I am interested in describing synaptic circuits in the olfactory bulb, the first relay station for odor processing in the brain. In the mammalian olfactory system, sensory inputs converge in the olfactory bulb in spatially segregated anatomical structure called glomeruli. Olfactory neurons expressing the same olfactory receptor project in specific glomeruli where they transmit sensory information to ~25 mitral and tufted cells, the principal output neurons of the bulb. Each glomerulus is surrounded by local juxtaglomerular neurons that shape the output of mitral and tufted cells. Juxtaglomerular cells include different types of neurons like inhibitory periglomerular cells, excitatory external tufted cells and mixed dopaminergic-GABAergic short axon cells.
My earlier work focused on intraglomerular excitatory interactions that amplify the complex and unique long-lasting synaptic response of mitral and tufted cells to an olfactory nerve input. I demonstrated the unexpected role of external tufted cells in driving the pluri-synaptic feed-forward excitatory pathway that mediates the prominent slow component of the mitral/tufted cell response. Currently, my goal is to understand the influence and function of intraglomerular inhibition on the output of the bulb. To address this issue, we are using paired electrophysiological recordings in bulb slices from transgenic mice expressing a fluorescent marker in specific PG cell subtypes in order to describe the synaptic circuits they form and their impact on mitral and tufted cells.

Selected Publications

De Saint Jan D., Hirnet D., Westbrook GL., Charpak S. (2009) External tufted cells drive the output of olfactory bulb glomeruli. J Neurosci., 29 (7) : 2043-52.

Najac D., De Saint Jan D., Reguero L., Grandes P., Charpak S. (2011) Monosynaptic and polysynaptic feed-forward inputs to mitral cells from olfactory sensory neurons. J Neurosci., 31 (24) : 8722-9.

Najac M., Charpak S., De Saint Jan D. (Submitted) Intraglomerular lateral inhibition promotes spike timing variability in principal neurons of the olfactory bulb.

Awards, Fellowships and Honours

2013            ANR (French Research National Agency) starting grant for young researchers (until 2015)
2002            Postdoctoral fellowship “Human Frontier Science Program Organisation” (until 2005)
2000            Fellowship of Fondation pour la Recherche Médicale (until 2001)
1997            Fellowship of Ministère de la Recherche et de l’Enseignement Supérieur (until 2000)

• Olfactory bulb physiology
• Patch-clamp recordings from dissociated cells, cultured neurons or acute brain slices
• Paired recording, whole-cell and single channel recording
• Two-photon guided targeted patch-clamp recording in freely breathing anesthetized mouse