Small-world properties of brain Functional Connectivity Networks are affected by emotional stimuli

The aim of this study was to examine whether Functional Connectivity Networks (FCN) obtained during exposing the humans to emotional stimuli, vary according to the characteristics of the stimuli. Twenty-eight participants passively viewed emotional pictures from International Affective Picture System (IAPS) ranging across both arousal and pleasure dimensions. Electroencephalographic (EEG) signals were simultaneously recorded from 19 scalp sites. Relative Wavelet Entropy (RWE) was estimated for all EEG electrode pairs. Different RWE thresholds were set in order to form the corresponding FCNs. Graph theory metrics, such as Density, Cluster Coefficient and Global Efficiency were calculated for all FCNs. It was found that arousal significantly affected small-world properties of FCNs formed from 42 to 170 msec; low arousing pictures elicited FCN with higher Density, higher Cluster Coefficient and higher Global Efficiency as compared to high arousing ones.