Frontal EEG Asymmetry of Emotion for the Same Auditory Stimulus

Abstract

Emotions play an important role in human interaction and decision-making processes. Frontal asymmetry in brain activity is a promising neurophysiological indicator of emotion. Emotions are psychologically explained by the valence-arousal model, but as yet, frontal asymmetry has not been fully explained by this model. In this study, we explored frontal asymmetry of emotions based on the valence-arousal model using the same auditory stimulus. Changes in emotional states using self-report questionnaires were investigated before and after the auditory stimulus. Spectral power and weighted phase lag index were calculated in the delta, theta, alpha, beta, and gamma bands. Phase-amplitude coupling was also measured to explore communication among different frequency bands associated with emotions. After the auditory stimulus, alpha power decreased in both left and right frontal regions and the deltaweighted phase lag index in the left-right regions was increased. However, no frontal asymmetry was identified after the auditory stimulus. Additionally, we explored the brain changes according to the valencearousal model based on emotional states. After the auditory stimulus, frontal asymmetry of alpha power was clearly observed only for negative valence. This finding was possible because subjective emotions were considered despite listening to the same stimulus. Finally, phase-amplitude coupling identified lefthemisphere dominance after the auditory stimulus, regardless of subjective emotions. These results may help us understand frontal asymmetry associated with emotional mechanisms. In addition, these findings can be used directly in the brain-computer interface to improve emotion recognition performance for realworld practical applications. INDEX TERMS Electroencephalogram (EEG), Emotion, Frontal asymmetry, Power spectral density (PSD), Weighted phase lag index (WPLI), Phase-amplitude coupling (PAC).

Comparing Neural Correlates of Human Emotions across Multiple Stimulus Presentation Paradigms

“…Figure 6 depicts the average neural pattern changes for fear vs. joy emotional states. In general, these pictures show that CSP filters appeared as generally smoother and physiologically more relevant, with strong weights in relevant brain regions, as expected from findings in the literature [26,32,33,45,46,65]. With respect to each of the considered paradigm, the findings are elaborated subsequently.…”

“…Often, within this domain, asymmetric frontal cortical activity is studied by comparing alpha oscillation responses across the left and right brain regions. Lee et al [26] reported a decrease in alpha power within the right and left frontal brain regions. Otten and Jonas [52] conducted a study to evoke emotions using emotion-evoking words, and compared pleasant, unpleasant, and neutral conditions.…”

“…While reviewing the literature focusing on emotion elicitation with sounds or auditory stimuli, we observed that various features have been explored and studied [26,32,33]. In one study, Lee et al [26] reported a decrease in alpha power within the right and left frontal brain regions. Moreover, phase lag index values for each of the frequency bands of delta, theta, alpha, beta, and gamma were calculated.…”

“…Performing the literature review, we found various studies which analyzed alpha oscillation responses while the participants were experiencing different emotional states [26][27][28][29][30][31][32]. Often, within this domain, asymmetric frontal cortical activity is studied by comparing alpha oscillation responses across the left and right brain regions.…”

“…While reviewing the literature, we found that most of the EEG emotion recognitionbased studies have used a single method to elicit emotions [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. Thus, the question as to "whether different stimuli of elicitation for same emotion generate any subject and stimuli independent correlates" remains unanswered.…”