Abstract
Functional infrared imaging (fIRI) is a validated procedure to infer autonomic arousal. Currently, fIRI signals are analysed through descriptive metrics, such as average temperature changes in a region of interest (ROI). However, the employment of mathematical models could provide a powerful tool for the accurate identification of autonomic activity and investigation of the mechanisms underlying autonomic arousal. A linear temporal statistical model such as the general linear model (GLM) is particularly suited for its simplicity and direct interpretation. In order to apply the GLM, the thermal response linearity and time-invariance of fIRI have to be demonstrated, and the thermal impulse response (TIR) needs to be characterized. In this study, the linearity and time-invariance of the thermal response to sympathetic activating stimulation were demonstrated, and the TIR for employment of the GLM was characterized. The performance of the GLM-fIRI was evaluated by comparison with the GLM applied on synchronous measurements of the skin conductance response (SCR). In fact, the GLM-SCR is a validated procedure to estimate autonomic arousal. Assuming the GLM-SCR as the gold standard approach, a GLM-fIRI sensitivity and specificity of 86.4% and 75.9% were obtained. The GLM-fIRI may allow increased performances in the evaluation of autonomic activity and a broader range of application of fIRI in both research and clinical settings for the assessment of psychophysiological and psychopathological states.
Highlights
Functional infrared imaging is a non-invasive methodology that is employed in biomedical applications to evaluate the skin superficial temperature of a body, providing spatial and temporal information in a contactless modality
Skin temperature is modulated by vasodilatation and vasoconstriction, which are themselves regulated by autonomic activity
The first PC was convolved with double-events functions, and the β values were computed for each subject for the double-event stimuli, as described in the methods section
Summary
Functional infrared imaging (fIRI) is a non-invasive methodology that is employed in biomedical applications to evaluate the skin superficial temperature of a body, providing spatial and temporal information in a contactless modality. This technique is widely employed to infer autonomic arousal through the modulation of cutaneous temperature, which is a known expression of the psychophysiological state of the subject. FIRI often exploits time-dependent variations of the skin temperature of the face to infer sympathetic and parasympathetic responses [1]. Skin temperature is modulated by vasodilatation and vasoconstriction, which are themselves regulated by autonomic activity.
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