Frontal ERP slow waves during memory encoding are associated with affective attitude formation.

A neutral stimulus can acquire valence by being paired with a valenced stimulus, leading to a new attitude towards the previously neutral stimulus. There is, however, considerable debate about the mechanisms that underlie this process of affective attitude formation. Therefore, in the present study we employed a single-trial, intentional learning procedure that paired neutral with valenced words while recording ERP activity, and measured subsequent memory and subsequent attitudes for the pre-experimentally neutral words immediately following learning. Using traditional as well as single-trial ERP analyses, we found that frontal slow wave (FSW) activity, elicited while stimuli were being paired, was associated with both subsequent memory for the word pairs and subsequent attitudes towards the pre-experimentally neutral words. Specifically, FSW activity during the pairing of neutral with positive words was related to more positive subsequent attitudes, while during the pairing of neutral with negative words, it was associated with more negative subsequent attitudes, towards the pre-experimentally neutral words. Given that this FSW activity was also related to successful subsequent episodic memory retrieval for the word pairs, these findings provide evidence that the transfer of valence may depend on a process that supports associative episodic encoding during word paring. Further, a single-trial, mixed-effects model indicated that the relationship between encoding FSW activity and subsequent attitudes depended on the strength of the episodic memory trace. Thus, the present study provides novel evidence that a common mechanism contributes to both episodic memory encoding and affective attitude formation.