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

Probabilistic functional tractography of the human cortex revisited

In patients with pharmaco-resistant focal epilepsies investigated with intracranial electroencephalography (iEEG), direct electrical stimulations of a cortical region induce cortico-cortical evoked potentials (CCEP) in distant cerebral cortex, which properties can be used to infer large scale brain connectivity. In 2013, we proposed a new probabilistic functional tractography methodology to study human brain connectivity. We have now been revisiting this method in the F-TRACT project (f-tract.eu) by developing a large multicenter CCEP database of several thousand stimulation runs performed in several hundred patients, and associated processing tools to create a probabilistic atlas of human cortico-cortical connections. Here, we wish to present a snapshot of the methods and data of F-TRACT using a pool of 213 epilepsy patients, all studied by stereo-encephalography with intracerebral depth electrodes. The CCEPs were processed using an automated pipeline with the following consecutive steps: detection of each stimulation run from stimulation artifacts in raw intracranial EEG (iEEG) files, bad channels detection with a machine learning approach, model-based stimulation artifact correction, robust averaging over stimulation pulses. Effective connectivity between the stimulated and recording areas is then inferred from the properties of the first CCEP component, i.e. onset and peak latency, amplitude, duration and integral of the significant part. Finally, group statistics of CCEP features are implemented for each brain parcel explored by iEEG electrodes. The localization (coordinates, white/gray matter relative positioning) of electrode contacts were obtained from imaging data (anatomical MRI or CT scans before and after electrodes implantation). The iEEG contacts were repositioned in different brain parcellations from the segmentation of patients' anatomical MRI or from templates in the MNI coordinate system. The F-TRACT database using the first pool of 213 patients provided connectivity probability values for 95% of possible intrahemispheric and 56% of interhemispheric connections and CCEP features for 78% of intrahemisheric and 14% of interhemispheric connections. In this report, we show some examples of anatomo-functional connectivity matrices, and associated directional maps. We also indicate how CCEP features, especially latencies, are related to spatial distances, and allow estimating the velocity distribution of neuronal signals at a large scale. Finally, we describe the impact on the estimated connectivity of the stimulation charge and of the contact localization according to the white or gray matter. The most relevant maps for the scientific community are available for download on f-tract. eu (David et al., 2017) and will be regularly updated during the following months with the addition of more data in the F-TRACT database. This will provide an unprecedented knowledge on the dynamical properties of large fiber tracts in human.Peer reviewe

Successful Insular Glioma Removal in a Deaf Signer Patient During an Awake Craniotomy Procedure

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Limb shaking

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VIDEO-EEG ILLUSTRATION OF TRANSIENT EPISODES OF LOSS OF CONSCIOUNESS CORRELATED WITH PLATEAU-WAVES DUE TO INTRACRANIAL HYPERTENSION

International audienceA 54-year-old woman, with relapsing Mantle B-cell Lymphoma, was admitted for recurrent unresponsive episodes. During video-EEG recording, patient became transitory unresponsive for 12 minutes with starring and brachiofacial automatisms (video), with correlated diffuse EEG delta activity that resolved spontaneously, without epileptic discharge, cardiac arrhythmia, or hypotension (figure). No intracranial lesion existed on neuroimaging. Lumbar puncture revealed increased CSF pressure and infiltrating lymphomatous cells, confirming a diagnosis of leptomeningeal metastases. Transient neurological events can be linked to increased intracranial pressure generating a decrease of cerebral perfusion and EEG "plateau-waves" 1-5. EEG allow to distinguish this entity from differential diagnoses

Long‐term cognitive outcome after radiosurgery in epileptic hypothalamic hamartomas and review of the literature

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Orientation of Temporal Interference for Non-invasive Deep Brain Stimulation in Epilepsy

In patients with focal drug-resistant epilepsy, electrical stimulation from intracranial electrodes is frequently used for the localization of seizure onset zones and related pathological networks. The ability of electrically stimulated tissue to generate beta and gamma range oscillations, called rapid-discharges, is a frequent indication of an epileptogenic zone. However, a limit of intracranial stimulation is the fixed physical location and number of implanted electrodes, leaving numerous clinically and functionally relevant brain regions unexplored. Here, we demonstrate an alternative technique relying exclusively on non-penetrating surface electrodes, namely an orientation-tunable form of temporally interfering (TI) electric fields to target the CA3 of the mouse hippocampus which focally evokes seizure-like events (SLEs) having the characteristic frequencies of rapid-discharges, but without the necessity of the implanted electrodes. The orientation of the topical electrodes with respect to the orientation of the hippocampus is demonstrated to strongly control the threshold for evoking SLEs. Additionally, we demonstrate the use of Pulse-width-modulation of square waves as an alternative to sine waves for TI stimulation. An orientation-dependent analysis of classic implanted electrodes to evoke SLEs in the hippocampus is subsequently utilized to support the results of the minimally invasive temporally interfering fields. The principles of orientation-tunable TI stimulation seen here can be generally applicable in a wide range of other excitable tissues and brain regions, overcoming several limitations of fixed electrodes which penetrate tissue and overcoming several limitations of other non-invasive stimulation methods in epilepsy, such as transcranial magnetic stimulation (TMS).Funding Agencies|European Research Council (ERC) under the European Unions Horizon 2020 Research and Innovation ProgramEuropean Research Council (ERC) [716867]; Excellence Initiative of Aix- Marseille University-AMIDEX, a French "Investissements dAvenir" programFrench National Research Agency (ANR); Knut and Alice Wallenberg FoundationKnut &amp; Alice Wallenberg Foundation</p

One step closer to a global tool for rapid screening of major depression in epilepsy: Validation of the French NDDI-E

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Applicative accuracy at entry and target points for robot-assisted depth electrodes implantation for drug-resistant epilepsy. Monocentric retrospective analysis of 1090 consecutive trajectories

International audienceBackground: The implantation of SEEG electrodes with robotic assistance has become a standard procedure for invasive intracranial recordings in drug-resistant epilepsy. As compared with laser registration, the use of bony fiducials enables to reach a superior accuracy but requires the placement of 5 to 6 bony markers prior to imaging. Defining bony landmarks on Leskell G-frame is an option whose theoretical registration accuracy (rms value provided by the software) seems satisfactory. However data regarding the applicative accuracy on that method on a great number of procedures in real word conditions has been largely unknown until now. The objective of the present study was to assess the applicative accuracy obtained through this registration method.Methods: Monocentric retrospective analysis of the concordance between the planned and actual trajectories in 73 consecutive patients undergoing intracranial recordings for intractable epilepsy between Oct 2018 and Feb 2023. For each lead, the coordinates of the entry point and target point of the planned trajectory and those of the actual trajectory defined on the postoperative CT were automatically extracted via a dedicated MatLab® script. The Euclidian distance of error in mm at the entry point and target point were computed, as well as the angular deviation in degree between the trajectories. The statistical analysis (uni, multivariate, mixed model) was conducted with R software® (Version 2022.12.0+353)Results: A total of 1090 trajectories (73 patients) were evaluated. The mean Euclidian distance of error at the entry point was 0.86 mm (+/-0.58). At the target point, it was 2.15 mm (+/- 0.72). The mean angle of deviation in degree was 1.23. For orthogonal trajectories, the mean error was 0.55 and 0.43 mm in y and z respectively. The orthogonality of the trajectory was significantly associated with a smaller error at the entry point and target point (p 0.05). The length of the trajectory was significantly correlated to the magnitude of error at the target (p < 0.001; r=0.37). This was found to be ascribable to a certain degree of flexibility of the electrode not to the registration method.Conclusions: These applicative accuracy data show that this registration method does not differ significantly from the one based on additional bony markers. It has the advantage of a homogeneous distribution of the markers around the whole volume of the skull. In addition, it does not require the placement of bony fiducials, which saves time. The mean error at the entry remains infra-millimetric and is consistent with the results of similar studies. The order of magnitude of the difference is not clinically relevant and derives mainly from methodological differences in the metrics for quantifying accuracy

Electrical stimulation for seizure induction during SEEG exploration: a useful predictor of postoperative seizure recurrence?

International audienceObjective Direct electrical stimulations of cerebral cortex are a traditional part of stereoelectroencephalography (SEEG) practice, but their value as a predictive factor for seizure outcome has never been carefully investigated. Patients and method We retrospectively analysed a cohort of 346 patients operated on for drug-resistant focal epilepsy after SEEG exploration. As potential predictors we included: aetiology, MRI data, age of onset, duration of epilepsy, age at surgery, topography of surgery and whether a seizure was induced by either low frequency electrical stimulation (LFS) or high frequency electrical stimulation. Results Of 346 patients, 63.6% had good outcome (no seizure recurrence, Engel I). Univariate analysis demonstrated significant correlation with favourable outcome (Engel I) for: aetiology, positive MRI and seizure induced by stimulation. At multivariate analysis, informative MRI, type II focal cortical dysplasia and tumour reduced the risk of seizure recurrence (SR) by 47%, 58% and 81%, respectively. Compared with the absence of induced seizures, the occurrence of ictal events after LFS significantly predicts a favourable outcome on seizures, with only 44% chance of disabling SR at last follow-up. Conclusion Among the already known predictors outcome, seizure induction by LFS therefore represents a positive predictive factor for seizure outcome after surgery