Summary of "In search of the language switch : an fMRI study of picture naming in Spanish-English Bilinguals"
Main argument: Language switching is a part of a general executive attentional system and that languages are represented in overlapping areas of the brain in early bilinguals.
The brain bases of bilingualism have concentrated on two basic questions:
(1) The nature of language representation. That is, are a bilinguals' two languages represented in distinct of overlapping areas of the brain.
(2) The second basic question in the neuropsychology of bilingualism concerns that neural correlates of language switching, that is, the areas that are active when bilinguals switch from one language to the other.
The current study was designed to investigate two separate question:
(1) The study intended to address differences in the neurological areas that are active for each language. The results revealed no differences between the two languags in our particular regions of interest, which included the dorsolateral prefrontal cortex, the supramarginal gyrus, the inferior frontal gyrus, and the superior temporal gyrus. It appears that for early bilinguals processing of their two languages does not result in different areas of activation for each language.
(2) The study was designed to investigate the areas that are involved in switching between two languages. The only are that revealed increased activity for language switching relative to single-language processing was dorsolateral prefrontal cortex.
Two possible limitations of neuroimaging methods such as PET and fMRI:
(1) Do not have the spatial resolution to detect the subtle differences that occur in language processing. Improved resolution might uncover the smaller areas in brain regions that are devoted exclusively to language switching or to one language but not the other.
(2) A second limitation of fMRI for tapping language function in bilinguals may be with the nature of the problem itself.
Future studies combining techniques such as event-related potentials, fMRI or PET, and behavioral techniques might be able to uncover further differences between languages beyond those that have been uncovered so far. Through the combination of methodologies we may begin to understand more clearly the nature of language switching and language representation in the bilingual brain.