35 research outputs found

    Disruption of Rolandic Gamma-Band Functional Connectivity by Seizures is Associated with Motor Impairments in Children with Epilepsy

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    Although children with epilepsy exhibit numerous neurological and cognitive deficits, the mechanisms underlying these impairments remain unclear. Synchronization of oscillatory neural activity in the gamma frequency range (>30 Hz) is purported to be a mechanism mediating functional integration within neuronal networks supporting cognition, perception and action. Here, we tested the hypothesis that seizure-induced alterations in gamma synchronization are associated with functional deficits. By calculating synchrony among electrodes and performing graph theoretical analysis, we assessed functional connectivity and local network structure of the hand motor area of children with focal epilepsy from intracranial electroencephalographic recordings. A local decrease in inter-electrode phase synchrony in the gamma bands during ictal periods, relative to interictal periods, within the motor cortex was strongly associated with clinical motor weakness. Gamma-band ictal desychronization was a stronger predictor of deficits than the presence of the seizure-onset zone or lesion within the motor cortex. There was a positive correlation between the magnitude of ictal desychronization and impairment of motor dexterity in the contralateral, but not ipsilateral hand. There was no association between ictal desynchronization within the hand motor area and non-motor deficits. This study uniquely demonstrates that seizure-induced disturbances in cortical functional connectivity are associated with network-specific neurological deficits

    The EUREC4A-Ocean/Atmosphere campaign: status

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    International audienceThe ocean fine scale (from the mesoscale to the submesoscale) is susceptible to impact air-sea exchange and has an integral effect on the large scale atmosphere and ocean dynamics. Many recent advances in understanding underlying processes have been obtained from modeling efforts and only few in-situ observational studies exist one of them being the EUREC4A-OA/ATOMIC campaign that was added to the EUREC4A atmospheric campaign. This experiment took place in January-February 2020 in the Northwest Tropical Atlantic Ocean with the aim to collect synchronized ocean and atmosphere data to improve our understanding of the role of fine scale processes in the internal ocean dynamics and air-sea interaction.Four oceanographic vessels, coordinated with air-borne observations and autonomous ocean platforms (underwater gliders, Saildrones, drifters), simultaneously acquired ocean and atmosphere data east of the island of Barbados and further south, up to the border of French Giuana. This way, ocean and atmospheric data was acquired in two contrasting regions: (1) the Trade wind region and (2) a region filled with mesoscale eddies. Operations allowed investigating upper ocean processes from small to mesoscale and from sub-diurnal to monthly.A variety of mesoscale eddies were crossed with diverse characteristics, ranging from shallow cyclonic and anticyclonic eddies to the deep reaching structures. Some of these eddies, and in particular North Brazil Rings, have been previously observed and described in dedicated oceanographic experiments. Nonetheless, the EUREC4A-OA/ATOMIC campaign brings in new details about the vertical structure, the dynamics and the potential impact on air-sea interactions of these mesoscale features.With the various observing platforms it was possible to sample the upper-ocean in great detail, resolving frontal scales and stratification. For example, the remnants of the Amazon plume, flowing northward along the shelf-break and being advected far offshore though NBC rings, create a rich variety of submesoscale fronts and a strong barrier layer impacting air-sea exchange of heat and momentum. The ongoing analyses on the ocean dynamics regional and local structures and specifics of air-sea interaction will be highlighted in this presentation
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