The Implications of Bilinguality and Bilingual Aphasia

Biology 202
2004 Second Web Paper
On Serendip

The Implications of Bilinguality and Bilingual Aphasia

Prachi Dave

The bilingual, and the polyglot, for that matter is an individual whose status as the speaker of two or more languages has been widely discussed. The past has seen a disdainful view of bilinguals transform slowly into a more positive and currently, even glowing, regard for their language flexibility. A point of view concerning language learning among infants involves the conception that babies are born with the innate capacity to learn any language in which it is immersed (1) (furthermore, exposure to multiple languages allows the infant to learn as many), and therefore the baby is a universal language speaker, giving support to Chomsky's conception of the existence of a "universal grammar" that forms the basis of every existent language. Bilingual ability and status have implications for the individual's identity and for neurolinguistic study involving a wider academic interest. Particularly, bilingual aphasia is fast becoming, for the study of the bilingual brain, that which aphasia was for the now heavily studied monolingual brain.

Human language has captured both the artistic and scientific imagination for, perhaps, centuries. Bilingualism, therefore appeals equally to the same imagination for both it's theoretic and practical implications. Bilingualism as a cognitive state that supposedly requires the sharing of cognitive resources has been openly frowned upon and a dates and ignorant assertion by Laurie (1980, in Wei, 2000) (3) declared:

"If it were possible for a child to live in two languages at one equally well, so much the worse. His intellectual and spiritual growth would not thereby be doubled , but halved. Unity of mind and character would have great difficulty asserting itself in such circumstances."

this point of view, among other myths (2), had been very popular and eventually blended into a purist, monolingual viewpoint of bilinguals which accepted into the bilingual category only those who are absolutely proficient in both their languages while all other speakers of more than one language have been relegated to either one of a long list of subordinate categories (alingual, semilingual, covert bilingual) (3), (4). This view has been emphatically refuted by Grosjean (1989) (4) who asserts the need to define bilinguals in accordance to the contexts of language usage. The former view has to a great extent been obliterated and bilingualism is now believed to be advantageous in cultural, social, cognitive and even transnational domains. These successive realisations to which researchers in this field have come have broadened the scope for it's study.

Researchers have been very interested lately in understanding the cortical representation of both a native and a second language. Particularly, curiousity as to whether or not these languages converge upon similar brain areas has been piqued given various contradictory findings that indicate both the shared and divergent representation of language in the bilingual brain. Those who want to understand the regions involved in language processing and production have looked both to neuroimaging studies among normal bilinguals and studies involving clinical populations of bilingual aphasics. In support of the view that propounds anatomical overlap between first and second languages, Chee et al. (1999) (5), (6) showed, in an fMRI study that during word-stem completion among Mandarin-English bilinguals, the task resulted in similar activation of the left prefrontal region, involving the inferior frontal gyrus, the supplementary motor area and the occipital and parietal areas bilaterally, during the task in both languages. These results argue for shared lexicons between first and second languages. The structural dissimilarity between Mandarin and English provide a rigorous test for the hypothesis regarding shared cortical representation for bilinguals' languages for it is surprising that two such divergent languages overlap in terms of lexical representation.

Additionally, Illes et al. (1999) (7) provided support for the above findings whereby in another fMRI study, they also showed inferior frontal gyrus activation among Spanish-English bilinguals performing semantic judgment tasks in both languages. These studies concern a question integral to the study of language, that is, to what extent do overlapping cortical representations for vastly differing languages imply similarity between them in terms of personal identification and comfort with the languages? This is a question to which we will return in the following paragraphs. These studies, although showing what seem to be reliable findings, are confounded such that although age of language acquisition (a factor thought to affect language lateralisation in the brain) (8) remains stable at approximately age twelve, level of language proficiency (a further issue impacting upon language lateralisation) (8) is unreported or reported as "moderate." The lack of attention paid to such intervening variables must be corrected if reliable results are to be obtained. Certainly, however, a swift scan of the frequently cited literature supporting shared anatomical correlates between native and second languages is limited (9), (10) and often barely comparable due to the variety of linguistic tasks employed to understand either language comprehension or production in the bilingual brain. The findings, however, that second language learners may display shared cortical areas between their languages are interesting for they implicitly refute the classic assertion of a critical window of time for language-learning (by implying similar proficiency in both first and second languages) and they reiterate the phenomenon of brain plasticity. The latter statement a propos plasticity is particularly relevant in terms of Obler's stage hypothesis (11) which asserts that language learning moves from right hemisphere lateralisation in the early stages to left hemisphere overlap with the native language as proficiency increases. However, a test of this hypothesis requires some knowledge of findings whereby L1 and L2 are seemingly separately localised in the brain.

In 1997, Kim et al (12) used the fMRI method to examine cortical activation among a range of bilinguals who were proficient in various languages. The participant pool was divided into two groups, early (L2 acquisition before the age of five) and late (after the age of twelve) bilinguals. The results suggested anatomical variation between early and late bilinguals such that although early bilinguals showed similar activation in both Broca's and Wernicke's areas during a silent sentence generation task while late bilinguals displayed common activation in Wernicke's but not in Broca's area. These results indicate a role for late language acquisition, suggesting that the "critical period" concept cannot be discarded and that to some extent language learning after a certain age is differentially represented in the brain. This point of view both confounds the conclusions that can be drawn from studies cited earlier but adds confounds inherent to the study. The study included sentence generation tasks which can barely be compared to the early single-word generation studies for the former requires additional and more complex linguistic tasks in contrast to the latter. Additionally, a silent sentence generation task is a measure whose accuracy is difficult to measure across participants. However, other reports do support the finding that L1 and L2 may be anatomically separate in the bilingual brain (13) both in scientific terms and in experiential terms whereby the difficulty of becoming proficient in a second language beyond a certain age indicates, intuitively, that some corresponding anatomical difference too, must exist.

Not only do observations from various experiemental studies provide a source of information reagrding the interaction between different languages in terms of cortical representation, but recovery patterns among bilingual aphasics (14), (15), (16) too allow for the contruction of hypotheses regarding the anatomical correlates of language. The patterns of recovery, selective, parallel, differential, antagonistic, blended and successive (17) observed in previous cases of bilingual aphasia, when combined with the knowledge gleaned from neuroimaging studies must allow for a more comprehensive assessment of the processes involved in maintaining the two languages in the brain. The scientific examination of bilingual aphasics must be combined with studies concerned with impact of this impairment on the identity of aphasics (18), for identity is often attached to one's language and damage to this ability may also cause devastating effect on the aphasic himself.

The study of bilinguals and bilingual aphasia has a great deal of promise both for the study of identity as attached to language and for the mapping of multiple languages in the brain. Studies of bilingual aphasics and the recovery patterns observed within and among their languages have challenged existing accounts of language representation in the brain. A consolidation and analysis of the various findings is ongoing and will perhaps lead to a growth in knowledge regarding the various aspects bilingualism.

References

1)Timothy Mason's Site

2)A Note on Myths about Language, Learning, and Minority Children

3) Wei, L. (2000).The Bilingualism Reader. Routledge: London ; New York.

4) Grosjean, F. (1989) Neurolinguists beware! The bilingual is not two monolinguals in one person. Brain and Language, 36, 3-15.

5)Nature: Science Update

6) Chee, M. W. L., Tan, E. W. L., & Thiel, T. (1999). Mandarian and English single word processing studied with functional magnetic resonance imaging. The Journal of Neuroscience, 19, 3050 056.

7) Illes, J., Francis, W. S., Desmond, J. E., Gabrieli, J. D. E., Glover, G. H., Poldrack, R., Lee, C. J., & Wagner, A. D. (1999). Convergent cortical representation of semantic processing in bilinguals. Brain and Language, 70, 347 63.

8) Obler, L. K., Zatorre, R. J., & Galloway, L. (2000) Cerebral lateralization in bilinguals: methodological issues, pp. 381-394. In Wei, L.The Bilingualism Reader. Routledge: London ; New York.

9) Klein, D., Milner, B., Zatorre, R. J., Zhao, V., & Nikelski, J. (1999). Cerebral organization in bilinguals: A PET study of Chinese English verb generation. NeuroReport, 10, 2841 846.

10) Chee, M. W. L., Caplan, D., Soon, C. S., Sriram, N., Tan, E. W. L., Thiel, T., & Weekes, B. (1999). Processing of visually presented sentences in Mandarian and English studies with fMRI. Neuron, 23, 127 37.

11)Acquisition of second languages

12)Kim, K. H. S., Relkin, N. R., Lee, K. M., & Hirsch, J. (1997). Distinct cortical areas associated with native and second languages. Nature, 388, 171 74.

13)Study sheds light on how brain processes languages

14) Junque, C., Vendrell, P., Vendrell-Brucet, J. M., & Tobena, A. (1989). Brain and Language, 36, 16-22.

15) Nilipour, R., & Ashayeri, H. (1989). Alternating antagonism between two languages with successive recovery of a thrid in a trilingual aphasic patient. Brain and Language, 36, 23-48.

16) Paradis, M., &Goldblum, M. (1989). Selective crossed aphasia in a trilingual aphasic patient followed by reciprocal antagonsim. Brain and Language, 36, 62-75.

17)The Neurocognition of Recovery Patterns