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Poster B21, Wednesday, November 8, 3:00 – 4:15 pm, Harborview and Loch Raven Ballrooms

The Left Inferior Frontal Gyrus is Necessary for Syntactic Phrase Formation: Evidence from Transcranial Magnetic Stimulation

Lars Meyer1, Anne Elsner1, Philipp Kuhnke1, Angela D. Friederici1, Gesa Hartwigsen1;1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

Language comprehension requires the grouping of words into syntactic phrases, because the sheer number of sentences’ words prohibits their individual encoding into verbal working memory. Virtually all neuroimaging studies on syntactic phrase formation report activity of the left inferior frontal gyrus (lIFG). Yet, this evidence is only correlative, and it is further questioned by unequivocal evidence from patients with tissue damage to the lIFG due to stroke or tumor lesions. Here, we employed repetitive transcranial magnetic stimulation (rTMS) to establish the functional necessity of the lIFG in the formation of syntactic phrases. To this end, we presented 48 healthy young adults with sentences that allow for two alternative ways of grouping their words into syntactic phrases (e.g., The client sued the murderer with the corrupt lawyer.). Participants indicated their grouping choice via button press. At the critical point in the sentences (i.e., at the offset of the murderer, where participants either continued or terminated a syntactic phrase), we transiently perturbed task processing in the lIFG with high-frequency rTMS. Without rTMS, participants are known to be biased to terminate a syntactic phrase at this point in the sentence. Strikingly, rTMS to the lIFG, compared to the disruption of a conservative control area (i.e., right IFG), significantly reduced this bias—indicating participants’ disability to form a syntactic phrase from the presented word sequence. Our result provides the first causal evidence for a functional necessity of the lIFG in in the grouping of words into syntactic phrases.

Topic Area: Grammar: Syntax

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