Amplifying the redistribution of somato-dendritic inhibition by the interplay of three interneuron types.

Loreen Hertäg,Henning Sprekeler,Hermann Cuntz

doi:10.1371/journal.pcbi.1006999

Abstract

GABAergic interneurons play an important role in shaping the activity of excitatory pyramidal cells (PCs). How the various inhibitory cell types contribute to neuronal information processing, however, is not resolved. Here, we propose a functional role for a widespread network motif consisting of parvalbumin- (PV), somatostatin- (SOM) and vasoactive intestinal peptide (VIP)-expressing interneurons. Following the idea that PV and SOM interneurons control the distribution of somatic and dendritic inhibition onto PCs, we suggest that mutual inhibition between VIP and SOM cells translates weak inputs to VIP interneurons into large changes of somato-dendritic inhibition of PCs. Using a computational model, we show that the neuronal and synaptic properties of the circuit support this hypothesis. Moreover, we demonstrate that the SOM-VIP motif allows transient inputs to persistently switch the circuit between two processing modes, in which top-down inputs onto apical dendrites of PCs are either integrated or cancelled.

Highlights

Note that autapses were not included and that we chose the convention that the weight parameters wi are positive
The dynamical properties of the circuit are described by its eigenvalues, which are given by the zero crossings of the characteristic polynomial of the matrix W, 0 = det ((US←S − λ1) (UV←V − λ1) − US←VUV←S), (5)
We extend the rate dynamics (see equation (1)) with linear differential equations describing the evolution of an adaptation current in order to derive qualitative changes in the bifurcation structure when adaptation is present

Summary

Introduction

The dynamical properties of the circuit are described by its eigenvalues, which are given by the zero crossings of the characteristic polynomial of the matrix W , 0 = det ((US←S − λ1) (UV←V − λ1) − US←VUV←S) , (5) The transition between the attenuation and the amplification regime ((i) and (ii)) is determined by the condition that the amplification index (equation (24) in main text) is equal to one (for the symmetric case wVV = wSS = wr and wSV = wVS = w).

Results

Conclusion