Assessment of Emotion Elicitation Using Multimodal Physiological Sensors and Phase Synchronization

Emotion influences human life and impacts daily life activities. The central nervous system (CNS) and peripheral nervous system (PNS) interact intricately to produce emotional experiences. There are various studies related to the interaction of the CNS-PNS during psychophysiological states. However, emotion-oriented, CNS-PNS phase synchronisation studies are limited. In this work, an attempt is made to investigate the interaction between the CNS and PNS using electroencephalogram (EEG) and photoplethysmogram (PPG) during emotional elicitation evoked by audio–visual stimuli. For this, EEG and PPG signals from the publicly accessible DEAP database are utilized. EEG signals are segmented into four frequency bands: theta (4–8 Hz), alpha (8–13 Hz), beta (13–30 Hz), and gamma (30–45 Hz). Subsequently, the instantaneous phases of EEG and PPG are computed and employed to determine the phase synchronization index (PSI). Finally, the Wilcoxon Rank-sum test is performed to estimate the statistical significance of the PSI in low verus high levels of arousal and valence emotional states. Results show that the theta band of the EEG has the highest phase synchronization with the PPG signals. In low arousal, there's higher phase synchronization, whereas high valence exhibits higher phase synchronization. The FC5, C3, PO3, and F4 electrodes are found to be statistically significant (
p
< 0.01) for arousal. For valence PO4 (
p
< 0.01) is found to be statistically significant in discriminating valence levels. It is also evident that PSI based on the theta and alpha bands can distinguish levels of arousal and valence. Hence, the proposed approach can be used to better understand the CNS-PNS interaction in various emotional states under clinical conditions.