A study was made of human embryos at the end of 8 weeks and foetuses aged
9 weeks. It was shown that at the beginning of the foetal period the cortical
plate, which is the primordium of the neocortex, covers the whole surface of the
cerebral hemisphere. The plate consists of 8&#8211;12 rows of densely packed cells.
Below the cortical plate is the subplate

Rapalska, Katarzyna

Woźniak, Witold

English

Via Medica Journals

Folia Morphol. Vol. 63, No. 4, pp. 499–502Copyright © 2004 Via MedicaISSN 0015–5659www.fm.viamedica.plS H O R T  C O M M U N I C A T I O N499Address for correspondence: Prof. Witold Woźniak, Department of Anatomy, University School of Medical Sciences, ul. Święcickiego 6,60–781 Poznań, Poland, tel. +48 61 854 65 65, e-mail: wwozniak@amp.edu.plEarly development of the neocortex in humanfoetuses aged 9 weeksWitold Woźniak, Katarzyna RapalskaDepartment of Anatomy, University School of Medical Sciences, Poznań, Poland[Received 20 August 2004; Accepted 20 October 2004]A study was made of human embryos at the end of 8 weeks and foetuses aged9 weeks. It was shown that at the beginning of the foetal period the corticalplate, which is the primordium of the neocortex, covers the whole surface of thecerebral hemisphere. The plate consists of 8–12 rows of densely packed cells.Below the cortical plate is the subplate.Key words: human neuroembryology, cortical plate, neocortexINTRODUCTIONThe ontogenesis of the neocortex has fascinatedmany scientists [8]. It is also of great clinical interest,because abnormalities in the cortical layers as well asabnormalities of the neurotransmitter system andneuronal connections may result in many disorders.Most studies on the development of the humanneocortex have been performed either in the em-bryonic period or in the 2nd and 3rd trimesters of preg-nancy [1, 3, 4, 6, 7].The aim of the present study is a description ofthe cortical plate in human foetuses aged 9 weeks.MATERIAL AND METHODSThe study was performed in 5 embryos aged8 weeks (developmental stage 23) and 7 foetusesaged 9 weeks. The crown-rump length of the foet-uses was between 35 and 48 mm. All embryos andfoetuses were sectioned serially in the horizontal,frontal, and sagittal planes and stained accordingto various methods (Mallory, H+E, and silver salts).RESULTSIn embryos at stage 23 (8 weeks) the corticalplate was well marked on the dorsolateral and bas-al surfaces of the cerebral hemisphere (Fig. 1). Itwas thickest in the insular region, which is an in-dented area. In the thickest area the plate consist-ed of 8 to 10 rows of densely packed cells and theirprocesses (Fig. 2). The wall of the cerebral hemi-sphere had distinct layers, the thickest being theintermediate layer (Fig. 3).In foetuses at 9 weeks the cortical plate covered thewhole surface of the neopallium. It was thickest in thearea of the insula (Fig. 4, 5). The cortical plate was com-posed of 8–12 rows of cells which formed columns ar-ranged perpendicularly to the surface of the hemisphere.The lamination of the hemispheric wall was thesame as in embryos of stage 23 (Fig. 6). The ven-tricular and subventricular zones were of differentthicknesses. The ventricular zone on the cross-sec-tion was wider. The subventricular zone containedoval groups of cells. The subplate was irregular inthickness with loosely packed cells (Fig. 5).DISCUSSIONCorticogenesis refers to the formation of the cor-tical plate, which forms the primordium of the neo-cortex [5]. It is evident from the study performedthat the cortical plate in foetuses of 9 weeks extendsover the whole cerebral surface.Zecevic et al. [10] showed that in 9-week-old foe-tuses isolated cells in the deepest region of the cor-tical plate are weakly immunoreactive for calretinin.500Folia Morphol., 2004, Vol. 63, No. 4Figure 1. Frontal section of the brain in an embryo at stage 23. H+E. l — lamina  terminalis, th — thalamus, pc — choroid  plexus,hyp — hypophysis, ci — internal capsule, lm — medullary lamina of the thalamus, vl — lateral ventricle, III — 3rd ventricle.Figure 2. Transverse section of the brain wall in a foetus atstage 23. Impregnation with silver according to the Ogawamethod. CR — Cajal-Retzius cells, st — stellate cells, f — nervefibres, m — marginal layer, c — cortical plate, sc — subplate,i — intermediate layer.Figure 3. Transverse section of the brain wall in a foetus atstage 23. Impregnation with silver according to the Ogawamethod. m — marginal layer, c — cortical plate, sc — subplate,i — intermediate layer, su — subventricular layer, v — ventricularlayer, pc — choroid plexus.lmth501Witold Woźniak et al., Early human foetal neocortexThe morphology of these labelled cells resem-bles that of developing pyramidal neurons withapical dendrites oriented toward the pia. Uylingset al. [9] also noted immunocytochemical differen-tiation of cortical neurons in the early foetal peri-od. This is accompanied by proliferation and apop-tosis [2].REFERENCES1. Chabas A, Briones P, Sabater J (1979) Prenatal humanbrain development. Dev Neurosci, 2: 65–73.2. Chan WY, Lorke DE, Tiu  SC, Yew DT (2002) Prolifera-tion and apoptosis in the developing human neocor-tex. Anat Rec, 267: 261–276.3. Lan LM, Yamashita Y, Tang Y, Sugahara T, TakahashiM, Ohba T, Okamura H (2000) Normal fetal brain de-velopment: MR imaging with a half-Fourier rapid ac-quisition with relaxation enhancement sequence. Ra-diology, 215: 205–210.4. Levine D, Barnes PD (1999) Cortical maturation in nor-mal and abnormal fetuses as assessed with prenatalMR imaging. Radiology, 210: 751–758.Figure 5. Transverse section of the cerebral wall in a foetus aged9 weeks. Toluidine blue according to Nissl’s method. m —  mar-ginal layer, c — cortical plate, sc — subplate, i — intermediatelayer, sv — subventricular layer, v — ventricular layer, el — lat-eral eminence, Æ tangential migration.Figure 4. Transverse section of the brain in a foetus aged9 weeks. Toluidine blue according to Nissl’s method.c — cortical plate, pc — choroid plexus, ncd — caudate nu-cleus, put — putamen, Æ tangential migration, el — lateraleminence.Figure 6. Sagittal section of the cerebral wall in a foetus aged9 weeks. Toluidine blue according to Nissl s method. ml — lami-na limitans of dura, a — arachnoid, sa — subarachnoid space,pm — pia mater, m — marginal layer, c — cortical plate,sc — subplate, i — intermediate layer, sv — subventricularlayer, v — ventricular layer.502Folia Morphol., 2004, Vol. 63, No. 45. Marin-Padilla M (1992) Ontogenesis of the pyramidalcells of the mammalion neocortex and developmentalcytoarchitectonicsa; a unifying theory. J Comp Neu-rol, 321: 223–240.6. Müller F, O’Rahilly R (1990) The human brain at stages21–23, with particular reference to the cerebral corti-cal plate and to the development of the cerebellum.Anat Embryol, 182: 375–400.7. Rapalska K, Woźniak W (2002) Differentiation of thecortical plate in early human fetuses. Folia Morphol,61: 233.8. Tiu SC, Yew DT, Chan WY (2002) Development of thehuman cerebral cortex: A histochemical study. ProgrHistochem Cytochem, 38: 1–149.9. Uylings HBM, Delalle I, Petanjek Z, Koenderink MJT(2002) Structural and immuno-cytochemical differen-tiation of neurons in prenatal and postnatal humanprefrontal cortex. Neuroembryol, 1: 176–186.10. Zecevic N, Milosevic A, Rakic S, Marin-Padilla M (1999)Early development and composition of the human pri-mordial plexiform layer: An immunohistochemicalstudy. J. Comp Neurol, 412: 241–254.

Early development of the neocortex in human foetuses aged 9 weeks

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Early development of the neocortex in human foetuses aged 9 weeks

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