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G Percheron

Publications and source records attributed to G Percheron.

At least 37 records · Page 2Linked to original sources
PubMed1991

Morphological taxonomy of the neurons of the primate striatum.

A quantitative taxonomy of primate striatal neurons was elaborated on the basis of the morphology of Golgi-impregnated neurons. Dendritic arborizations were reconstructed from serial sections and digitized in three dimensions by means of a video computer system. Topological, metrical, and geometrical parameters were measured for each neuron. Groups of neurons were isolated by using uni- and multidimensional statistical tests. A neuronal species was defined as a group of neurons characterized quantitatively by a series of nonredundant parameters, differing statistically from other groups, and appearing as a separate cluster in principal component analysis. Four neuronal species were isolated: (1) the spiny neuronal species (96% of striatal neurons) characterized by spine-free proximal dendrites (up to 31 microns) and spine-laden distal dendrites, which are more numerous, shorter, and less spiny in the human than in the monkey, (2) the leptodendritic neuronal species (2%) characterized by a small number of long, thick, smooth, and sparsely ramified dendrites, (3) the spidery neuronal species (1%) characterized by very thick dendritic stems and a large number of varicose recurrent distal processes, and (4) the microneuronal species (1%) characterized by numerous short, thin, and beaded axonlike processes. All striatal neurons give off a local axonal arborization. The size and shape of cell bodies were analyzed quantitatively in Golgi material and in materials treated for Nissl-staining, immunohistochemical demonstration of parvalbumin and histochemical demonstration of acetylcholinesterase. Only three types were distinguishable: small, round cell bodies corresponding to either spiny neurons or microneurons, medium-size elongated cell bodies, which were parvalbumin-immunoreactive and corresponded to leptodendritic neurons, and large round cell bodies, which were acetylcholinesterase-positive and corresponded to spidery neurons. Thorough analysis of previously elaborated classifications revealed that spidery neurons do not exist in rats and cats and that large cholinergic neurons in these species correspond to leptodendritic neurons. From this, it can be assumed that the dendritic domain of striatal cholinergic neurons is considerably smaller in primates than in other species. Computer simulations based on both the frequency of each neuronal species and their three-dimensional dendritic morphology revealed that the striatum consists of two intertwined dendritic lattices: a fine-grain lattice (300-600 microns) formed by the dendritic arborizations of spiny, spidery, and microneurons, and a large-grain lattice (1,200 microns) formed by the dendritic arborizations of leptodendritic neurons. This suggests that cortical information can be processed in the striatum through two different systems: a fine-grain system that would conserve the precision of the cortical input, and a large-grain system that would blur it.

Animals↗
PubMed1991

Topography of the projection from the central complex of the thalamus to the sensorimotor striatal territory in monkeys.

The distribution of axons arising from the central complex (or centre médian-parafascicular complex) and terminating in the striatum was studied in seven macaques and one squirrel monkey. Deposits of anterograde tracers were made in the two lateral-most subdivisions of the central complex, i.e., the middle part (or pars media) and the lateral part (or pars paralateralis). All injections avoided the pars parafascicularis. The intrastriatal distribution of labeled axonal endings was mapped in relation to the standard ventricular (CA-CP) system of coordinates. Labeled endings were observed in the major posterior and dorsal parts of the putamen (excluding its anteromedial and ventral parts) and also in a restricted ventrolateral part of the caudate nucleus. The topography of the central territory of the striatum, defined as the striatal space receiving axons from the central complex, was found to correspond exactly to that of the cortical sensorimotor territory delineated after cortical injections. The termination pattern of the central axons within the striatum was patchy. Viewed as a whole, the irregular and hazy patches formed oblique streaks, parallel one with the other. The three-dimensional reconstructions of data from transverse sections revealed that the streaks were bi-dimensional pictures of three-dimensional parasagittal layers covering the whole anteroposterior extent of the cortical sensorimotor territory of the striatum. Our work shows that the pars media of the central complex, which receives selectively pallidal afferent axons (François et al., '88: Brain Res. 473:181-186), is the main source of the centroputaminal projection. The probable implication of this in a closed sensorimotor loop of the basal ganglia is discussed.

Animals↗
PubMed1991

Topographic distribution of the neurons of the central complex (centre médian-parafascicular complex) and of other thalamic neurons projecting to the striatum in macaques.

The distribution of the neurons of the central complex (or "centre médian-parafascicular complex") and of other thalamic regions projecting to the striatum was studied using a cartographic technique based on ventricular landmarks. The brain of a macaque was used as a reference for the cytoarchitectonic study of the complex. Three parts were isolated: the pars parafascicularis (or medial part), the pars media (or middle part) and the pars paralateralis (or lateral part). Wheat germ agglutinin conjugated to horseradish peroxidase was stereotaxically injected into either the sensorimotor or the associative territory of the striatum (i.e. the striatal space occupied by the axonal endings coming from either the sensorimotor or the associative cortex) of four macaques. Neurons projecting to the sensorimotor territory of the striatum were found to be located within the pars media (middle part) of the central complex while neurons projecting to the associative territory of the striatum were located within the pars parafascicularis. In all experimental cases, labelled neurons were scarce or absent in the pars paralateralis (or lateral part). Outside the central complex, neurons projecting to the sensorimotor territory of the striatum were scattered within the lateral part of the lateral mass, in the intralaminar nuclei and in the posterior part of the internal lamina. Neurons projecting to the associative territory of the striatum were observed mainly in the paraventricular region, dorsal to the rostral part of the lateral mass, and in the dorsolateral part of the nucleus oralis medialis. Our three-dimensional analysis of the clusters of the central complex cells projecting to the two striatal territories justifies the partitioning of the central complex into three parts. The pars media (or middle part), which projects to the sensorimotor territory of the striatum, receives selectively pallidal afferent axons. It belongs to the Nauta-Mehler loop, a closed loop linking the central complex to the basal ganglia. The pars parafascicularis, which projects to the associative territory of the striatum, seems more related to oculomotor neuronal systems. The pars paralateralis (or lateral part) appears to have very little, if any, relation with the striatum.

Afferent Pathways↗
PubMed1990

Topographic distribution of pallidal neurons projecting to the thalamus in macaques.

The respective topographic distribution of the pallidal neurons projecting to the central complex (centre médian-parafascicular complex) and to the oral part of the lateral mass of the thalamus was studied by using a topographic technique based on ventricular landmarks. WGA-HRP was stereotactically injected into the central complex of 4 macaques and into the oral part of the lateral mass of the thalamus of 3 others. Neurons projecting to the central complex were located in the caudal, lateral and ventral region of the ipsilateral medial nucleus of the pallidum. Pallidal neurons projecting to the lateral mass of the thalamus were more numerous and occupied the entire volume of the medial pallidum apart from a small rostral and dorsomedial region. The location of the pallido-central complex neurons appeared to be included in that of the neurons projecting to the lateral mass. As very few neurons of this shared region were unlabeled, it is very likely that the same pallidal neurons project to both targets. The pallido-central complex neurons were located in the region crossed by axons coming from the putaminal sensorimotor territory of the striatum. These results provide further evidence that Nauta and Mehler's loop is a real closed loop probably involved in sensorimotor processing.

Animals↗
PubMed1990

[Anatomo-physiologic substratum of akinesia in primates].

Severe akinesia can be observed in macaques following MPTP injections destroying dopaminergic nigrostriatal neurons. Akinesia also results from inhalation of toxic substances inducing bilateral lesions of the two pallidal nuclei and of the pars reticulata of the substantia nigra, and not of the pars compacta. Most of the recent studies of the anatomo-physiological substratum of akinesia used MPTP injections. Deoxyglucose studies have shown a clear increase in the neuronal activity of the medial nucleus of the pallidum and of its thalamic projection territory. Electrophysiological studies have shown a major modification of the spontaneous activity of medial pallidal neurons which is influenced in an excessive and non selective manner by sensorimotor inputs. Analysis of the relative three dimensional geometry of nervous arborizations have shown that the striato-pallido-nigral system is extremely convergent. Akinesia consecutive to nigrostriate lesions could be linked to an excessive and anarchic activation of this system. The contradiction which exists between akinesia with an abnormal activity of the medial pallidum and akinesia with bilateral pallidal lesions could only be apparent if akinesia was linked to the ineffective emission or to the interruption of messages to the thalamus.

Animals↗
PubMed1988

A topographic study of the course of nigral axons and of the distribution of pallidal axonal endings in the centre médian-parafascicular complex of macaques.

The combination of autoradiographic and topographic methods in macaques reveals that nigral axons only cross through the medial part of the parafascicular nucleus and end more dorsally and anteriorly in the thalamus. Pallidal endings are scarce in the centre médian and essentially located in the lateral parafascicular nucleus. It is proposed here to consider the centre médian-parafascicular complex as a part of the basal ganglia.

Animals↗
PubMed1987

Golgi study of the primate substantia nigra. I. Quantitative morphology and typology of nigral neurons.

Neuronal morphology was analyzed in the pars compacta, reticulata, and lateralis of the substantia nigra of humans and macaques. Golgi-impregnated dendritic arborizations, reconstructed from serial sections, were described by using topological, metrical, and geometrical parameters measured in three dimensions. Morphological parameters were statistically analyzed. Cell bodies and axons were also described. The primate substantia nigra comprises few local circuit microneurons. It consists mainly of large projection neurons having large cell bodies and sparsely branched dendritic arborizations. In all subdivisions, "complex endings" and "thin processes" can be found on nigral dendrites. Axons of large neurons occasionally had initial collaterals that never form profuse arborizations. Pars reticulata neurons had a cell body surface of 520 micron2, 4 dendritic stems, and 13 dendritic tips. The total dendritic length (L) was 7,100 micron, the highest dendritic length (Lm) 1,200 micron, and the mean length of dendritic segments 320 micron. Pars lateralis neurons were similar except for their larger cell bodies (650 micron2) and longer dendritic segments (440 micron). Pars compacta neurons had larger cell bodies (860 micron2), thicker and more numerous (5 stems, 19 tips), and longer dendrites (L = 10,500 micron; Lm = 1,400 micron). Large neurons of monkeys had the same topological characteristics as human neurons but shorter dendrites. The overall shape of arborizations was highly variable and not characteristic in any subdivision. A hierarchical typology of nigral neurons is proposed, which comprises two neuronal species, the compacta and reticulata species, and a lateralis subspecies. Pallidal neurons (Yelnik et al., '84) belong to the reticulata species. The position of these species in relation to higher hierarchical levels is discussed.

Animals↗
PubMed1987

Golgi study of the primate substantia nigra. II. Spatial organization of dendritic arborizations in relation to the cytoarchitectonic boundaries and to the striatonigral bundle.

The spatial organization of Golgi-stained dendritic arborizations of the substantia nigra was studied in three dimensions by using a video computer system. Dendritic orientation was analyzed in relation to the cytoarchitectonic boundaries and to the direction of the axons of the striato-pallidonigral bundle. All the brains, humans and macaques, were sectioned according to the same ventricular planes. The striatal bundle is made up of dense fascicles of very thin parallel axons. Sixty neurons located in the pars reticulata, lateralis, and compacta were reconstructed from serial sections. In the anterior pars reticulata and lateralis, the dendritic arborizations spread in all directions inside the striatal bundle. Below the pars compacta fringes, the dendrites of pars reticulata neurons extend ventrolaterally in the bundle. Because one nigral arborization can cover the whole thickness of the striatal bundle, we are led to believe that nigral neurons exert a role of convergence of the corticostriatal information similar to that of pallidal neurons (Percheron et al., '84a,b). The pars reticulata neurons appear to receive information mainly from the associative striatal territory. The pars lateralis neurons, conversely, appear to receive information from the sensorimotor territory. The anterior pars compacta neurons are organized in such a way that their ventral dendrites, located inside the pars reticulata, are ventrolaterally oriented, perpendicular to the striatal bundle. Their dorsal dendrites remaining in the pars compacta can receive other input. At more caudal levels, the posterior pars compacta neurons have dendrites radiating outside the striatal bundle.

Animals↗
PubMed1986

Instruments and techniques for the stereotactic surgery based on the CA-CP ventricular system of coordinates in monkeys.

The most widely used conventional stereotactic method utilizing the Horsley-Clarke coordinate system does not allow accurate intracerebral placements. Improving the precision of stereotactic surgery in monkeys has become imperative in neurological research to limit the waste of animals. This problem can be resolved with the use of a stereotactic technique based on ventricular landmarks utilizing "orthogonal teleradiography". The radiological devices and the stereotactic apparatus developed for the use with this technique are described. The apparatus allows the intercommissural plane of the animal to be placed parallel to the rails of the stereotactic frame by means of a head rotation around the ear bars. In addition, the technique uses metric reticles to make the interchange between ventricular and mechanical coordinates possible. The ventriculographic and stereotactic procedures are also described.

Animals↗
PubMed1986

[Relations between the basal ganglia and the thalamus of the primate. New morphologic data. New physiopathologic interpretations].

Considerable progress has been made over the last few years in our knowledge of the thalamus and basal ganglia and their relationships to the cerebral cortex. More detailed topographic studies in the macaque have demonstrated the separation, in the lateral region of the thalamus, between afferent cerebellar and basal ganglia territories. These territories fail to correlate with the subdivision between ventral and dorsal elements or the limits of a single cytoarchitectonic nucleus. The cerebellar territory corresponds to VIL (or VPLo) which projects towards the primary cortex, and to VIM (or area X) and DI (or VLc) which project towards premotor cortex. The nigral (and tectal) territory corresponds to VOM (or VAmc) and to some parts of the medial nucleus and projects mainly towards the oculomotor area, supplementary motor area and prefrontal cortex. In return, the oculomotor area and substantia nigra project towards the colliculus superior. Several thalamic nuclei constitute the pallidal territory: VOL (or VLo) projects mainly towards supplementary motor area, LPo (or VApc) and Do towards the prefrontal cortex. The median center, which receives afferents from pallidum and motor cortex, projects towards the striatum but also the motor cortex. The parafascicular nucleus projects towards the striatum and premotor cortex. It is still not possible to transpose data acquired in the macaque to man, but functional reinterpretations are possible. A system which involves the median pallidum, VOL and supplementary motor area could control motor initiative and flow of movement. A second system, involving the substantia nigra, colliculus superior, thalamic relay and oculomotor area could control posture. The pallidum and substantia nigra, anterior part of lateral mass, medial nucleus and prefrontal cortex could elaborate motor programmes.

Animals↗
PubMed1985

A histological atlas of the macaque (Macaca mulatta) substantia nigra in ventricular coordinates.

An atlas of the macaque substantia nigra was established in ventricular coordinates. Having verified that nigral contours are stable in both Macaca mulatta and Macaca speciosa, the antero-posterior sequence of four subdivisions was described on eight vertico-transverse levels after a comparison between histological and histochemical data. The pars reticulata constitutes the anterior pole containing pale, small cell-bodies scattered among the numerous endings of the striato-pallido-nigral fibres. Anteriorly, the pars compacta forms the dorsal border of the substantia nigra, but more posteriorly, it leaves the dorsal border and develops ventral fringes. Its large cell-bodies, most often pigmented, rich in Nissl bodies and in acetylcholinesterase, are closely spaced among a few axonal fascicles. The pars lateralis contains a low density of cell-bodies and corresponds to the hilum of entrance of the striato-pallido-nigral fibres and gives rise to a nigro-tectal projection. The pars mixta, dorsally located, contains a low density of neurons varying considerably in size. It represents the hilum of exit of nigral axons which project to various targets.

Anatomy, Artistic↗
PubMed1984

A Golgi analysis of the primate globus pallidus. I. Inconstant processes of large neurons, other neuronal types, and afferent axons.

The present paper is a Golgi study, with high-power lenses, of the primate globus pallidus. Two kinds of inconstant processes of large neurons are first described: complex endings and thin processes. Complex endings are thick apparatuses terminally located on dendrites having many appendages of various types. Contacts were observed not only between striatal axons and these complex endings but also between complex endings and the soma, dendritic stems, dendritic portions or complex endings of other large pallidal neurons. Thin processes were usually beaded, very thin, and arose from any part of the dendritic tree. Contacts were seen between them and soma or dendrites of other large neurons. These thin processes were very similar to initial axonal collaterals and together constitute a common pool of processes. Complex endings and thin processes were essentially observed in the lateral nucleus of the pallidum where they apparently are evenly distributed inside the nucleus but randomly distributed on individual neurons. Two neuronal types other than large pallidal neurons were isolated: the smallest were considered to be local circuit neurons, while intermediate-sized neurons might be the origin of a particular efference. Many striatal axons gave no branches over long distances and collaterals were of two types and most frequently were short (less than 50 micron). Larger axonal arborization were rarely encountered. In addition to parallel contacts, numerous very short ones were observed. All these contacts between striatal axons and dendrites of large pallidal neurons seem to be irregularly distributed.

Afferent Pathways↗
PubMed1984

A Golgi analysis of the primate globus pallidus. II. Quantitative morphology and spatial orientation of dendritic arborizations.

The morphology of pallidal neurons was analyzed quantitatively in Golgi-impregnated brains of men and macaques (Macaca irus). Selected neurons were drawn with a camera lucida and reconstructed from serial sections. Dendritic arborizations were analyzed in three dimensions using a video computer microscope (Yelnik et al., '81). Morphological (topological and metrical) parameters were computed, and the overall geometry of arborizations was studied in three dimensions with the aid of principal component analysis (Yelnik et al., '83). Statistical tests were used in order to compare human with simian large neurons and the lateral with the medial pallidum. All neurons were found to belong to a single neuronal population. Particular neurites may be added randomly onto pallidal dendrites, mainly in the lateral pallidum. Large pallidal neurons are characterized by sparsely branched dendritic arborizations (4 stems, 13 tips) with thick, smooth, and long dendrites (longest dendrite = 1,000 micron, total dendritic length = 7,600 micron). All arborizations are discoidal in shape with mean dimensions of 1,500 X 1,000 X 250 micron. Pallidal discs are always parallel to the lateral border of each pallidal nucleus and thus perpendicular to striatal axons to which they present their greatest extent. They may be traversed by a large number of these axons. The existence of other pallidal neuronal groups, "intermediate" and "local circuit" neurons, identified in their fine morphological features by François et al. ('84), was confirmed quantitatively in the present study.

Animals↗
PubMed1984

A Golgi analysis of the primate globus pallidus. III. Spatial organization of the striato-pallidal complex.

An atlas of transverse sections of the globus pallidus and striatum was established in macaque with reference to ventricular coordinates. The three-dimensional geometry of the striato-pallidal complex was investigated by means of sagittal and horizontal reconstructions. Both a personal case studied with autoradiography and data from literature were used to analyze the distribution of cortical axons into the striatum. One may distinguish two striatal territories: one, somatotopically arranged, sensorimotor territory extending over the major part of the putamen; and the other, an associative territory, comprising the caudate nucleus and antero-medial and postero-inferior parts of the putamen. The striato-pallido-nigral bundle was studied using Golgi, Perls, and Fink-Heimer techniques. The bundle is described in four parts: prepallidal (subdivided into caudato-pallidal and putamino-pallidal subparts), transpallidal, pallido-nigral, and nigral. The tracing of the limit between the caudate (associative) and putaminal (essentially sensorimotor) territories shows that the two components are of roughly the same size in the pallidum. The data were compared with geometry and orientation of the dendritic arborizations of large pallidal neurons analyzed in Yelnik et al. ('84). Each pallidal dendritic disc is able to receive axons from a wide region of the striatum. This leads to a convergence on pallidal neurons of striatal axons from different striatal somatotopic strips and from the sensorimotor and associative territories. This is an indication that the globus pallidus may have an integrative role.

Animals↗
PubMed1984

Localization of nigrostriatal, nigrothalamic and nigrotectal neurons in ventricular coordinates in macaques.

The topography of the substantia nigra and its subdivisions was first analysed in macaques by using a topographic technique based on ventricular landmarks. This study shows the stability of the contours of the substantia nigra and its subdivisions in various species of macaques. The anteroposterior sequence of four subdivisions was standardized by defining eight verticotransverse levels, regularly interspaced and systemically used for each experimental case. Neurons of the substantia nigra sending axons to the striatum, thalamus and superior colliculus were identified by the technique of retrograde transport of horseradish peroxidase. The nigrostriatal labeled neurons were essentially located in the ipsilateral pars compacta but also scattered dorsally in the pars mixta and ventrally in the pars reticulata. In addition, the existence of a crossed nigrostriatal pathway was demonstrated in monkeys. Nigrothalamic labeled neurons were found in the whole pars reticulata at rostral levels and only in the medial part at more caudal levels. Comparatively, nigrotectal labeled neurons were also found in the whole pars reticulata at rostral levels, but caudally, they were confined to the lateral part of the pars reticulata and the pars lateralis. It thus appears that these three nigral components may overlap at some levels of the substantia nigra. This is discussed in relation to the existence of branched axons already documented. However, the present results underline the strong tendency of the nigrotectal neurons to be segregated from the nigrothalamic ones and to be laterally located in monkeys. In addition, two nigrotectal components have been identified on the basis of their topography and their somata size: one with large somata located in the pars lateralis, probably specific to primates, and the other with smaller somata located in the pars reticulata. These two components may indicate the existence of two different functional systems.

Animals↗
PubMed1983

Principal component analysis: a suitable method for the 3-dimensional study of the shape, dimensions and orientation of dendritic arborizations.

Our study proposes an objective method of describing 3-dimensional dendritic arborizations of neurons in the best possible conditions. The method is based upon a particular exploitation of statistical "principal component analysis". For each arborization, 3 principal axes are calculated which are its axes of inertia. The first two axes define the "principal plane" of the arborization. The shape of the arborization is determined from the statistical distribution of its dendritic points along each of these axes. Shapes are quantified by using an "index of axialization" (a) and an "index of flatness" (p) both of which may vary from zero to 1. The dimensions of the arborization, "length" (1), "width" (w) and "thickness" (t) are also measured along the principal axes. Orientation of arborizations is quantified by considering the orientation of the first principal axis for axialized arborization (a close to 1) and/or the orientation of the principal plane for flattened arborizations (p close to 1). In both cases 2 angles (azimuth and polar angle) are calculated. For spherical arborizations (a and p close to 1), no orientation is significant. The significance level of the defined orientations is evaluated from the values of the shape indices. Several examples are illustrated and other existing methods are discussed.

Animals↗