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PubMed1985

[Small oscillations in fetal cardiac rhythm: a sign of well-being? A new approach to the diagnostic value of spontaneous recordings of fetal cardiac rhythm in pregnancy].

The authors suggest an indirect evaluation of the electrocortical activity of the fetus by looking at evidence of cyclical variations in fetal cardiac rhythm. These are shown up by periodic changes in the variability of the rhythm. The narrow association that has been established between small changes in episodes of cardiac rhythm and deep sleep--which is itself evidence of satisfactory cortical development--make this type of tracing, under certain conditions, an excellent sign of fetal wellbeing. This means that the value of small variabilities in fetal heart rhythm takes on greater importance as a prognostic feature.

Animals↗
PubMed1994

[Biopercular polymicrogyria associated with congenital ophthalmoplegia caused by nuclear lesion of the common oculomotor nerve].

Developmental pseudobulbar palsies seem to be different from the adult form described by Foix, Chavany and Marie. They usually include a major speech delay and severe epileptic seizures. In one clinicopathological case, neuroradiological imaging showed a macrogyric aspect of both rolandic operculi and unilateral destruction of pes pedunculari. Microscopic examination showed a four-layered polymicrogyria involving the first temporal gyrus and in the brainstem a selective destruction of the left oculomotor nucleus. Thus, the macrogyric aspect could be related to post migratory disorder occurring late in the cortical development. The brain stem lesion, destroying unilaterally the third cranial nerve nucleus gives a good example of the complex somatotopia of this oculomotor nucleus.

Abnormalities, Multiple↗
PubMed1993

Thymus histogenesis in the lizard, Chalcides ocellatus.

Different stages of thymus morphogenesis and thymocyte differentiation have been studied at the ultrastructural level in the lizard, Chalcides ocellatus. On stage 36 of embryonic development, the thymus primordium was composed principally of undifferentiated epithelial cells and some lymphoid stem-cells. From stage 37 to 38, the lymphoid stem-cells differentiate into lymphoblasts and then transform into typical lymphocytes. A clasmotosis phenomenon seems to be involved in this transformation. In the developing cortical regions, lymphoblasts accumulated rapidly, stretching the epithelial cells which become stellate in shape. From stage 39 to 40, a phase of intense proliferation occurs and numerous lymphocytes die in the thymic tissue and are phagocytosed by macrophages. On stage 41, the presence of interdigitating cells in the medullary area completed cortico-medullary differentiation. On neonatal and juvenile lizards, small cortical thymocytes differentiated and the thymus possessed all characteristic of an adult thymus. Thus, at birth, the histogenesis of the lizard thymus was achieved and the only further modification consisted in a gain of weight.

Aging↗
PubMed1998

Ovarian hormones influence the morphology, distribution, and density of tyrosine hydroxylase immunoreactive axons in the dorsolateral prefrontal cortex of adult rhesus monkeys.

The maturation, adult functioning and dysfunction of the prefrontal cortex in disorders such as schizophrenia show gender biases in human and non-human primates. Although the basis for the hormone influence suggested in these observations is unknown, one possibility is that circulating hormones stimulate catecholamine innervation in the frontal lobe. This innervation is essential for prefrontal cortical function, and gonadal, especially ovarian hormones, profoundly influence catecholamine function and physiology in subcortical structures. This study was undertaken to determine whether influence is also exerted upon the catecholamine innervation of the association cortex by combining ovarian hormone manipulation with immunocytochemistry for tyrosine hydroxylase in the dorsolateral prefrontal cortex of adult female macaque monkeys. Qualitative and quantitative analyses of immunoreactive fibers were carried out and compared in cortices of ovariectomized animals, ovariectomized animals treated with estrogen, ovariectomized animals treated with estrogen followed by progesterone, and in intact, age- and sex-matched controls. These analyses revealed striking, layer-specific anomalies in fiber morphology and profound reductions in fiber density in ovariectomized animals. While hormone replacement with estrogen alone had limited influence, estrogen followed by progesterone was particularly effective in restoring tyrosine hydroxylase innervation in ovariectomized animals. Thus, ovarian hormones appear to be potent regulators of the catecholamine innervation of the primate prefrontal cortex. Such regulation is anticipated in the gender differences observed in prefrontal cortical development and function, and may also be relevant for the prefrontal dysfunction in disorders such as schizophrenia.

Analysis of Variance↗
PubMedDate not supplied

Postnatal development of functional properties of visual cortical cells in rats with excitotoxic lesions of basal forebrain cholinergic neurons.

In the rat, visual cortical cells develop their functional properties during a period termed as critical period, which is included between eye opening, i.e. postnatal day (PD) 15, and PD40. The present investigation was aimed at studying the influence of cortical cholinergic afferents from the basal forebrain (BF) on the development of functional properties of visual cortical neurons. At PD15, rats were unilaterally deprived of the cholinergic input to the visual cortex by stereotaxic injections of quisqualic acid in BF cholinergic nuclei projecting to the visual cortex. Cortical cell functional properties, such as ocular dominance, orientation selectivity, receptive-field size, and cell responsiveness were then assessed by extracellular recordings in the visual cortex ipsilateral to the lesioned BF both during the critical period (PD30) and after its end (PD45). After the recording session, the rats were sacrificed and the extent of both cholinergic lesion in BF and cholinergic depletion in the visual cortex was determined. Our results show that lesion of BF cholinergic nuclei transiently alters the ocular dominance of visual cortical cells while it does not affect the other functional properties tested. In particular, in lesioned animals recorded during the critical period, a higher percentage of visual cortical cells was driven by the contralateral eye with respect to normal animals. After the end of the critical period, the ocular dominance distribution of animals with cholinergic deafferentation was not significantly different from that of controls. Our results suggest the possibility that lesions of BF cholinergic neurons performed during postnatal development only transiently interfere with cortical competitive processes.

Animals↗
PubMed1993

Capacity of the retinogeniculate pathway to reorganize following ablation of visual cortical areas in developing and mature cats.

The purpose of the present study was to determine the pattern and density of retinal projections to the dorsal lateral geniculate nucleus (dLGN) following ablation of visual cortical areas in developing cats of different postnatal ages and in mature cats. The terminations of retinal projections to the dLGN were evaluated following the injection of tritiated amino acids into one eye. Regardless of age, a visual cortical ablation of areas 17 and 18 induces massive death of neurons within the regions of the dLGN that are linked topographically to the cortical areas removed. However, the pattern of retinal projections to these degenerated regions of the dLGN differs depending upon whether the cortical lesion is incurred early in postnatal life or in adulthood. Following ablation on the day of birth (P1), virtually all surviving cells were found in the C-complex of dLGN with only a token number in the A-laminae. Correspondingly, retinal projections were maintained to the C-complex of the nucleus and were barely detectable in the degenerated A-laminae. However, in cats in which areas 17 and 18 had been removed in adulthood (> or = 6 months of age) retinal projections were maintained to the A-laminae even though nearly all neurons in those laminae had degenerated. Moreover, a subgroup of animals that incurred area 17 and 18 ablations at P1 showed that the modification of retinal projections to the A-laminae occurs within the first postnatal month, and an additional subgroup showed that retinal projections become increasingly resistant to the degenerative events in the dLGN that follow ablation of areas 17 and 18 at progressively older ages during the first postnatal month. Furthermore, retinal inputs also respond, in an age-dependent way, to degeneration of neurons in the C-complex induced by extension of the cortical ablation to include extrastriate visual areas.

Age Factors↗
PubMed1982

Development and change of cortical field potentials during learning processes of visually initiated hand movements in the monkey.

Field potentials on the surface and at 2.5-3.0 mm depth in the cerebral cortex were recorded in various areas with chronically implanted electrodes and the potentials which preceded hand movements in response to a light stimulus were observed during the process of learning the skilled conditioned movement. A naive monkey had to lift a lever by wrist extension within duration of the light stimulus lasting for 900, 700 or 510 ms depending on the stage of the learning process. In addition to some responses in the striate gyrus, significant short-latency responses to the light stimulus appeared bilaterally in certain areas of the prefrontal and prestriate cortices at an early stage of learning in which the monkey still lifted the lever randomly, and they became gradually larger as the monkey was trained further. Short-latency responses were also often noted in the bilateral premotor cortices during an early stage of learning. When the monkey started to respond to the stimulus by the appropriate movement, early surface-positive (s-P), depth-negative (d-N) premovement potentials appeared in the forelimb motor cortex, and the responses in the premotor cortex increased in size. As the movement became faster and more skillful, late s-N, d-P premovement potentials, that are known to be mediated by the neocerebellum and superficial thalamo-cortical projections, emerged after the early s-P, d-N potentials and became more marked, larger and steeper in the forelimb motor cortex contralateral to the moving hand. All the premovement potentials in the different cortical areas thus developed into steady and constant states and remained so for many months thus maintaining their established patterns. Such successive appearances of premovement field potentials in various cortical areas were related to learning processes of the movement and the implication of these findings was discussed.

Animals↗
PubMed1991

Changing patterns of synaptic input to subplate and cortical plate during development of visual cortex.

1. The development of excitatory activation in the visual cortex was studied in fetal and neonatal cats. During fetal and neonatal life, the immature cerebral cortex (the cortical plate) is sandwiched between two synaptic zones: the marginal zone above, and an area just below the cortical plate, the subplate. The subplate is transient and disappears by approximately 2 mo postnatal. Here we have investigated whether the subplate and the cortical plate receive functional synaptic inputs in the fetus, and when the adultlike pattern of excitatory synaptic input to the cortical plate appears during development. 2. Extracellular field potential recording to electrical stimulation of the optic radiation was performed in slices of cerebral cortex maintained in vitro. Laminar profiles of field potentials were converted by the current-source density (CSD) method to identify the spatial and temporal distribution of neuronal excitation within the subplate and the cortical plate. 3. Between embryonic day 47 (E47) and postnatal day 28 (P28; birth, E65), age-related changes occur in the pattern of synaptic activation of neurons in the cortical plate and the subplate. Early in development, at E47, E57, and P0, short-latency (probably monosynaptic) excitation is most obvious in the subplate, and longer latency (presumably polysynaptic) excitation can be seen in the cortical plate. Synaptic excitation in the subplate is no longer apparent at P21 and P28, a time when cell migration is finally complete and the cortical layers have formed. By contrast, excitation in the cortical plate is prominent in postnatal animals, and the temporal and spatial pattern has changed. 4. The adultlike sequence of synaptic activation in the different cortical layers can be seen by P28. It differs from earlier ages in several respects. First, short-latency (probably monosynaptic) excitation can be detected in cortical layer 4. Second, multisynaptic, long-lasting activation is present in layers 2/3 and 5. 5. Our results show that the subplate zone, known from anatomic studies to be a synaptic neurophil during development, receives functional excitatory inputs from axons that course in the developing white matter. Because the only mature neurons present in this zone are the subplate neurons, we conclude that subplate neurons are the principal, if not the exclusive, recipients of this input. The results suggest further that the excitation in the subplate in turn is relayed to neurons of the cortical plate via axon collaterals of subplate neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1990

Bihemispheric Axonal Bifurcation of the Afferents to the Visual Cortical Areas during Postnatal Development in the Rat.

Numerous cortical neurons in the juvenile and adult rat project to visual areas of both hemispheres whereas the vast majority of subcortical structures projecting to the visual cortex send strictly ipsilateral projections (Dreher et al., 1990). In the present study, the authors have sought to determine whether this pattern of axonal bifurcation in the connectivity of the visual areas undergoes a change during postnatal development. Two retrograde fluorescent dyes were used, fast blue (FB) and diamidino yellow (DY). Large multiple injections of one of the dyes were placed in all visual areas of one hemisphere and a small injection of the other dye was placed in area 17 of the opposite hemisphere. Labelled neurons were observed in subcortical and cortical structures on the side of the small injection. The experiments were performed on ten neonatal albino rat pups aged between 3 and 12 postnatal days (p.n.d.) at the time of injection and the results were compared with those obtained in the juvenile and adult animals, as reported in the preceding paper. In the thalamus of newborn animals, neurons belonging to nuclei located away from the midline send strictly ipsilateral cortical projections. However, in the midline nuclei of the intralaminar thalamic complex, a small region of overlap was observed between neurons projecting ipsilaterally and neurons projecting contralaterally in animals aged less than 9 postnatal days. In addition, in these neonatal animals a small number of bilaterally projecting neurons was detected in this region of overlap. In all other subcortical structures examined (ventral tegmental area, diagonal band of Broca, claustrum), the laterality of the projection was the same in the newborn and the adult animals. In particular, in the claustrum of neonatal animals, as in adult animals, there was a large contingent of contralaterally projecting neurons and only a very small number of bilaterally projecting neurons. The results in the cortex contrast with those observed in subcortical structures. Whereas ipsilaterally projecting neurons were distributed in a broadly similar way in newborn and adult animals, the laminar and areal distribution of contralaterally projecting neurons in newborn animals clearly differed from those observed in the adult animals. Furthermore, double labelled neurons were more numerous in animals aged less than 12 days than in adults. The proportions of such bilaterally projecting neurons were computed with respect to the numbers of neurons sending ipsilateral projections to area 17. These proportions are constant at all ages in the claustrum and cortical area 8. In areas 18a, 29 and 35 on the other hand, the proportions of bilaterally projecting neurons increase after 5 days and reach a peak in the period extending from 9 to 11 days of age when more than half of the neurons projecting ipsilaterally also send an axonal branch to the contralateral cortex. In cortical areas 29 and 35, this peak is followed by a sudden drop to the adult level at 12 postnatal days, whereas the return to the adult level is gradual in area 18a. These results demonstrate that, in subcortical structures and in cortical area 8, the laterality of the afferent connections to the visual cortex does not change during postnatal development. By contrast, cortical areas 18a, 29 and 35 go through a stage when numerous cells send bifurcating connections to both hemispheres. The timing of the decrease in proportions of bilaterally projecting neurons in these areas suggests that numerous neurons retract their callosal axonal branch when the adult pattern of callosal connectivity is established at 9 - 11 days of age.

Journal Article↗
PubMed2000

Cortical cell orientation selectivity fails to develop in the absence of ON-center retinal ganglion cell activity.

Neuronal activity is necessary for the normal development of visual cortical cell receptive fields. When neuronal activity is blocked, cortical cells fail to develop normal ocular dominance and orientation selectivity. Patterned activity has been shown to play an instructive, rather than merely permissive, role in the segregation of geniculocortical afferents into ocular dominance columns. To test whether normal patterns of activity are necessary to instruct the development of cortical orientation selectivity, we studied ferrets raised without ON-center retinal ganglion cell activity. The ON-center blockade was produced by daily intravitreal injections of DL-2-amino-4-phosphonobutyric acid (APB). Effects of this treatment on the development of orientation selectivity in primary visual cortex were assessed using extracellular electrode recordings and optical imaging. In animals raised with an ON-center blockade starting after visual cortical cells are visually driven but still poorly tuned for orientation, cortical cell responsivity was maintained, but no maturation of orientation selectivity was seen. No recovery of orientation tuning was seen in animals treated with APB during the normal period of orientation development and then allowed several months of development without treatment. These results suggest that patterns of neuronal activity carried in the separate ON- and OFF-center visual pathways are necessary for the development of orientation selectivity in visual cortical neurons of the ferret and that there is a critical period for this development.

Aminobutyrates↗
PubMed1986

Beta-nerve growth factor in developing mouse cerebral cortical synaptosomes: measurement by competitive radioimmunoassay and bioassay.

The existence of beta-nerve growth factor (beta NGF) in mouse cerebral cortical synaptosomal extracts was assessed using a newly developed radioimmunoassay and by bioassay. Displacement curves of labeled beta NGF in the radioimmunoassay by synaptosomal extracts were parallel to the beta NGF standard curves. In contrast, both mitochondrial and nonsynaptosomal extracts produced displacement curves in the beta NGF radioimmunoassay which were nonparallel to standard beta NGF. Intraventricular injections of purified beta NGF in amounts 5 and 100 ng/mouse (six to 120 times that of whole brain beta NGF concentrations) did not alter the endogenous synaptosomal beta NGF concentrations. Synaptosomal extracts contained beta NGF in relatively higher concentrations than the extracts of whole brain or cerebral cortex. Synaptosomal beta NGF levels undergo a developmental change. The beta NGF concentrations were highest in synaptosomal extracts of 12-day-old mouse cerebral cortex (the youngest age studied), and levels decreased with increasing age. Synaptosomal extracts of 12-day-old mouse cerebral cortex produced neurite outgrowth in the pheochromocytoma cell line 12 bioassay system and this response was completely inhibited by beta NGF antibodies. In the pheochromocytoma cell line 12 cell bioassay, synaptosomal extracts also caused cell-cell aggregation which was unaffected by beta NGF antibodies. These results provide evidence for the existence of beta NGF in relatively high concentration in nerve terminals of mouse cerebral cortex.

Animals↗
PubMed2003

Dual regulated RNA transport pathways to the cortical region in developing rice endosperm.

Prolamine and glutelin RNAs are localized to two subdomains of the cortical endoplasmic reticulum (ER), the protein body ER and the cisternal ER, in developing rice seeds. The addition of nearly full-length prolamine sequences at the 3' untranslated region of a reporter RNA redirects its localization from the cisternal ER to the protein body ER. Deletion analysis of prolamine RNA sequences indicates the presence of two partially redundant cis elements required for protein body ER targeting. The addition of glutelin 3' untranslated region to protein body ER cis sequences, however, redirects RNA localization to the cisternal ER. These results indicate that there are at least two regulated RNA transport pathways as well as a constitutive pathway to the cortical ER.

3' Untranslated Regions↗
PubMed1990

Glutamate toxicity in immature cortical neurons precedes development of glutamate receptor currents.

Cationic fluxes resulting from glutamate receptor activity have recently been implicated in neurotoxicity. Immature cortical neurons are insensitive to the toxic effects of glutamate receptor stimulation. However, these neurons are killed by glutamate via a non-receptor-mediated mechanism thought to stem from glutamate's ability to inhibit cystine uptake. To examine the basis for their resistance to receptor-mediated toxicity, we have studied the development of glutamate receptor-mediated inward currents in cortical neurons in culture using the whole-cell voltage-clamp technique. We report that in immature cortical neurons (prepared from day-17 fetal brain and cultured for 1-3 days), N-methyl-D-aspartate, quisqualate, and glutamate are able to evoke only very small inward currents in a low percentage of neurons. After 7 days of culture, greater than 80% of neurons examined exhibited currents activated by these glutamate receptor agonists. Although most neurons expressed glutamate agonist-evoked currents after 7 days in culture, the amplitude of these currents was less than 10% of that observed after 15 days in culture. In contrast to currents activated by glutamate receptor agonists, those activated by gamma-aminobutyric acid reached maximal levels after only 2 days of culture. These results indicate that the delayed development of glutamate receptor-mediated currents accounts for the resistance of immature cortical neurons to glutamate receptor-mediated toxicity.

Animals↗
PubMed2003

Loss of Emx2 function leads to ectopic expression of Wnt1 in the developing telencephalon and cortical dysplasia.

Leptomeningeal glioneuronal heterotopias are a focal type of cortical dysplasia in which neural cells migrate aberrantly into superficial layers of the cerebral cortex and meninges. These heterotopias are frequently observed as microscopic abnormalities in the brains of individuals with central nervous system (CNS) malformations and epilepsy. Previous work has demonstrated that the function of Emx2, which encodes a homeodomain transcription factor, is essential for development of the cortical preplate, which gives rise to the marginal zone and subplate. However, transcriptional targets of EMX2 during CNS development are unknown. We report that leptomeningeal glioneuronal heterotopias form in Emx2(-/-) mice that are equivalent to human lesions. Additionally, we observed ectopic expression of Wnt1 in the embryonic roofplate organizer region and dorsal telencephalon. To determine the phenotypic consequences of such Wnt1 misexpression, we deleted a putative EMX2 DNA-binding site from the Wnt1 enhancer and used this to misexpress Wnt1 in the developing murine CNS. Heterotopias were detected in transgenic mice as early as 13.5 days postcoitum, consistent with a defect of preplate development during early phases of radial neuronal migration. Furthermore, we observed diffuse abnormalities of reelin- and calretinin-positive cell populations in the marginal zone and subplate similar to those observed in Emx2-null animals. Taken together, these findings indicate that EMX2 is a direct repressor of Wnt1 expression in the developing mammalian telencephalon. They further suggest that EMX2-Wnt1 interactions are essential for normal development of preplate derivatives in the mammalian cerebral cortex.

Animals↗
PubMedDate not supplied

Malformation of cortical and vascular development in one family with parietal foramina determined by an ALX4 homeobox gene mutation.

Vascular and cortical anomalies have been found in a family with parietal foramina type 2 (PFM2), which is determined by the ALX4 gene. It is believed that ALX4 has a bone-restricted expression. We report a case of PFM with age-related size variation in a 4-year-old boy, as well as in his mother, aunt and grandfather. MR imaging of the child demonstrates prominent malformations of cortical (polymicrogyric cortex with an unusual infolding pattern) and vascular development (persistence median prosencephalic vein), associated with high tentorial incisure periatrial white matter changes.

Abnormalities, Multiple↗
PubMed1986

An autoradiographic study of the postnatal development of pericruciate cortical projections to the neostriatum and the claustrum of the cat.

The postnatal development of corticostriatal and corticoclaustral projections was traced by light-microscopic autoradiography following injections of tritiated proline and leucine into the pericruciate cortex of kittens, 2-56 days of age, and adult cats. A medial-lateral topography of the corticostriatal pathways was present at birth, with a smaller and more restricted projection arising from the lateral pericruciate region. During postnatal development, the volume of the ipsilateral caudate nucleus filled by labelled corticostriatal fibers was reduced by 30% and these projections became constricted within the dorsolateral head and body of the caudate nucleus. During the first postnatal week, terminal fields were diffuse but lacked homogeneity since irregular patches of intensely labelled elements clustered near the internal capsule. By the end of the first month, a fenestrated organization became apparent within the caudate nucleus where elongated clusters of intensely labelled fibers radiated from the internal capsule and partially or completely surrounded islands of neuropil virtually devoid of label. Pericruciate inputs were confined to the dorsal parts of the rostral putamen and claustrum and the patchy nature of these terminal fields was limited to small labelled clusters close to the capsular margins. Contralateral terminal fields were labelled less intensely and occupied areas symmetrical to those within the ipsilateral neostriatum and claustrum.

Amino Acids↗
PubMed1998

Cortical and cognitive development in 4th, 8th and 12th grade students. The contribution of speed of processing and executive functioning to cognitive development.

This study investigated cortical/cognitive relations in 30 4th, 8th and 12th grade students. All students were administered the Figural Intersection Test, a measure of cognitive development, and performed, three times with different targets, an event-related potential (ERP) oddball/selective-attention task. Two independent factors emerged from the ERP task that predicted development--speed of processing (P300 latency to Block 1 targets) and maturation of executive functioning (a composite ERP variable calculated as the ratio of RT and P300 latency divided by the accuracy to Block 2 targets). These two variables loaded on orthogonal factors in a principal components analysis, and were the only variables included in a stepwise regression of physiological variables on cognitive development. Speed of processing is modulated by myelination and synaptogenesis, and executive functioning is modulated by maturation of the frontal system. These electrophysiological markers could index these cortical transformations underlying cognitive development.

Adolescent↗
PubMed1982

The early involvement of subcortical structures during the development of a cortical seizure focus.

Cortical surface electrodes and bipolar depth electrodes were implanted stereotaxically in the ventral posterolateral and paracentral thalamic nuclei, amygdala, hippocampus, and putamen in adult cats to determine the progressive involvement of these structures in the generalization of an experimentally induced seizure disorder. Prior to (45-65 days) and following (50-70 days) subpial injection of 0.04 ml of aluminum hydroxide in the sensorimotor cortex, 30 min EEG records were obtained regularly in each animal. At the time of aluminum hydroxide injection, there was no persistent abnormal EEG activity resulting from electrode implantation. In all animals, intermittent slow waves and epileptiform activity appeared in subcortical or extrafocal structures prior to the development of epileptiform activity in the primary focus. These abnormalities were frequently associated with brief clinical seizures and were clearly independent of abnormal activity in the primary focus. Only later in the development of the seizure disorder was activity in the secondary foci observed to be dependent on frequent epileptiform activity in the primary focus. These results demonstrate that multiple, independent foci develop in subcortical structures before the occurrence of a well developed, fully "mature" cortical primary focus.

Aluminum Hydroxide↗