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, wherein 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 of which includes two pleasantness levels. 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 (> 30Hz) was most sensitive to arousal modulation. Specifically, the high connectivity over the right hemisphere occurred during the pleasant elicitation, whereas that over the left hemisphere occurred during the negative elicitation. In addition, short-range connections in the frontal regions became weaker with increasing arousal level, whereas long-range connections were enhanced. Concerning the spectral analysis, the most significant valence-dependent changes were found at the intermediate arousing elicitations over the prefrontal and occipital regions. The valence classification showed a maximal recognition accuracy of 86.37%