(Uno, et al. 2009) SLIバイリンガル少女「EM」
Cortex. 2009 Feb;45(2):154-63. Epub 2008 Feb 5.
Cognitive neuropsychological and regional cerebral blood flow study of a Japanese-English bilingual girl with specific language impairment (SLI).
Uno A, Wydell TN, Kato M, Itoh K, Yoshino F.
University of Tsukuba, Tsukuba, Japan. uno@human.tsukuba.ac.jpAbstract
We report here on an investigation into the possible factors which might have contributed to language impairment (LI) in EM, a 14-year-old Japanese-English bilingual girl. EM was born in the UK to Japanese parents with no other siblings, and used English to communicate with all other people except for her parents. A delay in her English language development was identified at primary school in the UK, which was attributed to her bilingualism. The deficiency in her English language skills persisted into her adolescence despite more than adequate educational opportunities (including additional language support). At the start of her secondary education, language ability/literacy attainment tests were conducted in both English and Japanese, and the results suggested specific language impairment (SLI) in both languages. Further, her brain Single Photon Emission Computed Tomography (SPECT) revealed significantly lower Regional Cerebral Blood Flow(rCBF) in the left temporo-parietal area, which is also similar to the area of dysfunction often found among Japanese individuals with SLI.
PMID: 19150517 [PubMed - indexed for MEDLINE]
Cognitive neuropsychological and regional cerebral blood flow study of a Japanese-English bilingual girl with specific language impairment (SLI). - PubMed - NCBI
特異性言語障害(SLI)を伴う日本語・英語バイリンガル少女の認知学的神経精神学的局所脳血流研究
要旨
14歳の日本語・英語バイリンガル少女EMの言語障害に寄与した可能性のある因子に関する研究を報告する。EMは英国で日本人両親のもとに生まれ、兄弟はいなかった。両親以外へのコミュニケーションには英語を使用した。英語の言語発達の遅れが英国の小学校で確認されたが、バイリンガルによるものと考えられた。十分な教育機会(追加的な言語サポートを含む)にもかかわらず、英語の言語スキルの欠如は思春期まで持続した。中等教育の開始時に、英語と日本語の言語能力到達テストが行われた。結果は、両言語の特異性言語障害を支持するものであった。加えて、脳のSPECTは左側頭葉頭頂領域の局所脳血流量(rCBF)の有意な低下を示した。それはSLIを伴う日本人にしばしば見出される機能低下領域に類似している。
SLIバイリンガルに限らず、日本人の精神疾患の症例報告は海外と比べると少ない。これは症例数が少ないわけではなく、精神疾患の原因を前世に求めたりする日本人の悪しき習慣がが災いし、発表の機会を失っているように考えている。その意味で、これは日本人SLIバイリンガルの貴重な報告である。しかも単なる1例報告なのに、英国Brunel大学・筑波大学・慶応大学医学部・国立精神保健研究所・東京歯科大学による大規模な国際研究となっている。
さて、この論文の導入部分には、このような記述がある。
Approximately half the world's children are exposed to more than one language1 and a frequently addressed question concerning bilingual development is whether bilingual children demonstrate a developmental delay in each language compared with monolingual children. Some suggested that there is a significant developmental language delay in bilingual children2,3, while others4 found that the bilingual children had comprehension vocabularies in each language comparable to that of monolinguals.
世界中の小児の約半数が、複数の言語に曝されている。そしてバイリンガルの発達に関する以下の問題が、しばしば話題となる。はたして、バイリンガル小児はモノリンガル小児と比較すると、それぞれの言語で発達障害を示すのだろうか。バイリンガル小児においては有意な言語発達遅滞が認められることを示す者がいる一方で、バイリンガル小児はモノリンガルと同等の語彙理解を有するとする者もいる。
著者らはパイリンガル児童の言語発達遅滞に関して、肯定的な研究と否定的な研究の両方を提示している。一見すると、中立的な記述に見える。しかし引用している論文を調べると、そうでないことがわかる。
まず肯定的な研究から。一つ目はこれ。
Rosenblum T, Pinker S. (1983) Word magic revisited: Monolingual and bilingual children’s understanding of the word-object relationships. Child Dev 54: 773-780.
Word magic revisited: monolingual and bilingual children's understanding of the word-object relationship. - PubMed - NCBI
(Rosenblum & Pinker 1983) バイリンガルは名前を覚えにくい - Record of Self-Development
就学前の児童に関して、モノリンガルよりもバイリンガルのほうが物の名称を覚えにくいという論文。
もうひとつの肯定的研究はこれ。
Umbel VM, et al. (1992) Measuring bilingual children’s receptive vocabularies. Child Dev, 63: 1012-1020.
Measuring bilingual children's receptive vocabularies. - PubMed - NCBI
(Umbel, et al. 1992) バイリンガル小児の語彙力獲得は各言語で別々 - cyberdoctor’s diary
バイリンガルの語彙力は各言語でまったく独立に獲得される。分かりやすく言えば、モノリンガルが1年間で覚えられる量の言葉が、バイリンガルが覚えるのには2年かかってしまう。
どちらの研究も、バイリンガルが言語学習において不利な条件にあることを明らかにしている。
一方でバイリンガルの言語発達遅滞を否定する論文として挙げられているのが以下の論文。
Pearson, B. Z., et al. (1993) Lexical development in bilingual infants and toddlers: Comparison to monolingual norms. Language Learning, 43, 93-120.
(Pearson, Fernández & Oller 2006) バイリンガルの語彙発達 - Record of Self-Development
バイリンガルとモノリンガルとで、語彙発達に差がないという研究である。しかしこの研究の対象は、8ヶ月から30ヶ月の幼児である。つまり、3歳未満までしか調査対象としていない。それで言語の発達について何が言えるというのか？ その後の言語発達に問題がないという確証が、どこにあるというのか？
逆に言えば、「バイリンガルとモノリンガルは言語発達に差がない」とする研究としては、こんな意味のない研究しか存在しないのだろう。バイリンガルにおいて言語発達遅滞がおこることは、もはや疑いようのない事実なのである。そして言語発達遅滞は精神遅滞を引き起こす。なぜなら、人は通常第一言語で思考するからである。第一言語の発達が不十分であれば、思考も不完全となってしまう。
INTRODUCTION
Approximately half the children in the world are exposed to more than one language (e.g., (de Houwer 1995)). However, the literature on bilingual development is very limited in comparison to the literature on second language learning in terms of both the number of studies reported and the number of subjects per study (Hoff-Ginsberg 1997). An often addressed question on bilingual development is whether bilingual children demonstrate a developmental delay in each language compared with monolingual children. Some studies have supported the idea that there is a significant developmental language delay in bilingual children (e.g., (Rosenblum & Pinker 1983); (Umbel, et al. 1992)). For example, Rosenblum and Pinker (1983) found that bilingual children aged five and over had smaller comprehension vocabularies in each of their languages than age-matched monolingual children. However, (Pearson, et al. 1993)'s longitudinal study following bilingual and monolingual children from the age of 8 months to 30 months revealed that the bilingual children had comprehension vocabularies in each language comparable to that of monolinguals. (Hoff-Ginsberg 1997) therefore argued that bilingual development might cause some delay in the development of each language but not so much as to cause these children to be outside the normal range of variation in the rate of language development.
導入
全世界の小児のほぼ半数は、ひとつ以上の言語に曝されている。しかしながら、バイリンガルの発達に関する文献は、第2言語学習の文献と比較すると、報告された研究数と1研究あたりの主題の両面から非常に限定的である。単言語の小児と比べると、バイリンガルの小児は両方の言語の発達障害を示すのかどうかというバイリンガルの発達に関する質問が、しばしば耳に入る。いくつかの研究は、バイリンガル小児には有意な発達言語遅滞があるという考えを支持している。例えば、RosenblumとPinkerは、5才以上のバイリンガル小児は同年齢の単言語小児よりも各言語の語彙理解力が低いことを見出した。しかしながら、Pearsonによるバイリンガルと単言語の8ヶ月から30ヶ月の小児の縦断的研究は、バイリンガル小児が両言語において単言語小児と同程度の語彙理解力を有していることを示した。Hoff-Ginsbergは、それゆえバイリンガルの発達は両言語の発達において何らかの遅滞を生じるが、言語発達の程度が正常範囲から外れるものはそれほど多くないと主張した。
(Bishop 1997) has extensively discussed abnormal monolingual language development, in particular children with specific language impairment (SLI). In brief, SLI is defined as a disorder in the development of language despite adequate educational opportunities and normal intelligence. It requires a significant discrepancy between the child’s verbal and nonverbal abilities in the absence of any additional disorders (e.g., mental retardation or autism) (e.g., (Bishop 2001); (Williams, et al. 2000); (Botting & Conti-Ramsden 2003)?. Most children with SLI are poor at acquiring new vocabulary, which is reflected in their performance on tests for receptive vocabulary. For example, research on incidental learning of word meanings revealed that children with SLI understood fewer new words than age-matched normal controls after a few brief exposures to the new words in the naturalistic context of a television program (Oetting, Rice & Swank 1995). (Gleitman 1994) postulated the following process for the acquisition of new vocabulary in children: (1) the acquisition of knowledge of the concepts that words express, (2) the extraction of phonological patterns from incoming speech, and (3) the mapping of (1) and (2), that is, mapping each concept to a phonological pattern. Conceivably, poor word learning in children with SLI may be linked with a deficit at one of these processing stages. (Bishop 1997) argued that deficient vocabulary learning in children with SLI is not attributable to abnormal conceptual development or lack of symbolic representation. Rather, it is attributable to poor phonological perception and memory in these children. This is because vocabulary acquisition depends on the setting up of long-term phonological representations in the lexicons, and phonological representations in these children’s lexicon may be under-specified.
Bishopは、異常な単言語の言語発達、特に特異性言語障害の小児を広範囲に検討している。手短に言えば、SLIは十分な教育機会と正常の知能にもかかわらず生じた言語発達障害として定義される。小児の言語と非言語能力の間に有意の不一致があり、他の障害（たとえば精神遅滞や自閉症）が存在しないことを要する。SLIを伴う多くの小児は、新しい語彙の獲得に劣り、それは語彙受容試験の成績に反映する。たとえば単語の意味の付随的な学習の調査では、テレビ番組に自然文脈に新しい単語が短時間出現する場合、SLIを伴う小児は年齢をマッチさせた正常の対照よりも新しい単語をあまり理解しないことが明らかである。Gleitmanは、小児の新しい語彙の獲得に次のような過程を仮定している。①単語が表現する概念の獲得、②聴き言葉からの音韻パターンの抽出、③①と②のマッピング、各概念と音韻パターンのマッピングである。おそらく、SLIを伴う小児の稚拙な単語学習は、これらの過程のいずれかの段階の欠損と結びついている。Bishopは、SLIを伴う小児の不完全な語彙学習は、異常な概念発達や象徴表現の欠落に起因しているのではないと唱えている。むしろ、それはこのような小児の稚拙な音韻認知と記憶に起因している。なぜなら、語彙獲得は長期間の語彙音韻表現に依存しており、このような小児の語彙の音韻表現は明確ではないだろうから。
More recently, research into LI (language impairment) or SLI in bilingual children started to emerge, although the numbers are still few. Hakasson et al. (2003) revealed for example that Swedish-Arabic children with LI developed both languages “in the same implicational way” (Salmeh et al., 2004, p.66) as those bilingual children without LI, but showed slower development in both languages. Salmeh et al. (2004) in their longitudinal study followed the grammatical development of Swedish-Arabic bilingual children with LI and normal children (aged between four and seven) for 12 months. Their results also confirmed that their children both with and without LI developed grammatical structures in both languages in the same implicational way. However it was found that the children with LI seemed to be more vulnerable to language exposure. They were more affected by lack of the language exposure than the bilingual children without LI. Moreover, Paradis, Crago, and Rice (2003) compared French-English bilingual SLI children (mean age = 6;11) with age-matched monolingual French and English SLI children, and found that these bilingual and monolingual children both showed a difficulty in processing grammatical morphology to the same extent. Paradis et al. therefore concluded that “their dual language knowledge was not causing them to have different patterns in this domain of morphosyntax than monolinguals”, (Paradis et al., 2003; p. 123).
Further, Bishop (1997) also discussed etiological factors in SLI (albeit in monolinguals), including the language environment, genetics and neurobiology. She argued that genetic factors have been strongly implicated in the etiology of SLI. For example, the concordance of SLI among monozygotic twins is said to be almost 100% (Bishop et al., 1995). Similarly, Plante (1991) argued that developmental language disorders such as SLI are biologically transmittable, as her study revealed family aggregations of SLI. Ors, Ryding, Lindgren, Gustafsson, Blennow and Rosen (2005) considered identifying neurobiological features for SLI as one of the main lines of SLI research and cited studies of morphometric analyses of MRI (magnetic resonance imaging) (e.g., Plante, 1991; Plante et al., 1991) or studies using functional imaging techniques such as SPECT (single photon emission computed tomography) and PET (positron emission tomography) (e.g., Saper et al., 2000). For example, Plante, et al.’s (1991) morphometric study with MRI revealed an atypical perisylvian asymmetry in SLI children – the asymmetry was seen by an atypically larger right perisylvian area compared to normal controls, while the left perisylvian area was of the same size as that of the normal controls. Plante (1991) further stated that for the majority of normal controls the asymmetry was seen with the left perisylvian area it being greater than that of the right. Plante et al. thus argued that the atypical perisylvian asymmetry in the SLI children might be due to the brain’s “overproliferation of neurons that migrate out to the cerebral surface” during its development, and a possible “failure of regressive events which occur late relative to the prenatal developmental course of the affected region” (Plante et al., 1991; p.63).
In SPECT/PET studies, it has been shown that there is a linear relationship between local changes in the cerebral blood flow and glucose consumption, thus indicating local neuronal activity (Saper et al., 2000). Ors et al. therefore argued that there are morphological and functional differences in children with SLI compared to children without SLI.
Ors et al. (2005) using SPECT compared the regional cerebral blood flow (rCBF) of children with SLI and children with attention deficit hyperactivity disorder (ADHD), and found that the SLI children had symmetrical rCBF values in the left and right temporal areas whereas the ADHD children showed a typical asymmetry with the left temporal region predominant. Further, SLI children showed lower rCBF values in the right parietal as well as the subcortical regions, while the ADHD children showed symmetrical rCBF values in these areas. Both ADHD and SLI children, however, revealed lower rCBF values in the right frontal area compared to the left frontal area.
Researchers in Japan have also investigated these neurobiological abnormalities in Japanese SLI children using SPECT (e.g., Uno et al., 1997; 1999,Haruhara et al., 1999), and have reported abnormalities in the rCBF in the left temporo-parietal regions, that is, the rCBF values in the left temporo-parietal regions were significantly reduced compared to those of the right.
Moreover, Jodzio, Gasecki, Drumm, Lass and Nyka (2003) asserted that rCBF SPECT has a significant contribution to neurolinguistic research, although their patients were all neurological patients with left-hemisphere cerebral vascular accidents (CVAs). They revealed a significant correlation between the language processing abilities (measured by BDA - Boston Diagnostic Aphasia Examination) of 50 neurological patients with left-hemisphere CVAs with a wide range of pathologies, and rCBF SPECT imaging. In particular it was found that the most prominent deficits in Wernicke’s aphasia were found in the left temporal and parietal areas. Wernicke’s aphasia is characterized as a receptive language aphasia with comprehension deficit.
In the present study, we report on a case study of a Japanese-English bilingual adolescent girl residing in the UK, whose behavioral data in both Japanese and English suggested that she might have SLI. Her brain SPECT also indicated that the etiology of her SLI might be due to neurobiological functional deficit rather than language environment. Parental consent for publication of the case notes/data was obtained.
CORTEX
