Fig. 1

Autonomic testing and monitoring physiological signals. (a) Shown is a sample timeline of autonomic tests performed in each session. The tests include a set of sympathetic tests (standing-squatting-standing [one minute of each, in succession] and cold pressor test [immersion of hand in ice water for up to three minutes]), a set of parasympathetic tests (deep breathing [respiratory rate of six breaths per minute for seven minutes] and diving reflex test [refrigerated gel-filled compresses on the face for one minute with one minute of recovery]), and Valsalva maneuver (restricted and forced exhalation for 15 s with one minute of recovery). (b) Physiological signals for each participant were recorded by a six lead electrocardiogram (in red, wires attached to four foam adhesive electrodes placed at each shoulder and each ankle) and a respiratory belt (in green, around the torso). Recorded from the left hand were noninvasive blood pressure (in blue, small inflatable cuff on middle phalanx of middle finger) and electrodermal activity (in gold, dry, metal electrodes on distal phalanx of index and ring finger). Eye tracking glasses (in purple) were placed to record pupil diameter and gaze location