Recording of the sympathetic thermal response by means of infrared functional imaging

Infrared functional imaging was used to record the temperature variation of the hands associated with sympathetic skin response. The aim was at identifying a complementary method to monitor the emotional sweating. Sudomotor and thermal skin response was measured after delivering of unexpected sub-painful electric stimulation of the median nerve at wrist. 10 healthy volunteers, once given their informed consent, were enrolled. (0.3±0.2) °C decreasing of the hand temperature was recorded after each stimulation for all subjects. This decreasing was associated to the onset of the sudomotor response. Temperature decreasing was synchronous but delayed with respect to the clear-cut sympathetic skin response electrically recorded. Different latencies and durations for the thermal and the electric responses were recorded, thermal responses being later and slower with respect to the electric responses. The sudomotor thermal response may be used in the future as complementary or alternative monitoring of the activity of the autonomous system in conditions where the traditional sympathetic skin response cannot be recorded.