The bilingual brain as revealed by functional neuroimaging

Functional neuroimaging, used in conjunction with experimental cognitive tasks, has been extremely successful in establishing functional specialization as a principle of brain organization in man. Positron emission tomography activation techniques and functional magnetic resonance imaging assess localized increases in cerebral blood flow associated with mental processes. The advent of these noninvasive neuroimaging techniques opened a “new era” in the investigation of language organization in healthy individuals. Neuroimaging studies of bilinguals and polyglots have highlighted the potential role of variables, such as age of acquisition, degree of proficiency, level of exposure, dominance/maternality on functional brain mapping of multiple languages. Consistent results indicate that attained proficiency, and maybe language exposure, are more important than the age of acquisition as a determinant of the cerebral representation of languages in bilinguals/polyglots. Indeed, increasing language proficiency appears to be associated at the neural level with the engagement of a common network within the dedicated language areas. Here we have reviewed the functional imaging literature on bilingualism.