Neural correlates of encoding in novel word learning

A central observation in the recognition memory literature is that neural processes occurring during encoding of stimuli are predictive of their later recognition and recall. Compared to items that are later forgotten, encoding of correctly recognised items has been associated with greater amplitude between 400 ms and 800 ms post stimulus onset across centro-parietal sites (the difference-due-to-memory ERP effect), increased EEG power in the theta and gamma frequency bands and decreased EEG power in the alpha and beta bands, and increased theta-gamma phase-amplitude coupling. Importantly, theories of encoding based on these findings imply that these effects should be domain-general. In this pre-registered study, we tested this assumption by exploring neural correlates of successful encoding in learning of novel names for novel concepts. Following the previous studies, we used three different measures of neural activity, ERPs, time-frequency representations of power, and phase-amplitude coupling; however, for either of these measures, we could not reject the null hypothesis of no difference between the novel names that were later recalled and those that were not. We provide three possible interpretations of our findings, and our main conclusion is that the existing theories of encoding may be underspecified and that properly-powered pre-registered studies are needed to further constrain these theories.