The dynamics of deductive reasoning: an fMRI investigation.

Although the basis for deductive reasoning has been a traditional focus of philosophical discussion, the neural correlates and mechanisms that underlie deductive reasoning have only recently become the focus of scientific investigation. In syllogistic deductive reasoning information presented in two related sequential premises leads to a subsequent conclusion. While previous imaging studies have identified frontal, parietal, temporal, and occipital complexes that are activated during these reasoning events, there are substantive differences among the findings with respect to the specific regions engaged in reasoning and the contribution of language areas. Further, little is known about the various stages of information processing during reasoning. Using event-related fMRI and an auditory and visual conjunction technique, we identified a long-range supramodal network active during reasoning processes including areas in the left frontal and parietal regions as well as the bilateral caudate nucleus. Time courses of activation for each of these regions suggest that reasoning processes emerge during the presentation of the second premise, and remain active until the validation of the conclusion. Thus, areas within the frontal and parietal regions are differentially engaged at different time points in the reasoning process consistent with coordinated intra-network interactions.