Abstract
The hedonic meaning of words affects word recognition, as shown by behavioral, functional imaging, and event-related potential (ERP) studies. However, the spatiotemporal dynamics and cognitive functions behind are elusive, partly due to methodological limitations of previous studies. Here, we account for these difficulties by computing combined electro-magnetoencephalographic (EEG/MEG) source localization techniques. Participants covertly read emotionally high-arousing positive and negative nouns, while EEG and MEG were recorded simultaneously. Combined EEG/MEG current-density reconstructions for the P1 (80–120 ms), P2 (150–190 ms) and EPN component (200–300 ms) were computed using realistic individual head models, with a cortical constraint. Relative to negative words, the P1 to positive words predominantly involved language-related structures (left middle temporal and inferior frontal regions), and posterior structures related to directed attention (occipital and parietal regions). Effects shifted to the right hemisphere in the P2 component. By contrast, negative words received more activation in the P1 time-range only, recruiting prefrontal regions, including the anterior cingulate cortex (ACC). Effects in the EPN were not statistically significant. These findings show that different neuronal networks are active when positive versus negative words are processed. We account for these effects in terms of an “emotional tagging” of word forms during language acquisition. These tags then give rise to different processing strategies, including enhanced lexical processing of positive words and a very fast language-independent alert response to negative words. The valence-specific recruitment of different networks might underlie fast adaptive responses to both approach- and withdrawal-related stimuli, be they acquired or biological.
Highlights
Emotional stimuli are perceptually processed with higher priority than neutral stimuli
This is reflected in faster detection times of emotional compared to neutral stimuli in behavioral paradigms (e.g., [2]), in enhanced amplitudes of event related potentials and magnetic fields (ERPs, ERMFs) in electro- and magnetoencephalography (EEG, MEG) (e.g., [3,4,5,6,7]), as well as in an enhanced blood oxygen level dependent response in the visual cortex (e.g. [8])
Imaging data gave rise to a second proposal, according to which lateral orbital prefrontal cortex (PFC) regions are preferentially activated by negative stimuli, whereas ventromedial PFC regions are more sensitive to positive stimuli (e.g. [46,52])
Summary
Emotional stimuli are perceptually processed with higher priority than neutral stimuli (for review, see [1]). The data revealed enhanced activation in the anterior cingulate cortex (ACC) to negative pictures in the P1, whereas in the P2, both positive and negative pictures recruited this structure more than neutral ones Such emotional attention mechanisms, labeled motivated attention [14], have been postulated to ensure that an organism notices potentially revival relevant stimuli without effort. As for non-symbolic emotional stimuli, functional magnetic resonance imaging (fMRI) studies have revealed higher amygdala activity for arousing negative and/or positive words than for neutral words (e.g., [17,39,40,41,42,43,44]) suggesting that the amygdala, a key structure in emotional processing (e.g., [45]), preferentially processes emotional arousal. In verbal stimuli, there is so far no evidence for early valence-specific prefrontal activation (for review, see [58]), nor for the validity of any of the above hypotheses
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