Previous research examining lexical-retrieval difficulty in bilinguals with aphasia (BWA) has identified a verb-noun dissociation in naming in both first (L1) and second (L2) languages, i.e., a lower naming accuracy for verbs than nouns. Yet, the evidence is limited to typologically similar languages, and whether the same patterns of lexical impairment emerge in other linguistic contexts (i.e., discourse) is unclear. Lexical-retrieval difficulty has been commonly targeted in bilingual aphasia rehabilitation, but mainly focused on nouns. Whether similar patterns of treatment-induced language recovery emerge in both noun and verb treatment remains unclear. Studies implementing semantic-based treatment have shown robust treatment gains, but patterns of generalizations are inconsistent. Most evidence in bilingual aphasia rehabilitation has come from individuals speaking Indo-European languages. Given that the Chinese-speaking population is rapidly growing nationwide, future research needs to establish the evidence base for aphasia rehabilitation in this population. Hence, two studies were undertaken in this dissertation work to address these critical issues.
In Study 1, twelve Mandarin-English BWA were administered a battery of standardized naming and discourse tasks in both languages. A verb-noun dissociation was found across languages in single-word naming and discourse production. The magnitude of this verb-noun dissociation was similar in L1 and L2 in naming but was significantly larger in L2 than in L1 in discourse, depending on the specific task. Findings indicated a direct relationship between naming and lexical retrieval in discourse irrespective of the target language.
In Study 2, the same group of Mandarin-English BWA underwent semantic-based treatment targeting noun and verb retrieval. These participants demonstrated improvement on the overall aphasia severity and lexical retrieval based on their performance on the standardized language assessments. Results from weekly naming probes showed a positive treatment gain in both noun and verb treatment, but to a greater extent in verb treatment. Generalization to semantically-related items was captured in noun treatment. Cross-language generalization was identified in both treatments, but to a larger extent when training verbs. Additionally, widespread generalizations beyond the single-word level and to untrained naming tasks were found following both noun and verb treatment. However, more generalizations were captured after noun treatment, particularly in discourse and untrained naming tasks. These two studies provided strong evidence of bilingual language impairment and treatment-induced language recovery between nouns and verbs in Mandarin-English BWA.
The general discussion reviews key findings from Studies 1 and 2 and discusses clinical implications for studying bilingual aphasia recovery and language rehabilitation in future work. / 2024-08-24T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/45041 |
| Date | 24 August 2022 |
| Creators | Li, Ran |
| Contributors | Kiran, Swathi |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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