デカルト的意識の脳内表現 : 心の理論からのアプローチ (特集 : 「心の科学」)

Abstract

The biological basis of social interaction is reviewed from the perspective of "how our brain makes it possible to read other people's minds". Recent developments of cognitive neuroscience coupled with cognitive psychology demonstrated that brain disorders can impair certain social interactions due to malfunction of the "social brain". Brain imaging studies based on fMRI (functional Magnetic Resonance Imaging) studies suggest that a network of areas connecting the prefrontal and temporal cortex of the human brain forms the neural basis of mentalizing ("theory of mind" : ToM), that is, representing one's own and other people's mental state. Using event-related fMRI, we investigated the neural substrates of the working memory's executive (attention control) system with respect to differences in working memory capacity. To explore individual differences in the executive control process for the mentalizing task (ToM-task), we introduced a reading span test composed of short sentences to invoke mentalizing of other people's mental state. Two subject groups were selected : those with high working memory capacities, labeled high-span subjects (HSS) according to the reading span test, and those with low working memory capacities, labeled lowspan subjects (LSS). Results showed significant activation in three regions in comparison with controls : left dorsolateral prefrontal cortex (DLPFC), left inferior frontal gyrus (IFG) and left temporo-parietal junction (TPJ) area under the ToM task. For both HSS and LSS groups, the fMRI signal intensity increased in IFG and TPJ during the RST-initiated ToM task, while the left DLPFC region was uniquely activated in HSS group. Behavioral data also showed that performance was better in HSS than in LSS. The results suggest that the working memory's executive function related to representing one's own and other people's mental states is likely to be actively based in the left DLPFC in HSS.