We have investigated the expression of Doublecortin (Dcx) protein in the developing cerebellum of mouse from postnatal 2nd day to postnatal 22nd day and in young adults by immunohistochemistry. Strong expression of Dcx was present in the inner zone of the external granule cell layer, and remained strong while postmitotic granule cell precursors were present in this transitory layer. Descending granule cell precursors exhibited Dcx immunostaining not only while migrating but for a short time also after their settlement. Dcx-immunostained cells appeared in deep cerebellocortical territories and in the cerebellar white matter during the first postnatal week. These bipolar cells were arranged in the sagittal plane and built up transitory migratory streams during the second postnatal week and their number gradually decreased during the third postnatal week. Upward migration of bipolar cells was observed while leaving the migratory streams, penetrating the internal granule cell layer and the molecular layer. These cells were considered as precursors of late migrating molecular layer interneurons. However, a proportion of Dcx-immunostained cells underwent a bipolar-to-multipolar dendritic remodellation and — on the basis of strong morphological similarities — was taken for “multipotent progenitor cells”, described recently in the neocortex of adult rat.

We have studied the temporal and spatial characteristics of the development of unipolar brush cells (UBCs) in the human cerebellar vermis. Consistently with previous studies in rodents and cat, we have found that unipolar brush cells appear at a relatively late phase of cerebellar development and their development continues up to and beyond the first postnatal year. A series of 23 normal human brains, including 5 adult and 18 fetal or infant brains (between the 24th gestational week and the 11th postnatal month) were used. In order to visualize unipolar brush cells, calretinin-immunocytochemistry was performed on formaldehyde-fixed, paraffin-embedded blocks of the cerebellar vermis. Our results show that calretinin-immunoreactive unipolar brush cells are not yet present in the cerebellar vermis at the 28th gestational week. At birth, they are present in a relatively small number, mostly in the vestibular lobules. At the 3rd, 5th, 8.5th and 11th postnatal months the number of calretinin-immunoreactive unipolar brush cells gradually increase, first appearing in the vestibular lobules, followed by the invasion of the later developing vermal lobules, spreading in a rostro-caudal and proximo-distal direction. Although at the 11th postnatal month unipolar brush cells exhibited adult-like morphological and distributional features, their number appeared to be lower than in the adult cerebellum. The late maturation of unipolar brush cells implies that the cytoarchitectonical development of the human cerebellum is not completed by the end of the first postnatal year.

The postnatal development of the ganglionic (Purkinje) layer was studied in the mouse cerebellum from P0 to young adulthood with special emphasis to vermal lobules VI-VII (oculomotor vermis) in the mouse. In order to visualize Purkinje cells (PCs), toluidine blue staining of resin-embedded semithin sections and calbindin immunohistochemistry were utilized. The number of PCs in the whole cerebellum was 199,080+/-2966 at postnatal day eight (P8), 222,000+/-2979 at P20 and nearly the same, 225,800+/-7549 in young adults; i.e., there was an approximately 13.4% increase of PCs between P8 and adults. The number of PC somata aligned into a rostrocaudal stripe along the developing ganglionic layer increased by about 24% in vermal cerebellar lobule III but much more markedly (i.e., by 49%) in VI+VII between P6 and young adulthood. Between P6 and P16, the increase of the number of PCs in the ganglionic layer of lobules VI and VII resulted in the (delayed) completion of PC layer, caused by the (late) alignment of rostrocaudally dispersed PCs, although late postnatal migration of a smaller population of these cells cannot be excluded either. It is concluded that the oculomotor vermis belongs to the latest developing cerebellar cortical structures, which could be the reason for its frequent involvement in developmentally related disturbances and disorders.

We have studied the postnatal quantitative changes of cortical Purkinje neurons in the cerebellum of the cat at the following postnatal groups of age: P0, P42, P72 and adults. An unbiased counting method, the optical fractionator was used for the estimation of Purkinje cell numbers. A significant increase of Purkinje cell number was found between P0 (1.097×106) and P42/P72 (1.805×106 and 1.895×106) declining to 1.429×106 in the adult, still 30% higher than in the newborn. It was also observed that during the first few postnatal weeks large “gaps” were present in the Purkinje monolayer as revealed by Nissl staining and metabotropic glutamate receptor 1α immunocytochemistry. These Purkinje cell gaps were observed most frequently in well-definable areas, especially in the intermediate zone of the neocerebellum. Simultaneously with the numerical increase of Purkinje neurons between the P0 and P72 age groups, these gaps disappeared after the third postnatal week resulting in the completion of the Purkinje monolayer in the whole cerebellum.

In this paper we demonstrate the potential of the cellular nonlinear/neural network paradigm (CNN) that of the analogic cellular computer architecture (called CNN Universal Machine CNN-UM) in modeling different parts and aspects of the nervous system. The structure of the living sensory systems and the CNN share a lot of features in common: local interconnections ("receptive field architecture"), nonlinear and delayed synapses for the processing tasks, the potentiality of feedback and using the advantages of both the analog and logic signal-processing mode. The results of more than ten years of cooperative work of many engineers and neurobiologists have been collected in an atlas: what we present here is a kind of selection from these studies emphasizing the flexibility of the CNN computing: visual, tactile and auditory modalities are concerned.

The number of neurons, both GABA immunopositive and immunonegative, was determined in temporal epileptic foci of 7 patients after temporal lobectomy, and compared to neuronal numbers in temporal cortex of two controls taken from tumor operated patients. The thickness of the cortex of the epileptic cortex diminished by about 10%, while the number of nerve cells decreased to 67% of that of the control value: it was 19.000/mm3 vs. 28.000/mm3 found in the control. This decline was due to cell degeneration, which, however, was more severe for non-GABAergic nerve cells. Accordingly, the proportion of the GABA-positive neurons in the othervise diminished neuronal population increased to 36.4% from the 32% control value. The number of GABAergic terminals, however, decreased even further, explaining the resulting disinhibition during epileptic seizures.

Morphology, distribution and number of unipolar brush cells (UBCs) was studied in the cerebellar vermal lobules I-X of the chicken, rat, guinea pig, cat, and monkey using monoclonal mGluR1a antibody as a marker to visualise these recently described nerve cells (Mugnaini and Floris [1994] J. Comp. Neural. 339:174-180; Mugnaini et al. [1994] Synapse 16:284-311). The morphological appearance of mGluR1a immunopositive UBCs is similar in all species investigated: they are small cells, having a single, relatively short and thick dendrite, terminating in brush-like dendrioles. Although this, probably excitatory, cell type can be found all over the cerebellar cortex, highest density of UBCs can be seen in the vermal cortex. The present study, therefore, was focused on the quantitative morphology and distribution of UBCs in the 10 lobules of the vermis. Calculating the number of UBCs/1 Purkinje cell (PC), we have found differences in this value (average in vermal lobules I-X) from 1.04 in rat, 1.10 in chicken, 1.16 in guinea pig, 2.27 in monkey, and up to 2.44 in cat. The highest density of UBCs was observed in lobules I, IX, and X, whereas the lowest number of UBCs/1 PC was found in lobules IV-VI (in the mammals) and in lobules VII-VIII (in the chicken). In mammals, particularly the monkey and cat, an increased presence of UBCs was observed in vermal sub-lobules VIc-VIIb,c, a region defined as the oculomotor vermis because of its role in the control of saccadic eye movement. There is also a basic difference between chicken and mammals in the distribution of UBCs within the lobules: in mammals, the lowest density of these nerve cells was found in the peripheral portion of the lobules, near to the pia, while in the chicken, in contrast, the density of UBCs was the highest subpially with fewer UBCs located in the deepest curvature of the lobules. Finally, the functional significance of the differences in the density and in the distribution pattern of UBCs in the cerebellar vermis between the phylogenetically different species; investigated is briefly discussed. (C) 1999 Wiley-Liss, Inc.

The origin of the corticothalamic projections to the contralateral mediodorsal nucleus, the collateralization of cortical fibers and their synaptic organization in the ipsi- and contralateral mediodorsal nuclei were investigated in adult rats with double retrograde fluorescent and anterograde tracing. After tracer injections in the mediodorsal nuclei on either side, neurons were retrogradely labeled in all the areas of the contralateral prefrontal cortex in which ipsilateral labeling was also observed. Contralateral corticothalamic cells accounted for 15% of the labeled neurons in the orbital and agranular insular areas, while their proportion was lower (3%) in the anterior cingulate cortex. Up to 70% of the contralateral cortical neurons were double labeled by bilateral injections in the mediodorsal nuclei. At the electron microscopic level, unilateral injections of biotinylated dextran-amine in the orbitofrontal cortex resulted in anterograde labeling of small terminals and a few large boutons in the ipsilateral mediodorsal nucleus, while only small boutons were identified contralaterally. The diameter of postsynaptic dendritic profiles contacted by labeled small cortical endings was significantly larger in the ipsilateral mediodorsal nucleus than contralaterally. These findings demonstrate that dense contralateral cortical projections to the mediodorsal nucleus derive from the orbital and agranular insular areas, and that crossed corticothalamic afferents are mostly formed by collaterals of the ipsilateral connections. Our observations also point out the heterogeneity of corticothalamic boutons in the rat mediodorsal nucleus and morphological differences in the synaptic organization of prefrontal fibers innervating the two sides, indicating that ipsilateral cortical afferents may be more proximally distributed than crossed cortical fibers on dendrites of mediodorsal neurons.

Deals with the biological aspects of the receptive field (RF) concept and its possible cellular neural network (CNN) modeling. Three kinds of receptive field definitions are discussed: the experimentally measured RF, the mathematical model of the RF and its anatomical background. Previously, new RF-mapping techniques have revealed that neurons in the visual pathway exhibit striking RF dynamics, which implies that for adequate characterization the RF profile has to be examined in the space-time domain. Starting from these findings in the present study the neurons' static RF definition is purified and some experimental results of De Angelis et al. (1995) are modeled by the CNN. Our CNN model indicates that the spatio-temporal RF dynamics can be generated by time invariant synaptic strength values.

The cellular and subcellular localization of the mGluR5 metabotropic glutamate receptor subtype was studied in the rat cerebellar cortex, by using the preembedding immunoperoxidase and immunogold techniques.Light microscopic observations revealed an abundant, intense labeling of neurons in the granular layer as well as in the molecular layer. Lugaro and Golgi cells exhibited an intense mGluR5 immunoreactivity, while only a fraction of the neurons in the molecular layer were found to be mGluR5 immunopositive. In addition to a dense plexus of immunoreactive dendrites in the molecular layer of the cerebellar cortex, the mGluR5 immunopositive Golgi cell dendrites resembling axons at the light microscopic level were also labeled in the granular layer.At the ultrastructural level, mGluR5 immunoreactivity was present in neuronal elements postsynaptic to axon terminals of different morphology. By using a pre-embedding immuno-gold method, it was found that mGluR5 immunoreactivity is accumulated at the plasma membranes extrasynaptically as well as at the periphery of the postsynaptic specializations, mainly of the parallel fiber synaptic contacts.These findings provide morphological evidence that mGluR5 is expressed by a population of neurons in the cerebellar cortex and can synaptically be activated via the parallel fiber system. (C) 1997 Wiley-Liss, Inc.

Reorganization of the cerebellar glomerulus, the main synaptic complex within the granule cell layer, was investigated using quantitative morphological techniques. All afferents to the cerebellar cortex, including mossy-fibers, were surgically destroyed by undercutting the cerebellar vermis. Fifteen days after the operation, which resulted in the removal of the main excitatory afferent to the glomerulus, a significant reorganization of the whole synaptic complex was observed, whereas the structural integrity of the glomerulus was remarkably well preserved. This was indicated by the observation that the number of granule cell dendrites (approximately 50 per glomerulus), as well as the number of dendritic digits (approximately 210 per glomerulus) bearing most of the approximately 230 synaptic junctions per glomerulus, did not change significantly after mossy-fiber degeneration. The total number of synapses in the reorganized glomerulus did not change either, despite the disappearance of two-thirds of (excitatory) synaptic junctions caused by mossy-fiber degeneration. In the reorganized glomeruli, however, the inhibitory, GABA-containing Golgi axonal varicosities became the dominant synaptic type-about four-fifths (approximately 200) of all synapses within the glomerulus-whereas the dendritic synapses between the granule cells represented only one-fifth of all synaptic junctions. The quantitative data of the reorganized cerebellar glomerulus demonstrate both a remarkable constancy and a plasticity of the excitatory granule cells and inhibitory Golgi neurons building up this synaptic complex. Constancy (the preservation of certain specific structural features) is represented by an eventually unchanged number of dendrites and synaptic junctions within the deafferented glomerulus. Such constancy was made possible, however, by the morphogenetic plasticity of both nerve-cell types to produce new, dendro-dendritic and axo-dendritic synapses to compensate for the loss of mossy-fiber synapses.

In order to investigate whether thalamic synchronization may contribute to the binding of different cortical representations in visual information processing, we made a neuromorphic model of the thalamo-cortical loop, using the cellular neural network (CNN) model and simulator. It is demonstrated with the aid of this model that the cortico-thalamic feedback by synchronizing dLGN relay cell responses, provides a temporal code and this may induce correlated activities in the target cortical neuron population. Our results support the notion that using synchronization of temporally structured activities as general integration mechanism, the processing of visual information occurs simultaneously in the highly interconnected thalamo-cortical system.

In this paper we show cellular neural network (CNN) models of some basic types of cells characterized by diverse spiking patterns. After presenting some preliminary models (ion channels, neurons), CNN models of action potential generation are given, followed by an analysis of the rate-coding capabilities of the models. Furthermore, we show CNN models of synaptic connections. Finally, CNN models of neurons with diverse intrinsic firing patterns are presented.

Chronic changes in the thalamic mediodorsal nucleus (MD) after unilateral lesions of the prefrontal cortex were studied with the aid of quantitative light, and electron microscopic immunohistochemistry. Three months after the lesions, although the size of MD ipsilateral to the lesion did not change considerably, the neuronal density was significantly reduced. Conversely, as demonstrated by quantitative electron microscopy, the density of GABA immunostained axon terminals significantly increased in the lesioned side. It is suggested, that as MD does not contain GABA cells, the reactive hyperinnervation of the MD by GABA-containing axons is of extrinsic origin. This finding is also the morphological evidence of the potential of GABA-ergic nerve cells for reactive (induced) axonal sprouting.

The synaptic organisation of neurons in the nucleus medialis dorsalis (MD) was investigate by combined Golgi, and post-embedding gamma-aminobutyric acid (GABA) and/or glutamate (GLU) immunogold methods. The morphological features of the impregnated neurons in the MD (detailed by Kuroda et al. 1992a) were similar to thalamocortical relay cells present in other thalamic nuclei. GABAergic cell bodies could not be found. Distal dendritic branches of gold toned neurons established synaptic contacts with small and medium size glutamate as well as GABA-immunoreactive axonal endings. Large glutamate and GABA-positive axon terminals formed synaptic contacts with proximal dendrites. GABAergic axon terminals exhibited symmetric synaptic contacts and contained pleomorphic vesicles. Glutamate immunoreactive terminals formed asymmetric synapses and contained spheroid vesicles, although, some large glutamate immunoreactive endings contained pleomorphic vesicles. Synaptic glomerulus-like complexes could also be observed with the participation of glutamate-, and GABA-positive large axon terminals synapsing with Golgi impregnated proximal dendrites.

The distribution of octadecaneuropeptide (ODN)-like immunoreactivity (LI) and its relationship to gamma-aminobutyric acid (GABA)-LI were investigated in the cerebellar cortex of adult rats with electron microscopy. At the electron microscopic level, ODN-LI was found exclusively in glial cells. In addition to Bergmann glia and its processes, cerebellar astrocytes were also labelled, encapsulating unlabelled neuronal elements of the cerebellum. These ODN-LI glial processes were observed in close apposition to synaptic junctions, but immunoreactivity could not be found in the synaptic cleft or in association with neuronal membranes. Since GABA-LI is always associated with neuronal elements, the colocalization of GABA- and ODN-LI could not be confirmed in the cerebellar cortex. Our results do not support the assumption that ODN is a neuron-specific processing product of diazepam binding inhibitor. (C) 1994 Wiley-Liss, Inc.

Cortical feedback is the largest extraretinal projection to the lateral geniculate nucleus. This input is thought to modulate the transfer of visual information in a state‐dependent manner. The quantitative distribution and synaptology of axon terminals arising from different cortical areas is still an unsolved question. To address this problem, the synaptic termination pattern of corticogeniculate axons from cortical areas 17 and 18 entering the lateral geniculate nucleus of the cat was examined. The Phaseolus vulgaris leucoagglutinin anterograde tract tracing method was used for the labeling of corticogeniculate terminals. Postsynaptic targets were characterized by postembedding γ‐aminobutyric acid (GABA) immunocytochemistry. In both laminae A and A1, labeled corticogeniculate axons from area 17 established synaptic contacts with GABA‐immunopositive, interneuronal dendritic profiles more frequently (17.5% of all axons) than did labeled axon terminals from area 18 (7% of axons). Conversely, 76% of labeled corticogeniculate axons from area 17, as opposed to 87% of labeled axons from area 18, terminated on GABA‐immunonegative relay cell dendrites. Furthermore, the mean diameter of GABA‐negative relay cell dendrites postsynaptic to labeled axons from area 17 was significantly smaller than the diameter of relay cell dendrites synapsing with labeled terminals from area 18. These results indicate that the corticogeniculate axons from cortical areas 17 and 18 exhibit different synaptic termination patterns in the dorsal lateral geniculate nucleus of the cat, suggesting that these two projections may subserve different functions in visual information processing. © 1994 Wiley‐Liss, Inc.

Quantitative morphological changes of the developing Purkinje cells were studied from 6 to 90 postnatal (PN) days in the IVth lobule of vermis in the cerebellum of rats. The soma size (mean diameter) of Purkinje cells increased rapidly between 6 PN (on average 10 μm) and 18 PN (about 17 μm) days; it did not change between 18 and 25 PN days, but increased moderately again between 25 and 48 PN days (22–23 μm) and stabilized on the same value. In contrast, the number of Purkinje cells/100 μm (the “linear density”) decreased rapidly from 6 to 18 PN days. The molecular layer area belonging to 1 Purkinje cell increased rapidly from 6 to 25 PN days (from about 370 to 6,200 μm 2 ) and less rapidly between PN days 30 to 48 (up to 9,300 μm 2 ), followed by a moderate decrease at PN day 90 (about 6,600 μm 2 ). The volume belonging to 1 Purkinje cell dendritic arbor was about 5,500 μm 3 at PN day 6,93,000 μm 3 at PN day 25, and 100,000 μm 3 at PN day 90. The numerical density of dendritic spines in the molecular layer showed a biphasic curve: a rapid increase from PN days 6 to 21 followed by a significant but short decrease at PN day 25, moderate rise from PN days 25 to 48, and a subsequent decline between PN days 48 and 90. The number of spines belonging to 1 Purkinje cell showed two developmental “peaks”: the first peak at 21 PN days was moderate (5.6 × 10 4 spines/Purkinje cell) while the second maximum at 48 PN days was more significant (1.2 × 10 5 spines/Purkinje cell), which then declined to 6.3 × 10 4 spines/Purkinje cell at PN day 90. It is suggested that the temporary overproduction and the following decline in the number of Purkinje dendritic spines during the development of the cerebellar cortex may be the morphological indicator of the dynamics of synaptogenetic and of synaptic stabilization processes. © 1994 Wiley‐Liss, Inc.

THE cellular, and subcellular distribution of the mGluR5a metabotropic glutamate receptor was studied in the spinal cord of the rat using an antibody raised against a mGluR5a-specific carboxy-terminal peptide. Strong mGluR5a-immunoreactivity (mGluR5a-ir) was found in the laminae I-II of the dorsal horn, which gradually decreased towards the deeper layers. At the electron microscopical level, mGluR5a-ir was present exclusively in neuronal somata, and dendrites. Immunometal labelling revealed that mGluR5a-ir is concentrated at the periphery of postsynaptic densities of asymmetrical synapses or localized extrasynaptically at dendritic, and somatic membranes. The mGluR5a-immunoreactive dendritic profiles were often targeted by synaptic boutons with the morphological characteristics of C-fibre terminals. These observations provide evidence for mGluR5a being involved in the nociceptive transmission at the dorsal horn.

The numerical density of GABA immunopositive and GABA immunonegative neurons was quantitatively determined in 0, 12, 30 and 90 day-old neocortical transplants, derived from E17 rat embryos and transplanted into adult hosts. It was found that the original, very high neuronal density in the fetal transplant declined steadily after transplantation to the somatosensory cortex of adult rat. The decline in numerical density of GABA-positive neurons, however, was disproportionately larger than that of GABA-negative nerve cells: At 90 days the proportion of GABA-positive cells was 2.3% (in contrast to the 11.8% in the adult host cortex). The density of GABA-negative neurons, on the other hand, remained slightly higher than comparable values in the control cortex. The decline in density of GABA-positive neurons was continuous until the 90th post-transplantation day, while final, close to normal density values of GABA-negative nerve cells were already reached in 30 day-old grafts, with no significant change afterwards.