This project was primarily in the stages of planning for the majority of the past year. The accomplishments during this year include establishment and approval of a protocol, staff training, and conducting preliminary experiments. Experiment Overview Healthy men and women will be recruited for this randomized, controlled, double-blind study that will take place place on two separate days. In a within-subject, cross-over design, experimentally induced heat pain will be examined in response to transcutaneous (non-invasive) vagus nerve stimulation (via a region of the ear exclusively innervated by the vagus nerve) compared to stimulation of the earlobe (control site; innervated by cervical spinal nerves). The following will be collected before, during, and after experimental and control stimulation of the left external ear: warm sensation and heat pain thresholds, and ratings of mood, pain intensity and unpleasantness after short and long duration heat pain stimuli. Autonomic measures (heart rate, respiration, blood pressure, and heart rate variability) will also be collected throughout the study session. This study will allow us to address the following questions: 1. Does the experimental condition (vagus stimulation) compared to the control condition (earlobe stimulation) significantly decrease pain perception? 2. Does the experimental condition, compared to control, significantly improve mood? 3. Does mood mediate the effects of vagus stimulation on pain perception? In addition, we will determine whether vagus stimulation, compared to control, increases heart rate variability.
