Concept activation and coordination of activation procedure require two different networks.

In the present study, we used EEG-coherence analysis to assess general regional changes in neuronal activity related to semantic retrieval, testing the hypothesis that concept activation and coordination procedures are neurobiologically distinguishable. Four subjects had to decide whether or not a capital letter and a lower case letter have the identical name (e.g. Aa). This task requires two mental procedures: (i) the activation of concepts and (ii) their coordination, particularly when the interstimulus interval is shorter than the duration of concept activation. This memory retrieval of a concept appears to be subserved by two distinct networks: the left parietotemporal region for concept activation and the prefrontal region for coordination.