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The vagus nerve runs from the brain to many organs. Stimulating it can affect the experience of pain. The nerve can be stimulated on the surface of the left ear. Researchers want to study how this stimulation affects the perception of pain. They also want to study how mood affects the experience of pain.
To study the effects of mood and vagus nerve stimulation on the experience of pain.
Healthy people ages 18 and older who are fluent in English
Participants will be pre-screened with a 15-minute phone call.
Participants will have three 2-hour visits.
At the screening visit, participants will be screened with:
Medical and psychiatric history
Physical and psychological exams
Questionnaires about physical and psychiatric health and mood
A heat probe on the forearm. The temperature will be increased until it is painful
Participants will have 2 testing sessions within 7 days. Before the testing, they cannot do the following:
Eat, use nicotine, or exercise for at least 2 hours
Drink alcohol for 24 hours
Take certain medicines for 3 days
Urine drug screening
Left ear stimulation: In one session, the vagus nerve will be stimulated. In the other, an area
of the ear away from the vagus nerve will be stimulated. This will be done with mild electric
shocks that cause a tingling, pricking, or itchy feeling.
Heat applied to the forearm until it is painful but tolerable
Completing several forms on a computer or on paper about how they are feeling
Monitors on the chest and a finger clip to monitor heart, breathing, and blood pressure
Vagus nerve stimulation has shown favorable analgesic effects in humans and is supported by robust evidence in animals. Patients receiving invasive vagus nerve stimulation (iVNS) to treat refractory epilepsy and depression have reported relief from painful concomitant conditions (e.g., headache and lower back pain) and have shown analgesic responses to experimentally induced pain (e.g., heat pain and tonic pressure pain). In healthy participants, transcutaneous vagus nerve stimulation (tVNS), a non-invasive approach of vagal stimulation via the external ear, has shown similar favorable analgesic effects in response to painful mechanical, thermal, and pressure stimuli. Furthermore, in a randomized controlled trial on patients suffering from headaches, tVNS treatment reduced the number of headache days patients experienced per month. By contrast, some studies have reported no effect on painful concomitant conditions or decreased pain thresholds in response to vagus stimulation. Little work has been done to reconcile this discrepancy in the literature, which may be hindering access to a viable treatment option for some patients. The affective state of patients and participants is an important factor to consider when investigating pain perception, as there is substantial evidence that affective states modulate pain such that positive and negative mood states decrease and increase pain perception, respectively. To our knowledge, no studies have measured mood while investigating the effects of vagal stimulation on pain perception. It is plausible that mood may be a mediating variable in the relationship between vagus nerve stimulation and pain perception. Thus, the purpose of this study is to investigate the role of mood in analgesia produced by tVNS, the more feasible and non-invasive approach of vagal stimulation.
76 healthy participants will be enrolled in the study.
Design: In a randomized, controlled, double-blind study with healthy participants, the effects of tVNS (via the cymba conchae [Fig. 1a,b]) and earlobe (control) stimulation (Fig. 1a,c) in response to experimentally induced heat pain will be assessed in a within-subject, cross-over design. The following measures will be collected before, during, and after tVNS and control stimulation of the left ear: threshold measures of warm sensation and heat pain, and acute heat pain stimuli, followed by a 5min tonic heat pain paradigm. Ratings of mood and pain intensity and unpleasantness will be collected periodically before, during, and after the ear stimulation periods. Autonomic measures (heart rate, respiration, blood pressure, and heart rate variability) will also be collected throughout the study session.
We will compare thermal thresholds, mood ratings, and pain intensity and unpleasantness ratings of painful stimuli before, during, and after tVNS with earlobe (control) stimulation within each subject to 1.) determine whether tVNS significantly decreases pain perception compared to control stimulation, 2.) determine if tVNS is affecting mood and anxiety, and 3.) determine if mood is mediating the tVNS-induced analgesic effect. Autonomic measures will be analyzed to determine whether tVNS has an effect on heart rate variability.
Time Perspective: Cross-Sectional
National Institutes of Health Clinical Center
National Institutes of Health Clinical Center (CC)
Published on BioPortfolio: 2016-07-05T22:38:21-0400
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