Although it is widely accepted that nouns and verbs are functionally independent linguistic entities, it is less clear whether their processing recruits different brain areas. This issue is particularly relevant for those theories of lexical semantics (and, more in general, of cognition) that suggest the embodiment of abstract concepts, i.e., based strongly on perceptual and motoric representations. This paper presents a formal meta-analysis of the neuroimaging evidence on noun and verb processing in order to address this dichotomy more effectively at the anatomical level. We used a hierarchical clustering algorithm that grouped fMRI/PET activation peaks solely on the basis of spatial proximity. Cluster specificity for grammatical class was then tested on the basis of the noun-verb distribution of the activation peaks included in each cluster. Thirty-two clusters were identified: three were associated with nouns across different tasks (in the right inferior temporal gyrus, the left angular gyrus, and the left inferior parietal gyrus); one with verbs across different tasks (in the posterior part of the right middle temporal gyrus); and three showed verb specificity in some tasks and noun specificity in others (in the left and right inferior frontal gyrus and the left insula). These results do not support the popular tenets that verb processing is predominantly based in the left frontal cortex and noun processing relies specifically on temporal regions; nor do they support the idea that verb lexical-semantic representations are heavily based on embodied motoric information. Our findings suggest instead that the cerebral circuits deputed to noun and verb processing lie in close spatial proximity in a wide network including frontal, parietal, and temporal regions. The data also indicate a predominant—but not exclusive—left lateralization of the network.
Keywords: neuroimaging, noun-verb dissociation, meta-analysis, clustering algorithm, task demand, left inferior frontal gyrus
Citation: Crepaldi D, Berlingeri M, Cattinelli I, Borghese NA, Luzzatti C and Paulesu E (2013) Clustering the lexicon in the brain: a meta-analysis of the neurofunctional evidence on noun and verb processing. Front. Hum. Neurosci. 7:303. doi: 10.3389/fnhum.2013.00303
Received: 08 January 2013; Accepted: 06 June 2013;
Published online: 27 June 2013.
Edited by:Barbara Tomasino, IRCCS E.Medea, Italy
Reviewed by:Carlo Semenza, Università degli Studi di Padova, Italy
Copyright © 2013 Crepaldi, Berlingeri, Cattinelli, Borghese, Luzzatti and Paulesu. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.
*Correspondence: Davide Crepaldi, MoMo Lab, Dipartimento di Psicologia, Università di Milano-Bicocca, piazza dell'Ateneo Nuovo 1, 20126 Milano, Italy e-mail: firstname.lastname@example.org