Role of the left inferior frontal gyrus in transforming format types of action descriptions between stimuli and representations

We performed a functional magnetic resonance imaging study to elucidate the process involved in the transformation of the format types of action descriptions between stimuli and representations. We independently manipulated the format types of both stimuli (visual action [Vi] vs. verbal [Ve] stimulus) and internal representations (Vi vs. Ve representation) and set four types of experimental tasks. Each participant was required to generate a Vi or Ve representation after being presented with a Vi or Ve stimulus, according to each task. Increased activity in the left inferior frontal gyrus (IFG) (Brodmann areas 44 and 45) was found in the transformation contrast: ([Vi stimulus and Ve representation] + [Ve stimulus and Vi representation]) > ([Vi stimulus and Vi representation] + [Ve stimulus and Ve representation]). This result suggests that the left IFG is involved with the transformation process and has the function of generating an internal representation in a format different from that of externally presented stimuli.