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Brain and Nerve No to Shinkei Volume 33, Issue 1 （January 1981）

Brain and Nerve 脳と神経 33巻1号（1981年1月発行）

Japanese English

原著

日本人脳における言語領野の非対称性について LEFT-RIGHT HEMISPHERIC ASYMMETRY OF CORTICAL SPEECH ZONES IN JAPANESE BRAINS 新国茂 ¹ , 八島祐子 ¹ , 石下恭子 ¹ , 鈴木悟 ¹ , 大野悦人 ¹ , 熊代永 ¹ , 小林栄喜 ² , 粟博志 ² , 三原忠紘 ² , 朝倉哲彦 ² Shigeru Nikkuni ¹ , Yuko Yashima ¹ , Kyoko Ishige ¹ , Satoru Suzuki ¹ , Etsuto Ohno ¹ , Hisashi Kumashiro ¹ , Eiki Kobayashi ² , Hiroshi Awa ² , Tadahiro Mihara ² , Tetsuhiko Asakura ² ¹福島県立医科大学神経精神科 ²鹿児島大学医学部脳神経外科 ¹Department of Neuropsychiatry, Fukushima Medical College ²Department of Neurosurgery, Faculty of Medicine, University of Kagoshima pp.77-84

発行日 1981年1月1日 Published Date 1981/1/1

DOI https://doi.org/10.11477/mf.1406204703

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Abstract 文献概要
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I．はじめに

　Marc Dax （1836年）やBroca （1863年）が失語症と左大脳半球損傷との関係を指摘して以来，今日まで言語機能の左大脳半球優位性が明らかにされてきた^24）。一方，形態学的には，古くはHeschl （1878年）が側頭葉横側頭回（Heschl氏回）の左右差を指摘し，また，Kake—shita，^14），EconomoとHorn，^3），Pfeifer^19）らは，Wern—icke中枢の一部である側頭葉上面の左右差や個体差などを報告している。

　1968年，Geschwindら^11）は，成人脳100例についてtemporal planum （側頭平面）の左右差を検討した結果，65例で左側が大きいことを見い出し，また，初めてこの形態学的左右差と言語機能の左半球優位性との関連性について言及した。また，その後もTesznerら^26），Witelsonら^31）が，それぞれの方法で側頭平面では左が大きいことを確認した。さらに，1975年，Wadaら^30）は，胎児脳を含む生後2歳未満の幼児脳100例と17歳以上の成人脳100例とについて側頭平面の面積計測を行ない，幼児脳，成人脳ともに左が有意に大きいこと，また，胎児脳でも明らかに左が大きく，言語機能の左半球優位の形態学的基礎がすでに胎生期に存在することなどを報告した。同時に，彼らは前言語野のBroca中枢にも着目し，下前頭回後部（彼らはfrontal operculumと称し，以下，前頭弁蓋と表現する）の面積計測を行ない，その左右差について報告している。

Sixty-eight brains from Japanese persons were photographed and measured for the surface areas of the temporal planum and frontal operculum with a planimeter in a study to examine the morphological asymmetry of these cortical speech zones. Compari-son was also made between the hemispheres as to the number of the first and second transverse gyri which constitute the auditory cortex in humans. The results are summarized as follows:

1) In the adult group (54 cases above 17 years of age) the area of the temporal planum was signi-ficantly larger on the left than on the right side (p<0.001, Student's t-test); in the infant group (4 cases ranging in age from about 27 weeks of gesta-tion to 2 years) as well as in the child group (10 cases aged between 2 and 17 years) the zone tended to be larger on the left side. Both in males and females in the adult group the zone was found to be significantly larger on the left side (p<0.001 for both sexes). However, 5 out of 33 males were lacking in the right temporal planum and 4 had a larger zone on the right side. Whereas, none of 21 females showed such an extreme departure from normal.

2) In the adult group (54 cases) as well as in the child group (6 cases) the area of the frontal operculum tended to be larger on the left than on the right side though the difference was not sta-tistically significant. In the infant group (4 cases),however, there was no left-to-right difference.

3) The results as to the transverse gyri indicate that this cortical area comprised 1 gyrus on the left and 2 gyri on the right side in the largest propor-tion of cases (50%, or 34 out of 68 cases); there were 2 gyri on either side in 14 cases (20.6%), one gyrus each on both sides in 13 cases (19.1%), and 2 gyri on the left side and 1 gyrus on the right in 7 cases (10.3%). These figures suggest that mor-phological asymmetry might exist with regard to to the auditory cortex.

The unequivocal morphological asymmetry of the temporal planum implies its possible relationship with left hemisphere dominance in speech and lan-guage function and also suggests the functional importance of this particular cortical zone in the speech center.