Cortical Cytoarchitecture Research Articles

Double Labeling of Proliferating Neurons with Anti-BrdU and Anti-NeuN: An Improved Immunohistochemical Technique Utilizing Microwave Irradiation

The authors describe a double labeling immunohistochemical technique to facilitate the study of neuronal proliferation and migration. Proliferating fetal neuroblasts were labeled with 5-bromo-2′-deoxyuridine (BrdU), and the labeled mature neurons were identified with a monoclonal anti-BrdU antibody. To differentiate neurons from glia, the tissue was also treated with monoclonal anti-NeuN, an antibody that detects a nuclear antigen unique to neurons. Novel aspects of this procedure are the utilization of methacarn fixation of tissues and the denaturation of BrdUlabeled DNA with microwave irradiation rather than with either acid or alkali denaturation treatments. This method produces strong immunoreactivity for both BrdU labeled neurons and neurons reacting with anti-NeuN, thereby facilitating the quantitative study of the development of cortical cytoarchitecture. (The J Histotechnol 21:201–204, 1998)

Stem cells in the embryonic cerebral cortex: Their role in histogenesis and patterning

The cytoarchitectural simplicity of the cerebral cortex makes it an attractive system to study central nervous system (CNS) histogenesis--the process whereby diverse cells are generated in the right numbers at the appropriate place and time. Recently, multipotent stem cells have been implicated in this process, as progenitor cells for diverse types of cortical neurons and glia. Continuous analysis of stem cell clone development reveals stereotyped division patterns within their lineage trees, highly reminiscent of neural lineage trees in arthropods and Caenorhabditis elegans. Given that these division patterns play a critical part in generating diverse neural types in invertebrates, we speculate that they play a similar role in the cortex. Because stereotyped lineage trees can be observed from cells growing at clonal density, cell-intrinsic factors are likely to have a key role in stem cell behavior. Cortical stem cells also respond to environmental signals to alter the types of cells they generate, providing the means for feedback regulation on the germinal zone. Evidence is accumulating that cortical stem cells, influenced by intrinsic programs and environmental signals, actually change with development-for example, by reducing the number and types of neurons they produce. Age-related changes in the stem cell population may have a critical role in orchestrating development; whether these cells truly self-renew is a point of discussion. In summary, we propose that cortical stem cells are the focus of regulatory mechanisms central to the development of the cortical cytoarchitecture.

Stem cells in the embryonic cerebral cortex: Their role in histogenesis and patterning

The cytoarchitectural simplicity of the cerebral cortex makes it an attractive system to study central nervous system (CNS) histogenesis—the process whereby diverse cells are generated in the right numbers at the appropriate place and time. Recently, multipotent stem cells have been implicated in this process, as progenitor cells for diverse types of cortical neurons and glia. Continuous analysis of stem cell clone development reveals stereotyped division patterns within their lineage trees, highly reminiscent of neural lineage trees in arthropods and Caenorhabditis elegans. Given that these division patterns play a critical part in generating diverse neural types in invertebrates, we speculate that they play a similar role in the cortex. Because stereotyped lineage trees can be observed from cells growing at clonal density, cell-intrinsic factors are likely to have a key role in stem cell behavior. Cortical stem cells also respond to environmental signals to alter the types of cells they generate, providing the means for feedback regulation on the germinal zone. Evidence is accumulating that cortical stem cells, influenced by intrinsic programs and environmental signals, actually change with development—for example, by reducing the number and types of neurons they produce. Age-related changes in the stem cell population may have a critical role in orchestrating development; whether these cells truly self-renew is a point of discussion. In summary, we propose that cortical stem cells are the focus of regulatory mechanisms central to the development of the cortical cytoarchitecture. © 1998 John Wiley & Sons, Inc. J Neurobiol 36: 162–174, 1998

Transplantation of fetal neocortex ameliorates sensorimotor and locomotor deficits following neonatal ischemic-hypoxic brain injury in rats.

Ischemic brain injury in neonates can result in the degeneration of cortical and subcortical areas of brain and is associated with neurologic deficits. One approach to restoring function in conditions of ischemic brain injury is the use of neural transplants to repair damaged connections. This approach has been shown to reestablish neural circuitry and to ameliorate associated motor deficits in models of neonatal sensorimotor cortex damage. In this study, we utilized the Rice et al. rodent model of neonatal ischemic-hypoxic (IH) brain injury to assess whether transplantation of fetal neocortical tissue can promote functional recovery in tests of sensorimotor and locomotor ability throughout development and as adults. We show that animals that received neocortical grafts 3 days following the IH injury performed significantly better as adults on two measures of motor ability, the Rota-Rod treadmill and apomorphine-induced rotations, than did control animals that received sham transplants after the IH injury. Transplants were identifiable in 72% of the animals 10-12 weeks after implantation. Histochemical studies revealed that while the transplanted tissue did not establish normal cortical cytoarchitecture, cells and fibers within the grafts stained for nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d), choline acetyl transferase (ChAT), cholecystokinin (CCK), and glial fibrillary acidic protein (GFAP). These results suggest that transplantation of fetal neocortical tissue following IH injury in the neonatal period is associated with amelioration of motor deficits and that the grafted tissue demonstrated a neurochemical phenotype that resembled normal neocortex. This approach warrants continued investigation in light of potential therapeutic uses.

Aspartylglucosaminuria: radiologic course of the disease with histopathologic correlation.

Twelve living patients (aged 19 months to 32 years) with aspartylglucosaminuria were examined by magnetic resonance imaging (MRI), and the magnetic resonance (MR) images of 16 health volunteers (aged 4 to 32 years) were used as controls. One patient was examined twice. Postmortem MRI and histopathologic analysis were done on the brains of four additional adult patients. Signal intensities determined quantitatively on T2-weighted images differed significantly between patients and controls, being higher from the white matter (P < .0002) and lower from the thalami (P < .03) in the patients. The generally increased signal intensity of the white matter was most obvious in the young patients, with many focal areas of very high signal intensity in the subcortical white matter. The subcortical white matter showed a somewhat increased signal intensity even at the age of 32 years. In two of the four postmortem MR images, the distinction between the gray and white matter was still poor. At histopathologic analysis, the basic cortical cytoarchitecture was generally preserved but most neurons contained vacuoles, which were also found in the neurons of the deep gray matter. In two of the four autopsy cases the white matter showed diffuse pallor of myelin staining and some gliosis. Thus aspartylglucosaminuria is primarily a gray-matter disease also affecting white matter by delaying myelination.

Implants for sustained drug release over the somatosensory cortex of the newborn rat: a comparison of materials and surgical procedures

Drugs that interfere with neural transmission are an important tool in assessing the role of specific neurotransmitters in the development of the nervous system. Systemic drug treatments often produce neurodevelopmental effects with questionable specificity. Furthermore, many compounds of interest do not cross the blood-brain barrier. To overcome these limitations, either elvax or gelfoam implants have been previously employed to produce sustained drug release over specific brain regions. In this paper, stereotaxic coordinates are provided for reproducible insertion of drug-delivery systems over the rat somatosensory cortex at birth (P0), prior to the appearance of the cortical barrel pattern; a novel and simpler method for preparation of elvax 40p sheets is described; a new implantation technique is provided. Furthermore, we compare the efficiency and tolerability of elvax vs gelfoam implants, showing that gelfoam, but not elvax, significantly disrupts cortical cytoarchitecture. Finally, successful destruction of serotonin-containing terminals in layer IV of the primary somatosensory cortex of the newborn rat is demonstrated by application of parachloroamphetamine-containing elvax implants.

Radiation-induced, lamina-specific deletion of neurons in the primate visual cortex.

To examine the early determinants of cortical cytoarchitecture, we deleted specific neuronal classes in the primate visual cortex by ionizing irradiation at selected prenatal stages. Multiple doses of X-rays were delivered to the macaque monkey brain between embryonic day (E) 80 and E90 to block the division of cells destined to populate the superficial cortical layers, between E70 and E79 to eliminate neurons destined for the middle layers; and between E33 and E40 to delete neurons destined for the lateral geniculate nucleus (LGN) that project to the cortex. All animals were killed after birth, and their brains were processed for histological and electron microscopic analyses. Cell density and number in the LGN and visual cortex were determined by using three-dimensional, computer-aided morphometry. In animals irradiated with low doses (total of approximately 200 cGy) during the genesis of the LGN but before the onset of corticogenesis (E33-40), the LGN was reduced in both volume and number of neurons. Area 17 in these animals displayed only slight changes in cortical thickness, cell density, and area-specific cytoarchitectonic features, whereas the total surface devoted to area 17 was significantly diminished. In contrast, animals irradiated with low doses during the period of corticogenesis, after the completion of the LGN genesis, showed no significant change in the volume of the LGN or in the number of its cells. Moreover, in these animals, the surface of area 17 was not significantly altered, although the cortical layers generated at the time of irradiation had a significantly lower density and total number of cells, whereas the layers generated before and after the period of irradiation were spared. In contrast, cases exposed to high doses of X-ray (total > 300 cGy) showed more severe effects, including all layers. However, layers normally generated during irradiation were depleted and consisted of cell-sparse strata populated by densely packed neuropil (axons, small dendrites, dendritic spines, and synaptic boutons). These cell-sparse strata were situated deeper in the early irradiated animals than in the later irradiated animals, and their laminar position changed abruptly at the area 17/18 border. These results show that low doses of irradiation in a slowly developing primate brain can be used effectively to eliminate targeted classes of neurons before they reach their final position, providing an opportunity to examine the role of cell-cell interactions in the formation of circuitry and the role of specific cell classes in cortical development.

A two-process theory of schizophrenia: Evidence from studies in post-mortem brain

Glutamate and GABA are the principle neurotransmitters of the cerebral cortex and are known to modulate dopaminergic function. Evidence of structural abnormalities in the cortex raises the possibility that schizophrenia involves disturbances of cortical amino-acid neurotransmission. The psychotomimetic effects of phencyclidine, a glutamate antagonist, have been taken to suggest that schizophrenia involves reduced brain glutamate function. Direct evidence for diminished glutamate function in schizophrenia is lacking. However, in polar temporal cortex and hippocampus we reported evidence of an asymmetric loss of glutamate terminals, and of reduced GABA function, which may be secondary to the loss of glutamatergic input. Glutamate cell body markers are spared in temporal lobe; the neurones which degenerate may originate in frontal cortex. A number of studies have reported increases in markers of glutamatergic cell bodies and terminals in orbital frontal cortex in schizophrenia. These findings are consistent with the presence of an abnormally abundant glutamatergic innervation, which may be the result of an arrest in the normal process of cellular and synaptic elimination which occurs during development. There is evidence that frontal abnormalities in schizophrenia are genetically determined. We suggest that glutamatergic abnormalities in anterior temporal cortex in schizophrenia are the result of the degeneration of fronto-temporal projections. Orbital frontal projections to polar temporal cortex may be prone to degeneration because they arise from an unstable frontal cortical cytoarchitecture which has not completed the normal process of post-natal remodelling. The structural abnormality of the orbital frontal region may confer vulnerability to some intrinsic or extrinsic mechanism, which brings about a progressive degeneration of projections to polar temporal lobe.

Intrauterine cocaine exposure of rabbits: persistent elevation of GABA-immunoreactive neurons in anterior cingulate cortex but not visual cortex

The effects of prenatal cocaine exposure on the development of the rabbit cerebral cortex were studied. Two cortical areas were compared: primary visual cortex (VC) and anterior cingulate (ACC). ACC was selected because behavioral deficits observed in cocaine-exposed infants suggest the involvement of ACC. In addition, ACC receives dense dopaminergic innervation and cocaine's action in inhibiting the re-uptake of dopamine is believed to underly the rewarding properties of cocaine. VC was selected as a control area because there is no evidence of behavioral deficits associated with visual perception in cocaine-exposed infants, and because VC receives minimal dopaminergic innervation. Two aspects of cortical development was studied: (i) cortical morphology, growth and cytoarchitectonic organization; and (ii) the development of the GABAergic neurotransmitter system. Measures of postnatal cortical growth, including cortical lamination, cell number and soma size, were compared in cocaine-exposed or control (saline) rabbits aged P5–P60. There was no difference between cocaine and saline animals in any of these parameters, and cortical cytoarchitecture appeared normal. However, despite the absence of major abnormalities in cortical development, we found that the number of GABA-immunoreactive neurons in cocaine-exposed animals was significantly higher than normal in ACC. This effect was highly consistent, was present in all laminae and at all ages studied, and persisted into maturity (P60). In contrast, in VC, the number of GABA-immunoreactive neurons in cocaine-exposed animals did not differ from normal. We suggest that increased GABA immunoreactivity may reflect a compensatory response to excessive excitatory input to ACC. A change in the balance of excitation and inhibition in ACC, reflecting ‘noisy’ or dysfunctional intracortical circuitry, may underly the emotional lability and attentional deficits characteristically described in infants exposed in utero to cocaine.

The early development of thalamocortical and corticothalarnic projections

The early development of thalamocortical and corticothalamic projections in hamsters was studied to compare the specificity and maturation of these pathways, and to identify potential sources of information for specification of cortical areas. The cells that constitute these projections are both generated prenatally in hamsters and they make reciprocal connections. Fluorescent dyes (DiI and DiA) were injected into the visual cortex or lateral geniculate nucleus in fixed brains of fetal and postnatal pups. Several issues in axonal development were examined, including timing of axon outgrowth and target invasion, projection specificity, the spatial relationship between the two pathways, and the connections of subplate cells. Thalamic projections arrive in the visual cortex 2 days before birth and begin to invade the developing cortical plate by the next day. Few processes invade inappropriate cortical regions. By postnatal day 7 their laminar position is similar to mature animals. By contrast, visual cortical axons from subplate and layer 6 cells reach posterior thalamus at 1 day after birth in small numbers. By 3 days after birth many layer 5 cell projections reach the posterior thalamus. On postnatal day 7, there is a sudden increase in the number of layer 6 projections to the thalamus. Surprisingly, these layer 6 cells are precisely topographically mapped with colabeled thalamic afferents on their first appearance. Subplate cells constitute a very small component of the corticothalamic projection at all ages. Double injections of DiI and DiA show that the corticofugal and thalamocortical pathways are physically separate during development. Corticofugal axons travel deep in the intermediate zone to the thalamic axons and are separate through much of the internal capsule. Their tangential distribution is also distinct. The early appearance of the thalamocortical pathway is consistent with an organizational role in the specification of some features of cortical cytoarchitecture. The specific initial projection of thalamocortical axons strongly suggests the recognition of particular cortical regions. The physical separation of these two pathways limits the possibility for exchange of information between these systems except at their respective targets.

The contribution of arachidonic acid to the aetiology and pathophysiology of focal brain oedema; studies using an infusion oedema model

Arachidonic acid solution (2 to 15 mg/ml) was infused into the right forebrain white matter of anaesthetised cats over three hours to evaluate its contribution to the genesis and pathophysiology of vasogenic brain oedema. The 0.6 ml infusion increased local white matter water content by a mean of 11.3 ml/100 g tissue but did not increase cortical water content. Histological studies revealed local expansion and trabeculation of the white matter with aggregations of granulocytic neutrophils in the venules and perivenular brain. The adjacent cortical cytoarchitecture was normal. The white matter around the infusion site was stained lightly and over a variable area (15-20 mm2) by intravenously administered Evans Blue dye 2%. Regional cerebral blood flow (rCBF) adjacent to the frontal infusion did not change significantly during the period of infusion and remained similar to rCBF in the contralateral hemisphere. Following the arachidonic acid infusion regional CBF CO2 reactivity was normal and three was no asymmetry of either cortical somatosensory evoked potential (SEP) or motor evoked potential (MEP) waveforms. The increase in brain water content and changes in the ICP and ICP related biodynamics (pressure-volume index, lumped craniospinal compliance and CSF outflow resistance) were similar to those seen following infusion of 0.6 ml saline. These studies suggest that free intraparenchymal arachidonic acid, at concentrations exceeding those occurring in most neuropathological conditions, can increase the normal brain parenchymal capillary permeability but does not disrupt focal cerebrovascular and electrophysiological function. The clinical implications of these findings are discussed.

Efferent and Afferent Connections of Mouse Sensory-Motor Cortex Following Cholinergic Deafferentation at Birth

The present study investigates the effect of cholinergic basal forebrain lesions at birth on cortical connectivity in adulthood. We have previously shown that such neonatal lesions result in extensive cortical cholinergic deafferentation during early postnatal development, which is accompanied by abnormal morphogenesis of cortical cytoarchitecture (Höhmann at al., 1988). Here, we have used WGA-HRP to label anterogradely and retrogradely afferent and efferent projections of dorsal neocortex. Our results show an altered projection pattern from dorsal thalamus to layer IV of sensory-motor cortex following lesions among the cholinergic basal forebrain neurons (nBM), while corticothalamic projections from layer VI appear normal. In addition, corticofugal projections from layer V, labeled by striatal injection, appear to be expanded following the lesion. This indicates that cortical layers undergoing differentiation after the newborn nBM lesion present with long-term abnormalities in connectivity. The present results are compatible with the hypothesis that cholinergic afferents are instrumental in the regulation of cortical morphogenesis. Furthermore, our data show that ontogenetic disturbances can lead to structural abnormalities that persist long after the initial deficiency has abated. We discuss the significance of these results in relationship to human neurological disorders.

Thalamic Ablations and Neocortical Development: Alterations of Cortical Cytoarchitecture and Cell Number

The diversity of neocortical cytoarchitecture could arise from genetic prespecification of cell types and numbers in the ventricular zone, by interaction of cells with their immediate environment, efferent targets, or afferent inputs. Here, we examine the role of the thalamus as efferent target or afferent source in the early control of cell number and type in the developing neocortex. Electrolytic lesions of the thalamus were made in hamsters at birth prior to the thalamic innervation of layer IV. By postnatal day 7, when migration to the cortex is complete, there were no differences in cell number between the cortical plate contralateral and ipsilateral to the thalamic lesion, showing that the absence of thalamic input does not influence the last phases of neocortical cell generation or migration. However, the incidence of pyknotic cells was elevated in the upper half of the cortical plate at this time. By adulthood, the number of cells per unit column of cortex was reduced, due to the apparent absence of small, nonpyramidal cells of layer IV, as determined from Nissl-stained material. Therefore, some of the cytoarchitectonic variability of the neocortex could arise epigenetically by the interaction of neocortical cells with their afferent connections.

The early effects of methylmercury on the developing rat brain

The effects of organic mercury compounds on the development of the brain are well known since the exposure of people at a large scale to methylmercury in the Minamata Bay area and in Iraq. The neuropathological examination of the brains of children prenatally exposed revealed dysplasia of the cerebral and cerebellar cortex, neuronal ectopia and several other developmental disturbances. In this experimental study we examined developmental mechanisms involved in methylmercury-induced cerebral anomalies. By examining the fetuses soon after treatment we concentrated in the initial effects of the treatment. The pregnant rats were given 10 mg/kg methylmercury chloride i.p. on day 18. Already at 2 h after administration mitochondrial degeneration occurred in the endothelium of the cerebral capillaries. Subsequently hemorrhages developed interfering with the cellular arrangement in the ventricular zone, with neuronal migration in the intermediate zone and with the development of the cortical cytoarchitecture. Macrophages and cavities appeared in the hemorrhagic areas. It is suggested that the abnormalities seen in the experiments can be considered as the initial methylmercury-induced effects which, in combination with various other toxic effects, ultimately result in the anomalies that have been observed in the brains of children prenatally exposed to methylmercury.

Intrinsic connections and architectonics of the superior temporal sulcus in the rhesus monkey

The intrinsic connections of the superior temporal sulcus (STS) in the rhesus monkey were studied by anterograde and retrograde tracer techniques and correlated with a reevaluation of cortical cytoarchitecture. The polymodal region in the upper bank (area TPO) is divisible into four rostral-to-caudal architectonic sectors, exhibiting increasing degrees of laminar differentiation and cellularity as one proceeds caudally. These sectors, including the sulcal proisocortex (area Pro), are tied together in a sequence of reciprocal connections. Each rostrocaudal sector of area TPO also has reciprocal connections with the laterally adjacent area TAa, at the upper rim of the sulcus, and medially adjacent areas PGa and IPa, near the depth. A similar arachitectonic/connectional organization exists for unimodal vision-related cortex in the lower bank of the STS. Here a rostrocaudal sequence of reciprocal connections unites area Pro, rostral and caudal divisions of area TEa, and the extrastriate visual area OAa (MT). Area TEa also has reciprocal connections with adjacent segments of area TEm laterally, at the lower rim of the sulcus, and area IPa, medially, in the depth. In both upper and lower banks, caudal-to-rostral "forwardgoing" connections begin in supragranular layers of cortex and terminate in and around layer IV. Reciprocal, "backgoing" connections take origin from cells in infragranular layers and terminate mainly over the first layer of the caudally adjacent target zone. Orthogonally directed, "side-to-side" projections originate in both supra- and infragranular layers and terminate diffusely over all layers of cortex.

Neonatal lesions of the basal forebrain cholinergic neurons result in abnormal cortical development

The effect of electrolytic lesions of the neonatal forebrain on the morphogenesis of the mouse neocortex has been examined. Balb/C mice were lesioned unilaterally within 24 h of birth. The development of cortical cytoarchitecture was assessed in Nissl-stained sections, and the levels of presynaptic markers for cholinergic, noradrenergic and serotonergic afferents were measured in the fronto-parietal cortex ipsilateral and contralateral to the lesion at various postnatal ages and in adulthood. The basal forebrain (nBM) lesion resulted in a transient but severe reduction of cortical cholinergic markers and in abnormal cortical cytoarchitecture. Cytoarchitectural abnormalities were expressed as delay in the emergence of differentiated cell populations and affected sequentially more superficial layers with maturation following lesion. Furthermore, the location and extent of these morphologic abnormalities appeared to correlate with the degree of cholinergic denervation. Cortical monoamines were also temporarily reduced as a result of the lesion; however, pharmacologic lesions of the monoaminergic projections alone did not result in the abnormal cortical cytoarchitecture. Thus, the basal forebrain cholinergic projection appears to serve a role in regulating cortical differentiation.

A modular arrangement of neuronal processes in human cortex: disruption with aging and in Alzheimer's disease.

Studies were undertaken to assess whether or not neuron-specific immunostaining of the human brain can reveal unique cytoarchitectural features that may be affected by healthy aging and Alzheimer's disease (AD). Human prefrontal cortex (PFC) and anterior cingulate cortex (ACC) were stained with an antibody raised against the neurofilament protein 200,000 molecular weight subunit (NFP-200) using an avidin-biotin immunolocalization procedure. Immunostaining of cortex was neuron-specific and highlighted axons in particular. This staining has revealed an orderly arrangement of horizontal and vertical axon bundles which form latticelike compartments or modules throughout most of the matrix of the two cortical areas studied. The ACC shows this pattern to be intact in individuals through the ninth decade, while the PFC there was blurring of the modularity beyond the fifth decade. Irrespective of the age-related blurring of the latticelike arrangement of axons in PFC, neurologically normal elderly individuals nevertheless showed a highly organized appearance to the cortical matrix. By contrast, patients with AD showed a marked disruption of the modular arrangement of fibers in PFC, but not ACC. Differences between PFC fibers in controls and AD patients were also demonstrated with an axon-specific monoclonal antibody that reacted with phosphorylated epitopes of the NFP-200. The chaotic appearance of fiber staining in PFC seen in patients with AD was noted to be present in one subject who died in an early stage of the disease. The possible significance of this previously unknown aspect of cortical cytoarchitecture for normal cognitive functioning in humans is discussed.

Corticocortical connections of area 2 of somatosensory cortex in macaque monkeys: a correlative anatomical and electrophysiological study.

The cortical connections of electrophysiologically identified locations in the body representations in somatosensory cortex of macaque monkeys were investigated after injections of horseradish peroxidase, wheat germ agglutinin (WGA) conjugated with horseradish peroxidase, tritiated WGA, or tritiated proline. After extensive microelectrode mapping of portions of the body representations in areas 3b, 1, 2, and 5 and careful determinations of electrophysiological borders between areas, restricted injections of tracers were placed, usually into the representation of the hand in area 2. Other injections were placed in the foot representation in area 2 or in area 1, in the wrist representation in area 1, and in the forearm and wrist representation in area 5. Connection patterns were related to the physiological mapping results and to cortical cytoarchitecture. Injections confined to a lateral portion of area 2 representing the glabrous digits of the hand revealed reciprocal connections with the digit representations in areas 1 and 3b. Projections to area 2 were largely from layer III neurons in both of these fields, and return projections terminated largely in supragranular layers. Other inputs were from layer III cells in one or more separate locations in area 5 and in one or more closely spaced foci in the expected location of S-II in the lateral sulcus. These connections were also reciprocal with terminations apparent in layers IV and III. A few neurons in area 4 were labeled in some of these cases. Results were similar after an injection in the foot representation in area 2 with the differences that infragranular neurons, in addition to supragranular neurons, formed a substantial part of the projection to area 2, terminations as well as projections were noted from area 4, interconnections were found more rostrally in area 6, and a dense focus of label was apparent in the dorsal bank of cingulate sulcus in the apparent location of the supplementary motor area. Injections in the foot representation in area 1 revealed dense layer IV terminations in the foot representation in area 2, as well as connections with area 3b, the S-II region, and areas 5 and 7. The injection in the wrist representation in area 1 resulted in dense terminations in the portion of area 5 responsive to the distal forearm and hand, sparser connections with a lateral location in part of area 2 related to the hand, and interconnections with 3b and S-II.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunostaining of neurofilament protein in human postmortem cortex: a sensitive and specific approach to the pattern analysis of human cortical cytoarchitecture.

Antibodies raised against the 200 000 neurofilament protein (NFP) of rat brain have been successfully applied to the staining of human postmortem cortex using a modified immunoperoxidase procedure. Human anterior cingulate cortex which has been in formaldehyde fixative for as long as 4 years shows extensive and reliable staining of axons and, to a lesser degree, apical dendrites of cortical neurons. The immunostaining of 200 000 NFP in human cortex has revealed cytoarchitectural details not generally visible with other more conventional neuroanatomical stains, particularly when counterstaining with cresyl violet is employed. Potential applications of this approach to the pattern analysis of human cortical cytoarchitecture in both health and disease are discussed.

The vascularization of the human cerebellar cortex

The blood vessels of the cerebellar cortex were studied by two methods of injection: india-ink and low viscosity resin (Mercox). The study is divided into two parts: 1. (a) Pial vessels; few in number at the cerebellar surface, the pial vessels are quite dense, forming vascular laminae, within the sulci. Pial vessels do not frequently anastomose, 2. (b) Intracortical vessels closely resemble those of the cerebral cortex. They may be divided into three categories: short, middle and long. There exist three vascular layers within the cerebellar cortex: superficial, middle and deep. The superficial vascular layer is situated within the molecular layer, the middle within the Purkinje cell layer, and the deep within the granular layer. It is therefore possible to establish a correlation between these vascular layers and the cortical cytoarchitecture. We accorded particular attention to the vascularization of the Purkinje cells. Arteries parallel to the cerebellar surface (parallel arteries) are in close relationship to the Purkinje cells whereas capillaries and veins are scarce. It is highly probable that the majority of Purkinje cells obtain nutritive elements by these parallel arteries. Possible implications in physiology and pathology are subsequently discussed.