Neural imaging (PET, MEG, and fMRI) as a window into language development and processing

This chapter reviews Second Language Acquisition (SLA) studies utilizing positron emission tomography (PET), magnetoencephalography (MEG), and functional magnetic resonance imaging (fMRI). fMRI tracks the changes in the metabolism of neurons when a language-related task is performed. It tells us how much glucose is transported to the neurons in brain tissues, and therefore the likelihood that those neurons are active or not through the analysis of how oxygenated the tissue is. PET too measures regional cerebral blood flow but — unlike the fMRI — tracks the distribution of a radioactive isotope injected into the research subject’s bloodstream, as it is carried up into their brain. Magnetoencephalography (MEG) records tiny magnetic fields on the scalp which are time-locked to the presentation of language stimuli. The chapter describes the most utilized experimental paradigms, their strengths, and weaknesses. Research questions that are targeted by neuroimaging SLA studies concern: (a) whether native speakers and L2 learners activate the same brain areas (b) whether activation patterns vary depending on the language domain (syntax, phonology, semantics); (c) whether L1–L2 differences, proficiency and writing systems modulate those patterns.