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The present study combined the Independent Component Analysis (ICA) and low-resolution brain electromagnetic
tomography (LORETA) algorithms to identify the spatial distribution and time course of single-trial EEG
record differences between neural responses to emotional stimuli vs. the neutral. Single-trial multichannel
(129-sensor) EEG records were collected from 21 healthy, right-handed subjects viewing the emotion emotional
(pleasant/unpleasant) and neutral pictures selected from International Affective Picture System (IAPS). For
each subject, the single-trial EEG records of each emotional pictures were concatenated with the neutral, and a
three-step analysis was applied to each of them in the same way. First, the ICA was performed to decompose
each concatenated single-trial EEG records into temporally independent and spatially fixed components, namely
independent components (ICs). The IC associated with artifacts were isolated. Second, the clustering analysis
classified, across subjects, the temporally and spatially similar ICs into the same clusters, in which nonparametric
permutation test for Global Field Power (GFP) of IC projection scalp maps identified significantly different
temporal segments of each emotional condition vs. neutral. Third, the brain regions accounted for those significant segments were localized spatially with LORETA analysis. In each cluster, a voxel-by-voxel randomization
test identified significantly different brain regions between each emotional condition vs. the neutral. Compared
to the neutral, both emotional pictures elicited activation in the visual, temporal, ventromedial and dorsomedial
prefrontal cortex and anterior cingulated gyrus. In addition, the pleasant pictures activated the left middle prefrontal
cortex and the posterior precuneus, while the unpleasant pictures activated the right orbitofrontal cortex,
posterior cingulated gyrus and somatosensory region. Our results were well consistent with other functional
imaging studies, while revealed temporal dynamics of emotional processing of specific brain structure with high
temporal resolution.
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