The amygdala consists of nuclei which can be grouped into (i) the basolateral nuclear group (BLA), (ii) the superficial cortex-like laminated region (sCLR) which contains the cortical nuclei (Co), and (iii) the centromedial nuclear group.1 The BLA consists of the lateral nucleus (LA) and basal nucleus (BA). In turn, the BA consists of the basolateral nucleus and the basomedial nucleus. The centromedial nuclear group consists of the central nucleus (Ce), medial nucleus (Me), and intercalate cell mass (IC). In turn, Ce consists of a lateral (CeL) subdivision and a medial (CeM) subdivision. The centromedial nuclear group (Ce, Me, and IC) along with the bed nucleus of the stria terminalis (BNST) and sublenticular substantia innominata together comprise the centromedial extended amygdala.
The cellular composition of the BLA nuclei and the sCLR’s Co nuclei resembles that of the cerebral cortex in that the majority of the neurons are pyramidal-like glutamatergic cells while the rest are local GABAergic inhibitory interneurons.1 The inhibitory interneurons include parvalbumin-containing neurons which mainly synapse on the soma and proximal dendrites of the pyramidal cells and somatostatin-containing neurons which mainly synapse on the distal dendrites of the pyramidal neurons. By contrast, the composition of the Ce and Me nuclei resembles the striatum in that many of the neurons are similar to GABAergic medium spiny neurons.