Sentence Production in Bilingual and Multilingual Aphasia: A Scoping Review

Round 1

Reviewer 1 Report

This manuscript presents a review aiming to compare features of sentence production and syntactic errors in bi/multilingual individuals suffering from aphasia. 14 studies including a sentence production task and analysing linguistic performance in the first (L1) and additional languages (L2) are included. The goal of the review is highly interesting and the included studies are relevant. Nonetheless, the authors need to address a certain number of points and should better extract the main patterns and findings before I can recommend it for publication. Please find my comments below.

Methods
-Why were only sentence production tasks taken into account and not other tasks that tap into grammatical competence? Given that sentence production draws on multiple linguistic processes (grammatical, morphological, lexico-semantic, etc.) a more complete picture concerning the grammatical competence in sentence production more specifically could be drawn if contrasted with other tasks and tests evaluating grammatical competence.
-Van Lieshout et al. (1990) was published before the time range indicated in the methods section.

Results
-p.5 last paragraph: Beyond a listing of the heterogeneousity of patterns in the L1 and L2 in the different studies, it would be insightful if the authors could identify or speculate on factors explaining the differential patterns e.g. by establishing a link with the patients' specific language biography
-Table 3: The author conclusions are very heterogeneous. A more homogeneous structure across all studies with, for instance, a focus on grammatical aspects in sentence production and the relation between L1 and L2 would make it easier for the reader to extract the relevant information and to compare studies.

Discussion
-The relationship of the present results with findings in the literature on sentence processing in monolingual aphasia should be further elaborated.
-The relationship of the present results with findings in the literature on other levels of linguistic processing in bilingual aphasia should be discussed.
-The role of the (grammatical) properties of each language and the typological distance should be discussed. There is some mention of the role of this aspect in Table 3 but no further discussion elsewhere in the manuscript.
-Conclusion: It is surprising that the conclusion section only speaks about PPA whereas these represent only a minor part of the articles cited in the present review.

Minor issues :
Correct in-text ref Aboum & Bastiaanse to Abuom & Bastiaanse
Abuom T. O., and Bastiaanse R. 2013. Production and comprehension of reference of time in Swahili-English bilingual agrammatic speakers. Aphasiology, 27(2), 157–177. https://doi.org/10.1080/02687038.2012.699632

Author Response

Thank you for your comments. Please find our responses in the attachment. 

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is a scoping review presenting studies on sentence production in bilingual people with aphasia published in the last 30 years. The selected studies show that the non-dominant language is the most affected in cases of agrammatism. In the few papers where no dominance is detected, deterioration seems comparable. The authors point to the necessity of expanding research on the topic.

The topic is interesting and deserves a scoping review. The methodology of the scoping review is well applied by the authors, the table summarising studies' results is dense but clear, and the findings point towards interesting generalisations on L2 in aphasia, as well as suggesting methodological improvements (for example in the need to investigate people with balanced L1s). However, the manuscript needs substantial revision as it currently lacks consistency, as well as a solid representation of the literature outside of the papers selected for the review.

The aim of the manuscript is stated to be to answer the question: "What is the nature of sentence production impairments in bilingual aphasia?" (page 2), but the conclusion is that "participants with primary progressive aphasia have parallel deterioration when both languages (L1 and L2)" etc. (page 14), and goes on to be only on PPA, while the discussion distinguishes between the two. This is just the most evident example of the confusion the manuscript makes between people with aphasia (PWA) and primary progressive aphasia (PPA). The two are generally discussed separately as they stem from very different phenomena, but if the authors wish to discuss them together they should be consistent throughout the paper.

Moreover, the authors should expand their selection of background literature. It is rather strange to have only one reference for sentences such as "PWA with agrammatism show deficits in the production of complex sentences" (page 1) or "these features are comparable with features of monolingual agrammatism" (page 13).

Comments to the text:

abstract: "past researchers" > the studies featured

page one

"due to lack of appropriate words" > very vague, please rephrase

"Thompson found that..." > many authors did. See for example Garraffa & Grillo, 2008, Martini et al. 2020. Please rephrase as general statement and insert other references.

"Their findings are consistent..." > these are hypotheses to describe the findings, so they will be consistent by definition. Please rephrase.

page 4

please introduce Table 3 in the text, as it is quite dense with information.

Page 13

"In this review, the linguistic aspects of bilingual PWA were examined" > this is not a fair summary of the review. It is a review of studies on language production.

Discussion

Line 4 > would you have expected something different? Please explain the comparison with monolingual agrammatics better

"reviewed studies generally showed better language abilities and recovery of L1 in bilingual PWA are better than L2" > two main verbs in sentence. There are similar cases across the manuscript. Please proofread carefully.

The authors introduce one model of bilingual processing in the discussion (Ullman). Since it is not within the aims of the paper to support specific theories, it would be advisable to have a general observation on processing in L2 vs L1, and a few mentions of authors describing the phenomenon.

References

Please check references thoroughly. For example, both cited works by Ullman are missing.

Author Response

Thank you for your comments. Please find our responses in the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors addressed the main concern I had raised in the first round of reviews, namely the lack of cohesion in the aim of the paper (whether it was a scoping review on bilingualism in aphasia, primary progressive aphasia, or both). The manuscript is now more coherent and both aphasia and PPA are discussed in a sufficiently systematic fashion.

The introduction was also improved, with more background information (and literature) given on the topic.

While the manuscript has had considerable improvements on one hand, some sections of the manuscript feel overworked for this second version. This is particularly the case for the discussion section, and to a lesser extent the introduction, where the manuscript sometimes tackles theoretical considerations (for example on morphosyntax of verb morphology, freestanding elements, etc.) that do not feel relevant and necessary and feel detached from the aim. This is the case for example for the first and third paragraph of the Discussion.

I believe the authors should streamline the manuscript, keeping just the  theoretical discussions necessary to frame the main (general) findings in both the Introduction and the Discussion, which (the latter) should be a to-the-point summary of main findings and their meaning.  This is sufficient in scoping reviews like this one that aim to collect the available data (and not prove a theoretical point) and that answer a few basic questions. I believe after this, the manuscript will be easier to read and will more efficiently meet its aims. Keep it up!

1.1 among > in

page 1 - sentences produced by PWA ARE reduced

           - when you introduce PPA, please provide a brief description as you did for aphasia (it is a neurological disorder, etc.)

page 2, line 14 - poor abilities in comprehending. This comment is nested in a paragraph discussing sentence production in PWA and is therefore confusing.

page 2, last paragraph of 1.1 - merge with previous paragraph

                                               - I don't understand the relevance of discussing Indo-European languages. I think the authors just want to state the morphosyntax of verbs can be complex in some languages. Please consider rephrasing to a more general observation.

page 2, 1.2 - In bilingual aphasia, language comprehension and production are also affected > language comprehension and production are also affected in bilingual aphasia

page 2, 1.2 lines 1-3 - is this comment specific to bilinguals having one of these languages as one of theirs? If so, specify. If not, explain why it is relevant

page 5, results - the number of included papers is amended to 13 in the abstract but not in the rest of the manuscript. Please amend

page 6 - "To add, the study by Zanini et al. (2011) also reporting a similar idea as L2 that was greatly impaired was less frequently used." > unclear wording

page 14 - line 5 to end of paragraph. This digression does not feel relevant to the Discussion of this scoping review. It should either be moved to the Introduction section when the authors introduce production studies in monolingual aphasia, or removed. I feel similarly about the third paragraph.

second paragraph - abandoned sentences > incomplete?

last paragraph - bilingual aphasia finds it difficult > change to aphasics

                         "the role of grammatical properties" > please rephrase

references - Garraffa & Grillo (2008) is not present in the text.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.pdf