Wavelet Phase Coherence Estimation of EEG Signals for Neuromarketing Studies

Abstract: This paper presents an Electroencephalography (EEG), Pulse Plethysmography (PPG) and Galvanic Skin Response (GSR) study for neuromarketing studies, which are related to analysis of relationship between electrodes and emotional stress across to commercial advertisement. Neuromarketing is a field of study with respect the application of neuroscience methods to analyze consumer behavior related to markets. Wavelet coherence (WC) and phase difference (PD) were used for investigating how the marketing stimuli induced the degree of information flow occurs between electrodes of EEG. Pulse rate variability (PRV) obtained from finger PPG and computed the powers in high frequency (HF), low frequency (LF). The powers in the LF and HF bands are regulated by Autonomic nervous systems (ANS) and then, Skin conductance level (SCL) computed from GSR by measuring changes in the conductivity of the skin. These electrophysiological measurements computed to evaluate emotional stress. The signals were recorded simultaneously from 30 subjects for two stages: prior to advertising stimuli (control stage) and during the advertising stimuli (experimental stage) using iMotions system in Uskudar University (Istanbul, Turkey). The WC and PD for each electrode pairs were computed for five frequency sub-bands (delta, theta, alpha, beta and gamma) of EEG. While the value of WC was generally higher in experimental stage than control stage especially in the theta, alpha and beta frequency, the value of PD was generally lower especially in gamma band. An increase of interhemispheric coherence in experimental stage occurred in the anterior frontal -temporal-parietal- area. At the same time, the LF/HF ratio and SCL were generally higher in experimental stage. We investigated whether there were statistically significant differences in WC, PD, the LF/HF ratio and SCL between the experimental and control stage. Results were demonstrated significant differences in WC and PD, LF/HF ratio between experimental stage and control stage, but there was not in SCL.