Internal modeling of upcoming speech: a causal role of the right posterior cerebellum in non-motor aspects of language production

International audienceSome language processing theories propose that, just as for other somatic actions, self-monitoring of language production is achieved through internal modeling. The cerebellum is the proposed center of such internal modeling in motor control, and the right cerebellum has been linked to an increasing number of language functions, including predictive processing during comprehension. Relating these findings, we tested whether the right posterior cerebellum has a causal role for self-monitoring of speech errors. Participants received 1Hz repetitive transcranial magnetic stimulation during 15 minutes to lobules Crus I and II in the right hemisphere, and, in counterbalanced orders, to the contralateral area in the left cerebellar hemisphere (control) in order to induce a temporary inactivation of one of these zones. Immediately afterwards, they engaged in a speech production task priming the production of speech errors. Language production was impaired after right compared to left hemisphere stimulation, a finding that provides evidence for a causal role of the cerebellum during language production. We interpreted this role in terms of internal modeling of upcoming speech through a verbal working memory process used to prevent errors

Controle volontaire d'un automatisme sensorimoteur: la locomotion humaine

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 81425 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Contribution de la voie corticospinale aux modulations volontaires des automatismes sensori-moteurs (Etudes par TMS chez l'homme)

L'ensemble des travaux présentés dans cette thèse vise à mieux comprendre la contribution de la voie corticospinale (CS) aux modulations volontaires des automatismes sensori-moteurs chez l'homme. Nous avons étudié comment, au travers des modulations de l'excitabilité CS, les processus intentionnels s'expriment au cours de l'adaptation volontaire de la locomotion humaine. Une particularité de ce travail de thèse est d'avoir envisagé la question à la fois sur le versant moteur, en tentant de mettre en évidence un accès CS aux muscles proximaux pendant la marche, et sur le versant cognitif, en étudiant la contribution de cette voie aux fonctions cognitives liées à la motricité. Ce travail a été réalisé grâce à la Stimulation Magnétique Transcrânienne (TMS), technique non-invasive qui permet, chez l'homme, d'étudier les influences CS au cours de mouvements naturels.AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Ré-agir vite et bien à une perturbation de mouvement (étude des mécanismes corticaux par couplage EEG-TMS chez l'homme.)

Dans la vie de tous les jours, il arrive que nos actions soient perturbées par desvariations rapides des forces externes de notre environnement. Afin d'atteindre notre but, nousdevons alors réagir vite et bien à ces perturbations de mouvement, ce qui implique la mise enjeu à la fois de processus cognitifs et de processus sensori-moteurs. Nous nous sommesintéressés aux mécanismes corticaux (engagés notamment au niveau du cortex sensorimoteurprimaire) sous-tendant les interactions entre fonctions cognitive et sensorimotrice permettantd'adapter la réaction à la perturbation en fonction de notre intention, en nous efforçant de fairele lien entre les mécanismes impliqués au cours de la préparation et de la réalisation de laréaction. En utilisant le couplage EEG-TMS (avec enregistrement de l'EMG), nous avons menéune approche par stimulation-enregistrement, permettant d'observer simultanément lesmécanismes corticaux et corticospinaux précédant et suivant la stimulation, et ainsi de mieuxcomprendre le lien reliant l'activité cérébrale et le comportement.Dans l étude 1, nous avons utilisé une perturbation motrice centrale, c'est-à-dire quenous avons demandé au sujet soit de résister soit d'assister un mouvement évoqué directementau niveau cortical par TMS. Ceci nous a permis de montrer que les processus cognitifs peuventinfluencer directement l'excitabilité corticale et corticospinale, avant la mise en jeu deprocessus sensorimoteurs impliqués dans l exécution du mouvement. Lorsque le sujet s estpréparé à résister au mouvement évoqué par TMS, l'augmentation anticipée de l'activité desréseaux intracorticaux inhibiteurs de M1 diminue l'excitabilité corticale, menant à une diminutionde l excitabilité corticospinale, réduisant ainsi l amplitude du mouvement évoqué par TMS.Dans les études suivantes (2, 3 et 4), nous nous sommes intéressés aux mécanismescorticaux et corticospinaux impliqués dans la préparation et la réaction rapide à uneperturbation périphérique du mouvement. Nous avons demandé au sujet soit de résister soitde se laisser-faire par une extension passive du poignet, et avons étudié les mécanismesimpliqués dans la modulation de la composante à longue latence du réflexe d'étirement (LLSR,qui débute environ 50 ms après la perturbation), en fonction de l'intention. Concernantl excitabilité corticospinale, les résultats montrent que, lors de la préparation à uneperturbation périphérique, les phénomènes d'intégration sensori-motrice engendrés par lesafférences sensorielles dues à la perturbation sont pris en compte dans le réglage anticipé del'excitabilité corticospinale, afin que la réaction, déclenchée par les afférences sensorielles, soitadaptée à l'intention du sujet (étude 2). Au niveau cortical, une modification de l'activité desréseaux intracorticaux de M1 en fonction de l'intention précède la modulation de l'activitécorticale du cortex sensorimoteur primaire, liée à la genèse du LLSR, suggérant que desprocessus anticipateurs influencent l activité du cortex sensorimoteur primaire afin que saréponse précoce à la perturbation soit adaptée à l'intention du sujet (étude 3). Enfin, dansl étude 4, nous avons mis en évidence le rôle d'une aire motrice non primaire, la SMA proper,dans la modulation du réflexe d'étirement en fonction de l'intention.Ainsi, lorsque nous anticipons une perturbation motrice, des processus préparatoiresspécifiques (dépendants de notre intention), et différents de ceux impliqués avant la réalisationd un mouvement sans variation des forces externes, sont mis en jeu dans la SMA proper et lecortex sensorimoteur primaire de manière à ce que la réaction rapide, déclenchée au niveau ducortex sensorimoteur par les afférences sensorielles induites par la perturbation, soit adaptée àl intention du sujet.In everyday life, our actions can be perturbed by rapid variations of environmentalexternal forces. In order to achieve our goals, we have to react well and fast to thesemovement perturbations. This reaction implies both cognitive and sensorimotor processes. Wewere interested in the cortical mechanisms (mainly involving the primary motor cortex, M1)underlying the interaction between cognitive and sensorimotor functions that allows theadaptation of the reaction to the perturbation according to the intention. We tried to relate themechanisms implicated during the preparation with those implicated during the realization ofthe reaction. With combined EEG-TMS (with EMG recording), we used a stimulation-recordingapproach, allowing simultaneous observation of cortical and corticospinal mechanisms, bothbefore and after the stimulation. This approach helps to obtain to a better understanding of therelationship between cerebral activity and behavior.In the first experiment, we used a central motor perturbation, i.e. subjects were asked toresist or to assist a movement evoked directly at the cortical level using TMS. We showed thatcognitive processes can directly influence cortical and corticospinal excitability before anyinvolvement of the sensorimotor processes related to the movement execution. When subjectsprepared to resist the TMS-evoked movement, the anticipatory increased activity of theintracortical inhibitory networks of M1 decreased the cortical excitability, leading to adecreased corticospinal excitability and thus to a reduced TMS-evoked movement.In the following experiments (2, 3 and 4), we were interested in cortical andcorticospinal mechanisms engaged during the preparation and the reaction to a peripheralmovement perturbation. We asked subjects either to resist or to not-react (to let-go ) to apassive wrist extension, and we studied the mechanisms underlying the modulation of the longlatency stretch reflex (LLSR, starting about 50 ms after the perturbation) according to theintention. Concerning the corticospinal excitability, the results showed that, during thepreparation of a reaction to a peripheral perturbation, the anticipatory tuning of thecorticospinal excitability takes into account sensorimotor integrative phenomenons induced bythe afferent input due to the perturbation in such a way that the reaction, triggered by theafferent inputs, is adapted to the subject s intention (experiment 2). At the cortical level, achange of M1 intracortical network activity (before the perturbation) precedes the modulationof the primary sensorimotor cortex activity that is linked to the LLSR generation (after theperturbation). This strongly suggests that anticipatory processes preset the primarysensorimotor cortex in order to adapt its early response to the perturbation according to thesubject s intention (experiment 3). Finally, temporary inactivation of SMA proper (induced byTMS) showed that this non-primary motor area is also implicated in the modulation of thestretch reflex according to the intention (experiment 4).In conclusion, when we expect a motor perturbation, intention-specific preparatoryprocesses are engaged in SMA proper and the primary sensorimotor cortex that are differentfrom those involved in the realization of a movement without external force variations. Thesepreparatory processes allow the early motor reaction, generated by the primary sensorimotorcortex (triggered by the afferent input induced by the perturbation) to be adapted to thesubject s intention.AIX-MARSEILLE2-Bib.electronique (130559901) / SudocSudocFranceF

La conscience du mouvement humain

Ce texte est un rapport d'étape issu de l'ACI cognitique.Concepts and objectives Action consciousness seems to largely depend on the fact that it is carried out by our own body effectors, particularly our muscles, whose sensory compartment would thus play a determining part. One can nevertheless not deny the part of motor mechanisms (deriving from the motor command) in the arising of self movement consciousness. The first component of the project aims at bringing forward the knowledge about substrates and neural processes involved in learning, performing and consciously perceiving our symbolic movements. It tends to establish that writing is much more than a simple motor act, but rather that its performance provides cognitive cues which are integrated with those streaming from reading during linguistic learning. The goal of the second component of the project is to study, at the level of cerebral substrates, the interaction between motor and perceptive mechanisms in the emergence of awareness of our own movement. Two complementary fMRI experiments will be performed in which we will confront subjects to external forces in order to study how, during a voluntary movement, the subject can separate the part of the movement produced by himself from what is produced by the external forces. There will also be some fMRI methodological development aiming at a detection of functional activity based on a multi-scale analysis of the data. This will permit us to do a multi-subject (group) analysis that takes into account the complexity of the neural network and their inter-subject variability. Finally, technical developments necessary for the fMRI experiments are common for the whole project.Rappel des enjeux et objectifs La conscience de l'action semble largement attachée au fait que nous l'exécutons avec nos effecteurs corporels, et notamment nos muscles dont le compartiment sensoriel aurait alors une fonction déterminante. On ne peut néanmoins pas nier le rôle des mécanismes moteurs (liés à la commande du mouvement) dans l'émergence la conscience du mouvement de soi. Le premier volet de ce projet a l'ambition de faire avancer les connaissances concernant les substrats et les opérations neurales impliquées dans l'apprentissage, l'exécution et la perception consciente de nos gestuelles symboliques. Il se propose d'établir que le geste d'écrire est bien plus qu'un simple acte moteur et que son exécution est la source d'apports cognitifs qui s'intègrent à ceux de la lecture lors des apprentissages linguistiques. Le deuxième volet de ce projet a pour objectif d'étudier, au niveau des substrats cérébraux, l'interaction entre mécanismes moteurs et perceptifs dans l'émergence de la conscience du mouvement de soi. Pour cela, nous réaliserons deux expériences complémentaires en IRMf en confrontant le sujet à des variations de forces externes pour étudier comment, lors d'un événement volontaire, le sujet peut séparer consciemment ce qui provient de son action propre et ce qui est produit par ces forces externes. Nous réalisons également des développements méthodologiques en IRMf afin de mettre au point une méthode de détection d'activations fonctionnelles basée sur une analyse multi-échelle qui permette d'effectuer des analyses de groupe (multi-sujets) tout en prenant en compte la complexité des réseaux impliqués dans ces processus complexes et leur variabilité inter-sujets. Enfin les développements techniques nécessaires aux expérimentations IRMf sont communs à l'ensemble du projet

The contribution of the Exner’s area during reading: A neuronavigated TMS study

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Spoken language coding neurons in the Visual Word Form Area: Evidence from a TMS adaptation paradigm

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Cortical mechanisms underlying stretch reflex adaptation to intention: A combined EEG–TMS study

International audienceDuring voluntary motor acts, potential perturbations due to transient external forces are counteracted very quickly by short- and long-latency stretch reflexes (SLSR and LLSR, respectively). The LLSR, presumably linked to a transcortical loop, can be modulated by the subjects' intention. Here, we used combined TMS-EEG to study cortical mechanisms involved in this intention-related modulation both before and during the reaction to a mechanical perturbation. Subjects had to prepare for a brisk wrist extension under the instruction either to 'resist' the perturbation or to 'let-go'. Following the perturbation, the early cortical evoked activity (45-75 ms) was greater in the 'let-go' condition; moreover, its amplitude was negatively correlated with the LLSR amplitude, regardless of condition. After 100 ms the pattern reversed, the late evoked activity (presumably linked to the voluntary reaction) was greater in the 'resist' condition. The early and late evoked activities also differed in their topography. Therefore, the cortical mechanisms involved in the intention-related LLSR modulation differ from those involved in the voluntary reaction. In addition, in response to a single-pulse TMS delivered during the expectation of the mechanical perturbation, the TMS-evoked N100 amplitude decreased when subjects intended to 'let-go', suggesting anticipatory decreased activity of intracortical inhibitory sensorimotor networks. Taken together, these results support the idea that anticipatory processes preset the sensorimotor cortex so as to adapt its early reaction to the perturbation relative to the subjects' intention

Interactions Between Cognitive and Sensorimotor Functions in the Motor Cortex: Evidence from the Preparatory Motor Sets Anticipating a Perturbation

International audienceThe many signs of cognitive processes in the activation pattern of the primary motor cortex or in corticospinal (CS) excitability gave rise to the idea that the motor cortex is a crucial node in the processing of cognitive information related to sensorimotor functions. Moreover, it became clear that the preparatory motor sets offer a privileged window to investigate the interaction between cognitive and sensorimotor function in the motor cortex. In the present review, we examine how the study of the preparatory motor sets anticipating a mechanical movement perturbation contributes to enlightening this question. Following the initial observation made by Hammond that some components of the stretch reflex can be modulated by a prior intention either to resist or to relax in response to a subsequent perturbation, first evidence of the phenomenon was obtained in behaving monkeys /29/. Moreover, this study /29/ related this peripheral fact to the observed anticipatory activity of motor cortex neurons after a prior instruction telling the animal how to respond to the subsequent perturbation, which triggered the instructed movement. Indeed, this anticipatory activity was found to be different according to the instruction. In the 1980s, this work inspired a lot of studies in human beings that brought support to the idea of a cognitive tuning of the long latency stretch response (LLSR). Specifically, the M2 component of the response was shown to be modulated by a prior intent to resist versus to let go when faced with the perturbation. Recently, new approaches have been developed to obtain evidence of a cognitive tuning of CS excitability, thanks to transcranial magnetic stimulation (TMS). TMS has been used both as a reliable tool for quantifying the CS excitability via the motor evoked potentials (MEPs), and to centrally perturb the organization of movement. Such central perturbations offer the unique opportunity to activate the descending motor tracts while shunting, for a short time period, the ascending tracts assisting the movement. Thus, CS excitability was measured before the movement was perturbed. These studies demonstrated the readiness of the CS tract to be involved in anticipatory compensatory responses to central movement perturbations induced by TMS in relation to the subject's cognitive attitudes. The question of the cerebral regions upstream of the motor cortex that could be responsible for this modulation in CS excit-ability remains largely open