The processing of emotional connotation - An EEG-Study

Previous ERP studies on the selective processing of emotional and neutral words suggest that emotional words are processed in a facilitated manner. This enhanced processing of emotional content is indicated at relatively early processing stages by the so called Early Posterior Negativity (EPN). The EPN occurs over occipito-parietal sensors at around 200ms after stimulus-onset and is larger in response to emotionally arousing pleasant and unpleasant words than in response to neutral ones (e.g. Herbert at al., 2008; Kissler et al., 2007). These results suggest that emotional modulation of the EPN indicates an early tagging of emotionally arousing concepts (see Kissler et al. 2006).The main purpose of the present study was to provide further evidence for the view that the EPN reflects enhanced early semantic processing of emotional words.Event-related potentials were recorded using a 256-channel EEG during reading of high-arousal pleasant and unpleasant and low-arousing neutral nouns. Emotional and neutral words were presented randomly and together with a set of pseudowords and letterstrings to a total of 27 student participants. Stimuli were presented at two different processing rates (330ms, 600ms) in two different presentation paradigms (RSVP, ISI). At the end of the experiment, a surprise free-recall task was given to the subjects.Results were in line with the previous found modulation of the EPN by emotional (positive and negative) word content (valence). Additionally we observed this modulation especially in response to the positive words: Across the experimental manipulations, pleasant words were associated with an increased early posterior negativity. This facilitated processing of pleasant content was also reflected in better incidental memory performance for pleasant than unpleasant and neutral words.In the time window of the EPN at 200-300ms after word presentation a left hemispheric processing advantage occurred for words compared to the meaningless pseudowords and letterstrings. This differentiation between words and meaningless but wordlike pseudowords supports the interpretation of the EPN as indicator of lexical-semantic processing.