Anterior and Posterior Left Inferior Frontal Gyrus Contribute to the Implementation of Grammatical Determiners During Language Production

Abstract

The left inferior frontal gyrus (IFG) is a key region for language comprehension and production. Previous studies point to a preferential involvement of left anterior IFG (aIFG) in lexical and semantic processes, while the posterior IFG (pIFG) has been implicated in supporting syntactic and phonological processes. Here we used focal neuronavigated transcranial magnetic stimulation (TMS) to probe the functional involvement of left IFG in lexical and grammatical processing at the sentence level. We applied 10 Hz TMS effective or sham bursts to left aIFG and pIFG, while healthy volunteers performed an adjective-noun production task contrasting grammatical and lexical determiners. For each trial, we measured the time from the stimulus onset to the moment of articulation (response time) and the time from articulation onset to the end of articulation (duration). Focal TMS of IFG generally delayed response times. The TMS-induced delay in response times was relatively stronger for the grammatical condition compared to the lexical condition, when TMS targeted aIFG. Articulation of the determiner was generally shorter in trials presenting grammatical determiners relative to lexical determiners. The shorter articulation time for grammar determiners was facilitated by effective TMS to pIFG. Together, the effects of TMS on task performance provide novel evidence for a joint involvement of anterior and posterior parts of left IFG in implementing grammatical determiners during language production, suggesting an involvement of aIFG in the initiation and pIFG in the production of grammatically appropriate verbal responses at the sentence level.

Correspondence between the layered structure of deep language models and temporal structure of natural language processing in the human brain

“…We then rescaled the performance of the encoding model for each layer to one by normalizing the peak performance; this allows us to more easily visualize the temporal dynamics of encoding performance across layers. y We start by focusing on neural responses for correctly predicted words in electrodes at the inferior frontal gyrus (IFG; Broca's area; N = 46), a central region for semantic and syntactic linguistic processing (Goldstein et al, 2022;Hagoort, 2005;Hagoort & Indefrey, 2014;Ishkhanyan et al, 2020;LaPointe, 2012;Saur et al, 2008;.…”

“…We start by focusing on neural responses for correctly predicted words in electrodes at the inferior frontal gyrus (IFG; Broca’s area; N = 46), a central region for semantic and syntactic linguistic processing (Goldstein et al, 2022; Hagoort, 2005; Hagoort & Indefrey, 2014; Ishkhanyan et al, 2020; LaPointe, 2012; Saur et al, 2008; Yang et al, 2019).…”

Brain embeddings with shared geometry to artificial contextual embeddings, as a code for representing language in the human brain

“…Using a dense array of electrocorticographic (ECoG) micro-and macro-electrodes we recorded the neural activity in the IFG (Broca's area) of three epileptic participants while they listened to a 30-min audio podcast (see Materials and Methods). We focus on IFG as it has been positioned as a central hub for language processing, with an emphasis on semantic and syntactic processing (1,9,(13)(14)(15)(16)(17). Overall, we had a dense sampling of 81 electrodes in IFG, with 41, 14, 26 electrodes in participants 1-3 respectively (Fig.…”

Rapid computation of TMS-induced E-fields using a dipole-based magnetic stimulation profile approach

“…To illustrate the capability of the MSP to approximate different coil types we used models of two commercially available TMS coils (MagVenture Cool-B35 and Cool D-B80). The Cool-B35 is a highly focal small-diameter coil whereas the Cool D-B80 offers high depth penetration so in this sense they represent extreme cases that one might encounter for practical studies ( Cortes et al, 2013 ; Ishkhanyan et al, 2020 ; Kreuzer et al, 2019 ; Pavon et al, 2019 ).…”