Neuroscience seminar: Cortical circuitry (December 6th)

Dr. Mir-Shahram Safari

Assistant Professor- Shahid Beheshti University of Medical Sciences

 

"Shaping visual responses in primary visual cortex through cell-type specific inhibition"

 

When: December 6th, 2015(Azar15, 1394). 11:45 A.M

Where: Ferdowsi University of Mashhad- Faculty of Science -Amphitheater#1

 

Poster...

Abstract:

   Inhibitory interneurons are critical for proper cortical function. Due to differing physiology, biophysical properties, and synaptic targeting, they may contribute differently to ongoing computations in the surrounding local network. Two major interneuron classes are the fast-spiking Parvalbumin positive (PV) and non-fast spiking Somatostatin positive (SOM) interneurons. PV interneurons are found in nearly all cortical layers, have been associated with various computationally important processes such as thalamocortical feed-forward inhibition, gain modulation and cortical oscillations. However, given the intricate modularity and connectivity within neocortex, it remains unclear to what extent PV and SOM interneurons from distinct cortical layers interact with each other and with principal cells. In the first part of talk, I will present our study on Cholinergic modulation of inhibitory interneurons in different brain states. We compared visual response properties of inhibitory and excitatory neurons between different states by two-photon functional calcium imaging. We tested basal forebrain (BF) cholinergic projection involvement in these network activity changes. We analyzed effects of optogenetic or electrical activation of BF in mice on visual responses of GABAergic and excitatory neurons through in vivo whole-cell patch-clamp recordings. In the second part, I will talk about our study on functional connectomics in cortical microcircuit level. It is not clear how many GABAergic interneurons or their subtypes functionally connect with a pyramidal neuron and whether an activation of single GABAergic interneuron of a particular subtype is enough to play such a role or a certain number of grouped GABAergic interneuron are necessary. In the present study we addressed these questions by using the in vivo two-photon targeted double whole-cell recording method combined with optogenetics. We made a rough estimate of the number of functionally connected GABAergic, PV or SOM interneurons to a pyramidal neuron. Results showed that PV interneurons can act solo while somatostatin neurons act in chorus on cortical pyramidal cells.