Projects on Bilingual Aphasia Rehabilitation

The nature of cross-language rehabilitation individuals with bilingual aphasia:
We have conducted several experiments examining the interaction between facilitation and interference in the context of bilingual aphasia rehabilitation.

The first experiment investigated the nature of within- and between-language generalization in seventeen participants with Spanish/English bilingual aphasia who received semantic naming treatment. Participants received therapy in either English or Spanish and treatment outcomes were compared for trained items, within-language semantically related untrained items, between language translations of trained items and between-language translations of untrained semantically related items. Treatment for naming on Set 1 items resulted in significant improvement (ES > 4.0) on the trained items in 14/17 participants. Of the 14 participants who showed improvement, within-language generalization to semantically related items was observed in 10 participants. Between-language generalization to the translations of trained items was observed for 5 participants; whereas between-language generalization to the translations of the untrained semantically related items was observed for 6 participants.

In other study using the same methodology, a Chinese-English bilingual individual with aphasia was trained in Chinese and showed between-language generalization to the untrained English language. In a third study, a French-English-Amharic trilingual individual with aphasia, was trained first in French and then in English. This individual showed no within or between-language generalization and showed several instances of cross-language interference. Results of these studies illustrate that within- and between-language patterns are variable across participants and these differences are indicative of the interplay between facilitation (generalization) and inhibition (See Figure 1).

The discussion addresses these results within current theoretical models of lexical access and the influence of rehabilitation on these models. Rehabilitation outcomes also appear to be influenced by language proficiency, use, and the patient’s current language environment.

Neuroimaging Bilingual Aphasia

This study was aimed at examining the effect of current language use/exposure on the neural representation of languages in Spanish-English stroke patients with aphasia using a semantic judgment task. Functional magnetic resonance imaging was performed on three participants with aphasia and three normal controls who had demonstrated a shift towards dominance in their second language (English). The behavioral and imaging results indicate that all participants processed their non-dominant native language (Spanish) differently compared to their dominant second language (English). Specifically, increased activation was observed in the left frontal cortex and anterior cingulate gyrus during the weaker native language processing. Further, in participants with aphasia, increased bilateral activation was observed during the weaker native language processing, indicating that decreased language usage/proficiency results in a distributed network of activation. The results of this study demonstrate that the neural substrates of language recovery in bilingual stroke patients are similar to regions engaged by normal bilinguals but include additional regions reflecting a compensatory network to sub serve successful language processing.