Le LPGi est la région bulbaire qui contient le plus grand nombre de neurones exprimant Fos pendant l’hypersomnie de SP. 10% de ces neurones Fos dans le LPGi projettent au locus coereleus, une région SP-Off. Récemment, Sapin et al. ont montré que 70% des neurones exprimant Fos pendant l’hypersomnie de SP sont de nature GABAergique. Notre hypothèse est que le LPGi contient des neurones de nature SP-On dont une partie participerait à l’inhibition des noyaux SP-Off. Nous cherchons à vérifier cette hypothèse, d’autre part à identifier les régions afférentes au LPGi actives au cours du SP et enfin, à identifier les projections du LPGi. Nous avons utilisé l’enregistrement extracellulaire des neurones du LPGi chez le rat vigile en contention stéréotaxique. Nous avons couplé cette technique avec le protocole de privation/ rebond de SP par la technique de la piscine. L’analyse du taux de décharge des neurones enregistrés au sein du LPGi montre que celui-ci contient trois types neuronaux différents (SP-On, SP-Off et indifférents). L’analyse des données neuroanatomiques montre que l’afférence majeure du LPGi, active au cours du SP, réside dans le SLD. Le LPGi est donc bien impliqué dans le réseau du SP car il contient des neurones faisant varier leur taux de décharge avec les différents états de vigilance. Le SLD, considéré comme la structure exécutive du SP, de nature glutamatergique, exciterait le LPGi au cours du SP. Ce dernier, de nature GABAergique, inhiberait le noyau moteur facial. Ce travail met pour la première fois en évidence l’activité de la voie SLD-bulbe rachidien ventrolatéral et suggère que le LPGi participe en partie à l’atonie musculaire caractéristique du SP / The LPGi is a ventrolateral medullary area that contains the highest number of Fos-labelled neurons during a paradoxical sleep (PS) hypersomnia. Ten % of these Fos neurons project to the locus coeruleus, a PS-Off area and 70% of these Fos neurons are GABAergic. Our hypothesis is that the LPGi contains PS-On neurons involved in the inhibition of the PS-Off nuclei. Our aim was to check this hypothesis by recording the unit activity of the LPGi neurons, by identifying the afferent areas to the LPGi and determining its projection areas activated during PS. We have used extracellular unit recordings in the unanethetized head-restrained rat model and coupled this method to a selective PS deprivation using the flower-pot method. The analysis of the firing rate of the LPGi neurons showed that there are three different groups, SP-On, SP-Off and indifferent neurons. Moreover, the SLD, a PS-On area, is the main afferent to the LPGi activated during PS rebound. Our conclusion is that the LPGi is involved in the network generating PS. The SLD, considered as the PS executive area through glutamatergic neurons, may excite the LPGi during this state. The LPGi, through its GABAergic neurons, may inhibit the facial motor nucleus. This work provides for the first time evidence for a SLD-ventrolateral medulla pathway and suggests that the LPGi participates in the muscular atonia occurring during PS

The basal ganglia (BG) are a group of brain nuclei situated deep in the cerebral hemispheres. While BG were primarily associated with motor functions, in recent years there has been an increasing evidence that BG are also significantly involved in a wide range of non-motor functions. This work focused on some of the non-motor symptoms associated with two typical basal ganglia disorders: Parkinson's disease (PD) and Huntington's disease (HD). The first study concerned spatial navigation impairment in patients with HD. Their spatial navigation skills were tested using the Blue Velvet Arena, technique evaluating spatial navigation in real space, capable to selectively differentiate between two components of spatial navigation - allocentric (environment-oriented) and egocentric (self-oriented). Allocentric navigation is linked to hippocampal function, whereas egocentric navigation is usually associated with striatum, a structure predominantly affected in HD. We found that spatial navigation is not significantly affected in the early stages of HD and that in more advanced stages, when spatial navigation is already impaired, there is no significant difference between allocentric and egocentric navigation impairment. We speculate that the striatal involvement does not contribute to the impairment of the...