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International audience; We present an ultrafast thin-disk based multipass amplifier operating at a wavelength of 1030 nm, designed for atmospheric research in the framework of the Laser Lightning Rod project. The CPA system delivers a pulse energy of 720 mJ and a pulse duration of 920 fs at a repetition rate of 1 kHz. The 240 mJ seed pulses generated by a regenerative amplifier are amplified to the final energy in a multipass amplifier via four industrial thin-disk laser heads. The beam quality factor remains ∼ 2.1 at the output. First results on horizontal long-range filament generation are presented.

International audience; Lightning is highly destructive due to its high power density and unpredictable character. Directing lightning away would allow to protect sensitive sites from its direct and indirect impacts (electromagnetic perturbations). Up to now, lasers have been unable to guide lightning efficiently since they were not offering simultaneously terawatt peak powers and kHz repetition rates. In the framework of the Laser Lightning Rod project, we develop a laser system for lightning control, with J-range pulses of 1ps duration at 1kHz. The project aims at investigating its propagation in the multiple filamentation regime and its ability to control high-voltage discharges. In particular, a field campaign at the S ̈antis mountain will assess the laser ability to trigger upward lightning.

International audience; We study the use of frequency upconversion schemes of near-IR picosecond laser pulses and compare their ability to guide and trigger electric discharges through filamentation in air. Upconversion, such as Second Harmonic Generation, is favorable for triggering electric discharges for given amount of available laser energy, even taking into account the losses inherent to frequency conversion. We focus on the practical question of optimizing the use of energy from a given available laser system and the potential advantage to use frequency conversion schemes.

Les fonctions attentionnelles sont regulierement decrites comme un domaine perturbe en cas de naissance avant terme, y compris chez les enfants indemnes de sequelles neurologiques averees. Les etudes realisees chez ce type particulier de population posent la question de l’influence d’une prematurite a faible risque de survenue d’un deficit neurodeveloppemental sur le fonctionnement cognitif, notamment attentionnel.Dans le cadre conceptuel considerant l’attention comme pouvant etre fractionnee en differents processus, la passation d’une batterie modulaire informatisee (kiTAP) a ete proposee a un ancien grand premature de 10 ans correspondant aux criteres precites. Les donnees recueillies montrent une preservation de la fonction d’alerte et un manque patent de controle inhibiteur ainsi que de capacites d’orientation/reorientation de l’attention.Elles soulignent encore l’impact des difficultes de controle inhibiteur sur la performance attentionnelle d’ensemble et suggerent que cet impact se manifeste au travers d’un desequilibre dans la dynamique developpementale entre alerte et inhibition. Une grande prematurite, meme a « faible risque », pourrait ainsi modifier subtilement le fonctionnement cerebral, ici au niveau des operations attentionnelles. Ces memes donnees s’inscrivent dans le courant theorique considerant l’attention comme relevant de processus a la fois distincts et inclus dans un systeme d’ordre integratif.

Le syndrome de Gerstmann developpemental (SGD) est un desordre neurodeveloppemental caracterise par la presence d’une tetrade de symptomes : agnosie digitale, dyscalculie, dysgraphie et desorientation droite-gauche. Bien que l’existence de ce desordre en tant que reelle entite syndromique soit largement controversee, l’association de symptomes qui est censee s’y referer ne manque pas d’interet. Elle constitue un terrain propice a l’abord conceptuel du domaine de l’acquisition des competences arithmetiques et contribue notamment a la tenue de debats constructifs concernant la relation entre performances perceptivo-tactiles et numeriques. Dans ce contexte, le present document propose la description du profil neuropsychologique d’un enfant dont les capacites exprimees recoupent les criteres diagnostiques relevant du SGD. Les donnees quantitatives et qualitatives recueillies sont analysees et discutees d’un point de vue theorique. Les resultats obtenus permettent, avec toute la prudence necessaire, d’evoquer conjointement la question de l’implication d’un systeme neurocognitif specifique dans les performances numeriques et de l’existence de retombees pathologiques de ses eventuelles anomalies developpementales.

Le present article vise a illustrer l’apport d’une demarche neuropsychologique au bilan et a l’approche soignante d’un cas de dysphasie developpementale de type mnesique. Les auteurs s’attachent tout d’abord a eclairer l’impact diagnostique du bilan neuropsychologique, dans le contexte d’interface inherent a cette discipline ainsi qu’aux conceptions actuelles du langage oral. Le bilan neuropsychologique est ainsi situe par rapport a un instantane des autres donnees, ici principalement orthophoniques, recueillies. Ce document insiste ensuite largement et de facon concrete sur les aspects reeducatifs. L’etude de cas est presentee selon un axe couplant diagnostic, pratique reeducative et donnees evolutives. Une large illustration du programme de revalidation a orientation neuropsychologique realise a partir des reflexions synthetiques tirees du cadre nosologique utilise est proposee. Le niveau general de validite des actions entreprises est, encore, questionne au travers de l’etude des axes evolutifs quantitatifs et qualitatifs objectives, en lien suppose avec la realisation du programme de revalidation. Enfin, les liens de complementarite que la neuropsychologie entretient avec le domaine orthophonique sont abordes d’un point de vue a la fois diagnostique et soignant.

Summary: Developmental dyslexia and visuo-spatial attention. This paper gives an overview of the literature on the visuo-perceptual and visuo-attentional deficits of dyslexic children. The hypothesis that visuo-attentional problems cooccur with dyslexia was assessed through a task of search for a target among distractors. Serial-attentional visual processing was required in one task condition (searchfor 0 among Qs) whereas the other condition involved parallel/automatic processing (search for Q among 0 s). Ten dyslexic subjects constituted the experimental group. Their performance was compared to that of 20 non-dyslexic children, 10 matched for chronological age and 10 for reading age. The performance of dyslexic subjects was similar to that of children matched for chronological age in the parallel/automatic condition. In contrast, their performance differed by an increased search slope front that of the two control groups in the seriallattentional condition. These results suggest the existence of visuo-attentional deficits in dyslexic children. Key words : visual search, parallel vs attentional processing, developmental dyslexia., Résumé Cet article propose une revue de la littérature relative aux troubles visuo-perceptifs et visuo-attentionnels des enfants dyslexiques. L'hypothèse de troubles visuo-attentionnels associés aux difficultés d'apprentissage de la lecture est testée par le biais d'une épreuve de recherche d'une cible parmi des distracteurs. Cette épreuve comprend deux conditions expérimentales mettant en jeu des traitements visuels sériels/attentionnels pour la première (recherche d'un 0 parmi des Q ) et parallèles!automatiques pour la seconde (recherche d'un Q parmi des 0 ). La population expérimentale se compose de 10 sujets dyslexiques dont les performances sont comparées à celles de 10 sujets non dyslexiques de même âge chronologique et 10 sujets non dyslexiques de même niveau de lecture. Les résultats montrent que les sujets dyslexiques ont des performances comparables à celles des sujets témoins de même âge chronologique en condition parallèle/automatique. Par contre, leurs performances se différencient de celles des deux groupes contrôles, par une pente de recherche plus éle- vée, en condition sérielle/attentionnelle. Ces résultats suggèrent l'existence de troubles visuo-attentionnels chez les enfants dyslexiques. Mots-clés : recherche visuelle, traitements parallèles vs attentionnels, dyslexie développementale., Marendaz Christian, Valdois S., Walch Jean-Pierre. Dyslexie développementale et attention visuo-spatiale. In: L'année psychologique. 1996 vol. 96, n°2. pp. 193-224.

The stability of perceptual asymmetries was studied in two groups of 6-year-old, right-handed children (normal, NL, and poor, PL) learning reading, by means of two experiments occurring at a year's interval (Experiment I and Experiment II). A dichhaptic procedure derived from S. F. Witelson's method (1974, Cortex , 10 , 3–17) was used. With group data, perceptual asymmetries were stable over time, whereas with individual data, perceptual asymmetries were highly variable. NL children demonstrated a left-hand advantage at the group level in both Experiment I and Experiment II, with relatively little individual evolution over time. No significant hand advantage was found in PL children in Experiment I, but dramatic alterations occurred in Experiment II where all PL children shifted to a left-hand advantage. This shift was accompanied by an improvement in spatial performance. Such changes in perceptual asymmetry might be of an adaptive nature. Individual changes across time may be related to developmental plasticity (cerebral maturation) and/or neurocognitive flexibility (differential activation of cerebral subsystems).

Tactual laterality effects (T.L.E.) were examined in first- and second-grade children when performing a dichaptic task. Our procedure, a modified version of Witelson's standard dichaptic task, emphasized the type of errors made, so that we could construct a weighted index (W.I.) for scoring rather than a strictly dichotomous one. The same data were compared using the two types of scoring indexes stated above. T.L.E. occurred consistently with the W.I. scores only, both in two independent groups or in the same group at a year's interval, suggesting (1) that a strictly dichotomous index might lead to loss of information, (2) that the results are reliable at least at the group level. Results are discussed in terms of possible applications of such a procedure to investigating the relationship between performance (spatial processing) and brain organization (hemispheric balance).

Significant efforts have been dedicated to control lightning with lasers [1] to protect sensitive sites like rocket launching pads and airports. We report on a dedicated European large framework project towards this goal, called Laser Lightning Rod (llr-fet.eu) [2] . In this project, a unique laser system has been developed, providing 720 mJ, < 1 picosecond pulses at 1 kHz repetition rate, i.e., TW-class peak power and kW average power [3] . This thin disk laser has been further frequency doubled (SHG) and tripled (THG) to provide high intensity outputs at 1030 nm, 515 nm and 343 nm, with conversion efficiencies up to 45% and 30%, respectively. Nonlinear propagation and filamentation of this laser could be characterized over 130 meters in a dedicated hall (LAL in Orsay), both in a collimated geometry, and using a 40 cm diameter beam expander. The whole system will be transported to the top of the Santis Mountain (2481 m altitude) in Switzerland in April 2021, one of the locations with the highest lightning occurrence in Europe. The site has been fully equipped to host the laser transmitter in the harsh meteorological conditions encountered on the top of the mountain. The site has also been fully equipped with state of the art lightning detection and measurement devices (a lightning mapping array, an interferometer, high-speed cameras, current sensors, a field mill, etc.) to register the triggering and guiding effects of the laser on the lightning process. This site is especially interesting as it generates mostly upward flashes from the 123 m tall tower communications tower. The laser will be aimed to the top of this tower in order to extend its height by the length of the filaments , realizing a "laser lightning rod".

Electric currents circulating between charged clouds and the earth surface during lightning discharges are responsible for considerable damages and casualties. It is therefore important to develop better protection methods in addition to the traditional Franklin rod. Here we present the first demonstration that filaments formed by short and intense laser pulses can guide lightning discharges over considerable distances. We believe that this experimental breakthrough will lead to progress in lightning protection and lightning physics. An experimental campaign was carried out on the S\"antis Mountain in Northeastern Switzerland during the Summer of 2021 with a high repetition rate terawatt laser. The guiding of an upward negative lightning leader over a distance of 50 m was recorded by two separate high-speed cameras. The guiding of negative lightning leaders by laser filaments was corroborated in three other instances by VHF interferometric measurements, and the number of X-ray bursts detected during guided lightning events was significantly increased. While this research field has been very active for more than 20 years with many research groups around the world working to achieve this goal, this result demonstrates lightning guiding by lasers, which may lead to the development of a laser lightning rod. This work paves the way for new atmospheric applications of ultrashort lasers and represents a significant step forward in the development of a laser based lightning protection for airports, launchpads or large infrastructures., Comment: Laser-guided lightning. Nat. Photon. (2023)