第29回 音声が関与した紙メディアの読みにおける言語産出過程の認知神経科学的考察

摘要

前回は視覚を用いた読みに触覚が加わることによる視覚野と体性感覚野の感覚統合の問題，および指で頁をめくったり，行を追ったり，下線を引いたりという行為における運動野の関与と運動野から発する末梢神経への感覚信号の伝達の問題を扱った．これらの問題では感覚器官から視覚野および体性感覚野に至る過程での信号処理および感覚統合後の信号処理の問題，さらに運動野から末梢神経を経た信号伝達を考えたにすぎない．%The twenty-ninth article of this series will focus on language production process in the reading of paper media. Particular attentions will be paid to a newly involved factor "sound" in the reading. The overall contents are described in the following sequence.rn(1) IntroductionrnIn previous articles, main concerns are transmission process of visual sensation signals in the reading of paper media. This article newly introduces the issue of "sound", and discusses the language production and language comprehension processes in the reading.rn(2) Different kinds of reading and their brain mechanismrnIn the history of communication, firstly appeared was communication by sound. By invention of characters, communication by writing became prevalent. In oral reading, a feedback loop is formed among eye, brain and speech muscles.rn(3) Auditory pathway and speech perception associated with oral readingrnCommunication by sound and oral reading involve auditory organs. Auditory information is perceived as air vibrations and transmitted through auditory pathway and finally processed at auditory area of brain.rn(4) Perception and cognition of languagernWord cognition is the initial stage of language production and language comprehension. Word cognition takes place by referring to a mental lexicon of the individual brain. Word cognition includes: speech language by auditory sensation and written language by visual sensation.rn(5) Language production process in the readingrnMain analytical tools are PET and fMRI. Language production process can be localized on the brain. Activation studies by PET provide information regarding high-order brain mechanism through the change of regional cerebral blood flow.rn(6) Language production process as high-order brain functionsrnStudies of aprophoria (word blindness) provide information for localizing the language operational capability on the brain. Language-related functions of brain are right-left assymetric in nature.rn(7) Association area playing roles of high-order brain functionsrnAssociation area is any area of the cerebral cortex not devoted to primary sensory or motor functions. Association area integrates information from sensory area and motor area and plays high-order brain functions.rn(8) Reading of paper media and brain mechanismrnAlthough visual sensation plays main roles in reading of paper media, oral reading and haptic reading using finger touch involve motor area, and then forms feedback loops among receptor, brain, and effector. This feedback loop has a possibility of deepen and stabilizing comprehension and memorization by reading.rn(9) EpiloguernAnalysis of a variety of reading method in this article will provide a variety of informations not only for improving paper-based book designing, but also for forseeing the future of electronic display devices.