Functional neuroanatomy of three-term relational reasoning

In a recent study we demonstrated that reasoning with categorical syllogism s engages two dissociable mechanisms. Reasoning involving concrete sentence s engaged a left hemisphere linguistic system while formally identical argu ments. involving abstract sentences, recruited a parietal spatial network. The involvement of a parietal visuo-spatial system in abstract syllogism re asoning raised the question whether argument forms involving explicit spati al relations (or relations that can be easily mapped onto spatial relations ) are sufficient to engage the parietal system? We addressed this question in an event-related fMRI study of three-term relational reasoning, using se ntences with concrete and abstract content. Our findings indicate that both concrete and abstract three-term relational arguments activate a similar b ilateral occipital-parietal frontal network, However. the abstract reasonin g condition engendered greater parietal activation than the concrete reason ing condition, Wr conclude that arguments involving relations that can be e asily mapped onto explicit spatial relations engage a visuo-spatial system, irrespective of concrete or abstract content. (C) 2001 Elsevier Science Lt d. All rights reserved.