Dissociating Affective Salience and Valence in (Very) Long-Latency ERPs.

While affective salience effects have been observed consistently in the late positive potential (LPP), no event-related potential (ERP) component has consistently shown ordered valence effects. A recent study, showing images of facial attractiveness, however suggests the existence of valence-related effects at very long latencies (1000-3000 ms post stimulus). This could offer new insights into the time-course of affective neural processing. Yet, it remains unclear whether the long-latency effect was specific to facial attractiveness, or to valence in general. To corroborate the existence of a long-latency valence effect, we presented distinctly positive, neutral, and negative valenced IAPS images to a large sample of 224 participants while recording their electroencephalogram (EEG). Larger ERP amplitudes were elicited by both positively and negatively valenced compared to neutral stimuli (an affective salience effect) from roughly 500 until 1300 ms, followed by an ordered valence effect of larger amplitudes to negatively compared to positively valenced images from 1500 until 2500 ms. These findings corroborate the previously observed sequence of an affective salience effect followed by a long-latency valence effect. However, the polarity of this valence effect was reversed from that of the facial attractiveness study. Allostasis is discussed as potential reconciling factor. Effects in the N2 and P300 components were also found, but could not be clearly labeled as an affective salience or a valence effect. These results fit with two-stage emotion theories such as the theory of constructed emotions.