Catégorie d'actualités : Parution

(a) Aix Marseille Université, CNRS, LPL, 13100, Aix-en-Provence, France
(b) Aix Marseille Université, Institute of Language, Communication and the Brain, Brain and Language Research Institute, 13100, Aix-en-Provence, France
(c) Aix Marseille Université, CNRS, LPC, 13331, Marseille cedex 3, France
(d) Aix Marseille Université, INSERM, INS, 13005, Marseille, France

Publ. 18 mars 2019

Résumé

The current study set out to examine the spatiotemporal dynamics of predictive processing during syntactic processing. To do so, we conducted an MEG experiment in which we contrasted MRI-constrained sources elicited by nouns and verbs when they were preceded by a predictive syntactic context (i.e., possessive pronouns for nouns, and personal pronouns for verbs) versus a non-predictive syntactic context (visually matched symbols). The results showed rapid (from ~80 ms onwards) noun-verb differences in the left and (to a lesser extent) right inferior frontal gyri (IFG), but only when those nouns and verbs were preceded by the syntactically predictive context (i.e. their corresponding pronoun). Furthermore, the contrast between possessive and personal pronouns that preceded the rapid noun-verb modulations in the (L)IFG also produced differences in source activation in various regions of the prefrontal cortex (the superior frontal and orbitofrontal cortex). We suggest the data show that syntactic unification manifests very early on during processing in the LIFG. The speed of such syntactic unification operations is hypothesized to be driven by predictive top-down activations stemming from a domain-general network in the prefrontal cortex.

(a) Aix Marseille University
(b) Aix-Marseille University, Oslo University Hospital-Rikshospitalet
(c) Aix Marseille University, CNRS, LPL
(d) Aix-Marseille University, AP-HM, Neurophysiologie Clinique
(e) Aix-Marseille University, Cleveland Clinic Foundation
(f) Aix-Marseille University, CNRS, LPC

Publ. 2 avril 2019

Résumé

Language production requires that semantic representations are mapped to lexical representations on the basis of the ongoing context to select the appropriate words. This mapping is thought to generate two opposing phenomena, “semantic priming,” where multiple word candidates are activated, and “interference,” where these word activities are differentiated to make a goal-relevant selection. In previous neuroimaging and neurophysiological research, priming and interference have been associated to activity in regions of a left frontotemporal network. Most of such studies relied on recordings that either have high temporal or high spatial resolution, but not both. Here, we employed intracerebral EEG techniques to explore with both high resolutions, the neural activity associated with these phenomena. The data came from nine epileptic patients who were stereotactically implanted for presurgical diagnostics. They performed a cyclic picture-naming task contrasting semantically homogeneous and heterogeneous contexts. Of the 84 brain regions sampled, 39 showed task-evoked activity that was significant and consistent across two patients or more. In nine of these regions, activity was significantly modulated by the semantic manipulation. It was reduced for semantically homogeneous contexts (i.e., priming) in eight of these regions, located in the temporal ventral pathway as well as frontal areas. Conversely, it was increased only in the pre-SMA, notably at an early poststimulus temporal window (200–300 msec) and a preresponse temporal window (700–800 msec). These temporal effects respectively suggest the pre-SMA’s role in initial conflict detection (e.g., increased response caution) and in preresponse control. Such roles of the pre-SMA are traditional from a history of neural evidence in simple perceptual tasks, yet are also consistent with recent cognitive lexicosemantic theories that highlight top–down processes in language production. Finally, although no significant semantic modulation was found in the ACC, future intracerebral EEG work should continue to inspect ACC with the pre-SMA.