カナ表記した文字・単語の処理および内語に関わる脳活動計測 Measurement of Neural Activity Related to Processing of Katakana Characters, Words and Inner Speech

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著者

    • 藤巻 則夫 FUJIMAKI Norio
    • 独立行政法人 通信総合研究所 基礎先端部門 関西先端研究センター 脳機能グループ Brain Function Group, Kansai Advanced Research Center, Basic and Advanced Research Division, Communications Research Laboratory

抄録

カナ文字と疑似文字およびこれらの文字列を視覚呈示して, 形態・音韻・意味処理を段階的に変えた課題を実験し, fMRIとMEGを使って脳活動部位と潜時を計測した.形態処理に関わる脳活動として, 刺激呈示後約200ms以内に視覚前野外側部, 紡錘状回, 側頭後下部で活動が現れ, (1) カナ文字と疑似文字とでは脳活動に差がなく, (2) 単一の文字では脳活動に左右差がないが, 文字列に対しては左半球優位となった.音韻処理については, 約200ms以降にウェルニケ野, 縁上回, ブローカ野ないし島の活動が現われた.なお音韻処理を細分化するため, 内語だけを行う別の課題の実験を行ったが, 音韻処理に関わる3部位とも顕著な負荷依存性を示し, 連動して活動することがわかった.意味処理は, 今回の課題では分離できなかったが, ウェルニケ野などの音韻処理の部位に重なって活動を生じた可能性がある.

This review summarizes a recent experiment conducted using fMRI and MEG to measure neural activation related to orthographic (more generally visual form), phonological, and lexico-semantic processes for visually presented Japanese katakana (phonogram) characters, pseudocharacters, and strings of these characters. Activity related to visual form processing was observed at latencies earlier than about 200 ms in the lateral extrastriate visual cortex, fusiform gyrus, and posterior inferior temporal areas. (1) The activation was the same between katakana characters and pseudocharacters, and between katakana strings or words and pseudocharacter strings. (2) The activation occurred in both hemispheres for single characters, but was left-lateralized for strings of characters. The activity related to phonological processing was observed at latencies later than about 200 ms in Wernicke's area, the supramarginal gyrus, and Broca's area or insula. To investigate differences in functional roles between the phonology-related areas, we conducted another experiment that required inner speech but no other phonological processes, and found that activity at all three phonological areas depended significantly on task demands. This result suggests that these areas worked together for inner speech, although they may each play different roles. Although activation for semantic processing could not be dissociated from that for the other processes in this study, there is a possibility that the semantic processing shares activation foci, e.g., near Wernicke's area, with the phonological processing.

収録刊行物

  • 音声言語医学

    音声言語医学 42(2), 188-194, 2001-04-20

    The Japan Society of Logopedics and Phoniatrics

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各種コード

  • NII論文ID(NAID)
    10008579235
  • NII書誌ID(NCID)
    AN00034826
  • 本文言語コード
    JPN
  • 資料種別
    REV
  • ISSN
    00302813
  • データ提供元
    CJP書誌  J-STAGE 
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