The cerebellar projection from the raphe nuclei in the cat as studied with the method of retrograde transport of horseradish peroxidase

Summary Following injections of horseradish peroxidase (HRP) in the cerebellar cortex and nuclei of the cat, the distribution of labeled cells in the raphe nuclei was mapped. The findings confirm those made previously in studies of retrograde cell degeneration following cerebellar ablations (Brodal et al., 1960a), and in addition reveal new details in the projection of the raphe nuclei onto the cerebellar cortex and nuclei.All the raphe nuclei except nucleus linearis intermedius and nucleus linearis rostralis project onto the cerebellar cortex. The nuclei raphe obscurus and pontis contribute the greatest number of afferents to the cerebellum.With the exception of lobule VI which probably is the recipient of a weak projection, all parts of the cerebellar cortex receive afferents from the raphe nuclei. The heaviest projection is to the vermis of lobules VIIA and X, and to crus II. The afferents to the cerebellar nuclei are few in number (Tables 2–6).The observations indicate that each raphe neuron probably projects to more than one terminal site in the cerebellum.The findings are discussed with reference to other efferent and afferent studies of the raphe nuclei. All these studies indicate that the raphe nuclei have widespread efferent and afferent connections, making them capable to participate in a variety of regulatory functions.List of abbreviations f.apm. Ansoparamedian fissure - f.icul. Intraculminate fissure - f.in.cr. Intercrural fissure - fl. Flocculus - f.pc. Preculminate fissure - f.pfl. parafloccular fissure - f.ppd. Prepyramidal fissure - f.pr. Fissura prima - f.prc. Precentral fissure - f.prc.a Precentral fissure a - f.p.l. Posterolateral fissure - f.p.s. Posterior superior fissure - f.sec. Fissura secunda - HII–HX Hemispheral lobules II–X - HVIIA cr.I, cr. II Crus I and II of lobule HVIIA - HVIIIA,B Sublobules A and B of lobule HVIII - Li Nucleus linearis intermedius - Lr Nucleus linearis rostralis - l.ans. Ansiform lobule - N.f. Nucleus fastigii - N.i.a. Nucleus interpositus anterior - N.i.p. Nucleus interpositus posterior - N.l. Nucleus lateralis - pfl.d. Dorsal paraflocculus - pfl.v. Ventral paraflocculus - Rd Nucleus raphe dorsalis - Rm Nucleus raphe magnus - Rob Nucleus raphe obscurus - Rpa Nucleus raphe pallidus - Rpo Nucleus raphe pontis - Sc Nucleus raphe centralis superior - s.int.cr.1 Intracrural sulcus 1 - s.int.cr.2 Intracrural sulcus 2 - I–VI Vermian lobules I–VI - VIIA,B Anterior and posterior sublobule of lobule VII - VIIIA,B Anterior and posterior sublobule of lobule VIII     

The diencephalo-olivary projection in the cat as studied with retrograde transport of horseradish peroxidase

Summary The projection from certain diencephalic regions (zona incerta, Forel's fields, the parafascicular and subparafascicular nuclei, the periventricular grey and the hypothalamus) to the inferior olive in the cat was studied by means of retrograde protein tracing. Small injections of horseradish peroxidase were made into various parts of the inferior olive from a ventral approach. The number of retrogradely labelled neural cells in the diencephalic nuclei of all cats is presented in Table 2. The majority of the labelled cells was found in the parafascicular and subparafascicular nuclei, especially within the medial part of the former. The connection is ipsilateral, and the caudal as well as the rostral part of the olivary complex appears to receive the descending afferents. The findings are discussed and related to recent observations concerning descending afferents to the olivary complex.     

Olivary afferents from the pretectal nuclei in the cat

Summary The organization of the projection from the pretectal region to the inferior olive in the cat was studied by means of retrograde protein tracing and experimental degeneration. Small injections of horseradish peroxidase (HRP) were made into various parts of the inferior olive from a ventral approach. The number of nerve cells in the pretectal nuclei retrogradely labelled with HRP was counted and put in relation to the site of injection. Labelled cells were only found in the posterior pretectal nucleus (NPP), the nucleus of the optic tract (NOT) and the anterior pretectal nucleus (NPA). Most labelled cells were found in NPP and NOT in cases in which the rostral or caudal levels of the principal olive were labelled by the injection. NAP labelling occurred in one case with a very rostral injection of the inferior olive. Unilateral electrolytical destruction of the pretectal region produced terminal degeneration in the ipsilateral inferior olive. The heaviest ipsilateral degeneration was found in the upper half of the principal and dorsal accessory olives, and caudally in the ventrolateral outgrowth, the dorsal cap and nucleus with the adjacent part of the medial accessory olive. Some functional implications of the findings are discussed.     

Cerebellar afferent projections from the vestibular nuclei in the cat: An experimental study with the method of retrograde axonal transport of horseradish peroxidase

Summary Details of cerebellar afferent projections from the vestibular nuclei were investigated by the method of retrograde axonal transport of horseradish peroxidase (HRP) in the cat. The distribution of labeled cells in the vestibular nuclei following HRP injections in various parts of the cerebellum indicates that vestibular neurons in the medial and descending nuclei and cell groups f and x project bilaterally to the entire cerebellar vermis, the flocculus, the fastigial nucleus and the anterior and posterior interpositus nuclei. In addition, labeled cells (giant, medium and small) were consistently found bilaterally in the superior and lateral vestibular nuclei following HRP injections in the nodulus, flocculus, fastigial nucleus, and following large injections in the vermis. No labeled cells were observed in cases of HRP injections in crus I and II, the paramedian lobule, paraflocculus and lateral cerebellar nuclei. The present findings indicate that secondary vestibulocerebellar fibers project to larger areas in the cerebellum and originate from more subdivisions and cell groups of the vestibular nuclear complex than previously known.List of Abbreviations B.c. superior cerebellar peduncle (brachium conjunctivum) - D descending (inferior) vestibular nucleus - f cell group f in descending vestibular nucleus - g group rich in glia cells, caudal to the medial vestibular nucleus - HIX hemispheral lobule IX - HVIIA cr. Ia, p; cr. IIa, p anterior and posterior folia of crus I and II of the ansiform lobule - HVIIB, HVIIIA, B sublobules A and B of hemispheral lobules VII and VIII - i.c. nucleus intercalatus (Staderini) - L lateral vestibular nucleus (Deiters) - l small-celled lateral group of lateral vestibular nucleus - M medial (triangular or dorsal) vestibular nucleus - N. cu. e. accessory cuneate nucleus - N. f. c. cuneate nucleus - N. mes. V mesencephalic nucleus of trigeminal nerve - N.tr. s. nucleus of solitary tract - N. VII facial nerve - pfl. d. dorsal paraflocculus - pfl. v. ventral paraflocculus - S superior vestibular nucleus (Bechterew) - Sv. cell group probably representing the nucleus supravestibularis - Tr. s. solitary tract - x small-celled group x, lateral to the descending vestibular nucleus - y small-celled groupy, lateral to the lateral vestibular nucleus (Deiters) - z cell group dorsal to the caudal part of the descending vestibular nucleus - I–VI vermian lobules I–VI - V, VI, XII cranial motor nerve nuclei - VIIA, B; VIIIA, B anterior and posterior sublobules of lobules VII and VIII - IX uvula - X nodulus; dorsal motor nucleus of vagus nerve On leave from the Laboratory of Neurobiology and Department of Anatomy, Faculty of Science, Mahidol University, Bangkok, Thailand, under the Felllowship Program of the Norwegian Agency for International Development (NORAD)     

Olivary afferents from the brain stem reticular formation

Summary The projections from the brain stem reticular formation to the inferior olive have been studied in cats in which microinjections of horseradish peroxidase have been made into the inferior olive from a ventral approach. Retrogradely labelled cells were observed within the reticular formation proper of the medulla, pons and mesencephalon (within the nucleus reticularis parvicellularis, reticularis ventralis, reticularis gigantocellularis, reticularis lateralis, reticularis pontis caudalis, reticularis pontis oralis, cuneiformis and subcuneiformis). Labelled cells were also found within the lateral reticular nucleus (the nucleus of the lateral funiculus), the paramedian reticular and the perihypoglossal nuclei. The connections are bilateral (the projection from the lateral reticular nucleus is only contralateral). The observations demonstrate a more widespread origin for the reticulo-olivary fibres than has previously been shown and indicate that the medullary reticular formation is the area with the highest number of cells projecting to the olivary complex.Abbreviations ß nucleus ß - Br.c. superior cerebellar peduncle (brachium conjunctivum) - Br.p. middle cerebellar peduncle (brachium pontis) - C.i. inferior colliculus - C.r. inferior cerebellar peduncle (restiform body) - Cu nucleus cuneiformis - D dorsal accessory olive - dl dorsal lamella - dors.c. dorsal cap - dorsomed.c.col. dorsomedial cell column - F.l.m. medial longitudinal fasciculus - Ic or ic nucleus intercalatus - l lateral - M medial accessory olive - m medial - N.III,V,VI,VII,X,XII root fibres of cranial nerves - N.c. nucleus cuneatus - N.c.e. external (accessory) cuneate nucleus - N.c.t. nucleus of corpus trapezoideum - N.l.l. nucleus of lateral lemniscus - N.m.X dorsal motor (parasympathetic) nucleus of vagus - N.mes. mesencephalic trigeminal nucleus - Nr nucleus ruber - Nrl or N.r.l lateral reticular nucleus (nucleus of lateral funiculus) - Nrp or N.r.p. nucleus reticularis paramedianus - N.r.t. nucleus reticularis tegmenti pontis - nucl. nucleus ß - Ol.s. superior olive - P principal olive - ph or P.h. nucleus praepositus hypoglossi - PN perihypoglossal nuclei - Pp nucleus peripeduncularis - Py pyramid - Rg or R.gc. nucleus reticularis gigantocellularis - Rl or R.l. nucleus reticularis lateralis (of Olszewski) - Rp or R.pc. nucleus reticularis parvicellularis - Rpc or R.p.c. nucleus reticularis pontis caudalis - Rpo or R.p.o. nucleus reticularis pontis oralis - Rv or R.v. nucleus reticularis ventralis - Scu nucleus subcuneiformis - S.n. substantia nigra - Tr.sp.V. spinal tract of trigeminal nerve - T.s. tractus solitarius surrounded by nucleus of solitary tract - vl ventral lamella - vlo or ventrolat outgr. ventrolateral outgrowth - V.m. medial vestibular nucleus - I-XV transverse sections through the olive from caudal (I) to rostral (XV) - III,IV,V,VI,VII,X and XII motor nuclei of cranial nerves (X: nucleus ambiguus)     

The reticulocerebellar projection in the cat as studied with retrograde transport of horseradish peroxidase

Summary Injections of horseradish peroxidase into the various parts of the cerebellar cortex and the cerebellar nuclei in the cat result in labelled cells within the reticular formation proper. All the reticular nuclei (with the exception of the reticular formation of the mesencephalon) send fibres to the cerebellum. The highest number of labelled neurons after cerebellar injections is found in the caudal reticular formation, especially within nucleus reticularis ventralis, nucleus reticularis lateralis and nucleus reticularis gigantocellularis. Another region for an accumulation of labelled cells is the rostral part of nucleus reticularis pontis caudalis.Except for the paraflocculus, all cerebellar cortical areas and all cerebellar nuclei receive afferents from one or more of the nuclei within the reticular formation proper, but the largest number of labelled neurons is observed in cases with injections including the intermediate-lateral part of lobulus simplex and the adjacent areas of the anterior lobe and crus I. The projection is bilateral with an ipsilateral preponderance (the cerebellar nuclei appear to receive a higher number of fibres from the contralateral side). Cells of all sizes are labelled, but labelled giant cells are found only after large cortical injections.     

The trigemino-olivary projection in the cat as studied with retrograde transport of horseradish peroxidase

Summary The trigemino-olivary projection was studied in cats which from a ventral approach were injected with horseradish peroxidase into various parts of the inferior olive. Retrogradely labelled cells of all sizes were present in all three divisions of the spinal sensory nucleus: nucleus caudalis, nucleus interpolaris and nucleus oralis. The projection is bilateral with the highest number of labelled cells on the contralateral side. No retrogradely labelled cells are found in the principal nucleus, but some cats showed a few retrogradely labelled cells within the ipsilateral mesencephalic nucleus.The findings are discussed and related to recent observations concerning the distribution of the direct trigemino-cerebellar fibres.     

The vestibulothalamic projections in the cat studied by retrograde axonal transport of horseradish peroxidase

Summary Horseradish peroxidase (HRP) was injected or iontophoretically ejected in various thalamic nuclei in 63 adult cats. In 11 other animals HRP was deposited outside the thalamic territory. The number and distribution of labelled cells within the vestibular nuclear complex (VC) were mapped in each case. To a varying degree all subgroups of VC appear to contribute to the vestibulothalamic projections. Such fibres are distributed to several thalamic areas. From the present investigation it appears that generally speaking, there exist three distinct vestibulothalamic pathways with regard to origin as well as to site of termination of the fibres. One projection appears to originate mainly in caudal parts of the medial (M) and descending (D) vestibular nuclei and in cell group z. This pathway terminates chiefly in the contralateral medial part of the posterior nucleus of the thalamus (POm) including the magnocellular part of the medial geniculate body (Mgmc), the ventrobasal complex (VB) and the area of the ventral lateral nucleus (VL) bordering on VB. A second projection originates mainly in the superior vestibular nucleus (S) and in cell group y and terminates mainly in the contralateral nucleus centralis lateralis (CL) and the adjoining nucleus paracentralis (Pc). A third, more modest, pathway originates chiefly in the middle M and D, with a minor contribution from S and cell group y, and terminates in the contralateral ventral nucleus of the lateral geniculate body (GLV). There is some degree of overlap between the origin of these three vestibulothalamic pathways.Abbreviations B.c. brachium conjunctivum - CeM nucleus centralis medialis thalami - CL nucleus centralis lateralis thalami - CM nucleus centrum medianum - D nucleus vestibularis descendons - f cell group f - g cell group g - GLD corpus geniculatum laterale dorsalis - GLV corpus geniculatum laterale ventralis - i.e. nucleus intercalatus - L nucleus vestibularis lateralis - LD nucleus lateralis dorsalis thalami - LIM lamina medullaris interna - Lim nucleus limitans - LP nucleus lateralis posterior thalami - M nucleus vestibularis medialis - MD nucleus medialis dorsalis thalami - MGmc corpus geniculatum mediale, pars magnocellularis - MGp corpus geniculatum mediale, pars principalis - N.cu.e. nucleus cuneatus externus - N.f.c. nucleus fasciculi cuneati - N.mes. V nucleus mesencephalicus nervi trigemini - NR nucleus ruber - N.tr.s. nucleus tractus solitarius - N. VII nervus facialis - N. VIII nervus statoacusticus - PC pedunculus cerebri - Pc nucleus paracentralis thalami - Pf nucleus parafascicularis - p.h. nucleus prepositus hypoglossi - PO posterior thalamic group - PO1 lateral part of PO - POm medial part of PO - Prt nucleus pretectalis - Pul pulvinar - R nucleus reticularis thalami - S nucleus vestibularis superior - Sg nucleus suprageniculatus - SN substantia nigra - Sv nucleus supravestibularis - Tr.s. tractus solitarius - VA nucleus ventralis anterior thalami - VL nucleus ventralis lateralis thalami - VPL nucleus ventralis posterior lateralis - VPL1 lateral part of VPL - VPLm medial part of VPL - VPM nucleus ventralis posterior medialis - x cell group x - y cell group y - z cell group z - V nucleus motorius nerve trigemini - X nucleus dorsalis nerve vagi - XII nucleus nervi hypoglossi     

Cerebellotectal projections studied in cats with horseradish peroxidase or tritiated amino acids axonal transport

Summary After injections of horseradish peroxidase (HRP) into various parts of the superior colliculus (SC) in 14 cats, retrogradely labeled neurons were found in parts of all deep cerebellar nuclei. The present study demonstrated that there are three main origins of the cerebellotectal projections in regard to the locations of the cell bodies: (1) the caudal half approximately of the fastigial nucleus (NM) including the subnucleus medialis parvocellularis (SMP), (2) the ventral and lateral parts of the posterior interpositus nucleus (NIP), and (3) the ventral part of the dentate nucleus (NL) including the subnucleus lateralis parvocellularis (SLP).The pathways and terminations of these projections have also been shown autoradiographically. Thus, fibers from NM crossed within the cerebellum and terminated in the intermediate and deep gray layers of the bilateral SC. Fibers from NIP and NL passed within the superior cerebellar peduncle, which crossed in the tegmentum (decussation of the peduncle) and ended in the two layers of the contralateral SC. In addition, some cerebellofugal fibers were found to terminate in the nuclei interstitialis of Cajal and Darkschewitsch, as well as in parts of pretectum and thalamus.The tecto-ponto- (and olivo-) cerebellotectal loop (cf. Kawamura 1980) has been established morphologically and it is briefly commented on in correlation with the propagation of the teleceptive (optic and acoustic) impulses.Abbreviations AI Stratum album intermedium - AP Stratum album profundum - Cc Crus cerebri - CM Corpus mamillare - EW Nucleus of Edinger-Westphal - f.apm. Ansoparamedian fissure - Flm Fasciculus longitudinalis medialis - f.p.l. Posterolateral fissure - f.ppd. Prepyramidal fissure - f.pr. Fissura prima - f.p.s. Posterior superior fissure - f.sec. Fissura secunda - GI Stratum griseum intermedium - GP Stratum griseum profundum - GS Stratum griseum superficiale - L. Left - MG Medial geniculate body - ND Nucleus of Darkschewitsch - NIA Nucleus interpositus anterior - Nint Nucleus interstitialis of Cajal - NIP Nucleus interpositus posterior - NL Nucleus lateralis (dentatus) - NL-NIA Transition area of nucleus lateralis (dentatus) and nucleus interpositus anterior - NM Nucleus fastigii - Npa Nucleus pretectalis anterior - Npc Nucleus of posterior commissure - Npm Nucleus pretectalis medialis - Npp Nucleus pretectalis posterior - NR Nucleus ruber - Nto Nucleus of optic tract - N.III Oculomotor nerve - O Stratum opticum - PC Posterior commissure - pm. Paramedian lobule - Pg Periaqueductal gray substance - R. Right - Rf Fasciculus retroflexus - SC Superior colliculus - SCC Commissure of SC - Z Stratum zonale - III Nucleus of oculomotor nerve - V, VI, VIIA, VIIB, VIIIA, VIIIB, IX Cerebellar lobules of Larsell Working in the Anatomical Department of Iwate Medical University for six months (several periods during the year 1981)     

A cervical primary afferent input to vestibular nuclei as demonstrated by retrograde transport of wheat germ agglutinin-horseradish peroxidase in the rat

Summary Wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) was microiontophoretically injected into the vestibular nuclear complex of the rat. Retrogradely labeled neurons were found in ipsilateral spinal ganglia C₂-C₃ only if the injection site was in the caudal part of the medial vestibular nucleus (MVN). Injections into rostral parts of the MVN, the superior, lateral and descending vestibular nuclei (SVN, LVN, DVN), the nucleus of the solitary tract (STN) and the reticular formation did not result in spinal ganglion labeling. Thus, the caudal part of the MVN appears to be the main vestibular termination site for rostral cervical primary afferents.Abbreviations Cu cuneate nucleus - DVN descending vestibular nucleus - ECN external cuneate nucleus - g7 genu of the facial nerve - icp inferior cerebellar peduncle - In intercalated nucleus - LVN lateral vestibular nucleus - mlf medial longitudinal fasciculus - MVN medial vestibular nucleus - PrH prepositus hypoglossi nucleus - Ro Roller's nucleus - sol solitary tract - SVN superior vestibular nucleus - 12 hypoglossal nucleus     

The cerebellar corticonuclear and nucleocortical projections in the cat as studied with anterograde and retrograde transport of horseradish peroxidase

Summary The cerebellar parafloccular corticonuclear and nucleocortical connections were studied in the cat by means of anterograde and retrograde transport of horseradish peroxidase.Previous investigations have given evidence that the cortex of the paraflocculus can be subdivided into three zones. These zones are recognized as C₂, D₁ and D₂. The material presented is compatible with the findings from previous reports with other methods that each of these zones sends its Purkinje axons to separate regions within the cerebellar nuclei. These terminal fields are the lateral part of nucleus interpositus posterior (the alleged nuclear zone C₂) and the dentate nucleus and its transition area with nucleus interpositus anterior (the supposed nuclear D zones). The parafloccular corticonuclear fibres appear to terminate along a continuous mediolateral band extending from the NL through the NL-NIA transition area into the lateral NIP. This observation is in concordance with our previous findings concerning the termination of the cerebellar corticonuclear fibres (Dietrichs and Walberg 1979, 1980; Dietrichs 1981). Within the NL and NL-NIA transition area the Purkinje axons from the ventral paraflocculus terminate ventral to those from the dorsal paraflocculus.The nucleocortical projection shows the same zonal arrangement as the corticonuclear connection, indicating the presence of a corticonuclear-nucleocortical reciprocity.The findings are discussed with reference to previous studies on the parafloccular corticonuclear and nucleocortical connections, and some comments are made concerning the cerebellar zonal subdivision of this cortical area.     

The cerebellar corticonuclear and nucleocortical projections in the cat as studied with anterograde and retrograde transport of horseradish peroxidase

Summary The cerebellar corticonuclear and nucleocortical connections of lobulus simplex, crus I and II in the cat were studied by means of anterograde and retrograde transport of HRP. Previous experimental studies give evidence that the cortex of the cerebellar hemisphere in a lateromedial direction can be subdivided into five longitudinal zones. These are recognized as zones D₂, D₁, C₃, C₂ and C₁. Our observations indicate that each cortical zone has its own field of termination in the cerebellar nuclei, and that these nuclear fields are similar to those receiving afferents from the corresponding zones within the paramedian lobule (Dietrichs and Walberg, 1979).The Purkinje axons from each folium terminate from medial to lateral along a continuous band which loops through the cerebellar nuclei from the ventromedial part of nucleus interpositus posterior to the dorsolateral part of the same nucleus, from where it proceeds into the lateral part of nucleus interpositus anterior and the transition area between nucleus interpositus anterior and the dentate nucleus, to end within the latter. In addition to this arrangement there is a rostrocaudal organization within the hemispheral cortex so that the nuclear bands receiving Purkinje axons from the rostral folia (lobulus simplex) are situated slightly ventral to those receiving terminal fibres from the middle folia (crus I), which again are situated ventral to the terminal bands for the caudal folia (crus II).The nucleocortical projection shows largely the same zonal arrangement as the corticonuclear, but labelled nuclear neurons are in some cases found bilaterally within the fastigial nucleus. This nucleus does not receive Purkinje axons from lobulus simplex, crus I and crus II.The findings are discussed with reference to previous investigations on the cerebellar corticonuclear and nucleocortical connections, and some comments are made concerning the use of HRP as an anterograde tracer.Research Fellow, The Norwegian Research Council for Science and the Humanities     

The cerebellar corticonuclear and nucleocortical projections in the cat as studied with anterograde and retrograde transport of horseradish peroxidase

Summary The cerebellar corticonuclear and nucleocortical connections of the anterior lobe were studied in the cat by means of anterograde and retrograde transport of HRP.Previous experimental studies have given evidence that the cortex of the anterior lobe can be subdivided in a mediolateral direction into seven longitudinal zones: A, B, C₁, C₂, C₃, D₁ and D₂. An analysis of the present material shows that the Purkinje axons from each cortical zone have their own terminal region within the cerebellar nuclei, and that these areas correspond to those receiving terminal corticonuclear fibres from the same zones in other parts of the cerebellum (Dietrichs and Walberg 1979, 1980). The terminal fields are the rostral part of the fastigial nucleus (the nuclear A zone), the medial nucleus interpositus anterior (the nuclear B zone), the ventromedial nucleus interpositus posterior (the nuclear C₁ zone), the dorsolateral nucleus interpositus posterior (the nuclear C₂ zone), the lateral nucleus interpositus anterior and the medial part of the transition area between the dentate nucleus and nucleus interpositus anterior (the nuclear C₃ zone), the lateral part of this transition area and the medial dentate nucleus (the nuclear D₁ zone) and the lateral part of the dentate nucleus (the nuclear D₂ zone). The nuclear zones have no sharp borders. The seven main terminal fields are connected by areas where scanty terminal fibres occur, indicatin that the Purkinje axons from each folium of the anterior lobe from medial to lateral terminate along a continuous band which loops through the cerebellar nuclei.With few exceptions the nucleocortical projection shows the same zonal arrangement as the corticonuclear, but there is in addition a weak nucleocortical connection to the anterior lobe from the middle and caudal parts of the fastigial nucleus.These and other findings are discussed with reference to previous studies on the corticonuclear and nucleocortical projections, and some comments are made concerning the zonal subdivision of the anterior lobe.     

The cerebellar corticonuclear and nucleocortical projections in the cat as studied with anterograde and retrograde transport of horseradish peroxidase

Summary The cerebellar paramedian corticonuclear and nucleocortical connections in the cat were studied by means of anterograde and retrograde transport of HRP.Previous experimental studies have given evidence that the paramedian cortex in a lateromedial direction can be subdivided, into six longitudinal zones. These are recognized as zones D₂, D₁, C₃, C₂, C₁ and B. An analysis of our material suggests that each cortical zone has its own field of termination in the cerebellar nuclei and that the Purkinje fibres from one zone have only one terminal region. The nuclear terminal areas for the fibres from the described cortical zones are the ventral nucleus lateralis (the D₂ zone), the transition area between the nucleus lateralis and nucleus interpositus anterior (the D₁ zone), the dorsolateral nucleus interpositus posterior (the C₂ zone), the ventromedial nucleus interpositus posterior (the C₁ zone), and the dorsomedial nucleus interpositus anterior (the B zone). A separate nuclear terminal region for the fibres from a cortical C₃ zone could not be positively demonstrated, but a comparison of cases makes it likeky that it is located in the transition area of nucleus lateralis and nucleus interpositus anterior, medially to the D₁ zone.The rostral folia of the paramedian lobule project more laterally in the cerebellar nuclei than do the caudal folia. Furthermore, our findings indicate that the axons of the Purkinje cells in one folium from medial to lateral terminate along a mediolateral nuclear band which loops from the dorsomedial nucleus interpositus anterior down into the ventral nucleus interpositus posterior, and from a bend in this part to the dorsal nucleus interpositus posterior, and hence into the transition zone of nucleus interpositus anterior and nucleus lateralis, from here to proceed caudally to its end.The nucleocortical projection shows with some exceptions the same zonal arrangement as the corticonuclear, but a few labelled nuclear neurons were in some cases found in the fastigial nucleus. This nucleus does not receive Purkinje axons from the paramedian lobule. This shows that although retrogradely labelled nuclear cells usually were located among or just adjacent to anterogradely filled terminal fibres, there is not a complete reciprocity in the corticonuclear and nucleocortical projections. The observations furthermore indicate that the cortical afferents terminate as mossy fibres.The advantages and problems encountered with the use of HRP as an anterograde tracer are discussed and the observations are related to previous observations on the corticonuclear and nucleocortical cerebellar projections.     

Cerebellar afferents from the paramedian reticular nucleus studied with retrograde transport of horseradish peroxidase

Summary Details in the cerebellar projections from the paramedian reticular nucleus (PRN) were studied in cats and monkeys by means of retrograde axonal transport of horseradish peroxidase (HRP). In the cat the majority of the fibres projects to the anterior lobe and to the vermis of the posterior lobe (with the exception of lobules VIIB and VIIIA). A less conspicuous projection was found to the lobulus simplex, the crura and the flocculus. The cerebellar nuclei, the paramedian lobule and the paraflocculus appear to be weakly connected with the PRN. A similar distribution of the cerebellar afferent fibres was found in the monkey material. The three subgroups of the PRN in the cat are not equal in their projection. The dorsal group appears to be connected with the greater part of the cerebellar cortex and with all nuclei. The ventral group lacks a connection with lobulus IX, the flocculus and the paraflocculus, and the accessory group appears to have its strongest connection with lobulus I (lingula), the flocculus and the vermal lobules VII–X. The findings are discussed in relation to other studies on the efferent and afferent connections of the nucleus.On leave from the Laboratory of Neurobiology and Department of Anatomy, Faculty of Science, Mahidol University, Bankok, Thailand, under the Fellowship Program of the Norwegian Agency for International Development (NORAD)     

A note on the anterograde transport of horseradish peroxidase within the olivocerebellar fibres

Summary In cats with unilateral injections of horseradish peroxidase in the inferior olive which were processed according to the Mesulam (1978) technique crossed olivocerebellar fibres can be followed on both sides of the brain stem into the cerebellum to the level of the granular layer. The observations indicate that perikaryal uptake of horseradish peroxidase is not a prerequisite for the visualization of the fine preterminal fibres.Research Fellow, The Norwegian Research Council for Science and the Humanities     

Cortical neurons projecting to the pontine nuclei in the cat. An experimental study with the horseradish peroxidase technique

Summary Horseradish peroxidase (HRP) injections in various portions of the cat pontine nuclei resulted in retrograde labeling of neurons in layer V of the ipsilateral cerebral cortex.Corticopontine neurons, pyramidal in type, have been found to be labeled in the entire cortex, confirming the previous findings of anterograde degeneration studies. Most (91%) of the labeled cells were 14–26 m in diameter (mean 19.4±4.5 m SD). Small (10–20 m) and medium (20–40 m) cells represent 51.5% and 47.7%, respectively, of the total number of the labeled neurons. The populations of the neurons of various sizes were almost identical in different cortical areas, and were different from the populations of corticoreticular and corticospinal cells.Corticopontine cells were well labeled in experimental cases of 3-days' survival time, confirming the topographical organization established previously by degeneration studies for this projection system. However, in cases of shorter survival time (20–27 h), the number of labeled neurons was very small.The relative paucity of labeled Corticopontine neurons in the sigmoid and lateral gyri is discussed with reference to other cortical descending neurons (e.g., the corticotectal, corticoreticular and corticospinal) which have hitherto been identified morphologically as well as physiologically.Abbreviations AL gyrus lateralis anterior - ASigm gyrus sigmoideus anterior - ASup gyrus suprasylvius anterior - Br.p. brachium pontis - Cor gyrus coronalis - L left - L.m. lemniscus medialis - MEct gyrus ectosylvius medius - MSup gyrus suprasylvius medius - N.dl. nucleus dorsolateralis - N.l. nucleus lateralis - N.m. nucleus medianus - N.p. nucleus peduncularis - N.pm. nucleus paramedianus - N.r.t. nucleus reticularis tegmenti pontis - N.v. nucleus ventralis - Ped corticospinal and corticopontine fibers in cerebral peduncle - PSigm gyrus sigmoideus posterior - R right     

Brain stem projections of rat lumbar dorsal root ganglia studied with choleragenoid conjugated horseradish peroxidase

Summary Brain stem projections from each of the L1–L6 lumbar dorsal root ganglia (DRGs) were investigated in adult rats following DRG injections of choleragenoid-horseradish peroxidase. All these DRGs projected throughout the rostrocaudal extent of the gracile nucleus (Gr). Labeling from L1–L6 DRGs was transported to successively more dorsomedial areas of Gr. Investigation of the Gr projections from the DRGs revealed a somatotopic organization which was most prominent in the middle part of Gr. The cuneate nucleus showed smaller projections from all investigated DRGs. Minor projections to the internal basilar nucleus, external cuneate nucleus, medial vestibular nucleus, ventral cochlear nucleus and trigeminal sensory nuclei were also found from some of the DRGs.Abbreviations AP area postrema - B-HRP choleragenoidhorseradish peroxidase - Cun cuneate nucleus - DRG dorsal root ganglion - ECN external cuneate nucleus - Gf gracile fasciculus - Gr gracile nucleus - MnA median accessory nucleus - MVN medial vestibular nucleus - WGA-HRP wheat germ agglutininhorseradish peroxidase     

Afferent innervation of extraocular muscles in the rat studied by retrograde and anterograde horseradish peroxidase transport

After injection of horseradish peroxidase (HRP) into extraocular muscles of rat perikarya were labeled mainly along the medial edge of the ophthalmic subdivision of the trigeminal ganglion but not in the mesencephalic nucleus of the trigeminal nerve. Injections of HRP into the trigeminal ganglion labeled simple as well as branching and meandering free fiber endings in extraocular muscles. No evidence for muscle spindles was found, but the meandering endings may be considered as candidates for stretch receptors.     

Projection of thalamic neurons to cat primary vestibular cortical fields studied by means of retrograde axonal transport of horseradish peroxidase

Summary The two vestibular cortical projection areas in the anterior suprasylvian sulcus and post-cruciate dimple regions were defined by evoked potential technique in anaesthetized cats. The thalamic location of neurons with axon terminals in these fields was determined using the method of retrograde axonal transport of horseradish peroxidase. The ascending vestibular pathway appeared to be separated also at the thalamic level, where cells in the ventro-posterolateral nucleus were found to project to the post cruciate dimple and cells in the posterior nuclear group to the anterior suprasylvian vestibular cortical fields.