Brain signatures of semantic activation for words that do not exist

The experience of making sense of novel words is ubiquitous in human communication. Still, novel words have traditionally been considered as meaningless by cognitive research. Here we combined behavioral, univariate and multivariate fMRI techniques, and computational modelling to explore whether and how novel words activate the neurocognitive hallmarks of semantic processing triggered by existing words, and whether this process is influenced by the presence of familiar functional linguistic elements, i.e., morphemes. We observed that semantic activation for novel words is comparable to that of existing words, provided that novel words contain a concatenation of identifiable morphemes. In addition, representational similarity analysis highlighted that existing words and novel words containing morphemes (but not novel words not containing morphemes) can activate fine-grained semantic representations. These results suggest that the difference in the neurocognitive underpinnings of semantic processing for existing and novel words might be quantitative rather than qualitative and based on how reliably linguistic form points to meaning.