engleski

Development of human amygdala ; correlation of in vitro MRI and histology

Amygdala plays a key role in emotional behavior and modulates cortical functions via robust connections. Human amygdala develops during early embryonic life and around 12 post-conceptual weeks (PCW) develops human specific characteristic transient modular organization (Nikolic and Kostovic, Anat. Embryol., 1986). The aim of this study was to determine basic structural and growth parameters using in vitro MR imaging as a first step for future in vivo analysis of developing human brain. Postmortem MRI on 11 human fetuses ranging between (10.5-40 PCW) was correlated with Nissl stained sections (Zagreb Neuroembryological collection, ranging from 4 to 40 PCW). The embryonic anlage of amygdala was seen on histological sections as early as 5 PCW. On MRI scans, reliable identification of amygdala was seen at 13 PCW. First division in nuclear territories (basolateral, corticomedial and central) is present on histological sections at 8 PCW weeks while MRI showed individual nuclei around 20 PCW. Internal transient modular organization of lateral nucleus, which on Nissl stained sections appears around 12 PCW on, was not determined on MRI with certainty. The measurements of amygdala volume showed fastest increase between 13 and 20 PCW (18 times) and moderate increase (3 times) was noticed between 28 and 40 PCW. Based on both structural and volumetric measurements, we propose existence of two developmental phases in prenatal development of amygdala. First period is characterized by intensive growth and correlates with productional neurogenetic events (proliferation, cell migration, aggregation and differentiation), while the second correlates with development of fiber connections. In conclusion, amygdala shows intensive growth and advanced maturation during early fetal life, parallel with the development of limbic and frontal cortex. The level of internal organization in human fetus is in contrast with expected later function in social behavior (Bachevalier, Behav Neurosci. 2006).

MRI; amygdala; human

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