Brain Dynamics During Arousal-Dependent Pleasant/Unpleasant Visual Elicitation: An Electroencephalographic Study on the Circumplex Model of Affect

Emotion regulation to pleasant and unpleasant stimuli involves several brain areas, such as the prefrontal cortex, amygdala, and insular cortex. However, how a specific arousal level affects such brain dynamics is not fully understood. To this effect, we propose an electroencephalography (EEG)-based study, where 22 healthy subjects were emotionally elicited through affective pictures gathered from the International Affective Picture System. Based on the circumplex model of affect, we used four arousing levels, each with two valence levels (i.e., pleasant and unpleasant). Considering these levels, we investigated the EEG power spectra and functional connectivity among channels. We then used this information to build an automatic valence classifier. The experimental results showed that the functional connectivity at the highest frequency bands (i.e., > 30 Hz) was most sensitive to arousal modulation. Specifically, high connectivity over the right hemisphere occurred during pleasant elicitation, whereas that over the left hemisphere occurred during negative elicitation. In addition, short-range connections in the frontal regions became weaker with increased arousal level, whereas long-range connections were enhanced. Concerning the spectral analysis, the most significant valence-dependent changes were found at intermediate arousing elicitations over the prefrontal and occipital regions. The automatic valence classification showed a recognition accuracy of up to 86.37 percent.