Abstract
The Complementary Learning Systems (CLS) theory provides a powerful framework for considering the acquisition, consolidation and generalisation of new knowledge. We tested this proposed neural division of labour in adult humans through an investigation of the consolidation and long-term retention of newly learned native vocabulary. Over three weeks, participants (n=20) learned the names and corresponding semantic descriptions of previously-unknown, uncommon objects and animals. Training was successful with a mean 88% gain. Functional neuroimaging data were acquired post-learning. Newly learned items were compared to two conditions: (i) previously known items to highlight the similarities and differences with established vocabulary; and (ii) unknown/untrained items to provide a control for non-specific perceptual and motor-speech output. Consistent with the CLS, retrieval of newly-learned items was supported by a combination of regions associated with episodic memory (including left hippocampus) and the language-semantic areas that support established vocabulary (left inferior frontal gyrus and left anterior temporal lobe). Furthermore, there was a shifting division of labour across these two networks in line with the consolidation status of the item; faster naming was associated with more activation of language-semantic areas and lesser activation of episodic memory regions. Neuroimaging measures of hippocampal activity during naming predicted more than half the variation in naming retention six months later.
Competing Interest Statement
The authors have declared no competing interest.