Neural substrates of priming effect for Japanese word and nonword when compared to figure form

The fundamental study of human memory systems is very important for the early checkup of disorders, such as Alzheimer's disease. In this study, as we reveal the fundamental mechanism of human memory and specify the neuronal substrates of human memory system, we conducted the functional magnetic resonance imaging (fMRI) experiment using word priming. We first conducted the behavioral experiments of the priming test, in which the response time and the percentage of correct answer were measured. And then, we investigate the neuronal substrate for word priming using fMRI. Our results would provide a better understanding of human memory systems. 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 die percentage of correct answers in word priming P/Y-condition was 100%. Averaged reaction time in word P/N-condition was 150 lms, while that of word P/Y-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. 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 included implicit memory access and the induced attention after successful retrieval.