Questions about whether a bilingual can ever fully acquire two language systems, each with monolingual proficiency, and debate over whether knowing two languages helps or hinders the processing of either language, have led to one of the most hotly pursued research questions among contemporary language scientists: Does a bilingual brain, even when a bilingual is using only one language, process linguistic information in the same manner as a monolingual brain? Can early dual-language exposure modify the neural tissue classically observed to underlie human language processing in a way that renders language processing in bilinguals fundamentally different from that of monolinguals? To a certain extent, this neural organization is influenced by environmental experiences and, therefore, many early childhood experiences, such as sensory deprivation, musical training, learning to read, and delays in language exposure, have the potential to yield a life-long impact on behavior as well as on brain organization ( Newman, Bavelier, Corina, Jezzard, & Neville, 2002 Neville & Bavelier, 2001 Ohnishi et al., 2001 Petersson, Reis, Askelof, Castro-Caldas, & Ingvar, 2000). Differential activation may further provide a fascinating window into the language processing potential not recruited in monolingual brains and reveal the biological extent of the neural architecture underlying all human language. The differential activation for bilinguals and monolinguals opens the question as to whether there may possibly be a “neural signature” of bilingualism. The results provide insight into the decades-old question about the degree of separation of bilinguals' dual-language representation. However, an important difference was that bilinguals had a significantly greater increase in the blood oxygenation level-dependent signal in the LIFC (BA 45) when processing English than the English monolinguals. fMRI analyses revealed that both monolinguals (in one language) and bilinguals (in each language) showed predicted increases in activation in classic language areas (e.g., left inferior frontal cortex, LIFC), with any neural differences between the bilingual's two languages being principled and predictable based on the morphosyntactic differences between Spanish and English. Results show that behaviorally, in English, bilinguals and monolinguals had the same speed and accuracy, yet, as predicted from the Spanish-English structural differences, bilinguals had a different pattern of performance in Spanish. If bilinguals' neural processing differs across their two languages, then differential behavioral and neural patterns should be observed in Spanish and English. The sentences exploited differences between Spanish and English linguistic properties, allowing us to explore similarities and differences in behavioral and neural responses between bilinguals and monolinguals, and between a bilingual's two languages. During functional magnetic resonance imaging (fMRI), participants completed a syntactic “sentence judgment task”. Highly proficient and early-exposed adult Spanish-English bilinguals and English monolinguals participated. Does the brain of a bilingual process language differently from that of a monolingual? We compared how bilinguals and monolinguals recruit classic language brain areas in response to a language task and asked whether there is a “neural signature” of bilingualism.
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