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Séminaire impromptu - Jean-Sébastien Jouhanneau In vivo monosynaptic excitatory transmission between layer 2 cortical pyramidal neurons.

Abstract :

 Cortical neurons integrate thousands of synaptic inputs to generate action potential outputs during network activity or cortical states. How cortical states affect synaptic integration is debated as very little is known about the properties of monosynaptic transmission in vivo. We made multiple two-photon targeted whole-cell recordings from monosynaptically connected excitatory pyramidal neurons in mouse primary somatosensory cortex in vivo and found a sparsely connected, structured network of small amplitude, reliable synaptic connections. In quiescent, hyperpolarized Downstates the majority of EPSPs were small in amplitude (<0.5 mV), with a small minority >1 mV. The coefficient of variation (CV = 0.74) could largely be explained by the presence of synaptic failures (22%). Both the CV and failure rates were reduced with increasing amplitude. The mean paired-pulse ratio was 1.15 and positively correlated with the CV. We then compared the amplitude of single spike evoked EPSPs between cortical states. We found that while the overall amplitude of EPSP did not change between Down and Up-states, small amplitude EPSPs showed an increase in amplitude while larger amplitude connection showed a reduction. Thus, we provide a new approach to study monosynaptic connections in vivo that will enable us to investigate the impact of network activity on monosynaptic transmission and the processing of sensory input in monosynaptically connected networks.

Selected publications

Jouhanneau J-S, Kremkow J, Dorrn AL and Poulet JFA (2015). In vivo monosynaptic excitatory transmission between layer 2 cortical pyramidal neurons. Cell Reports. 13(10):2098-106.

Jouhanneau J-S, Ferrarese L, Estebanez L, Audette N, Brecht M, Barth AL and Poulet JFA (2014). Cortical cfos expression reveals broad receptive field excitatory neurons targeted by POm. Neuron. 84(5): 1065-78.

Jouhanneau J-S, Ball SM, Molnar E and Isaac JTR (2011). Mechanisms of bidirectional modulation of thalamocortical transmission in barrel cortex by presynaptic kainate receptors. Neuropharmacology.

Yassin L, Benedetti BL, Jouhanneau J-S, Wen J, Poulet JF and Barth AL (2010). An embedded subnetwork of highly active neurons in the neocortex. Neuron. 68(6): 1043-50.