HIRATA Yoshihiro Hokkaido Univ., Res.Inst.for Electron.Sci.Res.Assoc., 電子科学研究所, 助手 (30250509)
KOBAYASHI Tetsuo Hokkaido Univ., Res.Inst.for Electron.Sci.Assoc.Prpf., 電子科学研究所, 助教授 (40175336)
TAKEUCHI Fumiya Hokkaido Univ., Res.Inst.for Electron.Sci.Res.Assoc., 電子科学研究所, 助手 (30281835)
|Budget Amount *help
¥4,600,000 (Direct Cost : ¥4,600,000)
Fiscal Year 1997 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1996 : ¥2,800,000 (Direct Cost : ¥2,800,000)
The objective of this research project is to delineate the intelligent visual processes to perceive and recognize Japanese characters and symbols, based on the behavioral observation and the measurement of brain activity. For the bbehavioral observation, we used a cognition task of visual forms, where the reaction time and the percent correct performance were measured. As the brain activity, we measured MEG responses while subjects performed the task. The main results are summarizedbelow :
1. The RT measured in two cognition tasks of single Kanacharacters to detect vowels and morphological features was not signijicantly different each other. However, the focal neural activities, as located from the MEG analysis, at 150-300 ms after the character onset differed in a manner that the left ventraloccipitotemporal region is selectively active across subjects in the vowel detection, but the areas from the ventralto parietaloccipital region were active in the morphology detection. These result
s suggest that the cortical neural activity in the visual extrastriate areas would be modidied, through topdown mechanisms, depending on the individual strategy to recognize written characters, i.e., more generally written sentences.
2. The RT measured ia a categorization task of threecharacter words and that in a vowel detection task of single characters was not different. However, RT was significantly shorter in a morphology detection task of symbols, which indicates the easiness of this tadk. Neural activites for these stimuli and tasks were commonly observed at 150-300 ms in the medialoccipital to ventraloccipital areas. In addition to these, the left occipitotemporal activity was selectively observed in the word task, but not character and symbol tasks. Taking into consideration of previous studies on various visual form processing, it is suggesed that the left ventraloccipitotemporal area subserves specific visual word processing and/or general processing of complex visual forms.