Cortical Organization of Bilingualism

Language is a uniquely human phenomenon. People are able to communicate infinite ideas to one another through the use of words. Across the world people communicate in numerous different languages. Although people readily attain proficiency at any language they are exposed to as a child, the difficulties of learning a language later in life, past the critical period, are well known. While the cortical representation of language is fairly well understood, the neural substrates of bilingualism are still unknown. Researchers questioning whether multiple languages are represented by the same or distinct brain regions have yet to agree on an answer. Proponents of identical representations for multiple languages of bilingual speakers contend that the same brain regions mediate languages regardless of the type of language or whether they are native or foreign (Klein, 1994; Chee, 1999; Klein, 1999). Numerous neuroimaging studies have revealed similar brain regions active while subjects process both native and foreign languages. Other studies have found contrasting results. Neuroimaging studies have detected differential brain activation in response to tasks in various languages of a multilingual speaker (Dehaene, 1997; Kim, 1997; Perani, 1998). Other cases of bilingual aphasia, in which only one language of a bilingual is disrupted following brain damage, provide further evidence for separate neural representations of multiple languages (Gomez-Tortosa, 1995; Moretti, 2001; Paradis, 1989). Intraoperative methods, which provide the most direct measures of brain activity, have demonstrated regions of brain selectivity to each language of a bilingual (Ojemann & Whitaker, 1978; Pouratian, 2000; Simos, 2001).