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Jean-Sébastien JouhanneauSynaptic mechanisms of sparse firing

Abstract :

 A defining feature of cortical layer 2/3 excitatory neurons
is their heterogeneity in activity with most neurons firing at extremely low rates and a small fraction of neurons responsible for the majority of the total spike output. Although sparseness of activity has computational advantages is underlying mechanisms is largely unknown. In a first step, I identified a subpopulation of higher firing neurons using multiple, targeted, in vivo whole-cell recordings in a mouse line expressing GFP under the activity-dependent promotor cfos. Next, I went on to investigate the mechanisms regulating sparseness using in vivo paired recordings of connected neurons. I show that while single uEPSPs have little effect on the firing rates of excitatory neurons and somatostatin-expressing GABA-ergic inhibitory neurons they evoke precisely timed action potentials in parvalbumin-expressing inhibitory neurons. Evoked parvalbumin-expressing neuron action potentials go on to inhibit the local excitatory network, thus providing a pathway for single spike evoked disynaptic inhibition that may enforce sparse and precisely timed cortical signalling.

Selected publications

1: *Ferrarese L, *Jouhanneau JS, Remme MWH, Kremkow J, Katona G, Rozsa B, Schreiber S, Poulet JFA. Dendrite-Specific Amplification of Weak Synaptic Input during Network Activity In Vivo. Cell Rep. 2018 Sep 25;24(13):3455-3465.e5. *Shared first-author.

2: Jouhanneau JS, Kremkow J, Poulet JFA. Single synaptic inputs drive high-precision action potentials in parvalbumin expressing GABA-ergic cortical neurons in vivo. Nat Commun. 2018 Apr 18;9(1):1540.

3: Jouhanneau JS, Kremkow J, Dorrn AL, Poulet JF. In Vivo Monosynaptic Excitatory Transmission between Layer 2 Cortical Pyramidal Neurons. Cell Rep. 2015 Dec 15;13(10):2098-106.

4: Jouhanneau JS, Ferrarese L, Estebanez L, Audette NJ, Brecht M, Barth AL, Poulet JF. Cortical fosGFP expression reveals broad receptive field excitatory neurons targeted by POm. Neuron. 2014 Dec 3;84(5):1065-78.