The development of the human amygdala during early embryonic life,

Abstract

The development of the human amygdaloid complex is described beginning at the time that it first appears, when the cerebral hemispheres begin to evaginate (approximately 8-9 m m ) , and including a fetus of 27.4 mm CR length Both Nissl and protargol silver series, transversely and sagittally sectioned, were used.The earliest cell migration representing the striatal complex is from the germinal epithelium in the region of the interventricular foramen, lateral to the primordial hippocampal formation. This is the characteristic topographic location of the amygdala, which, therefore, 1s the first portion of the human striatal complex to appear embwologically. All of the amygdaloid nuclei identified develop by the migration of neuroblasts from the germinal epithelium.The three main subdivisions of the amygdaloid complex (anterior amygdaloid area, corticomedial complex and basolateral nuclear group) are identifiable almost immediately after the primordial amygdala appears (9.5 m m in the material studied). In this embryo the cortical and medial nuclei are identifiable, but the central nucleus was not seen until 22.2 mm and the nucleus of the lateral olfactory tract was not identified even in the oldest fetuses.The basolateral complex differentiates much later than the corticomedial complex and all of the nuclear components became identifiable at the same time (20.7 mni embryo). However the basal nucleus is best represented, the accessory basal next in size, and the lateral only just appearing. In the oldest fetus the subdivisions of the basal and accessory basal nuclei seen in the adult brain are recognizable. Even before the individual nuclei appear, the basolateral complex is much larger than the corticomedial complex. The lateral to medial rotation of the amygdaloid complex has not yet begun in the oldest Petuses, but the posterior end of the lateral ventricle is beginning to turn anteriorly.During early development, all cells of the amygdala are derived from the lateral striatal ridge, the only one present until 14.0 mm. At 20.7 m m and later neuroblasts are contributed from the medial striatal ridge also. Although the greater part of the basolateral amygdaloid complex is derived from the lateral ridge, some cells are contributed from the medial ridge, particularly to the accessory basal nucleus. By contrast, the corticomedial complex is derived in part from the medial striatal ridge, after it appears, even though the early development is from the lateral ridge.Comparisons between the amygdala at different developmental stages and the amygdala in fishes, in amphibians, in reptiles and in lower mammals are made. The topographic relationships between the amygdala and the hippocampal formation, the piriform cortex and the caudate, the putamen and the globus pallidus are considered.The archistriatum, or amygdala, and the paleostriatum, or globus pallidus, are commonly considered old parts of the striatal complex phylogenetically ( Ariens Kappers, Huber and Crosby, '36; Crosby, DeJonge and Schneider, '66). In th...

The Neuro-Environmental Loop of Plasticity: A Cross-Species Analysis of Parental Effects on Emotion Circuitry Development Following Typical and Adverse Caregiving

“…Although the basic architecture of the human amygdala is present at birth (Humphrey, 1968;Ulfig et al, 2003), it does appear to undergo significant structural and functional remodeling and refinement across the infancy, childhood, and adolescent stages of development (see Tottenham, 2014;Tottenham and Sheridan, 2009 for a review). Although the most rapid postnatal volumetric growth occurs soon after birth (eg, over 100% increase in volume in 0-1 year followed by a 9% increase from years 1 to 2; Gilmore et al, 2012; also see Payne et al, 2010;Uematsu et al, 2012), the amygdala continues to increase in volume until 4 years of age in females and 18 years of age in males (Giedd et al, 1996;Mosconi et al, 2009;Nordahl et al, 2012;Schumann et al, 2004).…”

The Importance of Early Experiences for Neuro-Affective Development

“…Although there are several neural circuits affected by early-life adversity, the amygdala is a suitable choice for discussion because it develops early in postnatal life (Gilmore, et al, 2012;Humphrey, 1968;Ulfig, Setzer, & Bohl, 2003) mediates many of the emotional difficulties exhibited by those who experienced early-life adversity (e.g., hyper-emotionality), and because it is rich with stress hormone receptors particularly in early postnatal life (Avishai-Eliner, Yi, & Baram, 1996;Baram & Hatalski, 1998;Fenoglio, Brunson, Avishai-Eliner, Chen, & Baram, 2004;Moriceau, et al, 2004;Vazquez, et al, 2006). Youths who have experienced early caregiver deprivation tend to be highly anxious (Casey, et al, 2009;Goff, et al, 2012;, as has been found in other species that have experienced maternal deprivation (Berman, Rasmussen, & Suomi, 1994;Botero, Macdonald, & Miller, 2013;Caldji, et al, 1998;Callaghan & Richardson, 2013;Macri, Laviola et al, 2010;Sabatini, et al, 2007).…”

Computer ranking of the sequence of appearance of 73 features of the brain and related structures in staged human embryos during the sixth week of development

“…The amygdaloid area arises in a diencephalic position in stages 14 and 15 and joins with the slightly later emerging telencephalic part of the basal nuclei in stages 15 and 16. Humphrey (1968) maintained that the amygdaloid body is derived exclusively from the telencephalon in the human. According to Smart (19851, however, it comprises a diencephalic and a telencephalic part in the mouse.…”

“…According to Smart (19851, however, it comprises a diencephalic and a telencephalic part in the mouse. Humphrey (1968) described the development of the major subdivisions in the amygdaloid body already in embryos of 9.5 and 10.9 mm, belonging probably to stage 16 or possibly 17.…”

“…The cortical nucleus of the amygdaloid body is present. This is "a thin cell layer that lies parallel to the surface of the hemisphere and the underlying basolateral amygdaloid complex" (Humphrey, 1968).…”