Interneuron Types and Their Circuits in the Basolateral Amygdala.

Norbert Hájos

doi:10.3389/fncir.2021.687257

Abstract

The basolateral amygdala (BLA) is a cortical structure based on its cell types, connectivity features, and developmental characteristics. This part of the amygdala is considered to be the main entry site of processed and multisensory information delivered via cortical and thalamic afferents. Although GABAergic inhibitory cells in the BLA comprise only 20% of the entire neuronal population, they provide essential control over proper network operation. Previous studies have uncovered that GABAergic cells in the basolateral amygdala are as diverse as those present in other cortical regions, including the hippocampus and neocortex. To understand the role of inhibitory cells in various amygdala functions, we need to reveal the connectivity and input-output features of the different types of GABAergic cells. Here, I review the recent achievements in uncovering the diversity of GABAergic cells in the basolateral amygdala with a specific focus on the microcircuit organization of these inhibitory cells.

Highlights

TO THE CONNECTIVITY OF THE BASOLATERAL AMYGDALAAmygdala is the brain region where at least 13 different nuclei are defined with typical neuron types, developmental origin, and connectivity patterns (Pitkanen et al, 1997; Swanson, 2003), playing a role in surprisingly diverse functions, including aversive memory formation, decisionmaking, social interactions, affective and parental behavior, and homeostatic control, just to list a few (LeDoux, 2000; Phelps et al, 2014)
SST interneurons innervate the distal dendrites of pyramidal cells (Katona et al, 1999a; Wang et al, 2004), and are considered to control dendritic information processing in a feedback manner (Miles et al, 1996; Murayama et al, 2009), as these GABAergic cells are primarily excited by the local axon collaterals of principal neurons (Blasco-Ibanez and Freund, 1995; Maccaferri and McBain, 1995)
As a proof for the disinhibitory function of VIP interneurons, the activity of principal neurons, which was normally elevated by the US, could be significantly reduced if the elevated activity of VIP interneurons induced by the CS was suppressed by optogenetics. These results clearly show that: (i) VIP interneurons have disinhibitory function in the basolateral amygdala (BLA), (ii) they are strongly activated by salient stimuli and (iii) their activity changes during conditioning in a way that is characteristic for neurons signaling prediction errors

Summary

Introduction

TO THE CONNECTIVITY OF THE BASOLATERAL AMYGDALAAmygdala is the brain region where at least 13 different nuclei are defined with typical neuron types, developmental origin, and connectivity patterns (Pitkanen et al, 1997; Swanson, 2003), playing a role in surprisingly diverse functions, including aversive memory formation, decisionmaking, social interactions, affective and parental behavior, and homeostatic control, just to list a few (LeDoux, 2000; Phelps et al, 2014). Perisomatic inhibition refers to synaptic inputs formed by GABAergic axon terminals targeting the spine-free proximal dendrites, soma, or AIS of postsynaptic principal neurons (Figure 2A; Freund and Katona, 2007; Vereczki et al, 2016).

Results

Conclusion