Categorization of unilaterally presented emotional words: an ERP analysis

Abstract

This study is intended to clarify the functional role of different ERP components as indicators of the processing of emotions. The effect of emotional connotation of words on hemispheric lateralization is also explored. Visual ERPs were recorded to unilaterally presented positive, negative, and neutral words that should be categorized according to their emotional connotation. The P2 amplitude was larger to positive than to negative words whereas P3 amplitude was larger to positive words compared with neutral ones. The slow positive wave (SPW) was influenced by words emotionality at anterior and posterior sites differently. The amplitude of the N1 component was larger in the left hemisphere to contralaterally presented words. The P2 and P3 components were larger over the left hemisphere whereas the N3 and N4 components were larger over the right hemisphere to ipsilateral stimulation. The results support our hypotheses on the functional role of positive ERP components in the processing of an affective words connotation: the P2 wave reflects a general evaluation of emotional significance, the P3 a task-related decision, and the SPW an additional decision control in the context of the emotional experience of an individual. Neither the ``right hemisphere hypothesis'' nor ``valence hypothesis'' on lateralization of the processing of emotions were confirmed. Each hemisphere seems to exert its effect on emotion through specific hemispheric resources that are unequally allocated along the different stages of task processing and may cause alternation of hemispheric dominance.