Category-Specific Representation of Words Independent of Language and Input Modality.

Abstract:
Two experiments investigated neural substrates of semantic knowledge in the human brain using fMRI. We defined three criteria for identifying category specific brain regions. First, we used a similar task to contrast two categories, numerals and names of body parts, which are known to be dissociable in brain-lesioned patients. Second, we requested the active areas to discriminate between numbers and body parts in each of two languages in bilingual subjects. Third, we also tested category-specificity in each of two modalities of input (spoken and written words). Our experiment was replicated once in a block design paradigm and also in an event related paradigm. Several occipital and temporal areas were significantly affected by either modality, language or both. However we identified two distinct networks that were differentially active for a given category of words regardless of modality and language. Our results confirm that some brain areas code for the manipulation of specific categories of knowledge, and reveal that they abstract away from the specific characteristics of the input words.