Biology subjects

Carponcy, J.

Publications and source records attributed to Carponcy, J..

3 recordsLinked to original sources

bioRxiv2023

Synaptic strength dynamics at cortical synaptic pathways is encoded by vigilance states duration

Interactions among brain areas are essential to most cognitive functions. Neuronal interactions between these areas depend on the modulation of synaptic strength. However, this modulation remains poorly understood. We recorded evoked synaptic responses at four hippocampal pathways in freely moving male rats across 24 hours: the Perforant Path to Dentate Gyrus (PP-DG), Fornix to Prefrontal Cortex (Fx-PFC), Fornix to Nucleus Accumbens (Fx-NAc), and the Schaffer Collaterals to CA1 (SC-CA1). We preserved the temporal dynamics of vigilance states and synaptic responses and show for the first time that synaptic strength at these four hippocampal pathways oscillates, with a very slow periodicity. We demonstrate that synaptic strength at the PP-DG, Fx-PFC, Fx-NAc pathways show a positive correlation with the duration of active wakefulness (aWK) and a negative one with the duration of most sleep states (slow wave sleep (SWS) and rapid eye movement sleep (REM)), with a positive peak correlation time-lag of 1 to 10 minutes for aWK and SWS at these 3 pathways. In contrast, no significant correlation peak is found at the SC-CA1 pathway. Finally, a model based on hypnogram data and synaptic strength at the PP-DG pathway was able to predict the evolution of synaptic strength at the PP-DG, Fx-PFC and Fx-NAc pathways, but not at the SC-CA1 pathway. These results reveal that the temporal succession of vigilance states, particularly aWK and SWS, may contribute to memory processes through rapid modulation of synaptic strength at several pathways during the sleep-wakefulness cycle, suggesting that memory processes are not only dependent on sleep amount but also on sleep architecture.

neuroscience↗

bioRxiv2019

The GABA-Glutamate supramammillary-dorsal Dentate Gyrus pathway controls theta and gamma oscillations in the DG during paradoxical sleep

Several studies suggest that neurons from the lateral region of the SuM (SuML) innervating the dorsal dentate gyrus (DG) display a dual GABAergic and glutamatergic transmission and are specifically activated during paradoxical (REM) sleep (PS). The objective of the present study is to fully characterize the anatomical, neurochemical and electrophysiological properties of the SuML-DG projection neurons and to determine how they control DG oscillations and neuronal activation during PS and other vigilance states. For this purpose, we combine structural connectivity techniques using neurotropic viral vectors (rabies virus, AAV), neurochemical anatomy (immunohistochemistry, in situ hybridization) and imaging (light, electron and confocal microscopy) with in vitro (patch clamp) and in vivo (LFP, EEG) optogenetic and electrophysiological recordings performed in transgenic VGLUT2-cre male mice. At the cellular level, we show that the SuML-DG neurons co-release GABA and glutamate on dentate granule cells and increase the activity of a subset of DG granule cells. At the network level, we show that activation of the SuML-DG pathway increases theta power and frequency during PS as well as gamma power during PS and waking in the DG. At the behavioral level, we show that the activation of this pathway does not change animal behavior during PS, induces awakening during slow wave sleep and increases motor activity during waking. These results suggest that the SuML-DG pathway is capable of supporting the increase of theta and gamma power in the DG observed during PS and plays an important modulatory role of DG network activity during this state.\n\nSignificant statementAn increase of theta and gamma power in the dentate gyrus (DG) is an hallmark of paradoxical (REM) sleep (PS) and is suggested to promote learning and memory consolidation by synchronizing hippocampal networks and increasing its outputs to cortical targets. However the neuronal networks involved in such control of DG activity during PS are poorly understood. The present study identifies a population of GABA/Glutamate neurons in the lateral supramammllary nucleus (SuML) innervating the DG that could support such control during PS. Indeed, we show that activation of these SuML-DG projections increase theta power and frequency as well as gamma power in the DG specifically during PS and modulate activity of a subset of DG granule cells.

neuroscience↗

bioRxiv2018

Differential Recordings of Local Field Potential: A Genuine Tool to Quantify Functional Connectivity

Local field potential (LFP) recording is a very useful electrophysiological method to study brain processes. However, this method is criticized for recording low frequency activity in a large area of extracellular space potentially contaminated by distal activity. Here, we theoretically and experimentally compare ground-referenced (RR) with differential recordings (DR). We analyze electrical activity in the rat cortex with these two methods. Compared with RR, DR reveals the importance of local phasic oscillatory activities and their coherence between cortical areas. Finally, we show that DR provides a more faithful assessment of functional connectivity caused by an increase in the signal to noise ratio, and of the delay in the propagation of information between two cortical structures.

biophysics↗