Mechanisms underlying the response of mouse cortical networks to optogenetic manipulation

TL;DR

This study investigates how mouse cortical networks respond to optogenetic stimulation of PV interneurons, revealing layer-specific effects and proposing models with multiple inhibitory populations to explain the paradoxical responses observed.

Contribution

It introduces a multi-population network model that explains layer-specific responses of cortical circuits to PV photostimulation, advancing understanding of inhibitory network architecture.

Findings

PV photostimulation reduces PV activity in layer 5 but not in layer 2/3.

Three-inhibitory-population models explain responses in layer 2/3.

Layer 5 responses suggest SOM neurons receive inputs only from PCs and PV neurons.

Abstract

GABAergic interneurons can be subdivided into three subclasses: parvalbumin positive (PV), somatostatin positive (SOM) and serotonin positive neurons. With principal cells (PCs) they form complex networks. We examine PCs and PV responses in mouse anterior lateral motor cortex (ALM) and barrel cortex (S1) upon PV photostimulation in vivo. In layer 5, the PV response is paradoxical: photoexcitation reduces their activity. This is not the case in ALM layer 2/3. We combine analytical calculations and numerical simulations to investigate how these results constrain the architecture. Two-population models cannot account for the results. Networks with three inhibitory populations and V1-like architecture account for the data in ALM layer 2/3. Our data in layer 5 can be accounted for if SOM neurons receive inputs only from PCs and PV neurons. In both four-population models, the paradoxical effect implies not too strong recurrent excitation. It is not evidence for stabilization by inhibition.