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     

Thalamic afferents of area 4 and 6 in the dog: a multiple retrograde fluorescent dye study

In the present study, we compared the distribution of thalamocortical afferents of cortical area 4 to that of cortical area 6 in the dog, using fluorescent tracers. Multiple injections of combinations of two dyes (diamidino yellow dihydrochloride, Evans blue, fast blue, granular blue) were made into either the anterior and posterior sigmoid gyri or into the medial and lateral regions of the anterior sigmoid gyrus in the anesthetized dog. We found that the thalamic afferents of areas 4 and 6 arise from topographically organized bands of cells that traverse several thalamic nuclei and extend throughout the rostrocaudal extent of the thalamus. The most medial band included area 6-projecting neurons in the anterior nuclei, the rhomboid nucleus, the ventral anterior nucleus (VA), ventromedial nucleus (VM) and mediodorsal nucleus (MD). Within this band, cells projecting to medial area 6a tended to be more numerous in the anterior nuclei, anterior parts of VA and VM and anterior and caudal parts of MD. Fewer cells in MD but more cells in caudal parts of VA and VM projected to lateral area 6 a. Lateral bands of cells in central through lateral parts of VA and VL projected topographically to lateral area 4 on the anterior sigmoid gyrus and lateral through medial parts of postcruciate area 4. The most lateral band of cells in VL continued ventrally into the zona incerta. Area 4 also received input from VM and the central lateral (CL) and centrum medianum (CM) nuclei. Within regions of VA, VL and VM, cells from one band interspersed with cells from another, but there were very few double-labeled cells projecting to two cortical sites. When the present results are compared with our previous findings on the distribution of subcortical afferents to the motor thalamus, it appears that separate motor cortical areas may receive predominantly separate but also partially over-lapping pathways in the dog.Abbreviations AV Anterior ventral nucleus - AM anterior medial nucleus - Cb cerebellar nuclei - CeM central medial nucleus - CL central lateral nucleus - CM centrum medianum nucleus - EN entopeduncular nucleus - Hb habenula - LD lateral dorsal nucleus - MD mediodorsal nucleus - mt mammillothalamic tract - MV medioventral nucleus - Pf parafascicular nucleus - R reticular thalamic nucleus - rf retroflex fasciculus - Rh rhomboid nucleus - SN substantia nigra - VA ventral anterior nucleus - VL ventral lateral nucleus, principal division - VLd ventral lateral nucleus, dorsal division - VM ventral medial nucleus - VPL ventral posterior lateral nucleus - ZI zona incerta     

Projections to the rostral reticular thalamic nucleus in the rat

Summary Afferent pathways to the rostral reticular thalamic nucleus (Rt) in the rat were studied using anterograde and retrograde lectin tracing techniques, with sensitive immunocytochemical methods. The analysis was carried out to further investigate previously described subregions of the reticular thalamic nucleus, which are related to subdivisions of the dorsal thalamus, in the paraventricular and midline nuclei and three segments of the mediodorsal thalamic nucleus. Cortical inputs to the rostral reticular nucleus were found from lamina VI of cingulate, orbital and infralimbic cortex. These projected with a clear topography to lateral, intermediate and medial reticular nucleus respectively. Thalamic inputs were found from lateral and central segments of the mediodorsal nucleus to the lateral and intermediate rostral reticular nucleus respectively and heavy paraventricular thalamic inputs were found to the medial reticular nucleus. In the basal forebrain, afferents were found from the vertical and horizontal limbs of the diagonal band, substantia innominata, ventral pallidum and medial globus pallidus. Brainstem projections were identified from ventrolateral periaqueductal grey and adjacent sites in the mesencephalic reticular formation, laterodorsal tegmental nucleus, pedunculopontine nucleus, medial pretectum and ventral tegmental area. The results suggest a general similarity in the organisation of some brainstem Rt afferents in rat and cat, but also show previously unsuspected inputs. Furthermore, there appear to be at least two functional subdivisions of rostral Rt which is reflected by their connections with cortex and thalamus. The studies also extend recent findings that the ventral striatum, via inputs from the paraventricular thalamic nucleus, is included in the circuitry of the rostral Rt, providing further evidence that basal ganglia may function in concert with Rt. Evidence is also outlined with regard to the possibility that rostral Rt plays a significant role in visuomotor functions.Abbreviations ac anterior commissure - aca anterior commissure, anterior - Acb accumbens nucleus - AI agranular insular cortex - AM anteromedial thalamic nucleus - AV anteroventral thalamic nucleus - BST bed nucleus of stria terminalis - Cg cingulate cortex - CG central gray - CL centrolateral thalamic nucleus - CM central medial thalamic nucleus - CPu caudate putamen - DR dorsal raphe nucleus - DTg dorsal tegmental nucleus - EP entopeduncular nucleus - f fornix - Fr2 Frontal cortex, area 2 - G gelatinosus thalamic nucleus - GP globus pallidus - Hb habenula - HDB horizontal limb of diagonal band - IAM interanterodorsal thalamic nucleus - ic internal capsule - INC interstitial nucleus of Cajal - IF interfascicular nucleus - IL infralimbic cortex - IP interpeduncular nucleus - LC locus coeruleus - LDTg laterodorsal tegmental nucleus - LH lateral hypothalamus - LHb lateral habenular nucleus - ll lateral lemniscus - LO lateral orbital cortex - LPB lateral parabrachial nucleus - MD mediodorsal thalamic nucleus - MDL mediodorsal thalamic nucleus, lateral segment - Me5 mesencephalic trigeminal nucleus - MHb medial habenular nucleus - mlf medial longitudinal fasciculus - MnR median raphe nucleus - MO medial orbital cortex - mt mammillothalamic tract - OPT olivary pretectal nucleus - pc posterior commissure - PC paracentral thalamic nucleus - PF parafascicular thalamic nucleus - PPTg pedunculopontine tegmental nucleus - PrC precommissural nucleus - PT paratenial thalamic nucleus - PV paraventricular thalamic nucleus - PVA paraventricular thalamic nucleus, anterior - R red nucleus - Re reuniens thalamic nucleus - RRF retrorubral field - Rt reticular thalamic nucleus - Scp superior cerebellar peduncle - SI substantia innominata - sm stria medullaris - SNR substantia nigra, reticular - st stria terminalis - TT tenia tecta - VL ventrolateral thalamic nucleus - VO ventral orbital cortex - VP ventral pallidum - VPL ventral posterolateral thalamic nucleus - VTA ventral tegmental area - 3 oculomotor nucleus - 3V 3rd ventricle - 4 trochlear nucleus     

The distribution and topographical organization in the thalamus of anterogradely-transported horseradish peroxidase after spinal injections in cat and raccoon

Summary The distribution of anterogradely-transported horseradish peroxidase (HRP) was examined in the rostral mesencephalon and thalamus of cats and raccoons that had received injections of HRP in the cervical and/or lumbosacral enlargements of the spinal cord. Labeling was consistently observed in a large number of loci. All regions previously identified as targets of spinomesencephalic or spinothalamic fibers were included. Evidence of topographical organization was obtained in several regions. Adjacent fields of labeling were often separable on the basis of the distribution, appearance and topographical organization of the labeling. Subject to the methodological constraints imposed by the possibilities of transneuronal and/or collateral labeling, we conclude that a wide variety of loci in the thalamus receive direct spinal input. The organization of these projections suggests that each terminal region may be associated with different aspects of spinal cord function.Abbreviations A anterior pretectal nucleus - AD anterodorsal n. - AM anteromedial n. - AV anteroventral n. - CeM centromedial n. - CD centrodorsal n. (raccoon) - CL centrolateral n. - CM centre median - H habenula - L n.a limitans - LD laterodorsal n. - LG lateral geniculate - LGv lateral geniculate, ventral subnucleus - LP lateral posterior n. - LPvi lateral posterior n., ventral intermediate part - M medial pretectal n. - mc medial geniculate, magnocellular subnucleus - MD mediodorsal n. - MG medial geniculate - ML medial lemniscus - N pretectal nucleus of the optic tract - nBIC n. of the brachium of the inferior colliculus - O olivary pretectal n. - OT optic tract - P posterior nucleus of Rioch - Pc paracentral n. - Pf parafascicular n. - PO posterior group of thalamus - PP posterior pretectal n. - Pt parataenial n. - Pul pulvinar - Pv paraventricular n. of thalamus - R reticular n. - Re n. reuniens - Rh rhomboid n. - RN red nucleus - SG suprageniculate n. - Sm n. submedius - SN substantia nigra - Spf subparafascicular n. - Tg mesencephalic tegmentum - VA ventroanterior n. - VP ventroposterior thalamus (i.e. VPM, VPI, and VPL) - VL ventrolateral n. - VM ventromedial n. - VMb ventromedial n., basal part - VPI ventroposteroinferior n. - VPL1a ventroposterolateral n., lateral part - VPLm ventroposterolateral n., medial part - VPM ventroposteromedial n. - ZI zona incerta     

Forebrain connections of medial agranular cortex in the prairie vole, Microtus ochrogaster

 Fluorescent axonal tracers were used to investigate the connections of medial agranular cortex (frontal area 2, Fr2) in male prairie voles. The rostral and caudal portions of Fr2 (rFr2 and cFr2) have distinct but partially overlapping patterns of connections. Thalamic labeling after cFr2 injections was present in anteromedial nucleus (AM), ventrolateral nucleus (VL), lateral segment, mediodorsal nucleus (MDl), centrolateral nucleus (CL), ventromedial nucleus (VM), posterior nucleus (Po) and lateral posterior nucleus (LP). A band of labeled cells involving CL, central medial nucleus (CM) and rhomboid nucleus (Rh) formed a halo around the periphery of submedial (gelatinosus) nucleus (Sm). Within cFr2 there is a rostrocaudal gradient whereby projections from VL and MDl become progressively sparser caudally, whereas those from LP and Po become denser. Rostral Fr2 receives afferents from a similar group of thalamic nuclei, but has denser innervation from VL and MDl, lacks afferents from LP, and receives less input from nuclei around the periphery of Sm. Caudal Fr2 has extensive cortical connections including orbital cortex, rostral Fr2, Fr1, caudal parietal area 1 (Par1), parietal area 2 (Par2), and posterior parietal, retrosplenial and visual areas. Rostral Fr2 has similar connections with areas Fr1, Par1 and Par2; orbital connections focused in ventrolateral orbital cortex (VLO); connections with caudal Fr2; greatly reduced connections with posterior parietal cortex and the visual areas; and no connections with retrosplenial cortex. The axons linking rFr2 and cFr2 with each other and with other cortical areas travel predominately in the deep gray matter of layers VI and VII rather than in the white matter. Projections to the dorsal striatum from rFr2 are widespread in the head of the caudate, become progressively restricted to a dorsocentral focus more caudally, and disappear by the level of the anterior commissure. The projections from cFr2 are largely restricted to a focal dorsocentral region of the striatum and to the dorsolateral margin of the caudatoputamen. In comparison to area Fr2, the laterally adjacent area Fr1 has thalamic and cortical connections which are markedly restricted. Area Fr1 receives thalamic input from nuclei VL, anteroventral nucleus (AV), CL and Po, but none from mediodorsal nucleus (MD) or LP, and its input from VM is reduced. Cortical afferents to Fr1 originate from areas Fr2, caudal Par1 and Par2. Medial agranular cortex of prairie voles has a pattern of connections largely similar to that seen in rats, suggesting that area Fr2 in prairie voles is part of a cortical network that may mediate complex behaviors involving spatial orientation. Received: 20 May 1998 / Accepted: 14 October 1998     

Electrophysiological studies on the cerebellocerebral projections in monkeys

1. Responses evoked by stimulation of the cerebellar and thalamic nuclei were recorded by microelectrodes introduced at various depths in the cerebral cortex of monkeys (Macaca mulatta) under light Nembutal anaesthesia. 2. Stimulation of the medial (fastigial) cerebellar nucleus produced, at a latency of 4-5 msec, deep thalamo-cortical (T-C) responses (surface positive-deep negative potentials) mainly in the medial part of the precentral gyrus (area 4, "motor area for hindlimb") and in the superior parietal gyrus (area 5) on both contralateral and ipsilateral sides to the nucleus stimulated. 3. Stimulation of the lateral (dentate) cerebellar nucleus elicited, at a latency of about 3 msec, superficial T-C responses (surface negative-deep positive potentials) predominately in the lateral part of the precentral gyrus (area 4, "motor area for forelimb and face") and in the rostromedial part of the gyrus (area 6, premotor area) on the contralateral side. 4. Stimulation of the interpositus cerebellar nucleus set up superficial T-C responses chiefly in the motor area between those influenced by the medial and the lateral cerebellar nucleus stimulation and also in the premotor area on the contralateral side. 5. The respective areas responsive to the medial, interpositus and lateral nucleus stimulation overlapped considerably each other in the motor cortex. 6. Comparison of the responses in the cortex induced by stimulation of the cerebellar and thalamic nuclei indicated different relay portions in and around the VA-VL region of the thalamus for the superficial and the deep T-C responses respectively. 7. Functional implications of the results were discussed in referring to the cerebellocerebral projections in cats.     

Connections of the anterior ectosylvian visual area (AEV)

Summary We have previously described a visual area situated in the cortex surrounding the deep infolding of the anterior ectosylvian sulcus of the cat (Mucke et al. 1982). Using orthograde and retrograde transport methods we now report anatomical evidence that this anterior ectosylvian visual area (AEV) is connected with a substantial number of both cortical and subcortical regions. The connections between AEV and other cortical areas are reciprocal and, at least in part, topographically organized: the rostral AEV is connected with the bottom region of the presylvian sulcus, the lower bank of the cruciate sulcus, the rostral part of the ventral bank of the splenial sulcus, the rostral portion of the lateral suprasylvian visual area (LS) and the lateral bank of the posterior rhinal sulcus; the caudal AEV is connected with the bottom region of the presylvian sulcus, the caudal part of LS, the ventral part of area 20 and the lateral bank of the posterior rhinal sulcus. Subcortically, AEV has reciprocal connections with the ventral medial thalamic nucleus (VM), with the medial part of the lateralis posterior nucleus (LPm), as well as with the lateralis medialis-suprageniculate nuclear (LM-Sg) complex. These connections are also topographically organized with more rostral parts of AEV being related to more ventral portions of the LPm and LM-Sg complex. AEV also projects to the caudate nucleus, the putamen, the lateral amygdaloid nucleus, the superior colliculus, and the pontine nuclei. It is concluded that AEV is a visual association area which functionally relates the visual with both the motor and the limbic system and that it might play a role in the animal's orienting and alerting behavior.Abbreviations Ac aqueductus cerebri - AEs anterior ectosylvian sulcus - ALLS anterolateral lateral suprasylvian area - AMLS anteromedial lateral suprasylvian area - ASs anterior suprasylvian sulcus - Cd caudate nucleus - CL central lateral nucleus - Cl claustrum - Cos coronal sulcus - Crs cruciate sulcus - DLS dorsal lateral suprasylvian area - GI stratum griseum intermediale - GP stratum griseum profundum - IC inferior colliculus - LAm lateral amygdaloid nucleus - LGNd dorsal nucleus of lateral geniculate body - LGNv ventral nucleus of lateral geniculate body - Llc nucleus lateralis intermedius, pars caudalis - LM nucleus lateralis medialis - LPl nucleus lateralis posterior, pars lateralis - LPm nucleus lateralis posterior, pars medialis - Ls lateral sulcus - MD nucleus mediodorsalis - MG medial geniculate body - MSs middle suprasylvian sulcus - Ndl nucleus dorsolateralis pontis - Nl nucleus lateralis pontis - Np nucleus peduncularis pontis - Npm nucleus paramedianus pontis - Nrt nucleus reticularis tegmenti pontis - Nv nucleus ventralis pontis - Ped cerebral peduncle - PEs posterior ectosylvian sulcus - Pg periaqueductal gray - PLLS posterolateral lateral suprasylvian area - PMLS posteromedial lateral suprasylvian area - PSs presylvian sulcus - Pul pulvinar - Put putamen - R red nucleus - Sg suprageniculate nucleus - SN substantia nigra - Sps splenial sulcus - Syls sylvian sulcus - T trapezoid body - VA ventral anterior nucleus - VL ventral lateral nucleus - VLS ventral lateral suprasylvian area - VM ventral medial nucleus - VPL ventral posterolateral nucleus - VPM ventral posteromedial nucleus Sponsored by Max-Planck-Society during part of the studySponsored by Thyssen FoundationSponsored by Alexander von Humboldt-Foundation     

The cerebellar projections to the superior colliculus and pretectum in the cat: An autoradiographic and horseradish peroxidase study

Efferent projections from the cerebellar nuclei to the superior colliculus and the pretectum have been studied using both retrograde and orthograde labeling techniques in the cat. In order to identify what parts of the cerebellar nuclei project to the superior colliculus and the pretectum, the retrograde horseradish labeling technique was employed. In another set of experiments, tritiated amino acids were injected into each of the cerebellar regions from which the cerebello-tectal and cerebellopretectal projections arise, and the laminar and spatial distributions of orthograde labeling in the superior colliculus and the pretectum were compared.The results showed that the cerebello-tectal projections arise from two different regions of the cerebellar nuclei: the caudal half of the medial nucleus and the ventrolateral part of the posterior interposed nucleus. Fibers arising from the medial nucleus distribute bilaterally in the superficial zone of the intermediate gray layer in the superior colliculus, while those originating from the posterior interposed nucleus terminate contralaterally in the deeper aspect of the intermediate gray layer and in the deep gray and white layers. Although the lateral nucleus does not contribute to the cerebello-tectal projection, it projects profusely to the pretectum contralaterally. The origin of the cerebello-pretectal projection lies in the parvicellular part of the lateral nucleus. Among several pretectal nuclei, the posterior pretectal, the medial pretectal nucleus and the reticular part of the anterior pretectal nucleus receive the cerebellar afferents.The findings of the differential projections from the cerebellum to the superior colliculus and the pretectum suggest that the cerebellum exerts a regulatory influence on visuo-motor and somato-motor transfer in these midbrain structures by differential circuits.     

Topographical projections from the posterior thalamic regions to the striatum in the cat,with reference to possible tecto-thalamo-striatal connections

Summary Projections from the posterior thalamic regions to the striatum were studied in the cat by the anterograde tracing method after injecting wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) into the caudalmost regions of the lateroposterior thalamic nucleus (caudal LP), suprageniculate nucleus (Sg) and magnocellular division of the medial geniculate nucleus (MGm). The results were further confirmed by the retrograde tracing method after injecting WGA-HRP into the regions of the caudate nucleus (Cd) and putamen (Put) where afferent fibers from the caudal LP, Sg and MGm were distributed. Fibers from the MGm, Sg or caudal LP were distributed mainly in the medial, middle or lateral part of the caudal half of the putamen (caudal Put), respectively. Although there was a considerable overlap, thalamostriatal fibers from the caudal LP terminated more caudally than those from the MGm. On the other hand, thalamocaudate fibers from the MGm, Sg and lateral part of the caudal LP overlapped with each other in the ventrolateral part of the caudal half of the caudate nucleus (caudal Cd). Fibers from the medial part of the caudal LP were distributed in the ventral part of the caudal Cd. In the superior colliculus (SC) of the cats with WGA-HRP injections in the caudal LP, retrogradely labeled neuronal cell bodies were mainly seen ipsilaterally in the superficial SC layer, and simultaneously, anterogradely labeled axon terminals were observed in the striatum. On the other hand, when WGA-HRP was injected into the Sg or MGm, labeled SC neurons were mainly located in the intermediate and deep SC layers. Thus, ascending impulses from the superficial SC layer may possibly be conveyed ipsilaterally via the caudal LP to the ventral and ventrolateral parts of the caudal Cd and the lateral part of the caudal Put, whereas those from the intermediate and deep SC layers may be relayed via the Sg and/or MGm to the ventrolateral part of the caudal Cd and the middle and medial parts of the caudal Put.Abbreviations AC anterior commissure - Am amygdaloid nucleus - Cd caudate nucleus - Ce centromedial nucleus - CL centrolateral nucleus - Cl claustrum - CM-Pf centre médian-parafascicular complex - CP cerebral peduncle - d deep SC layer - EC external capsule - Ep entopeduncular nucleus - GP globus pallidus - i intermediate SC layer - IC internal capsule - Ip interpeduncular nucleus - LG lateral geniculate nucleus - LP lateroposterior nucleus - MD mediodorsal nucleus - MG medial geniculate nucleus - MGm magnocellular division of MG - MGp principal division of MG - NBIC nucleus of brachium of inferior colliculus - O oculomotor nucleus - OT optic tract - Pom medial division of posterior group of thalamus - Pt pretectum - Pul pulvinar nucleus - Put putamen - Pv paraventricular nucleus of thalamus - R reticular nucleus of thalamus - Rh rhomboid nucleus - RN red nucleus - s superficial SC layer - SC superior colliculus - Sg suprageniculate nucleus - SN substantia nigra - SNpc pars compacta of SN - SNpr pars reticulata of SN - V lateral ventricle - VA ventroanterior nucleus - VL ventrolateral nucleus - VM ventromedial nucleus - WGA-HRP wheat germ agglutinin-HRP conjugate     

The mode of nigro-thalamic transmission investigated with intracellular recording in the cat

Postsynaptic potentials evoked by stimulating the substantia nigra (SN) were recorded intracellularly from ipsilateral ventral medial (VM), ventral lateral (VL), and ventral anterior (VA) nuclei of the thalamus in cats anesthetized with sodium pentobarbital. SN stimulation evoked inhibitory postsynaptic potentials (IPSP) at a short latency in VM neurons (mean 1.68 ms, SD 0.23, n = 59). The IPSP were produced monosynaptically because linear regression analysis of latency vs. conduction distance between stimulating and recording sites indicated a synaptic delay of less than 0.6 ms. Conduction velocity for these fibers was calculated to be 4.48 m/s. The spots from which IPSP were produced with the lowest threshold were determined for each of 38 VM neurons. IPSP origins thus determined were distributed in the pars reticulata of the SN (SNr) and in the area where nigro-thalamic fibers run. Neurons which received IPSP from the SNr were distributed in the VM nucleus, ventromedial to the VL nucleus, where fibers from the contralateral brachium conjunctivum terminate. Convergence of nigral and cerebellar impulses was not observed in thalamic neurons sampled in this study. Stimulation of the entopeduncular nucleus (ENT) also produced monosynaptic IPSP in VL-VA neurons. The SNr-related cell group was located ventromedially and caudally to the ENT-related cell group. No convergence of nigral and pallidal influences was observed within thalamic neurons.     

Efferent fiber projections of the habenula and the interpeduncular nucleus. An experimental study in the opossum and cat

Summary A study of efferent fiber connections of the habenula and the inter-peduncular nucleus was conducted using anterograde degeneration techniques. Lesions were placed in the habenula of the opossum and the habenula and interpeduncular nucleus of the cat. Degeneration was studied by means of the Nauta and Fink-Heimer techniques.Fibers from the habenular nucleus of the opossum extended caudally and were traced bilaterally to the interpeduncular nucleus, dorsal tegmental nucleus of Gudden, deep (ventral) tegmental nucleus of Gudden, nucleus centralis superior and nucleus reticularis tegmenti pontis. Rostrally fibers were traced to the preoptic and septal region and the anterior and lateral hypothalamus.The medial and lateral habenular nuclei of the cat projected differentially to portions of the interpeduncular nucleus and the tegmental nuclei of Gudden. The medial habenular nucleus sent fibers to the paramedian subnucleus of the interpeduncular nucleus and to the deep tegmental nucleus; whereas the lateral habenular nucleus distributed to the apical and central subnuclei of the interpeduncular nucleus and the dorsal tegmental nucleus.Fibers from both the medial and lateral habenular nuclei were found to project bilaterally to the nucleus paraventricularis anterior, nucleus ventralis anterior, anterior medialis and anterior dorsalis of the thalamus, and the septal area.Fibers from the interpeduncular nucleus of the cat were represented bilaterally. Those passing rostral went to the lateral habenular nucleus, nucleus centromedianus and parafascicularis of the thalamus, and to the septal area. Those directed caudally projected to the nucleus centralis superior, and the dorsal and deep tegmental nucleus of Gudden.Abbreviations AC anterior commissure - AD nucleus anterior dorsalis - AM nucleus anterior medialis - AV nucleus anterior ventralis - BC brachium conjunctivum - CC corpus callosum - CD caudate nucleus - CI internal capsule - CL nucleus centralis lateralis - CM nucleus centromedianus - CP cerebral peduncle - DT dorsal tegmental nucleus (of Gudden) - EN entopeduncular nucleus - Fx fornix - GC central gray - GL lateral geniculate nucleus - GM medial geniculate nucleus - GP globus pallidus - HbPt habenulopeduncular tract - HVM ventromedial hypothalamic nucleus - IC inferior colliculus - IP interpeduncular nucleus - LHb lateral habenular nucleus - LL lateral lemniscus - LMN lateral mammillary nucleus - LP nucleus lateralis posterior - MD nucleus medialis dorsalis - MHb medial habenular nucleus - ML medial lemniscus - MMN medial mammillary nucleus - MP mammillary peduncle - NCM nucleus centralis medialis - OC optic chiasm - OT optic tract - Pf nucleus parafascicularis - Pul pulvinar - PUT putamen - RE nucleus reuniens - RN red nucleus - RPO preoptic area - RTP nucleus reticularis tegmenti pontisv (von Bechterew) - S stria medullaris - SC superior colliculus - SN substantia nigra - SPT septal area - VA nucleus ventralis anterior - VL nucleus ventralis lateralis - VM nucleus ventralis medialis - VPL nucleus ventralis posterolateralis - VPM nucleus ventralis posteromedialis - VT deep tegmental nucleus (of Gudden) - II optic nerve     

Tachykinin immunoreactivity in terminals of trigeminal afferent fibers in adult and fetal monkey thalamus

Summary Immunocytochemistry of fetal and adult monkey thalamus reveals a dense concentration of tachykinin immunoreactive fibers and terminals in the dorsolateral part of the VPM nucleus in which the contralateral side of the head, face and mouth is represented. The immunoreactive fibers enter the VPM nucleus from the thalamic fasciculus and electron microscopy reveals that they form large terminals resembling those of lemniscal axons and terminating in VPM on dendrites of relay neurons and on presynaptic dendrites of interneurons. Double labeling strategies involving immunostaining for tachykinins after retrograde labeling of brainstem neurons projecting to the VPM failed to reveal the origin of the fibers. The brainstem trigeminal nuclei, however, are regarded as the most likely sources of the VPM-projecting, tachykinin positive fibers.Abbreviations AB ambiguus nucleus - AN abducens nucleus - C cuneate nucleus - CD dorsal cochlear nucleus - CL central lateral nucleus - CM centre médian nucleus - D dendrite - DR dorsal raphe - DV dorsal vagal nucleus - EC external cuneate nucleus - FM medial longitudinal fasciculus - FN facial nucleus - G gracile nucleus - Gc gigantocellular reticular formation - HN hypoglossal nucleus - ICP inferior cerebellar peduncle - IO inferior olivary complex - LC locus coeruleus - LL lateral lemniscus - LM medial lemniscus - M5 motor trigeminal nucleus - NS solitary nucleus - OS superior olivary complex - P dendritic protrusion - Pb parabrachial nucleus - Pc parvocellular reticular formation - PLa anterior pulvinar nucleus - Pp prepositus hypoglossi nucleus - Ps presynaptic region - Py pyramidal tract - P5 principal sensory trigeminal nucleus - R reticular nucleus - RF reticular formation - RL lateral reticular nucleus - S5 spinal trigeminal nucleus - T terminal - T5 spinal trigeminal tract - VL lateral vestibular nucleus - VM medial vestibular nucleus - VMb basal ventral medial nucleus - VPI ventral posterior inferior nucleus - VPL ventral posterior lateral nucleus - VPM ventral posterior medial nucleus - VR ventral raphe - VS superior vestibular nucleus - VSp spinal vestibular nucleus - ZI zona incerta - 5 trigeminal nerve - 6 abducens nerve - 7 facial nerve     

An autoradiographic study of efferent connections of the globus pallidus in Macaca mulatta

Summary Radioactive amino acids were injected into restricted regions of the globus pallidus of rhesus macaques to allow identification of the organization and courses of efferent pallidal projections. The previously identified projection of the internal pallidal segment (GPi) to ventral thalamic nuclei showed a topographic organization, with the predominant projection from ventral GPi being to medial and caudal ventralis anterior (VA) and lateralis (VL) and from dorsal GPi to lateral and rostral VA and VL. Pallidal efferent fibers also extended caudally and dorsally into pars caudalis of VL, but they spared the portion of pars oralis of VL shown by others to receive input from the cerebellum. In addition to centromedian labeling in all animals, the parafascicular nucleus was also labeled when isotope was injected into dorsal GPi. The medial route from GPi to the midbrain tegmentum was more substantial than has been shown before, and along this route there was an indication that some fibers terminated in the prerubral region. The projection to the pedunculopontine nucleus was extensive, and fibers continued caudally into the parabrachial nuclei.Pallidal projections to the thalamus seem to be topographically organized but spare thalamic regions that interact with area 4. Caudally directed efferent fibers follow multiple routes and extend more caudally than to the pedunculopontine nuclei.Abbreviations Cd caudate nucleus - CM centromedian nucleus - CT central tegmental tract - DPCS decussation of superior cerebellar peduncle - F fornix - FLM medial longitudinal fasciculus - GPe globus pallidus, pars externa - GPi globus pallidus, pars interna - HbL lateral habenular nucleus - HbM medial habenular nucleus - Is interstitial nucleus - LM medial lemniscus - MD dorsomedial nucleus - PbL lateral parabrachial nucleus - PbM medial parabrachial nucleus - PCS superior cerebellar peduncle - Pf parafascicular nucleus - PPN pedunculopontine nucleus - Put putamen - R reticular nucleus - Rmg red nucleus, pars magnocellularis - Rpc red nucleus, pars parvocellularis - S stria medullaris - SI substantia innominata - SNc substantia nigra, pars compacta - SNr substantia nigra, pars reticulata - St subthalamic nucleus - ST stria terminalis - THI habenulointerpeduncular tract - TM tuberomamillary nucleus - TMT mamillothalamic tract - VA nucleus ventralis anterior - VAmg nucleus ventralis anterior, pars magnocellularis - VAp nucleus ventralis anterior, pars principalis - VI nucleus ventralis intermedius - VLc nucleus ventralis lateralis, pars caudalis - VLm nucleus ventralis lateralis, pars medialis - VLo nucleus ventralis lateralis, pars oralis - VPL nucleus ventralis posterior lateralis - X area X Supported by National Institutes of Health, grant RR00166, Rehabilitation Services Administration, grant 16-P-56818, and PHS grant NS10804     

Ascending projections from the nucleus of the brachium of the inferior colliculus in the cat

Summary Ascending projections from the nucleus of the brachium of the inferior colliculus (NBIC) in the cat were studied by the autoradiographic tracing method. Many fibers from the NBIC ascend ipsilaterally in the lateral tegmentum along the medial border of the brachium of the inferior colliculus. At midbrain levels, fibers from the NBIC end in the superior colliculus, the pretectum, the central gray and the peripeduncular tegmental region bilaterally with ipsilateral predominance. NBIC fibers to the superior colliculus are distributed densely to laminae VI an III throughout the whole rostrocaudal extent of the colliculus. In the pretectum, NBIC fibers terminate in the anterior and medial nuclei and the nucleus of the posterior commissure. NBIC fibers to the dorsal thalamus are distributed largely ipsilaterally. Many NBIC fibers end in the dorsal and medial divisions of the medial geniculate body, but few in the ventral division. The NBIC also sends fibers to the suprageniculate, limitans and lateralis posterior nuclei and the lateral portion of the posterior nuclear complex; these regions of termination of NBIC fibers constitute, as a whole, a single NBIC recipient sector. Additionally, the NBIC sends fibers to the centralis lateralis, medialis dorsalis, paraventricular and subparafascicular nuclei of the thalamus.Abbreviations APtC Pars compacta of anterior pretectal nucleus - APtR Pars reticulata of anterior pretectal nucleus - BIC Brachium of infertior colliculus - CG Central gray - CL Nucleus centralis lateralis - CP Cerebral peduncle - D Dorsal division of medial geniculate body - IC Inferior colliculus - LG Lateral geniculate body - LP Nucleus lateralis posterior - Lim Nucleus limitans - M Medial division of medial geniculate body - MD Nucleus medialis dorsalis - ML Medial lemniscus - NBIC Nucleus of brachium of inferior colliculus - NPC Nucleus of posterior commissure - PN Pontine nuclei - Ppr Peripeduncular region - Pt Pretectum - Pbg Parabigeminal nucleus - Pol Lateral portion of posterior nuclear complex - Pom Medial portion of posterior nuclear complex - Pul Pulvinar - Pv Nucleus paraventricularis - R Red nucleus - SC Superior colliculus - Sg Nucleus suprageniculatus - Spf Nucleus subparafascicularis - V Ventral division of medial geniculate body - VPL Nucleus ventralis posterolateralis - VPM Nucleus ventralis posteromedialis - II,III,IV,VI Tectal laminae     

Subcortical afferent and efferent connections of the superior colliculus in the rat and comparisons between albino and pigmented strains

Summary Subcortical connections of the superior colliculus were investigated in albino and pigmented rats using retrograde and anterograde tracing with horseradish peroxidase (HRP), following unilateral injection of HRP into the superior colliculus. Afferents project bilaterally from the parabigeminal nuclei, the nucleus of the optic tract, the posterior pretectal region, the dorsal part of the lateral posterior-pulvinar complex and the ventral nucleus of the lateral lemniscus; and ipsilaterally from the substantia nigra pars reticulata, the pars lateralis of the ventral lateral geniculate nucleus, the intergeniculate leaflet, the zona incerta, the olivary pretectal nucleus, the nucleus of the posterior commissure, the lateral thalamus, Forel's field H₂, and the ventromedial hypothalamus. Collicular efferents terminate ipsilaterally in the anterior, posterior and olivary pretectal nuclei, the nuclei of the optic tract and posterior commissure, the ventrolateral part of the dorsal lateral geniculate nucleus, the pars lateralis of the ventral lateral geniculate nucleus, the intergeniculate leaflet, and the zona incerta; and bilaterally in the parabigeminal nuclei and lateral posterior-pulvinar complex (chiefly its dorsal part). The general topographical patterns of some of the afferent and efferent projections were also determined: the caudal and rostral parts of the parabigeminal nucleus project to the caudal and rostral regions, respectively, of the superior colliculus; caudal superior colliculus projects to the most lateral, and lateral superior colliculus to the most caudal part of the terminal field in the dorsal lateral geniculate nucleus; caudolateral superior colliculus projects to the caudal ventrolateral part of the ventral lateral geniculate nucleus, while rostromedial parts of the colliculus project more rostrally and dorsomedially. Following comparable injections in pigmented and albino animals, fewer retrogradely labelled cells were found in subcortical structures in the albino than in the pigmented rats. The difference was most marked in nuclei contralateral to the injected colliculus. Thus, the effects of albinism on the nervous system may be more widespread than previously thought.M. R. C. Scholar     

Organization of the thalamo-cortical connexions to the frontal lobe in the rhesus monkey

Summary In 25 rhesus monkeys horseradish peroxidase was injected in different parts of the frontal cortex. The retrogradely labelled thalamic neurons formed longitudinal bands, some of which crossed the internal medullary lamina, and extended from one thalamic nucleus into another. On the basis of these findings the frontal cortex was subdivided into seven transverse cortical strips which receive afferents from seven longitudinal bands of thalamic neurons. The most rostral transverse strip receives afferents from the most medial thalamic band which is oriented vertically and extends through the most medial part of the MD into the medial pulvinar. Progressively more caudally located transverse strips receive afferents from progressively more laterally located thalamic bands which in part are situated in the VL and show an increasing tilt towards the horizontal. Moreover, those parts of the various bands which are situated along the dorsal and lateral margin of the thalamus project to the medial portions of the transverse cortical strips, i.e. along the medial margin of the frontal lobe, while the other parts situated ventromedially in the thalamus project to the lateral portions of these strips, i.e. along the lateral margin of the frontal lobe.These data provide an alternative view of the organization of the thalamus and suggest that this structure contains a matrix of longitudinal cell columns which in some cases extend across specific nuclear borders and may represent the basic thalamic building blocks in respect to the thalamo-cortical connexions.     

Fastigial nucleus projections in the midbrain and thalamus in dogs

Efferent connections to midbrain and thalamus from portions of the cerebellar fastigial nucleus were investigated using autoradiographic techniques. Bipolar stimulating electrodes were placed in the fastigial nucleus of anesthetized beagles and the area which produced maximal increases in blood pressure and heart rate was localized in each dog. A mixture of [3H]leucine and [3H]proline (4:1) was injected into that area and autoradiograms were prepared. Injections filled the rostral and various parts of the caudal fastigial nucleus. The rostral-caudal extent of injection sites were mapped in the horizontal plane from sequential coronal, thionin-stained sections and "primary" and "secondary" injection zones were defined according to specific criteria. Labeled axons reached the mesencephalon via the contralateral uncinate fasiculus. Ascending fibers assembled in a diffuse contingent at the prerubral level adjacent to the ventrolateral periaqueductal gray. The heaviest projections were contralateral to the injection site, but ipsilateral terminals were observed as well. In the midbrain, axons entered the contralateral and ipsilateral superior colliculus to branch repeatedly and terminate in the deep and intermediate layers. Additional terminals were observed bilaterally in the nuclei of the posterior commissure and pretectal areas at the midbrain-diencephalic junction. In the thalamus, labeled axons formed into three groups which terminated in: the contralateral paraventricular complex and medial dorsal nucleus; the contralateral central medial, paracentral, parafasicular and central lateral nuclei, and the contralateral ventral medial and ventral lateral nuclei. There was a sparse projection to the ipsilateral ventral lateral nucleus. The contralateral projection to the ventral medial and ventral lateral nuclei was marked by dense clusters of label ventral to the internal medullary lamina extending, in the dorsal ventral lateral nucleus, to its rostral pole. Projections to specific somesthetic thalamus or the hypothalamus were not observed. These ascending projections in the canine brain generally conform to those described in other nonprimate mammals. The fastigial nucleus presumably provides information concerning equilibrium and body proprioception to the superior colliculus and to thalamic nuclei including both specific motor relay and "nonspecific" midline and intralaminar nuclei, much the same as reported in the cat. The projection to the ventral medial and ventral lateral thalamic nuclei terminate in areas known to participate in the control of axial and proximal limb muscle activity.(ABSTRACT TRUNCATED AT 400 WORDS)     

Origins of the pretectal and tectal projections to the central lateral nucleus in the cat

The pretectal and tectal projections to the thalamic intralaminar nuclei in the cat were studied following horseradish peroxidase injections centered in the central lateral nucleus. Retrogradely labeled neurons were found in both the pretectum and the superior colliculus, ipsilateral and, to a lesser extent, controlateral to the injection site. Labeled pretectal neurons were found throughout all pretectal nuclei; the densest concentrations were in the medial pretectal nucleus, the anterior pretectal nucleus and the nucleus of the posterior commissure. The major source of tectal projections were the small neurons in the stratum griseum intermediate.     

猫丘脑中央外侧核的皮质下传入联系

本实验用HRP逆行性轴浆运输技术,对猫丘脑中央外侧核的传入纤维联系及其局部定位关系进行了观察。投射至丘脑中央外侧核尾侧区的主要核团包括:外侧膝状体腹核背侧带、丘脑网状核特别是它的背侧部、上丘深层,以同侧为主。板内核、丘脑下部外侧区和黑质网状部神经元的轴突终止在同侧丘脑中央外侧核吻侧区。丘脑中央外侧核全长的传入起自脑干网状结构和前庭神经核,呈双侧投射。前者以同侧为主,后者以对侧占优势。同侧未定带,顶盖前区、动眼神经核周围的细胞群、对侧三叉神经感觉主核、楔束核、薄束核以及小脑齿状核内也含有少量标记细胞。我们还观察到HRP注射中心区位于中央外侧核并扩散至丘脑腹前核者,同侧脚内核含大量HRP阳性细胞,而Gudden被盖腹侧核内充满密集的标记终末。这些结果表明,丘脑中央外侧核可能涉及多种感觉和运动功能。     

Distribution of premotor neurons for orbicularis oculi motoneurons in the cat, with particular reference to possible pathways for blink reflex

After injecting horseradish peroxidase into the facial nucleus regions containing orbicularis oculi motoneurons, labeled neuronal cell bodies were found in the lateral medullary reticular formation, pretectal olivary nucleus, sensory trigeminal nuclei, lateral and medial parabrachial nuclei, ventromedial reticular formation medial to the facial nucleus, red nucleus and its surroundings, anterior horn of the upper cervical cord, medullary raphe nuclei, oculomotor nucleus and its surroundings, nuclei of Darkschewitsch, Cajal and Edinger-Westphal, ventral part of the midbrain central gray, pontine tegmentum, lateral vestibular nucleus and deep layers of the superior colliculus.