be placed at a different position on the ear
Magnitude of the Nociceptive Withdrawl Reflex
Muscle responses of the biceps fermoris to an electrical stimulation of the sural nerve will be measured using an electromyogramm
Area of Secondary Hyperalgesia
Von Frey filaments will be used to assess the spatial extent of experimentally induced hyperalgesia
Changes of Pressure Pain Threshold
Pressure will be applied over the thenar eminance of the hand until the participant reports a painful sensation
Perceived Pain Intensity and Unpleasantness
Perceived intensity and unpleasantness of heat stimuli will be assessed using rating scales. The intensity rating scale ranges from 0, indicating no perception, to 100, indicating the pain threshold, and up to 200, indicating the most tolerable pain. The unpleasantness rating scale ranges from -100 for 'extremely unpleasant,' through 0 for 'neutral,' to 100 for 'extremely pleasant.
Change in Autonomic Nervous System Activity
The activity of the autonomic nervous system will be measures using electrocardiogramm and galvanic skin response
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Schweinhardt Petra
Lead sponsor
Balgrist University Hospital
Sponsor institution
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