Middle short gyrus of the insula implicated in speech production: intracerebral electric stimulation of patients with epilepsy.

International audiencePURPOSE: Different lines of evidence have suggested an involvement of the insular cortex in speech production. These have included results from lesion studies, functional imaging techniques, and electrical stimulation of the human insular cortex during invasive evaluation of epileptic patients. METHODS: We evaluated 25 patients who had drug refractory focal epilepsy with at least one electrode stereotactically implanted in the insular cortex. RESULTS: Eight responses to insular cortex electrical stimulation were reported by five patients as speech arrest (five responses) and a lowering of voice intensity (three responses). CONCLUSIONS: Data from this study implicate the middle short gyrus of the insula in the production of speech and show the importance of intrainsular electrode implantation during invasive pre-resection evaluation by stereo-electroencephalography (SEEG) when speech arrest occurs early in seizure semiology

How should we define, construct and compare clusters in emerging S&T fields ? The case of nanotechnologies

Synthèse de l'intervention consultable sur internet : http://www.enid-europe.org/conference/abstracts/Kahane%20et%20alt%20%28mapping%29.pd

URBAN AND PERI URBAN HORTICULTURE AND THE CAPABILITY APPROACH THE CASE OF THE SOUTH-WEST PROVINCE OF CAMEROON

N° ISBN - 978-2-7380-1284-5International audienceThis paper uses the capability approach to analyse the impact of urban and peri urban horticulture on development in Africa. Is horticulture, considered as an innovation, able to improve the capabilities of people? This paper states that it is not the practice of horticulture which increases the capabilities of farmers but the level of capabilities that increases the chances of adopting horticulture. In order to answer the above question we have attempted to understand the context in which the agricultural sector and the farmers evolve in Africa, characterized by the urban transition towards a majority of urban population and the rise of nonfarm incomes. It appeared important to understand the underlying prerequisites for horticultural practices, that is, expensive agrochemical inputs and credit requirements

Studying Network Mechanisms Using Intracranial Stimulation in Epileptic Patients

Patients suffering from focal drug-resistant epilepsy who are explored using intracranial electrodes allow to obtain data of exceptional value for studying brain dynamics in correlation with pathophysiological and cognitive processes. Direct electrical stimulation (DES) of cortical regions and axonal tracts in those patients elicits a number of very specific perceptual or behavioral responses, but also abnormal responses due to specific configurations of epileptic networks. Here, we review how anatomo-functional brain connectivity and epilepsy network mechanisms can be assessed from DES responses measured in patients. After a brief summary of mechanisms of action of brain electrical stimulation, we recall the conceptual framework for interpreting DES results in the context of brain connectivity and review how DES can be used for the characterization of functional networks, the identification of the seizure onset zone, the study of brain plasticity mechanisms, and the anticipation of epileptic seizures. This pool of exceptional data may be underexploited by fundamental research on brain connectivity and leaves much to be learned

Category-Specific Visual Responses: An Intracranial Study Comparing Gamma, Beta, Alpha, and ERP Response Selectivity

The specificity of neural responses to visual objects is a major topic in visual neuroscience. In humans, functional magnetic resonance imaging (fMRI) studies have identified several regions of the occipital and temporal lobe that appear specific to faces, letter strings, scenes, or tools. Direct electrophysiological recordings in the visual cortical areas of epileptic patients have largely confirmed this modular organization, using either single-neuron peri-stimulus time-histogram or intracerebral event-related potentials (iERP). In parallel, a new research stream has emerged using high-frequency gamma-band activity (50–150 Hz) (GBR) and low-frequency alpha/beta activity (8–24 Hz) (ABR) to map functional networks in humans. An obvious question is now whether the functional organization of the visual cortex revealed by fMRI, ERP, GBR, and ABR coincide. We used direct intracerebral recordings in 18 epileptic patients to directly compare GBR, ABR, and ERP elicited by the presentation of seven major visual object categories (faces, scenes, houses, consonants, pseudowords, tools, and animals), in relation to previous fMRI studies. Remarkably both GBR and iERP showed strong category-specificity that was in many cases sufficient to infer stimulus object category from the neural response at single-trial level. However, we also found a strong discrepancy between the selectivity of GBR, ABR, and ERP with less than 10% of spatial overlap between sites eliciting the same category-specificity. Overall, we found that selective neural responses to visual objects were broadly distributed in the brain with a prominent spatial cluster located in the posterior temporal cortex. Moreover, the different neural markers (GBR, ABR, and iERP) that elicit selectivity toward specific visual object categories present little spatial overlap suggesting that the information content of each marker can uniquely characterize high-level visual information in the brain

The Insula and Its Epilepsies

Insular seizures are great mimickers of seizures originating elsewhere in the brain. The insula is a highly connected brain structure. Seizures may only become clinically evident after ictal activity propagates out of the insula with semiology that reflects the propagation pattern. Insular seizures with perisylvian spread, for example, manifest first as throat constriction, followed next by perioral and hemisensory symptoms, and then by unilateral motor symptoms. On the other hand, insular seizures may spread instead to the temporal and frontal lobes and present like seizures originating from these regions. Due to the location of the insula deep in the brain, interictal and ictal scalp electroencephalogram (EEG) changes can be variable and misleading. Magnetic reso- nance imaging, magnetic resonance spectroscopy, magnetoencephalography, positron emission tomography, and single-photon computed tomography imaging may assist in establishing a diagnosis of insular epilepsy. Intracranial EEG recordings from within the insula, using stereo-EEG or depth electrode techniques, can prove insular seizure origin. Seizure onset, most commonly seen as low-voltage, fast gamma activity, however, can be highly localized and easily missed if the insula is only sparsely sampled. Moreover, seizure spread to the contralateral insula and other brain regions may occur rapidly. Extensive sampling of the insula with multiple electrode trajectories is necessary to avoid these pitfalls. Understanding the functional organization of the insula is helpful when interpreting the semiology produced by insular seizures. Electrical stimulation mapping around the central sulcus of the insula results in paresthesias, while stimulation of the posterior insula typically produces painful sensations. Visceral sensations are the next most common result of insular stimulation. Treatment of insular epilepsy is evolving, but poses challenges. Surgical resections of the insula are effective but risk significant morbidity if not carefully planned. Neurostimulation is an emerging option for treatment, especially for seizures with onset in the posterior insula. The close association of the insula with marked autonomic changes has led to interest in the role of the insula in sudden unexpected death in epilepsy and warrants additional study with larger patient cohorts

Crises fébriles et syndrome d'épilepsie mésio-temporale. Une modélisation chez la souris de la théorie du double choc

Les crises fébriles représentent l'évènement épileptique le plus fréquent dans l'espèce humaine et touchent 5 % de la population. Bien que la bénignité de leur pronostic ait été établie par de nombreuses études prospectives, une infime proportion de ces enfants va développer un syndrome d'épilepsie mésio-temporale avec sclérose de l'hippocampe. L'hypothèse de ce travail est que la crise fébrile serait nécessaire mais non suffisante au développement de ce type d'épilepsie, un second élément au potentiel épileptogène serait ainsi indispensable. Notre travail a montré que les crises hyperthermiques chez la souris constituent une bonne approche pour modéliser les crises fébriles de l'enfant. Nous avons ainsi montré que les conséquences des crises hyperthermiques étaient différentes selon la séquence de survenue par rapport au second évènement épileptogène. (i) Lorsque la crise hyperthermique précède l'injection de kaïnate dans l'hippocampe, elle accélère la phase d'épileptogenèse et majore la dispersion des cellules granulaires du gyrus denté, sans modifier la perte cellulaire des neurones pyramidaux de la corne d'Ammon. Elle entraine également une modification du pattern des décharges rythmiques hippocampiques lors de la phase chronique, sans modifier la fréquence ni la durée de ces décharges. (ii) Lorsque la crise hyperthermique succède à la présence d'une dysplasie de la partie CA3 de la corne d'Ammon d'origine génétique, elle semble diminuer le risque de crise chez les animaux KO pour le gène de la double cortine. Pourtant, l'augmentation de la fréquence d'une néo-expression du NPY par les cellules granulaires, chez les animaux Hz pour cette mutation, suggère que les crises hyperthermiques favoriseraient la route vers une épilepsie, tout en activant la mise en place de mécanismes protecteurs contre la survenue des crises. En conclusion, les crises hyperthermiques faciliteraient la route vers l'épilepsie, mais n'auraient pas d'effet facilitateur sur la route vers la crise.Whereas febrile seizures are the most common seizure type in children and are reported in the history of mesial temporal lobe epilepsy, their role in its etiology remains controversial. They have been suggested to modify the functional organization of the hippocampus but to require another insult to induce epilepsy. To test this hypothesis, we developed a model of hyperthermic seizures in mice and examined their long-term consequences on a second insult induced either by (i) intra-hippocampal kaïnic acid injection in adult animals or by (ii) hippocampal dysplasia developed by double-cortin knock-out mice. (i) While adults, mice that were subjected to hyperthermic seizures developed epileptogenesis more rapidly than sham mice. The occurrence and duration of hippocampal paroxysmal discharges were not modified by hyperthermic seizures, as was their mean time-frequency. In this model, hyperthermic seizures increased the granular cells dispersion, but have no influence on the massif pyramidal cell loss. (ii) In preexisting hippocampal dysplasia, the occurrence of hyperthermic seizures did not increase the proportion of seizures in double-cortin knock-out mice after hyperthermic seizures, and suggest that hyperthermic seizures rather might decrease recurrent seizures via the neo-expression of NPY. In conclusion, hyperthermic seizures in immature mice might facilitate the route to epilepsy, but did not exacerbate the route to seizures.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Overt speech decoding from cortical activity: a comparison of different linear methods

IntroductionSpeech BCIs aim at reconstructing speech in real time from ongoing cortical activity. Ideal BCIs would need to reconstruct speech audio signal frame by frame on a millisecond-timescale. Such approaches require fast computation. In this respect, linear decoder are good candidates and have been widely used in motor BCIs. Yet, they have been very seldomly studied for speech reconstruction, and never for reconstruction of articulatory movements from intracranial activity. Here, we compared vanilla linear regression, ridge-regularized linear regressions, and partial least squares regressions for offline decoding of overt speech from cortical activity.MethodsTwo decoding paradigms were investigated: (1) direct decoding of acoustic vocoder features of speech, and (2) indirect decoding of vocoder features through an intermediate articulatory representation chained with a real-time-compatible DNN-based articulatory-to-acoustic synthesizer. Participant's articulatory trajectories were estimated from an electromagnetic-articulography dataset using dynamic time warping. The accuracy of the decoders was evaluated by computing correlations between original and reconstructed features.ResultsWe found that similar performance was achieved by all linear methods well above chance levels, albeit without reaching intelligibility. Direct and indirect methods achieved comparable performance, with an advantage for direct decoding.DiscussionFuture work will address the development of an improved neural speech decoder compatible with fast frame-by-frame speech reconstruction from ongoing activity at a millisecond timescale

: Seizure onset zone imaging

International audienceStereo-electroencephalography is used to localize the seizure onset zone and connected neuronal networks in surgical candidates suffering from intractable focal epilepsy. The concept of an epileptogenicity index has been proposed recently to represent the likelihood of various regions being part of the seizure onset zone. It quantifies low-voltage fast activity, the electrophysiological signature of seizure onset usually assessed visually by neurologists. Here, we revisit epileptogenicity in light of neuroimaging tools such as those provided in statistical parametric mapping software. Our goal is to propose a robust approach, allowing easy exploration of patients' brains in time and space. The procedure is based upon statistical parametric mapping, which is an established framework for comparing multi-dimensional image data that allows one to correct for inherent multiple comparisons. Statistics can also be performed at the group level, between seizures in the same patient or between patients suffering from the same type of epilepsy using normalization of brains to a common anatomic atlas. Results are obtained from three case studies (insular reflex epilepsy, cryptogenic frontal epilepsy and lesional occipital epilepsy) where tailored resection was performed, and from a group of 10 patients suffering from mesial temporal lobe epilepsy. They illustrate the basics of the technique and demonstrate its very good reproducibility and specificity. Most importantly, the proposed approach to the quantification of the seizure onset zone allows one to summarize complex signals in terms of a time-series of statistical parametric maps that can support clinical decisions. Quantitative neuroimaging of stereo-electroencephalographic features of seizures might thus help to provide better pre-surgical assessment of patients undergoing resective surgery