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Abstract:
The combination of words into phrases and sentences is the result of a basic computation, called Merge in theoretical linguistics. Recent functional magnetic resonance imaging (fMRI) studies provided initial evidence for an involvement of the left inferior frontal gyrus (IFG), and in particular of Brodmann area (BA) 44, in this operation. However, due to the correlational nature of fMRI, causal evidence for the role of BA44 in Merge is still missing. Furthermore, because of the poor temporal resolution of fMRI, it is unclear whether BA44 implements Merge generating top-down syntactic predictions or integrating words into constituents in a bottom-up fashion. Syntactic prediction and integration in phrasal building are at the basis of the distinction between left-corner (predictive) and bottom-up parsing models in computational linguistics. Here we present a combined online Transcranial Magnetic Stimulation (TMS) and Electroencephalography (EEG) approach to investigate the causal involvement of BA44 in Merge and the nature of its parsing process (left corner vs bottom-up). Using a two-word Early Left Anterior Negativity (ELAN) paradigm, we will selectively interfere with left-corner and bottom-up parsing operations in BA44 across two different experiments. In the first experiment, TMS will be delivered during the first word (the determiner EIN or the pronoun ER), disturbing the generation of predictions on the upcoming grammatical category (noun or verb). In the second experiment, TMS will be delivered during the second word, interfering with the bottom-up integration of two words into a phrase.
