Connections between the Zona Incerta of the Dog Diencephalon and the Substantia Nigra,Ventral Tegmental Field,and Pedunculopontine Tegmental Nucleus

Studies using technique based on retrograde and anterograde transport of horseradish peroxidase were performed to address the organization of the connections of different sectors of the zone incerta (ZI) of the diencephalon with substructures of the substantia nigra, ventral tegmental field, and pedunculopontine nucleus of the midbrain in dogs. These structures were found to be interconnected. The organization of these connections included elements demonstrating that segregated conduction of functionally diverse information can be transmitted via these pathways. In addition, the convergence of projections fibers from neurons in substructures of the midbrain nucleus described in all sectors of the ZI and to these neurons from neurons in all ZI sectors is evidence that functionally diverse information can be integrated both at the level of the ZI and at the level of the midbrain structures studied here.     

Branching axons from subcoeruleus area project to the nucleus raphe pontis and hypothalamic zona incerta, as studied with the double fluorescent retrograde tracing technique

In this study we utilized a double retrograde axonal tracing technique to investigate the possible existence of collateralized axonal projections of subcoeruleus area neurons to both raphe pontis nucleus and hypothalamic zona incerta. Following microinjections of fluorescent tracers (Fast blue (FB) and Diamidino yellow (DY] within raphe pontis and zone incerta, substantial numbers of double-labeled branched neurons have been found within the subcoeruleus area.     

Connections of the zona incerta to the reticular nucleus of the thalamus in the rat

This study demonstrated that there is a pathway from the zona incerta to the thalamic reticular nucleus. Injections of horseradish peroxidase or Fluorogold were made, using stereotaxic coordinates, into the rostral, intermediate or caudal regions of the thalamic reticular nucleus of adult Sprague-Dawley rats. The results show that the different regions of the thalamic reticular nucleus have distinct patterns of connections with the sectors of the zona incerta. In terms of the relative strength of the connections, injections made into the rostral regions of the thalamic reticular nucleus showed the highest number of labelled cells within the rostral and ventral sectors of the zona incerta; injections made into the intermediate regions of the thalamic reticular nucleus showed labelled cells in the dorsal and ventral sectors; while injections to the caudal regions of the thalamic reticular nucleus showed only a few labelled cells in the caudal sector of the zona incerta. Previous studies have shown that the zona incerta projects to the higher order thalamic nuclei but not first order thalamic nuclei. The labelling observed in the present study may represent collaterals of zona incerta to higher order thalamic nuclei projections.     

Afferent and efferent connections of the ventrolateral tegmental area in the rat

 The present study examined the organization of afferent and efferent connections of the rat ventrolateral tegmental area (VLTg) by employing the retrograde and anterograde axonal transport of Fluorogold and Phaseolus vulgaris-leucoagglutinin, respectively. Our interest was focused on whether the anatomical connections of the VLTg would provide evidence as to the involvement of this reticular area in audiomotor behavior. Our retrograde experiments revealed that minor inputs to the VLTg arise in various telencephalic structures, including the cerebral cortex. Stronger projections originate in the lateral preoptic area, the zona incerta, the nucleus of the posterior commissure and some other thalamic areas, the lateral substantia nigra, the deep layers of the superior colliculus, the dorsal and lateral central gray, the deep mesencephalic nucleus, the paralemniscal zone, the intercollicular nucleus, the external cortex of the inferior colliculus, the oral and caudal pontine reticular nucleus, the deep cerebellar nuclei, the gigantocellular and lateral paragigantocellular reticular nuclei, the prepositus hypoglossal nucleus, the spinal trigeminal nuclei, and the intermediate layers of the spinal cord. Most importantly, we disclosed strong auditory afferents arising in the dorsal and ventral cochlear nuclei and in the cochlear root nucleus. The efferent projections of the VLTg were found to be less widespread. Telencephalic structures do not receive any input from the VLTg. Moderate projections were seen to diencephalic reticular areas, the zona incerta, the nucleus of the posterior commissure, and to various other thalamic areas. The major VLTg projections terminate in the deep layers of the superior colliculus, the deep mesencephalic nucleus, the intercollicular nucleus and external cortex of the inferior colliculus, the oral and caudal pontine reticular nucleus, the gigantocellular and lateral paragigantocellular reticular nuclei, and in the medial column of the facial nucleus. From our data, we conclude that the VLTg might play a role in sensorimotor behavior. Accepted: 3 April 1997     

Organization of Projections of the Zona Incerta of the Diencephalon to Pallidal Structures in the Dog Brain

Detailed studies of the organization of individual sectors in the zona incerta of the diencephalon to functionally diverse pallidal structures in the dog brain were performed by antero- and retrograde axon transport of horseradish peroxidase. The results showed that neurons in the caudal sector of the zona incerta innervate the globus pallidus and entopeduncular nucleus, which receive more extensive innervation from motor structures. The same pallidal structures receive projections from occasional neurons in the dorsal and causal sectors of the zona incerta. No connections of the zona incerta with the limbic ventral pallidum were found.     

The cells of origin of the incertofugal projections to the tectum,thalamus, tegmentum and spinal cord in the rat: A study using the autoradiographic and horseradish peroxidase methods

Efferent projections of the zona incerta were examined in the rat using the autoradiographic and horseradish peroxidase methods, with special reference to the cytoarchitectonic structure of the zona incerta.Autoradiographic experiments showed that the incertofugal fiber systems reach ipsilaterally to the thalamus (lateral dorsal, central lateral, ventral lateral geniculate, parafascicular, subparafascicular and reuniens nuclei, and posterior nuclear complex), to the hypothalamus (dorsal, lateral and posterior hypothalamic areas), to the tectum (medial pretectal area, deep pretectal and pretectal nuclei, superior colliculus and periaqueductal gray) and to the midbrain tegmentum, pons and medulla oblongata (subcuneiform, cuneiform and red nuclei, nuclei of the posterior commissure and Darkschewitsch, interstitial nucleus of Cajal, pedunculopontine tegmental nucleus, oral and caudal pontine reticular nuclei, nucleus raphe magnus, gigantocellular reticular nucleus, pontine gray and inferior olivary complex). Contralaterally, incertal efferent fibers reach to the zona incerta.Cells of origin of the incertofugal fiber systems to the tectum, thalamus, tegmentum and spinal cord were examined using the retrograde horseradish peroxidase method. Cells of origin of the incertotectal pathway are located mainly in the ventral and caudal parts of the zona incerta and partly in the antero-polar, dorsal and postero-polar parts. Cells projecting to the thalamus (at least to the lateral dorsal and central lateral nuclei) are situated in the ventral and caudal parts of the zona incerta, but they are rare in the other incertal structures. Cells of origin of the incertotegmental system are located mainly in the dorsal, magnocellular and caudal parts and partly in the antero- and postero-polar parts, but they are not situated in the ventral part. Cells of the magnocellular part project more caudally to the medulla oblongata and spinal cord than those of the other parts of the zona incerta. Forel's field contains many cells projecting to the tegmentum.The results provide good evidence that the cells of origin of efferent projections are topographically organized and are related to cytoarchitectonic areas within the zona incerta.     

长翼蝠(Miniopterus Schrebersi)上丘与传递超声信息有关核团的传入联系—HRP法

用HRP逆行追踪法结合电生理学技术,对21只长翼蝠上丘(SC)超声信息的传入联系进行了形态学研究。13只动物上丘的听应部位电泳HRP后,标记神经元恒定地出现于双侧的下丘(IC,同侧为主)和外侧丘系背核(DNLL,对侧占优势)。约半数动物的同侧前外侧橄榄周核(ALPO)存在标记神经元。此外,标记神经元还出现于下列结构中,同侧的舌下神经前置核(n.Ⅻ)、小脑顶核(F)、黑质(SN)、后连合核(NPC)、丘脑(THa)、未定带(ZI),对侧的小脑齿状核(D)、双侧的中脑网状结构(MRF)、上丘(SC)。8只长翼蝠上丘的非听反应部位电泳HRP后,同侧的舌下神经前置核、小脑顶核、黑质、后连合核、丘脑、未定带,对侧的小脑齿状核,双侧的中脑网状结构及上丘亦见标记神经元。本实验提示:上丘的超声信息主要是经过同侧前外側橄榄周核和下丘以及对侧的外侧丘系背核中继传入的。     

Afferent connections of the laterodorsal thalamic nucleus in the rat

The laterodorsal thalamic afferent connections have been studied by means of the retrograde transport of horseradish peroxidase (HRP). The following new sources of projections to the laterodorsal thalamic nucleus (LD) were observed: the zona incerta, the lateral dorsal tegmental nucleus (bilaterally), the lateral hypothalamus and the precentral agranular cortex.     

Comparative Analysis of the Quantitative Characteristics of the Corticothalamic Projections of Parietal Cortex Fields 5 and 7

The quantitative distributions of corticothalamic efferent fibers after local lesioning of fields 5 and 7 of the parietal cortex were studied. The largest projections of field 5 and 7 were found to be to the reticular and parafascicular nuclei of the thalamus and the zona incerta. The number of efferent fibers of field 5 terminating in these nuclei was greater than the number of fibers running from field 7. The projections of field 7 to the posterolateral nucleus were greater than those of field 5. The numbers of parietal cortex efferent fibers terminating in the central lateral and ventral anterior nuclei and thalamic pulvinar were insignificant. Thus, the predominant projections of fields 5 and 7 to the reticular and parafascicular nuclei of the thalamus and the zona incerta may be determined by the need for inhibitory control of descending corticoreticular influences.     

大鼠屏状核的传入联系

采用WGA－HRP和CB－HRP法，追踪了16只大鼠屏状核的传入纤维联系，结果表明大脑皮质的躯体感觉区，视皮质及扣带皮质有细胞发出纤维投射到屏状核，后脑腹侧核，未定带，中缝背核及脑脚周核投射到屏状核，下后脑外侧核，视前大细胞核，斜角带核水平支和蓝斑青少量纤维投射到屏状核。     

Organization of the efferent projections of the pedunculopontine tegmental nucleus of the midbrain of the dog pallidum

Studies of the pedunculopontinopallidal projections of the dog brain based on the retrograde axonal transport of horseradish peroxidase demonstrated that the compact zone (PPNc) and the lateral area of the diffuse zone (PPNd) of the pedunculopontine tegmental nucleus (PPN) of the midbrain project to the globus pallidus, entopeduncular nucleus, and ventral pallidum. The medial area of the PPNd, adjacent to the chiasm of the upper cerebellar peduncles and seen in other animals as the mesencephalic extrapyramidal area (MEA), projects only to the globus pallidus. In dogs, this area of the tegmentum is not a major source of projections to the striopallidum, such that it is inappropriate to regard it as a separate structure, comment being restricted to the topical organization of PPNd projections to the pallidum. Projection fibers to pallidal structures arise from both cholinergic and non-cholinergic PPN neurons. __________ Translated from Morfologiya, Vol. 127, No. 2, pp. 19–23, March–April, 2005.     

Basal ganglia and other afferent projections to the peribrachial region in the rat: A study using retrograde and anterograde transport of horseradish peroxidase

The afferent projections to the peribrachial region in the rat were studied using retrograde and anterograde transport of horseradish peroxidase. Particular attention was paid to descending projections from the basal ganglia and related nuclei to the region of nucleus tegmenti pedunculopontinus. Following injection of peroxidase into nucleus tegmenti pedunculopontinus, few retrogradely-labelled neurons were found in the entopeduncular nucleus proper, but larger numbers were found with a wide distribution within the boundaries of the internal capsule and cerebral peduncle. Labelled cells were also consistently observed in the amygdala, the caudal globus pallidus, the subthalamus including zona incerta and subthalamic nucleus, the hypothalamus, the substantia nigra and the ventral tegmental area. Following iontophoretic injections of horseradish peroxidase into the entopeduncular nucleus, lateral hypothalamus, subthalamic nucleus or ventral tegmental area, terminal labelling was observed in and around the branchium conjunctivum in an area apparently corresponding to nucleus tegmenti pedunculopontinus in the rat.     

An autoradiographic analysis of ascending projections from the medullary reticular formation in the rat

Ascending projections from the several nuclei of the medullary reticular formation were examined using the autoradiographic method. The majority of fibers labeled after injections of [3H]leucine into nucleus gigantocellularis ascended within Forel's tractus fasciculorum tegmenti which is located ventrolateral to the medial longitudinal fasciculus. Nucleus gigantocellularis injections produced heavy labeling in the pontomesencephalic reticular formation, the intermediate layers of the superior colliculus, the pontine and midbrain central gray, the anterior pretectal nucleus, the ventral midbrain tegmentum including the retrorubral area, the centromedian-parafascicular complex, the fields of Forel/zona incerta, the rostral intralaminar nuclei and the lateral hypothalamic area. Nucleus gigantocellularis projections to the rostral forebrain were sparse. Labeled fibers from nucleus reticularis ventralis, like those from nucleus gigantocellularis, ascended largely in the tracts of Forel and distributed to the pontomedullary reticular core, the facial and trigeminal motor nuclei, the pontine nuclei and the dorsolateral pontine tegmentum including the locus coeruleus and the parabrachial complex. Although projections from nucleus reticularis ventralis diminished significantly rostral to the pons, labeling was still demonstrable in several mesodiencephalic nuclei including the cuneiform-pedunculopontine area, the mesencephalic gray, the superior colliculus, the anterior pretectal nucleus, the zona incerta and the paraventricular and intralaminar thalamic nuclei. The main bundle of fibers labeled by nucleus gigantocellularis-pars alpha injections ascended ventromedially through the brainstem, just dorsal to the pyramidal tracts, and joined Forel's tegmental tract in the midbrain. With the brainstem, labeled fibers distributed to the pontomedullary reticular formation, the locus coeruleus, the raphe pontis, the pontine nuclei, and the dorsolateral tegmental nucleus and adjacent regions of the pontine gray. At mesodiencephalic levels, labeling was present in the rostral raphe nuclei (dorsal, median and linearis), the mesencephalic gray, the deep and intermediate layers of the superior colliculus, the medial and anterior pretectal nuclei, the ventral tegmental area, zona incerta as well as the mediodorsal and reticular nuclei of the thalamus. Injections of the parvocellular reticular nucleus labeled axons which coursed through the lateral medullary tegmentum to heavily innervate lateral regions of the medullary and caudal pontine reticular formation, cranial motor nuclei (hypoglossal, facial and trigeminal) and the parabrachial complex.(ABSTRACT TRUNCATED AT 400 WORDS)     

An autoradiographic study of topographical relationships between pallidal and cerebellar projections to the cat thalamus

Summary Injections of ³H-leucine were made in the entopeduncular nucleus or dentate nucleus of the cerebellum in eight cats. The terminal projection zones of both pathways in the thalamus were studied using the sagittal plane and their relationships to one another as well as to cytoarchitectural boundaries of thalamic nuclei were compared. The data indicate that the territories controlled by the two projection systems are almost entirely segregated. The segregation is mainly along the antero-posterior axis as the main pallidal projection zone occupies the medio-ventral VA while the main dentate projection zone lies posterior to it in the VL. Furthermore, the dorsolateral part of the VA not occupied by pallidal projections receives dentate projections. In the VM, both afferent systems terminate in the lateral part of the nucleus with pallidal territory located anteriorly and dentate territory located posteriorly, again without overlap. As the delineations of nuclear subdivisions in the ventral thalamus of the cat have been a subject of some controversy, it is suggested that the boundaries of the VA, VL and VM in the cat thalamus be defined on the basis of basal ganglia and cerebellar projection zones.Abbreviations used in the Text and in Fig. 5 AM anterior medial nucleus - AV anterior ventral nucleus - BC brachium conjunctivum - CA anterior commissure - CC crus cerebri - CP posterior commissure - CD caudate nucleus - CE centrum medianum - CLN central lateral nucleus - DN dentate nucleus - EPN entopeduncular nucleus - FF Forel's field - FN fastigial nucleus - FR fasciculus retroflexus - HL lateral habenular nucleus - HM medial habenular nucleus - INA anterior interposite nucleus - INP posterior interposite nucleus - IC internal capsule - LD lateral dorsal nucleus - LG lateral geniculate body - MD medial dorsal nucleus - MTT mamillothalamic tract - NR red nucleus - OT optic tract - PAC paracentral nucleus - PF parafascicular nucleus - PV pulvinar - RT reticular thalamic nucleus - SM submedian nucleus - SN substantia nigra - SNr substantia nigra pars reticularis - STN subthalamic nucleus - VF ventral posterior nucleus - VA ventral anterior nucleus - VL ventral lateral nucleus - VM ventral medial nucleus - ZI zona incerta Supported in part by a grant from the American Parkinson Disease Association and NIH grant R01NS19280     

Diencephalic connections of the superior colliculus in the hedgehog tenrec

Using different tracer substances the pathways connecting the superior colliculus with the diencephalon were studied in the Madagascan hedgehog tenrec (Echinops telfairi), a nocturnal insectivore with tiny eyes, a small and little differentiated superior colliculus and a visual cortex with no obvious fourth granular layer. The most prominent tecto-thalamic projection terminated in the ipsilateral dorsal lateral geniculate nucleus. The entire region receiving contralateral retinal afferents was labeled with variable density. In addition, there was a widespread, homogeneously distributed collicular input to the lateralis posterior-pulvinar complex and a distinct tectal projection to the suprageniculate nucleus. The latter projections were bilateral with a clear ipsilateral predominance. Among the intra- and paralaminar nuclei the centralis lateralis complex was most heavily labeled on both sides, followed by the nucleus centralis medialis. The paralamellar portion of the nucleus medialis dorsalis and the nucleus parafascicularis received sparse projections. A clear projection to the nucleus ventralis medialis could not be demonstrated but its presence was not entirely excluded either. There were also projections to medial thalamic nuclei, particularly the reuniens complex and the nucleus paraventricularis thalami. The main tecto-subthalamic target regions were the zona incerta, the dorsal hypothalamus and distinct subdivisons of the ventral lateral geniculate nucleus. These regions also gave rise to projections to the superior colliculus, as did the intergeniculate leaflet. The pathways oriented toward the visual or frontal cortex and the projections possibly involved in limbic and circadian mechanisms were compared with the connectivity patterns reported in mammals with more differentiated brains. Particular attention was given to the tenrec's prominent tecto-geniculate projection, the presumed W- or K-pathway directed toward the supragranular layers.     

The sensory projections to the frontal association cortex in the dog

Afferents to the frontal association cortex (FAC) from structures involved in olfactory, visual and auditory functions were studied in 37 dogs using the method based on the retrograde axonal transport of horseradish peroxidase. Separate injections to FAC or to the mediodorsal thalamic nucleus (MD) showed that sensory afferents could reach FAC by two channels: by direct cortico-cortical projections and via MD. The olfactory input originating in the primary and secondary olfactory cortex run to FAC through both transcortical and subcortical pathways, while some subcortical structures, such as the anterior olfactory nucleus and olfactory tubercle, send abundant afferents to FAC only via MD. The visual projections taking their rise from a few separated areas of the visual association cortex reach FAC only transcortically. Most significant subcortical projection to FAC from the lateral geniculate nucleus, were transmitted via MD. On the contrary, auditory information was sent to FAC mainly through direct cortico-cortical pathways originating in the auditory association areas. Auditory input related by MD was very weak and originated from a limited region of the some cortex. Thus, independently from the way of transmission, auditory and visual projections terminated always in the dorsal zone of FAC, whereas the olfactory projection terminated in its ventral zone.     

Analysis of Possible Information Conduction Pathways and Integration in the Basal Ganglia System Based on Their Interactions with the Zona Incerta

Studies of the organization of projections between the zona incerta (ZI) of the midbrain and basal ganglia were performed to analyze the possible pathways conducting different information and its integration in the projection systems studied. The organization of projections between these structures in dogs revealed topical elements demonstrating the possible segregated conduction of functionally different information in the basal ganglia system. However, the most characteristic feature of these projection systems is the convergent conduction of functionally diverse information, which is evidence for the possible integration of functionally diverse information both at the level of the ZI and at the levels of all the basal ganglia structures studied here.     

Organization of Efferent Projections of the Pedunculopontine Nucleus of the Tegmentum of the Striatum in the Dog Brain

A method based on retrograde axonal transport was used to undertake detailed studies of the efferent projections of individual substructures of the pedunculopontine nucleus of the midbrain tegmentum to functionally diverse segments of striatal structures in dogs. The compact and diffuse zones of this nucleus were found to project to segments of the putamen, caudate nucleus, and nucleus accumbens, which are components of the limbic and motor systems. The medial part of the diffuse zone, adjacent to the decussation of the superior cerebellar peduncles (presumptively the mesencephalic extrapyramidal field) projected only to the dorsal segments of the caudate nucleus and putamen, which are parts of the motor system. __________ Translated from Morfologiya, Vol. 126, No. 6, pp. 11–15, November–December, 2004. Director: Doctor of Biological Sciences V. T. Shuvaev     

The organization of the crossed geniculogeniculate pathway of the rat: a Phaseolus vulgaris-leucoagglutinin study.

The intergeniculate leaflet of the thalamus is known to give rise to neuronal projections to the suprachiasmatic nuclei and the rostral part of the pineal gland. Via these projections the intergeniculate leaflet is considered to play a role in regulation of circadian rhythms. Iontophoretic injections of the anterograde tracer Phaseolus vulgaris-leucoagglutinin were placed in various subnuclei of the lateral geniculate nucleus in order to study the topographical organization of the crossed geniculogeniculate pathway in the rat. Injections involving neurons in the intergeniculate leaflet or the medial subpart of the ventral nucleus (which presumably is part of the intergeniculate leaflet of the thalamus too) gave rise to labeled nerve fibers in the opposite lateral geniculate nucleus. The axons contained in this pathway were followed either medially via the posterior commissure, or via the optic tracts and optic chiasm, to the contralateral hemisphere. In the contralateral lateral geniculate nucleus, the intergeniculate leaflet was most densely innervated, but a substantial innervation of the ventral lateral geniculate nucleus was observed as well. Only a few labeled fibers were observed in the dorsal subnucleus. However, the dense innervation of the contralateral intergeniculate leaflet not only covered the small zone between the dorsal and ventral nuclei, but also a dorsomedial part of the ventral nucleus that merged caudally with the lateral part of the zona incerta. In the remaining part of the ventral nucleus, single Phaseolus vulgaris-leucoagglutinin-labeled fibers surrounded specific cells. The demonstration of a divergent projection between the intergeniculate leaflet and specific subparts of the contralateral geniculate nuclei indicates that the two lateral geniculate nuclei are regulating each other. The function of this pathway is suggested to be related to the regulation of circadian rhythmicity, but experimental evidence for this hypothesis is still lacking.     

Spatial organization of the corticopalladial projection system of dog brain

Spatial organization of corticopallidal projectional system was studied in 11 outbred dogs by method based on horse radish peroxidase transport. It was demonstrated that globus pallidum receives projections predominantly from neocortical zones (motor, premotor, somatosensory, parietal and auditory and from insular field of mesocortex. Mesocortical (prelimbic, orbital and insular) and allocortical (entorhinal, piriform and periamygdalar) including archicortex (subicular part of hippocampal formations) fields project onto ventral pallidum. Entopeduncular nucleus receives projections from neocortical zones (motor, premotor, somatosensory, parietal and auditory), mesocortex (prelimbic, orbital, insular and cingular fields) and allocortex (entorhinal and periamygdalar fields). The data obtained indicate specificity of distribution of cortical afferent projectional fibres in each of nuclei studied which allows to consider globes pallidum as motor zone and ventral pallidum as limbic zone of paladial complex. As projections from functionally different cortical fields were revealed in entopeduncular nucleus it may be suggested that this is the exact site for interaction of functionally different information, including the one received from the cortex.