Non-linear dynamical coupling between different brain areas during evoked emotions: an EEG investigation

This study examined changes in the non-linear dynamical coupling between different brain areas in response to emotionally valenced (i.e. neutral, affective positive and negative) film stimuli in 76 healthy volunteers. EEG was recorded from 18 sites (10-20 system). A new dynamical measure, mutual dimension (Dm) was applied to the EEG. The Dm was calculated between each electrode paired to all other electrodes. The results were compared to coherence measures. Differential patterns of significant changes of Dm estimates were found in the two emotional conditions. When compared to the neutral viewing condition, the emotionally negative experience provoked significant decreases of short- and long-distance ipsi- and contralateral Dm estimates that were more left-sided (with a 'center of gravity' of Dm decrease at the F7 site), whereas the emotionally positive experience showed a pattern of symmetrically distributed ipsi- and contralateral increases of Dm estimates over central and posterior cortical regions (with 'main processing nodes' of Dm increases at T5 and T6 sites). It is concluded that estimates of the mutual dimension are sensitive to subtle aspects of emotional processing, not accessible by linear (i.e. coherence) analyses.