Analysis of intelligent visual processes by behavioral observation and MEG measurement

本研究的目的是通过对日本人的行为观察和脑活动的测量，来揭示日本人感知和识别汉字和符号的智能视觉过程。在行为观察中，我们使用了视觉形式的认知任务，测量了反应时和正确率。作为大脑活动的一部分，我们测量了受试者在执行任务时的MEG反应。主要结果如下：1.单汉字识别元音和形态特征的两种认知任务的反应时差异不显著。然而，从脑磁图分析，在150-300毫秒后的字符启动不同的方式，左腹枕颞区是选择性活跃的受试者在元音检测，但从腹顶枕区活跃的形态检测。这些结果表明，视纹外区的皮层神经活动将通过自上而下的机制进行修改，这取决于个体识别书写字符的策略，即，更普遍的书面证词。2.三字词分类任务和单字元音识别任务的反应时无显著差异。然而，在符号的形态检测任务中，RT明显较短，这表明该任务的容易性。这些刺激和任务的神经活动通常在150-300 ms时在内侧枕区到腹枕区观察到。除此之外，左枕颞活动在单词任务中被选择性地观察到，而不是字符和符号任务。结合以往对各种视觉形式加工的研究，我们认为左腹枕颞区是特定视觉文字加工和/或复杂视觉形式一般加工的主要区域。

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 results 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.