Eye Gaze–Induced Mental Stress Alters the Heart Rate Variability Analysis

The objective of this work was to investigate mental stress produced under eye fixation through the analysis of heart rate variability (HRV). The multichannel electrophysiological data (electrocardiogram, pulse plethysmogram along with electro-oculogram) were acquired from young, healthy male volunteers (aged 20-30 years; weight, 55-65 kg), and 20 trials per subject were recorded for 30 seconds of eye gaze followed by 10 seconds of relaxation. The parameters for HRV were calculated, analyzed, and compared before the feature extraction and classification of eye gaze from rest using “fuzzy C means clustering” and “Kohonen neural network.” Only HRV data were considered for final feature extraction and classification purposes as the pulse rate variability represented similar variations as HRV. Irrespective to subject and condition, analyses show changes in all the parameters, but with contradiction in 1 of 2 subjects that showed no change in at least 1 parameter. Furthermore, on the extracted features from frequency spectrum of HRV data (100 gaze and 100 relax), fuzzy C means clustering and Kohonen neural network were found to be efficient with an accuracy of 98%. This high accuracy in features classification strongly supports its practical implementation in the evaluation of mental stress level.