Development of Cajal-Retzius cells in the human auditory cortex.

We analysed the differentiation and areal distribution of Cajal-Retzius (C-R) cells in the human auditory cortex using acetylcholinesterase (AChE) technique on specimens ranging between 10 weeks of gestation (w.) and the 3rd postnatal month. AChE-reactive cells appear in the marginal zone of the prospective auditory cortex as early as 10 1/2 weeks of gestation. Analysis of primary and associative auditory cortex in subsequent stages of gestation and during early postnatal life reveals an age-dependent decrease in cell-packing density of C-R cells and an increase in thickness of the marginal zone. Large AChE-reactive cells were readily found in the early postnatal cortex. These and our previous data on the human frontal associative cortex demonstrate the presence of AChE-reactive C-R cells in both primary and associative cortical areas during late fetal and early postnatal life. The postnatal changes in the morphology and distribution of AChE-reactive C-R cells may serve as cellular parameters of the postnatal cortical maturation in man.

Prenatal and perinatal development of radial cell columns in the human auditory cortex.

The aim of this study was to analyse cytoarchitectonic development of radial cell columns in the human auditory cortex and to correlate these 'ontogenetic' cell columns with the 'adult' pattern of radial cell arrangement. For this cytoarchitectonic analysis, brains were obtained from human fetuses and infants ranging between 9 weeks of gestation and third postnatal month. Plastic and celloidin sections containing prospective auditory areas TC, TB and TA of Economo & Koskinas were stained by Nissl method. In youngest fetuses (8-13 weeks) radially oriented cell columns (1-3 cell wide 'ontogenetic' columns) were found in the whole thickness of the developing cortical plate. During the next developmental stage (13-26 weeks of gestation), radial cell columns were present in the superficial part of the cortical plate, while the deep part of the cortical plate showed a variable cell arrangement due to the formation of the subplate layer (13-15 weeks). The appearance of the pale bands, and development of the prospective granular layer (18-26 weeks). After 28 weeks, parallel to the intensive areal cytoarchitectonic differentiation and ingrowth of callosal afferents, there was a gradual regional rearrangement in the ontogenetic pattern of vertical cell columnation. In the area supratemporalis granulosa (TC), radial columnation was observed as increased granularity and the appearance of short cords composed of drop-like cells. In the area supratemporalis simplex (TB) there was a progressive differentiation of elongated cell columns, intervening fibrillar stripes with appearance of pyramidal cell cords in layers III ('organ pipe' formations).(ABSTRACT TRUNCATED AT 250 WORDS)

The development of medial geniculate body in man: changes in the cholinesterase (CHE) activity during fetal and perinatal life.

In the present study cholinesterase histochemical (ChE) techniques have been used to demonstrate differentiation and maturation of the medial geniculate body (MGB) in the human fetuses (ranging between 10.5 to 28 weeks) and infants (premature and three postnatal months). In the youngest specimens examined (10.5 to 15 weeks) moderate ChE activity was found in the neuropil of MGB. In the next developmental stage ChE activity is significantly increased with stronger reactivity in the peripheral part of MGB. In the fetuses between 22 to 26 weeks of gestation peak ChE reactivity was observed in MGB. Reactivity is strong and homogeneous. In the premature infant (28 weeks and older) ChE reactivity becomes inhomogeneous and irregular with appearance of ChE positive bands in the moderately stained MGB matrix. In addition, strongly ChE reactive cell bodies can be discerned. In 3-month-old infant brain we have found significant decrease of ChE reactivity in the neuropil of the MGB. In conclusion we can say that MGB shows very strong, transient ChE reactivity during second half of gestation. Since a great majority of ChE reactivity disappears during later postnatal development, it is very likely that strong fetal activity is related to the histogenetic events and maturation of MGB.

Development of the human fetal auditory cortex: growth of afferent fibres.

The sequential development and growth of the subcortico-cortical fibres have been studied by means of acetylcholinesterase (AChE; acetylcholine acetylhydrolase; EC 3.1.1.7) histochemistry on the serial sections obtained from brains of human fetuses ranging from 10 to 28 weeks of gestation. It was found that thalamic and basal telencephalic fibres approaching the fetal auditory cortex have very strong AChE reactivity during a prolonged period of growth. In the youngest fetuses (10.5 weeks) a prominent fibre system was seen emerging from the ventroposterior thalamic territory while the auditory neopallium was free of AChE staining. In older fetuses (16-18 weeks) AChE-positive fibres originating in the ventroposterior thalamus and basal telencephalon penetrate the 'subplate layer' of the auditory cortex. On the basis of AChE reactivity of the 'subplate layer' the auditory cortex can be delineated from the surrounding neocortical areas. In the oldest fetuses (22-28 weeks) AChE-positive fibres of thalamic origin penetrate the developing cortical plate of the auditory cortex.

Development of acetylcholinesterase (AChE) staining in human fetal auditory cortex.

In this study acetylcholinesterase (AChE) staining methods have been used to demonstrate the development of the prospective afferent fibres of auditory cortex in human fetuses ranging between 8 and 28 weeks of gestation. Earliest AChE positive staining was found in fetuses at 20--24 weeks in the neuropil of the marginal zone and throughout subplate layer of the auditory cortex. On the basis of this characteristic AChE staining pattern, the auditory cortex may be delineated from surrounding cortical areas. At 24--26 weeks, during intensive lamination of the cortical plate, AchE-positive reaction appears in the deep part of the cortical plate. In the oldest fetuses (28 weeks) a columnar pattern of vertical, darkly stained zones was seen in the middle third of the cortical plate. We conclude that AChE staining is characteristically distributed within cytoarchitectonic compartments and 'synaptic' layers of the developing auditory cortex. The AChE-positive layers coincide with the laminar pattern of synpatogeneis. Thus, AChE-positive reaction during development may serve as a parameter of cortical afferent (thalamic?) innervation of the auditory cortex. In addition, AChE reactivity may indicate the specific transmitter nature of the afferent fibres in the auditory cortex.

The laminar organization of the prospective auditory cortex in the human fetus (11--13.5 weeks of gestation).

The prospective auditory cortex was analysed in human fetuses at 11--13,5 post-ovulatory weeks with Nissl, Golgi and E.M. techniques. At 11--12 weeks, marginal, cortical plate, intermediate, subventricular and ventricular layers were recognized. Post-migratory neurons with developing dendrites were seen in marginal layer, cortical plate and superficial part of the intermediate zone only. At 12--13,5 weeks the superficial part of the intermediate zone is transformed into the true cortical layer--"subplate layer"--characterized by maturing neurons with growing dendrites, fine axonal arborization and low cell density. The neuronal circuitry elements are thus present very early in the prospective auditory cortex and distributed throughout the deep cortical plate of the "subplate layer" corresponding to the synaptic territory of other areas of the human fetal cortex.