Infrared imaging as measure of cognitve stress, validated through well-established stress markers: electrodermal activity and heart rate variability. A pilot study

Abstract

OBJECTIVE: To explore thermography as a possible new technique for the objectification of stress measurement. In such a way, we have compared it with well-stablished measures of stress, electrodermal activity (EDA) and heart rate variability (HRV) MATERIALS AND METHODS: 9 volunteer’s participants performed a cognitive task in which they should give different answers to each of five stimuli presented. The experimental session was composed for 15 minutes of acclimation, during which the participants answered psychometric tests, thereupon physiological and thermal recording started. Recording session consisted of three phases adaptation, stress task and recovery. Task was divided into three blocks, in which the display time of the stimuli was variable: 750ms, 500ms and 250ms. After that, a second session of psychometric test took place. RESULTS: Phase and block analysis showed significant differences in EDA (F=15.529 (1.740, 13.923), p=.00, nP2=.66; F=4.247 (1.740, 13.923), p=.041, nP2=.347) and thermal activity in all regions of interest studied (forehead, corrugator, periorbital, cheeks, ethmoid sinus, nose tip, perioral and chin). However, non-significant differences were founded in frequency HRV analysis (F=2.813 (1.290,13.318), p=.118, nP2=.26; F=.537 (1.290,13.318), p=.571, nP2=.063), neither in spectrum HRV analysis (F=1.369 (1.01, 8.079), p=.276, nP2=.146, F=1.205 (1.797, 14.374, p=.323, nP2=.131). DISCUSSION: Thermography is a promising methodology to measure stress in a non-invasiveness way, therefore thermal homeostatic process seems to react differently not only to physical and psychological stress, but also to different types of psychological stress.