EEG phase synchronization during emotional response to positive and negative film stimuli.

In the present study the patterns of interdependency between different brain regions were investigated as volunteers looked at emotional and non-emotional film stimuli. The main goal was to evaluate the emotion-related differences and to check their consistency during the elaboration of the same type of stimuli in repeated presentations. A measure called synchronization index (SI) was used to detect interdependencies in EEG signals. The hypotheses were that emotional-information processing could involve variation in synchronized activity and that two valence-specific emotions - happiness and sadness - differ from each other. The SI obtained was compared among the various experimental conditions and significant changes were found. The results demonstrated an overall increase of SI during emotional stimulation and, in particular, during sadness, which yielded a pattern involving a large exchange of information among frontal channels. On the other hand, happiness was associated with a wider synchronization among frontal and occipital sites, although happiness itself was less synchronized. We conclude that the SI can be successfully applied for studying the dynamic cooperation between cortical areas during emotion responses.