Neural differences in the mapping of verb and noun concepts onto novel words

A dissociation between noun and verb processing has been found in brain damaged patients leading to the proposal that different word classes are supported by different neural representations. This notion is supported by the facts that children acquire nouns faster and adults usually perform better for nouns than verbs in a range of tasks. In the present study, we simulated word learning in a variant of the human simulation paradigm that provided only linguistic context information and required young healthy adults to map noun or verb meanings to novel words. The mapping of a meaning associated with a new-noun and a new-verb recruited different brain regions as revealed by functional magnetic resonance imaging. While new-nouns showed greater activation in the left fusiform gyrus, larger activation was observed for new-verbs in the left posterior middle temporal gyrus and left inferior frontal gyrus (opercular part). Furthermore, the activation in several regions of the brain (for example the bilateral hippocampus and bilateral putamen) was positively correlated with the efficiency of new-noun but not new-verb learning. The present results suggest that the same brain regions that have previously been associated with the representation of meaning of nouns and verbs are also associated with the mapping of such meanings to novel words, a process needed in second language learning.