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Effect of treatment for bilingual individuals with aphasia: A systematic review of the evidence

Yasmeen Faroqi-Shaha, Tobi Frymarkb, Robert Mullenb, Beverly Wangb

a

b

University of Maryland, College Park, MD, USA

National Center for Evidence-based Practice in Communication Disorders, American SpeechLanguage Hearing Association, Rockville, MD, USA

*Corresponding Author:

Tobi Frymark National Center for Evidence-based Practice in Communication Disorders American Speech-Language Hearing Association 2200 Research Blvd, Rockville, MD 20850 301-296-8742 (o), 301-296-8588 (f) [email protected]

This is a preprint text of an article accepted for publication in the Journal of Neurolinguistics. Please cite this article in press as: Faroqi-Shah, Y. et al., Effect of treatment for bilingual individuals with aphasia: A systematic review of the evidence, Journal of Neurolinguistics (2010), doi:10.1016/j.jneuroling.2010.01.002

Abstract Language proficiency in bilingualism, and hence bilingual aphasia, is a multifaceted phenomenon: influenced by variables such as age of onset, literacy, usage patterns, and emotional valence. Although the majority of the world and growing US population is bilingual, relatively little is known about the best practices for language therapy in bilingual aphasia. This systematic review was undertaken to examine three crucial questions faced by speech-language pathologists during clinical decision making: outcomes when language therapy is provided in the secondary (less-dominant) language (L2), extent of cross-language transfer (CLT) and variables that influence CLT, and outcomes when language therapy is mediated by a language broker. Data from 14 studies (N=45 aphasic individuals) indicate that treatment in L2 leads to positive outcomes (akin to L1 treatment); CLT was found to occur in most studies, especially when L1 was the language of treatment. Although limited by the methodological quality of included studies, this systematic review shows positive findings for unilingual aphasia treatment and CLT. Implications for clinical practice, models of language representation in bilinguals, and future research directions are discussed.

Key Words: Aphasia; Bilingualism; Cross-Language Transfer; Multilingualism; SpeechLanguage Pathologist

1. Introduction More than half the world (and a rapidly growing US demographic) is bilingual1. Hence the occurrence of bilingual aphasia is more common than what can be gleaned from the literature. Speech-language pathologists (SLPs) are increasingly likely to provide services to bilingual aphasic clients (Ansaldo, Marchotte, Scherer, & Raboyeau, 2008; Centeno, 2009; Paradis, 2001). Given that the overarching goal of language treatment for individuals with aphasia is to achieve the maximum possible level of life participation, the goal of language treatment in the bilingual client becomes the improvement of communication in both languages. Providing language treatment to bilingual clients may pose challenges that are less evident when providing treatment to monolingual clients with aphasia. The obvious logistical challenges include access to bilingual assessment and treatment materials and availability of bilingual SLPs, or two SLPs speaking the relevant languages. There is also an important and largely unresolved conceptual challenge in the treatment of bilingual aphasia — whether to focus on a single language or include both languages in treatment. Experts who recommend bilingual therapy point out that inclusion of both languages ensures that the aphasic person is able to utilize all possible communicative strategies available to him/her (akin to using gesture or writing to aid verbal communication) (Ansaldo et al., 2008; Centeno, 2005; Kohnert, 2004). It is also argued that the bilingual speaking environment is the most natural for some bilinguals; thus, bilingual therapy is the best choice. However, some authors point out certain caveats and suggest that bilingual therapy can lead to increased code mixing-code switching, or could suppress

1

We use the term bilingual as used by Grosjean (1994) to refer to all individuals who use two or more languages or dialects in their daily communicative environment, irrespective of the context of use.

recovery of one language (Hemphill, 1976; Lebrun, 1988). In fact, there are reports of bilingual treatments leading to improvement of only one language (Paradis, 1993). From a neurolinguistic perspective, bilinguals possess an intermixed lexical and morphosyntactic organization (Golesteni et al., 2006; Gollan, Montoya, Fennema-Notestine, & Morris, 2005; Kroll & Stewart, 1994). The intermixed neurolinguistic organization is not only used to make the case for bilingual therapy, but can also be used to argue that therapy in a single language (henceforth unilingual therapy) will automatically transfer to the untrained language because of stimulation of shared neural networks (Kohnert, 2009; Watamori & Sasanuma, 1978). Unilingual therapy is also recommended for individuals who experience pathological code mixing-code switching or who live in a primarily monolingual environment (Abutelabi & Green, 2008; Ansaldo, Ghazi Saidi, & Ruiz, 2009). However, this prediction of cross-language transfer (CLT) with unilingual therapy has not been consistently borne out (e.g., Edmonds & Kiran, 2006; Faroqi & Chengappa, 1996; Filiputti, Tavano, Vorano, Luca, & Fabbro, 2002). Discussions of variables that influence success of CLT have questioned whether the first (L1) and second (L2) languages are equipotent in their prospects for language gains. One proposal is that language proficiency may interact with CLT potential such that low proficiency bilinguals are more likely than high proficiency bilinguals to experience CLT after unilingual therapy in L2 (Edmonds & Kiran, 2006). This is because the L2 of low proficiency bilinguals depends to a greater extent on borrowings from L1; while the L2 of high proficiency bilinguals is relatively independent of L1 (Jared & Kroll, 2001). However, CLT effects with L2 therapy are not always reported. The foregoing discussion raises several pertinent questions that are unresolved. Namely, do bilingual aphasic clients benefit from treatment provided in their L2? Does unilingual therapy

result in CLT? Do L1 and L2 differ in CLT potential? And do any factors (demographic, linguistic, aphasia-related, or otherwise) help predict success with L2 therapy and CLT? A cursory Medline search using the terms bilingualism and aphasia reveals 89 citations; the majority of which characterize the nature and recovery pattern of bilingual aphasia (Fabbro, 2001; Green, 2005; Levy, Goral, & Obler, 1999; Lorenzen & Murray, 2008; Goral, Levy & Obler, 2002; Obler & Mahecha, 1991) with only a small number focused specifically on the impact of treatment. This superficial look at the literature does not provide straightforward answers to the previously raised questions. Therefore a more comprehensive and meticulous examination of the literature is warranted2. This paper describes the findings of an evidence-based systematic review (EBSR) conducted by the American Speech-Language-Hearing Association’s (ASHA’s) National Center for Evidence-based Practice in Communication Disorders. The primary aim of this review is to synthesize and analyze the existing data on aphasia treatment for bilingual individuals. Knowledge of the current evidence is likely to assist SLPs in therapeutic decision making. In addition, it is hoped that this review will serve to highlight the empirical strength of the current evidence (or lack thereof) and identify unresolved questions in need of further research. An essential first step in initiating a systematic review of the literature was to formulate the questions for data extraction. In constructing the clinical questions, it was decided that the impact of L1 therapy on L1 outcomes in bilingual individuals was not a crucial issue because this is analogous to examining the efficacy of aphasia therapy in the native language of monolingual

2

It should be noted that a review article by Kohnert (2009) addressing CLT was published after the completion of the present study. The authors were unaware of this article prior to the completion of the present review and variations in clinical questions addressed, number of databases searched and study inclusion parameters led to a minimal number of overlapping studies (5) reported.

clients. And there is ample evidence of the success of aphasia therapy (Beeson & Robey, 2006; Holland, Fromm, DeRuyter, & Stein, 1996; Robey & Schultz, 1998). For this reason, we decided to focus on the effect of L2 therapy. Our second focus was to examine the occurrence of CLT in both directions (L1 to L2 and L2 to L1) and a third was to determine the effect of therapy that was mediated by a language broker when the therapist and client spoke different languages. Given that receptive and expressive language abilities can be relatively independent and treatment does not always generalize across both modalities, we decided to examine treatment effects on expressive and receptive language in separate analyses. Finally, we synthesized pertinent variables such as age of participant, age of L2 acquisition, pre-morbid proficiency in each language, language of the environment, aphasia characteristics, and time post onset to determine factors that might impact outcomes. This resulted in the following eight questions in three focus areas: Focus A: Language therapy in the secondary language (L2) 1. What is the effect of treatment provided by an SLP in L2 on the receptive language skills in the treated language (L2) for bilingual clients with neurologically-induced aphasia? 2. What is the effect of treatment provided by an SLP in L2 on the expressive language skills in the treated language (L2) for bilingual clients with neurologically-induced aphasia? Focus B: Cross-language transfer (CLT) of therapy outcomes 3. What is the effect of treatment provided by an SLP in L2 on the receptive language skills in the untreated language (L1) for bilingual clients with neurologically-induced aphasia? 4. What is the effect of treatment provided by an SLP in L1 on the receptive language skills in the untreated language (L2) for bilingual clients with neurologically-induced aphasia?

5. What is the effect of treatment provided by an SLP in L2 on the expressive language skills in the untreated language (L1) for bilingual clients with neurologically-induced aphasia? 6. What is the effect of treatment provided by an SLP in L1 on the expressive language skills in the untreated language (L2) for bilingual clients with neurologically-induced aphasia? Focus C: Therapy outcomes with a language broker 7. What is the effect of services provided by a language broker in L1 on the receptive language skills in the untreated language (L2) for bilingual clients with neurologically-induced aphasia? 8. What is the effect of services provided by a language broker in L1 on the expressive language skills in the untreated language (L2) for bilingual clients with neurologicallyinduced aphasia?

2. Method 2.1. Literature search A literature search was conducted during July and August 2009. Research studies were identified from 29 electronic databases using keywords pertaining to bilingualism or multilingualism and aphasia (see A.1 for a complete list of databases and Supplementary material for the expanded search terms). Inclusionary criteria that were used to determine eligibility were: research studies published in peer-reviewed journals from 1980 to August 2009 with original data pertaining to the EBSR question(s), publications in English language (due to ease of access and limited translation resources), and studies that included bilingual adults (ages 18 years or older) with neurologically-induced aphasia and described outcomes of language intervention. As mentioned earlier, bilingual individuals included all individuals who spoke two

or more languages in their daily life, irrespective of manner and age of acquisition (Grosjean, 1992; Grosjean, 1994). Interventions included any SLP treatment conducted in primary (L1) or secondary (L2) language targeting receptive and/or expressive language skills. Exclusion criteria were studies that described individuals with cognitive deficits, studies that included participants with heterogeneous etiologies (unless data could be separated), and interventions that were pharmacological, or utilized augmentative and alternative communication. Two authors (RM and TF) independently reviewed all citations for relevance based on the predetermined inclusion criteria. References from all full-text articles and narrative reviews were also hand-searched and when necessary, the study authors were contacted to obtain original data or studies. Inter rater reliability between the two authors for study inclusion was determined using the kappa statistic (Cohen, 1960). Study eligibility agreement between RM and TF was good, K = .852. Disagreements were discussed and resolved by consensus. A third author (YF-S) reviewed the full list of accepted and rejected bibliographies for completeness prior to final inclusion/exclusion. Figure 1 schematizes the literature search. Of the 174 citations reviewed, 36 were identified for preliminary inclusion. After obtaining the full text of these articles, more than half (64%; 23/36) were further eliminated. One study preliminarily accepted (Fabbro, Deluca, & Vorano, 1996) could not be obtained despite attempted correspondence with authors. An additional treatment study (Filiputti, et al., 2002) could not be included in our data analysis because it only provided overall language measures (for morphology, syntax, etc.) that were derived by combining expressive and receptive scores. Therefore, the data could not be evaluated for a specific clinical question(s).

A total of 161 citations were excluded from the review; the majority of which did not provide an intervention (50%, 81/161). Other reasons for exclusion were as follows: a) was not a study or systematic review (23%, 37/161), b) not age or population under review (6%, 10/161), c) did not provide original data or separate data from mixed populations or treatments (6%, 10/161), d) was not published in a peer-reviewed journal (7%, 12/161), e) did not target a question (6%, 10/161) or f) could not obtain full-text (1%, 1/161); leaving a total of 13 citations. One citation (Maragnolo, Rizzi, Peran, Piras, & Sabatini, 2009) provided data from two distinct studies resulting in 14 studies for review. The list of excluded articles with reasons for exclusion is provided as Supplementary material (see S2). ------------Insert Figure 1 about here---------Data extraction and coding Methodological quality of included studies was independently appraised by RM and TF on six indicators identified by ASHA’s levels of evidence scheme (ASHA, 2007). To minimize bias, studies were evaluated on whether or not they provided an adequate description of study protocol, whether assessors of outcomes were blinded to language of intervention, use of adequate sampling/allocation procedures, evidence of treatment fidelity, report of significance (p values) and report of precision (effect size and confidence intervals). Studies were not evaluated on ASHA’s seventh quality indicator, use of intention to treat, as no controlled trials were found in which this analyses was applicable. A description of quality indicators and corresponding quality markers are provided as Supplementary material (see S.3). Level of agreement between reviewers on study quality was good (K = 0.61 - 0.80; Landis & Koch, 1977). Each study was examined for the question(s) which it addressed and relevant pre- and post-therapy data were extracted. We computed statistical significance for the pre and post-treatment scores using the

McNemar’s change test (pRo

Late

NR

High

Edmonds & Kiran, 2006

Spanish IE>Rom

English IE>Ger

P1 Late P2 Early P3 Early

P1 High P2 Low P3 Low

P1 High P2 High P3 High

Telugu Dravidian>SouthCen

Kannada Dravidian>South

Early

High

High

Gil & Goral, 2004

Russian IE>Sla

Hebrew AA>Sem

Late

High

High

Goral et al., 2009

Hebrew AA>Sem

English IE>Ger

Early

High

High

Junque et al., 1989

Catalan IE>Rom

Spanish IE>Rom

Early

High

High

Khamis et al. 1993

Arabic AA>Sem

Hebrew AA>Sem

Late

High

High

Laganaro et al., 2003

NR

French IE>Rom

Late

NR

High

Marangolo et al., 2009

Flemish IE>Ger

Italian IE>Rom

Late

High

High

Meinzer et al., 2007

French IE>Rom

German IE>Ger

Early

High

High

Meirtch et al., 2009

German IE>Ger

English (L2) IE>Ger French (L3) IE>Rom

Late

NR

High

Penn & Beecham, 1992

Bantu NC>Ban

English IE>Ger

Late

High

NR

Faroqi & Chengapppa, 1996

Note. AA=AfroAsiatic; Ban=Bantoid; Early= < age 5; Ger=Germanic; IE=IndoEuroprean; Late= > age 5; NC=NigerCongo; NR=Note reported; Rom=Romance; Sem=Semitic; Sla=Slavic; South=Southern; SouthCen=SouthCentral

Supplementary Materials S1. Expanded Search Term ("Multilingualism"[Mesh] OR "Emigrants and Immigrants"[Mesh]) AND "Aphasia"[Mesh] ("Multilingualism"[Mesh] OR "Emigrants and Immigrants"[Mesh]) AND ("Language Disorders/rehabilitation"[Mesh] OR "Speech Disorders/rehabilitation"[Mesh] OR "Rehabilitation of Speech and Language Disorders"[Mesh]) AND ("Brain Injuries"[Mesh] OR ―Cerebrovascular Disorders‖[Mesh] OR ―Dementia‖[Mesh]) ("Multilingualism"[Mesh] OR "Emigrants and Immigrants"[Mesh]) AND ("Language Disorders/rehabilitation"[Mesh] OR "Speech Disorders/rehabilitation"[Mesh] OR "Rehabilitation of Speech and Language Disorders"[Mesh]) ("Multilingualism"[Mesh] OR "Emigrants and Immigrants"[Mesh]) AND ("Brain Injuries"[Mesh] OR ―Cerebrovascular Disorders‖[Mesh] OR ―Dementia‖[Mesh]) "Aphasia/rehabilitation"[Mesh] AND (multilingual* OR bilingual* OR trilingual* OR (english language) OR l1 OR l2 OR second* OR (cross linguistic) OR (cross language)) "Aphasia/rehabilitation"[Mesh] AND (multilingual* OR bilingual* OR trilingual* OR l1 OR l2 OR ("cross linguistic") OR ("cross language") OR ("limited proficiency") OR second*) ("Aphasia"[Mesh] OR "Anomia"[Mesh]) AND (multilingual* OR bilingual* OR trilingual* OR l1 OR l2 OR ("cross linguistic") OR ("cross language") OR ("limited proficiency") OR second* OR dual OR broker OR interpreter OR transfer) "Multilingualism"[MAJR] AND (interpreter OR broker) aphasia AND (*lingual* OR l1 OR l2 OR ell OR dual OR second* OR proficien*) AND (language AND (treatment OR therapy OR rehabilitation)) ((bilingual* OR multilingual* OR trilingual* OR polyglot OR (english language learner) OR (dual language) OR (l1) OR (l2)) AND aphasia) AND (treatment OR therapy OR rehabilitation OR intervention) "Aphasia"[Mesh] AND "Language"[Mesh] AND ("Reading"[Mesh] OR ―Speech‖[Mesh] OR ―Translating‖[Mesh] OR ―Writing‖[Mesh] OR ―Phonetics‖[Mesh] OR ―Semantics‖[Mesh] OR ―Vocabulary‖[Mesh]) AND (treatment OR therapy OR rehabilitation) ("Rehabilitation of Speech and Language Disorders"[Mesh] OR "Language Disorders/rehabilitation"[Mesh] OR "Speech Disorders/rehabilitation"[Mesh]) AND ("Aphasia"[Mesh] OR "Anomia"[Mesh])

(MM "Aphasia+") AND (MH "Multilingualism") Aphasi* AND (interpreter OR broker) "multilingual" ((MM "Multilingualism") OR (MH ―Multilingualism‖)) AND ((MM "Aphasia+") OR (MH ―Aphasia+‖)) ((XX "aphasia") OR (XX "aphasic")) AND (multilingual* OR bilingual* OR trilingual* OR polyglot OR (english language learner)) DE "BILINGUALISM" AND DE "APHASIA" (KW "multilingual/multicultural group" OR KW "multilingual" OR KW "bilingual") AND (KW "aphasia") ((ZW "bilingual") or (ZW "bilingual aphasia") or (ZW "bilingualism") or (ZW "bilinguals") or (ZW "multilingual") or (ZW "multilingual/multicultural group") or (ZW "multilingualism") or (ZW "english language learners")) and ((ZW "aphasia") or (ZW "aphasia treatment")) (DE "APHASIA" OR DE "AGRAMMATISM" OR DE "ANOMIA" OR DE "CONDUCTION aphasia" OR DE "JARGON aphasia" OR DE "WORD deafness") and (DE "MULTILINGUAL persons" OR DE "MULTILINGUALISM" OR DE "BILINGUALISM" OR DE "MULTICULTURALISM") ((ZU "aphasia") or (ZU "aphasia -- treatment") or (ZU "aphasic persons")) and ((ZU "multilingual persons") or (ZU "multilingualism") or (ZU "bilingualism")) (DE "Aphasia" OR DE "Acalculia" OR DE "Agnosia" OR DE "Agraphia" OR DE "Dysphasia") and (DE "Multilingualism" OR DE "Bilingualism") (DE "APHASIA") AND (DE "BILINGUALISM" OR DE "CODE switching (Linguistics)" OR DE "EDUCATION, Bilingual" OR DE "INTERFERENCE (Linguistics)" OR DE "LANGUAGE attrition" OR DE "MULTILINGUALISM") (DE "APHASIA") AND (DE "BILINGUALISM" OR DE "MULTILINGUALISM") DE=("agnosia" or "aphasia" or "traumatic brain injury tbi") and ("bilingualism") DE=("multilingualism" or "bilingualism" or "cultural background") and("speech therapy" or "language therapy") and ("agnosia" or "aphasia" or "traumatic brain injury tbi") DE=("aphasia") and ("bilingualism" or "code switching" or "cross cultural communication" or "diglossia" or "indigenous languages" or "language contact" or "language diversity" or "language

proficiency" or "language use" or "languages" or "multilingualism" or "second language learning" or "second languages" or "social factors" or "sociolinguistics" or "sprachbund") DE=("aphasia") and ("bilingualism" or "code switching" or "cross cultural communication" or "diglossia" or "indigenous languages" or "language contact" or "language diversity" or "language proficiency" or "language use" or "languages" or "multilingualism" or "second language learning" or "second languages" or "social factors" or "sociolinguistics" or "sprachbund") and ("speech therapy" or "therapy" or ―language therapy‖) DE=aphasia and (bilingual* or multilingual* or polyglot or (english language learner) or (dual language) or (l1) or (l2) or (cross linguistic)) TS=(((bilingual* OR multilingual* OR trilingual* OR polyglot OR (english language learner) OR (dual language) OR (l1) OR (l2) OR (cross linguistic)) AND aphasia) AND (treatment OR therapy OR rehabilitation OR intervention)) AND Language=(English) DE=‖aphasia‖ DE=‖aphasia‖ AND (DE=‖bilingualism‖ or DE=‖multilingualism‖ or DE=‖English (Second Language)‖ or DE=‖Second Language Learning‖) ("BILINGUAL" or "BILINGUALISM" or "BILINGUALS" or "MULTILINGUAL" or "MULTILINGUALISM" or "POLYGLOT" or "CROSS-CULTURAL") and ("APHASIA" or "APHASIC" or "APHASICS" or "APHASIOLOGICAL" or "APHASIOLOGY") (aphasia OR aphasic) AND (bilingual OR multilingual OR trilingual OR multicultural) (aphasia OR aphasic) AND (polyglot OR (english language learner) OR (dual language) OR cross)

Supplementary Materials S2. Bibliography of excluded studies and reasons for exclusion in systematic review S2.1 Did not address one or more clinical question April, R. S., & Han, M. (1980). Crossed Aphasia in a Right-handed Bilingual Chinese Man: A Second Case. Arch Neurol, 37(6), 342-346. Eviatar, Z., Leikin, M., & Ibrahim, R. (1999). Phonological processing of second language phonemes: A selective deficit in a bilingual aphasic. Language Learning, 49(1), 121-141. Filiputti, D., Tavano, A., Vorano, L., De Luca, G., & Fabbro, F. (2002). Nonparellel recovery of languages in a quadrilingual aphasic patient. International Journal of Bilingualism, 6(4), 395-410. Green, D. W., & Price, C. J. (2001). Functional imaging in the study of recovery patterns in bilingual aphasia. Bilingualism: Language and Cognition, 4(2), 191-201. Holland, A. L. (1983). Nonbiased assessment and treatment of adults who have neurologic speech and language problems. Topics in Language Disorders, 3(3), 67-75. Laganaro, M., & Overton Venet, M. (2001). Acquired alexia in multilingual aphasia and computer-assisted treatment in both languages: issues of generalisation and transfer. Folia Phoniatr Logop, 53(3), 135-144. Polczynnska-Fiszer, M., & Mazaux, J. M. (2008). Second language acquisition after traumatic brain injury: A case study. Disability and Rehabilitation, 30(18), 1397-1407. Robey, R. R. (1998). A meta-analysis of clinical outcomes in the treatment of aphasia. J Speech Lang Hear Res, 41(1), 172-187. Roger, P. (1998). Bilingual aphasia: The central importance of social and cultural factors in clinically oriented research. Aphasiology, 12(2), 134 - 137.

Wender, D. (1989). Aphasic victim as investigator. Arch Neurol, 46(1), 91-92. S2.2 Not a study or systematic review Abutalebi, J., & Green, D. (2007). Bilingual language production: The neurocognition of language representation and control. Journal of Neurolinguistics, 20(3), 242-275. Abutalebi, J., Tettamanti, M., & Perani, D. (2009). The bilingual brain: linguistic and nonlinguistic skills. Brain Lang, 109(2-3), 51-54. Ansaldo, A. I., Marcotte, K., Fonseca, R. P., & Scherer, L. C. (2008). Neuroimaging of the bilingual brain: evidence and research methodology. PSICO, 39(2), 131-138. Ansaldo, A. I., Marcotte, K., Scherer, L., & Raboyeau, G. (2008). Language therapy and bilingual aphasia: Clinical implications of psycholinguistic and neuroimaging research. Journal of Neurolinguistics, 21(6), 539-557. Bates, E., & Wulfeck, B. (1989). Comparative Aphasiology: A Cross-Linguistic Approach to Language Breakdown. Aphasiology, 3(2), 111-142. Bates, E., Wulfeck, B., & MacWhinney, B. (1991). Crosslinguistic research in aphasia: An overview. Brain Lang, 41, 123-148. Centeno, J. G. (2008). Multidisciplinary evidence to treat bilingual individuals with aphasia. Perspectives on Communication Disorders & Sciences in Culturally & Linguistically Diverse (CLD) Populations, 15(3), 66-71. Centeno, J. G., Anderson, R. T., Restrepo, M. A., Jacobson, P. F., Guendouzi, J., Müller, N., et al. (2007). Ethnographic and Sociolinguistic Aspects of Communication: Research-Praxis Relationships. The ASHA Leader, 12(9), 12-15. Costa, A., La Heij, W., & Navarrete, E. (2006). The dynamics of bilingual lexical access. Bilingualism-Language and Cognition, 9(2), 137-151.

Costa, A., Santesteban, M., & Cano, A. (2005). On the facilitatory effects of cognate words in bilingual speech production. Brain Lang, 94(1), 94-103. Faroqi-Shah, Y., & Thompson, C. K. (2007). Verb Inflections in Agrammatic Aphasia: Encoding of Tense Features. Journal of Memory and Language, 56(1), 129-151. Francis, N. (2008). Exceptional bilingualism. International Journal of Bilingualism, 12(3), 173193. Fredman, M., & Miller, N. (2001). Communication disorders in multilingual populations... selection of papers presented at the 2nd International Symposium on Communication Disorders in Multilingual Populations which took place in South Africa in July 2000. Folia Phoniatrica et Logopaedica, 53(3), 119-182. Goral, M., Levy, E. S., & Obler, L. K. (2002). Neurolinguistic aspects of bilingualism. International Journal of Bilingualism, 6(4), 411-440. Graham, M. S., & Avent, J. (2004). A Discipline-Wide Approach to Group Treatment. Topics in Language Disorders, 24(2), 105-117. Green, D. W., & Abutalebi, J. (2008). Understanding the link between bilingual aphasia and language control. Journal of Neurolinguistics, 21(6), 558-576. Hilton, L., & Kraetschmer, K. (1983). International trends in aphasia rehabilitation. Archives of Physical Medicine and Rehabilitation, 64(10), 462-467. Hilton, L. M. (1980). Language Rehabilitation Strategies for Bilingual and Foreign-Speaking Aphasics. Aphasia-Apraxia-Agnosia, 3(2), 7-12. Hughes, G. W. (1981). Neuropsychiatric aspects of bilingualism: A brief review. British Journal of Psychiatry, 139, 25-28.

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Supplementary Materials S3. ASHA levels of evidence scheme Indicator

Description

Quality Marker

Study protocol

The complete description of study protocol is provided in order to allow replication of study protocol.

Adequate description of protocol. Inadequate description of protocol. Protocol not stated.

Blinding

The practice of keeping the participants of the study or assessors unaware of the group to which a participant has been assigned. The method(s) used to choose and assign participants to the study.

Assessors blinded. Assessors not blinded. Blinding not stated

The procedure used to ensure that the treatment protocol is delivered as intended. The likelihood that the study findings occurred by chance.

Evidence of treatment fidelity. No evidence of treatment fidelity

Precision

The size or magnitude of any difference found between the treatment under investigation and the control condition.

Effect size and confidence interval reported or calculable. Effect size or confidence interval reported or calculable. Neither effect size nor confidence interval reported or calculable.

Intention to treat

Participants in a randomized controlled trial are analyzed according to the group to which they were initially assigned, regardless of whether or not they dropped out, fully complied to the treatment or crossed over and received other treatment.

Analyzed by intention to treat. Not analyzed by intention to treat.

Italics indicates highest quality marker

Sampling/allocation

Treatment fidelity

Significance

S3.1 Quality indicators used to evaluate included studies

Random sample adequately described. Random sample inadequately described. Convenience/hand-picked sample. Not stated.

P values reported or calculable. P values not reported or calculable.

S3.2 State of research Exploratory research: Treatment approaches are developed and assessed in the context of whether they show promise of being efficacious. Efficacy research: Treatment approaches are rigorously tested under ideal, highly controlled conditions to determine the outcomes that result. Effectiveness research: If an intervention demonstrates positive outcomes in the highly controlled setting of a clinical trial, then the controls are relaxed to test the intervention in a ―real-world‖ clinical setting. Cost-benefit and/or public policy: Once an intervention has been shown to be both efficacious and effective, research is conducted to study the political and economic environment in which the intervention is best delivered.

S3.3 Supplementary material reference S3 ASHA Leader [homepage on the Internet]. Rockville (MD): American Speech-LanguageHearing Association; c1997-2009 [2007 Mar 12; cited 2009 August 31]. Mullen R. The state of the evidence: ASHA develops levels of evidence for communication sciences and disorders. Available from http://www.asha.org/Publications/leader/2007/070306/f070306b.htm.