Tonic Pain and Transauricular Vagal Nerve Stimulation

Capaisin is a topically administered tonic pain model. Stemming from its chilly-origin, pain induced ressembels heat/light burning sensation which increases within 20minute of application to the forearm, before it plateaus. Associated pain can be stopped immediately by applying ice/cold water. Participants will be asked to rate (using a scale from 0 denoting no pain, to 10 denoting maximal pain) the intensity of the pain in 5 min time intervals.

Using the computerized pressure pain algometer tool (Nocitech, Aalborg, Denmark), cuffs placed on the calves of participants wll inflate at a consistent rate. Participants are instructed to rate the pain experiences using a visual analogue scale (VAS) and to press a button when the pain becomes intolerable. The VAS ranges from 0 denoting no pain, to 10 denoting maximal pain. Pain detection, namely the kPa where the VAS is at 1cm, and the pain tolerance, namely the kPa when the deflation-button is pressed, will be acquired.

Using the computerized pressure pain algometer tool (Nocitech, Aalborg, Denmark), cuffs placed on the calves of participants wll inflate at a consistent rate. Whilst participants have a constant pressure applied to their non-dominant leg, they are instructed to rate the pain experienced on the dominant leg as the cuff slowly inflates using a visual analogue scale (VAS) and to press a button when the pain becomes intolerable. The VAS ranges from 0 denoting no pain, to 10 denoting maximal pain. Conditioned pain detection, namely the kPa where the VAS is at 1cm, will be acquired.

Trapezius pressure pain perception will be acquired using a handheld pressure algometer (Somedic, Solna, Sweden). Perpendicular to the musle and halfway between the acrominion and the processus spinous vertebrae, the 1cm2 probe will be applied at a constant rate. When particpants first feel pressure pain, they will respond with a button-press.

Using the Neurolight, per pupil, a 3s light reflex will be acquired. This refers to the reflex following the exposure to a light flash.

Using a 3-lead system (reference electrode on the clavicle, whilst the other two leads reside on the sternum and V4), resting state electrocardiography will be acquired.

The ability to perceive your heart beats is described as cardioception. One means by which to assess this ability is the 'heartbeat couting task'. Herein, using a queue, participants are tasked to count their heartbeats in 3 undislosed and randomized durations (25, 35 and 35s). This value is then compare to the actual number of beats during each time interval, which is acquired via electrocardiography.