Investigation of neuronal substrates for language processing, using word priming

We investigated changes in the behavioral performance and brain activities associated with word priming in a Word Stem Completion (WSC) task in Japanese. In the behavioral results, we found obvious facilitatory effects in subject's performance. The percentage of correct answers in word non priming (P/N) condition was 94%, while the percentage of correct answers in word priming P/Y-condition was 100%. Averaged reaction time in word P/N condition was 1501ms, while that of word P/N-condition was 978ms and 3106ms in non word P/Y-condition respectively. In the fMRI experiment, the same tasks were performed by the block-design experimental paradigm without any overt response in MRI scanner. As the fMRI results, we found the activations in the bilateral middle and inferior frontal gyrus with right hemispheric prevalence, the superior and inferior parietal gyrus, and the supplementary motor area. The prefrontal-parietal network observed in our study is consistent with the activated areas in word stem task in English. These results suggested that the facilitatory effects observed in WSC-test include implicit memory access and the induced attention after successful retrieval.