Is the late positive potential (LPP) related to memory consolidation?

The late positive potential (LPP) is the component of the event-related potential (ERP) most consistently modulated by the emotional properties of stimuli. This component has been investigated in many studies, but little is known about the cognitive mechanism it reflects. In this study, we tested a model suggesting that the LPP reflects processes related to memory encoding and consolidation. To investigate this, we recorded EEG while participants read a series of neutral and negative words. Memory was then tested at both short (10-15 minutes) and long (12-36 hours, including a period sleep) delays. We predicted that LPP amplitude would be positively correlated with memory, and that this relationship would be stronger after a delay (reflecting a relationship between LPP amplitude and memory consolidation). Consistent with our predictions, we found that LPP amplitude predicted memory in the delayed memory test, but not the immediate memory test. In addition, memory for negative items, compared to neutral items, declined less across the delay, and LPP amplitude mediated this effect of emotion on memory decay.