Brain Activation and Deactivation in Human Inductive Reasoning: An fMRI Study

In order to study the cognitive neural mechanism of human inductive reasoning, both the positive and negative activation should be combined. However, most studies only focus on the positive activation and the negative activation of inductive reasoning has not been reported. The present study will examine the two aspects simultaneously. Two experimental tasks were designed according to the magnitude of shared attributes: sharing two common attributes (2T) and sharing one common attribute (1T), and rest acted as control task. 2T and 1T tasks are both inductive reasoning tasks. 2T task contains the component of perceptual features' integration, while 1T does not. Fourteen college students participated in this study. It was showed that, as compared to rest condition, induction activated a distributed regions including prefrontal cortex (BA 6, 9, 11, 46, 47), caudate, putamen, thalamus, etc., and these regions were related to task difficulty. This may reflect the important role the prefrontal-striatal-thalamus loop in inductive reasoning. The fMRI result also showed the significant negative activation of the right superior temporal gyrus (BA 22), the left angular gyrus (BA 39), bilateral middle frontal gyrus (BA 8, 9, 10), posterior cingulated cortex (BA 31) in inductive reasoning as compared to rest condition. These results were consistent with previous studies of default mode network. Future work were required to examine if there exist induction specific positive activation network and negative activation network, and what the relationship between the two networks.