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Biomedical subjects

M B Carpenter

Publications and source records attributed to M B Carpenter.

At least 19 recordsLinked to original sources
PubMed1995

The impact of legislation designed to reduce infant mortality.

In response to the slowing improvement in the nation's infant mortality rate in the mid-1980s, Congress passed a series of bills aimed at increasing women's access to prenatal care and enhancing available services through the Medicaid program. Other programs also received increased appropriations targeted at infant mortality reduction. Since then, dramatic changes have been made in state Medicaid and maternal and child health programs. Only a few evaluations of these initiatives have been completed, and the preliminary results seem to show that although Medicaid eligibility expansions improved access to appropriate prenatal care, enhanced services are needed to improve birth outcomes.

Female↗
PubMed1992

Immunocytochemistry of oculomotor afferents in the squirrel monkey (Saimiri sciureus).

Attempts were made to co-define afferents of the oculomotor nuclear complex (OMC) and their putative neurotransmitters in the squirrel monkey. Wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) and wheat germ agglutinin conjugated to enzymatically inactive HRP and coupled to colloidal gold (WGAapoHRP-AU) were used as retrograde tracers in combination with immunocytochemical methods. Primarily unilateral injections were made into portions of the OMC. Stabilized tetramethylbenzidine (TMB) and silver enhanced sections were immunoreacted with antisera for choline acetyltransferase (ChAT), glutamate (GLU), aspartate (ASP), aminobutyric acid (GABA), serotonin (5-HT) and cholecystokinin (CCK). Moderate numbers of ChAT-IR neurons in caudal regions of the medial vestibular nuclei (MVN) projected to the OMC. Tracer labeled ChAT-IR cells in the MVN projected ipsilaterally to the ventral nucleus (medial rectus subdivision) of the OMC and bilaterally with contralateral dominance to other OMC subdivisions. Cholinergic neurons in the dorsal paragigantocellular reticular nucleus (DPG) projected bilaterally to each half of the OMC. Cells of the DPG, considered to contain inhibitory burst neurons impinging upon the contralateral abducens nucleus, were shown to project to virtually all subdivision of the OMC. Abducens motor neurons were ChAT-IR, but abducens internuclear neurons were not. Cells in caudal parts of the nucleus prepositus (NPP) projecting to the ipsilateral ventral nucleus of the OMC were not ChAT-positive; ChAT-IR cells in rostral NPP did not project to the OMC. Unilateral OMC injections labeled cells ipsilaterally in the RiMLF, contralaterally in the pretectal olivary nucleus, the interstitial nucleus of Cajal and the infracerebellar nucleus and bilaterally in the superior vestibular nucleus, none of which were ChAT-IR. A small number of cells in the locus ceruleus projected ipsilaterally to the OMC. Although large numbers of vestibular neurons were GLU-IR and ASP-IR, only a few tracer labeled ASP-IR neurons in the contralateral MVN projected to the OMC. No other GLU- or ASP-positive neurons were immunoreactive for GABA, 5-HT or CCK, but cells of the lateral vestibular nucleus were surrounded by CCK-IR fibers and terminals.

Animals↗
PubMed1991

Distribution of cholinergic pallidal neurons in the squirrel monkey (Saimiri sciureus) based upon choline acetyltransferase.

The distribution of cells immunoreactive to choline acetyltransferase (ChAT-IR) in, and around the globus pallidus were studied in the squirrel monkey. Intrinsic pallidal ChAT-IR neurons in the globus pallidus were most numerous in ventrocaudal regions of the lateral pallidal segment (LPS) and in the oral pole of the medial pallidal segment (MPS). Smaller numbers of ChAT-positive cells were seen in portions of the medullary laminae of the pallidum. Computer measurements of somal areas of ChAT-IR cells in the globus pallidus, substantia innominata and putamen were made. Morphological features and somal areas of ChAT-IR cells in the globus pallidus and in the Ch4 group of the substantia innominata were strikingly similar. Cholinergic pallidal neurons appear to be part of the Ch4 cell group and have similar widespread cortical projections. The smaller cholinergic neurons in the striatum are considered to be intrinsic neurons which primarily act upon spiny striatal projection neurons. The possible local interaction of pallidal cholinergic neurons upon GABAergic neurons is unknown.

Animals↗
PubMed1990

Immunocytochemical features of the vestibular nuclei in the monkey and cat.

Immunocytochemical studies of the vestibular nuclei (VN) were done in the squirrel monkey and cat using polyclonal antisera. Brain stem sections were processed using the Avidin-Biotin peroxidase complex with diaminobenzidine as the chromagen. Choline acetyltransferase immunoreactivity (ChAT-IR) was most prevalent in the caudal medial (MVN), inferior (IVN) and peripheral superior (SVN) VN. Nearly all cells of groups x and z were ChAT-positive. None of the giant cells of the lateral vestibular nucleus (LVN) was ChAT-IR. Glutamate immunoreactivity (GLU-IR) was abundant in all VN and in cells of the vestibular ganglion (VG). Gamma-aminobutyric acid immunoreactivity (GABA-IR), was found in cells of rostral MVN, cell group y and in granules about giant cells in dorsal LVN. Substance P immunoreactive (SP-IR) was present in a small cells in MVN, IVN and the VG and in granules surrounding all large cells in LVN in both monkey and cat; SP-IR granules were most intense in ventral LVN in the monkey. Some cells in the dorsal parts of the fastigial nucleus (FN) were outlined by SP-IR granules in both species. Leucine-enkephalin immunoreactivity (ENK-IR) was identified only in granules surrounding cells of group x in the monkey. GLU was the only immunoreactive substance found in the giant cells of LVN. The disposition of ChAT-IR in the VN suggested participation in commissural systems, as well as projections to spinal cord and/or cerebellum. Small GABA-IR neurons in MVN probably represented both commissural and projection neurons; GABA-IR granules about cells in dorsal LVN and some cells in MVN and SVN appeared to represent Purkinje cell (PC) terminals. SP-IR granules surrounding cells in ventral LVN appeared to represent terminals of small SP-positive VG cells. The source of SP-IR granules around cells in dorsal LVN and some cells in FN and SVN remains unknown, but these fibers may originate from portions of the reticular formation known to contain large numbers of SP-positive neurons.

Animals↗
PubMed1990

Subthalamic nucleus of the monkey: connections and immunocytochemical features of afferents.

Retrograde and anterograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was studied in 7 squirrel monkeys with discrete injections of the subthalamic nucleus (STN). Injections labeled: (1) the lateral two-thirds of the nucleus (63% and 47%), (2) ventrolateral parts caudally (20%), (3) dorsomedial parts caudally (18%), (4) rostromedial parts (21%), (5) the medial third (38%) and (6) the lateral pole of the nucleus (9%). Afferents to the lateral two-thirds of the STN originated from two parallel cellular arrays in dorsal parts of the middle third of the lateral pallidal segment (LPS) and a single array in the rostral third of the LPS. Medial regions of the STN received input from cells in the rostral LPS. Small numbers of cells were retrogradely labeled in the centromedian-parafascicular (CM-PF) and the pedunculopontine (PPN) nuclei. No cells were labeled in the frontal cortex, the striatum, the substantia innominata (SI), the substantia nigra (SN) or the dorsal nucleus of the raphe. Virtually all pallidal neurons, including identified pallidosubthalamic neurons, were immunoreactive (IR) for gamma-aminobutyric acid (GABA). Pallidosubthalamic neurons were most numerous in regions of the LPS with the lowest density of leucine enkephalin-IR fibers. Substance P-IR fibers, found mainly in the medial pallidal segment, bore no relationship to pallidal afferents to the STN. Choline acetyltransferase-IR cells in the SI and the PPN were not retrogradely labeled with WGA-HRP granules. Anterograde transport in fibers and terminal fields surrounded retrogradely labeled cells in the LPS, suggesting a reciprocal relationship. The caudal third of the LPS and ventral region of the middle third of this nucleus, appeared to project few fibers to, or to receive few fibers from, the STN. A small number of STN efferents entered the medial border of the putamen, but no terminal fields were identified. STN projections to the pars reticulata of the SN appeared to represent about 10% of the projection to the LPS. No STN efferents were identified in the frontal cortex, the SI or the PPN. The hypothesis that STN afferents from the frontal cortex and CM-PF may represent collaterals of projections to other loci is discussed.

Animals↗
PubMed1989

Connectivity patterns of thalamic nuclei implicated in dyskinesia.

Thalamic nuclei implicated in the neural mechanisms of dyskinesia (1) have projections to components of the basal ganglia; (2) receive efferents from the corpus striatum, and/or (3) project fibers to regions of the cerebral cortex that generate signals which produce or modulate motor phenomenon. The neostriatum receives a major input from the intralaminar thalamic nuclei (ITN). Thalamostriate fibers projecting to the caudate nucleus (CN) and the putamen (Put) originate from different neuronal populations; clusters of cells in the rostral ITN and in the parafascicular nucleus (PF) project to the CN, while cells in the centromedian nucleus (CM) project to the Put. Smaller numbers of cells in the medial, dorsal and ventral nuclear subdivisions of the thalamus also project to the striatum. The amygdaloid nuclear complex receives afferents from the midline thalamic nuclei. Ventromedial and rostral parts of the subthalamic nucleus receive a small input from the centromedian-parafascicular nuclear complex. Segments of the globus pallidus (GP) and the substantia nigra (SN) do not receive afferents from either the cerebral cortex or the thalamus. Thalamic afferents originate ipsilaterally from the medial segment of the globus pallidus (MPS), and the pars reticulata of the substantia nigra (SNR), and contralaterally from the deep cerebellar nuclei (DCN). Each of these projections to nuclear subdivisions of the thalamus is distinctive without overlap. Projections from the MPS are to the ventral anterior pars principalis (VApc) and ventral lateralis, pars oralis (VLo) thalamic nuclei with collaterals to CM. The SNR provides projections to the ventral anterior, pars magnocellularis, the ventral lateral, pars medialis and the mediodorsal, pars paralaminaris thalamic nuclei. Output from the subthalamic nucleus (STN) projects to both the MPS and the SNR and could modulate influences upon thalamic nuclei. In the monkey the projection of STN to the GP is four times greater than to the SNR. The most massive input to the thalamus arises from the contralateral DCN and terminates in the so-called cell-sparse zone, which consists of the ventral posterolateral nucleus, pars oralis, the ventral lateral nucleus pars caudalis, and pars postrema and area x of Olszewski. Nuclear subdivisions of the thalamus receiving afferents from the MPS and the SNR have gamma-aminobutyric acid (GABA) as their major neurotransmitter; fiber systems originating from the DCN appear to have glutamate as their neurotransmitter.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Comparisons of the immunocytochemical localization of choline acetyltransferase in the vestibular nuclei of the monkey and rat.

Immunocytochemical studies of the brainstem were done in the squirrel monkey and rat using the same polyclonal antisera for choline acetyltransferase (ChAT). Cells immunoreactive for ChAT (ChATir) were evident in large numbers in visceral and motor cranial nerve nuclei in both species, but virtually no ChATir cells were seen in the vestibular nuclear complex of the rat. In the monkey ChATir cells were distributed in caudal parts of the medial (MVN) and in dorsal parts of the inferior (IVN) vestibular nuclei. Only a few immunoreactive cells were seen in the rostral MVN and none were found in cell group f of the IVN. Nearly all cells of group z and x, which do not receive primary vestibular afferents, were immunoreactive to ChAT. None of the cells in the superior and lateral vestibular nuclei, cell group y, the infracerebellar nucleus or the interstitial nucleus of the vestibular nerve were immunoreactive for ChAT. Cells immunoreactive to ChAT were present in large numbers in the rostral part of the nucleus prepositus in the monkey, but not in the rat. The relatively small number and distribution of ChATir cells in the MVN suggested they could constitute only a small fraction of the MVN neurons that contribute to a massive commissural system. Significant differences in cholinergic vestibular neurons appear to exist between the rat and the monkey.

Animals↗
PubMed1987

Vestibular and cochlear efferent neurons in the monkey identified by immunocytochemical methods.

Attempts were made to identify vestibular (VEN) and cochlear (CEN) efferent neurons in the squirrel monkey using retrograde transport of horseradish peroxidase (HRP) and immunocytochemical methods. HRP implants in the ampulla of the lateral semicircular duct retrogradely labeled cells of VEN bilaterally and some cells of CEN. VEN located lateral to the rostral part of the abducens nucleus formed a compact collection of cells, all of which were immunoreactive only to antisera for choline acetyltransferase (ChAT). CEN, identified by immunoreactivity to ChAT were located at the hilus of the lateral superior olive (LSO), along the lateral border of the LSO and sparsely near lateral parts of the ventral trapezoid nucleus (VTN). A small number of cells and fibers near the border of the VTN and lateral to the LSO were immunoreactive for leucine enkephalin (L-ENK). Fibers immunoreactive for L-ENK also were identified in the hilus of the LSO. No cells of the superior olivary complex were immunoreactive for antisera to ChAT, L-ENK, substance P, gamma-aminobutyric acid or glutamic acid decarboxylase. Cells of VEN and CEN can be identified by their immunoreactivity to ChAT, and some cells and fibers of CEN also contain L-ENK.

Animals↗
PubMed1985

Transneuronal transport in the vestibular and auditory systems of the squirrel monkey and the arctic ground squirrel. I. Vestibular system.

Transneuronal transport of [3H]proline, [3H]fucose, and [3H]leucine in various combinations from pledgets implanted in the ampulla of a single semicircular duct was studied in the squirrel monkey and arctic ground squirrel after long survival periods. Tritiated amino acids implanted in any single ampulla resulted in labeling of nearly all vestibular and auditory receptors, nearly all cells of the vestibular and spiral ganglia and central transport via nearly all root fibers of both nerves. Primary vestibular fibers were distributed to the vestibular nuclei (VN) and specific parts of the cerebellum in the pattern previously described. Transneuronal transport of [3H]proline by vestibular neurons was present in all known secondary pathways, except those projecting to thalamic nuclei. Observations were similar in both species, except for small differences in commissural vestibular projections. Major commissural transport was to all parts of the opposite medial vestibular nucleus (MVN) and to peripheral parts of the superior vestibular nucleus (SVN), but some transport was present in all contralateral VN, including ventral cell group y. Descending transneuronal transport was evident in vestibulospinal tract (VST) ipsilaterally and in the medial longitudinal fasciculus (MLF) bilaterally. Both [3H]proline and [3]fucose were transported transneuronally to the ipsilateral abducens nucleus (AN); with long survivals [3H]proline was transported peripherally via the ipsilateral abducens nerve root. Ascending transport in the MLF was bilateral, asymmetric and greatest contralaterally. Fibers entered the contralateral MLF near the AN and the lateral wing of the ipsilateral MLF rostral to most of the VN. Terminals in the trochlear nuclei (TN) were bilateral and greatest contralaterally. In the monkey terminals in ipsilateral oculomotor complex (OMC) were distributed uniformly in all subdivisions, except for the medial rectus subdivision (MRS), where terminals were more numerous. The greatest density of terminals was present contralaterally in the superior rectus subdivision (SRS) of the OMC; only sparse terminals were present in the MRS on that side. Transport in the ipsilateral abducens nerve roots in the monkey and the virtual absence of transport to the MRS of the contralateral OMC suggested transneuronal transport to abducens motor neurons, but not to internuclear neurons (AIN). The AIN project only to the MRS of the contralateral OMC and do not appear to receive vestibular input. Comparable observations were made in the AN, TN and OMC of the ground squirrel, although the representation of the extraocular muscles in the OMC is unknown.(ABSTRACT TRUNCATED AT 400 WORDS)

Abducens Nerve↗
PubMed1985

Transneuronal transport in the vestibular and auditory systems of the squirrel monkey and the arctic ground squirrel. II. Auditory system.

Transneuronal transport in the auditory system of the squirrel monkey and the arctic ground squirrel was studied after implantation of tritiated protein or glycoprotein precursors into the ampulla of a single semicircular duct. In both species, essentially the same pattern of transneuronal transport extended beyond the cochlear nuclei to the central nucleus of the inferior colliculus (CNIC), after survival periods ranging from 9 to 33 days. Animals displayed dense labeling over nearly all auditory receptors, nearly all portions of the spiral ganglion and throughout the cochlear nuclei (CN). Labeled fibers, mainly in the ventral acoustic stria, terminated over the ipsilateral lateral superior olive (LSO) and the lateral aspect of medial superior olive (MSO). Fibers continuing medially, decussated in an orderly manner, and terminated over the opposite medial nucleus of the trapezoid body (MNTB) and medial aspect of MSO. Labeled fibers projecting into the opposite lateral lemniscus (LL) terminated in the ventral nucleus of the lateral lemniscus (VNLL) and the CNIC. Fibers, but few terminals, were noted over the dorsal nucleus of the LL. The ipsilateral LL contained comparatively few labeled fibers, but sparse terminations occurred over portions of VNLL and CNIC. No transport of [3H]precursors was noted in the peripheral nuclei of the inferior colliculus or in the medial geneculate body on either side. Massive transport via the contralateral LL and the profuse terminals in the opposite CNIC suggested transneuronal transport via secondary and higher order auditory fibers. Although the largest number of fibers in the contralateral LL probably arose from the cochlear nuclei, higher order fibers also may have arisen from the ipsilateral LSO and the contralateral MSO and VNLL. Small numbers of fibers in both species descended from the region of the superior olivary complex (SOC) ventral to the facial motor nucleus. In the ground squirrel, scant auditory projections were traced into the opposite cochlear nuclei. Tritiated precursors in the endolymph passed most readily from labyrinth to cochlea, and transneuronal transport was more extensive in the auditory pathways than in the vestibular system at comparable times. Centrally transported [3H]fucose was cleared more promptly than [3H]proline in monkeys.

Animals↗
PubMed1985

Connections and oculomotor projections of the superior vestibular nucleus and cell group 'y'.

Attempts were made to determine brainstem and cerebellar afferent and efferent projections of the superior vestibular nucleus (SVN) and cell group 'y' ('y') in the cat using axoplasmic tracers. Injections of HRP, WGA-HRP and [3H]amino acids were made into SVN and 'y' using two different infratentorial stereotaxic approaches. Controls were provided by unilateral HRP injections involving the oculomotor nuclear complex (OMC), the interstitial nucleus of Cajal (INC) and the deep cerebellar nuclei (DCN). Large injections of SVN almost invariably involved 'y' and dorsal parts of the lateral vestibular nucleus (LVN). Smaller injections involved central and ventral peripheral parts of SVN. Discrete injections of 'y' involved small dorsal parts of LVN. Afferents to SVN are derived mainly from the vestibular nuclei (VN) and parts of the vestibulocerebellum. SVN receives afferents: bilaterally from caudal portions of the medial (MVN) and inferior (IVN) vestibular nuclei and 'y'; contralaterally from ventral and lateral parts of SVN and rostral MVN; and ipsilaterally from the nodulus, uvula and medial parts of the flocculus. Purkinje cells (PC) in medial parts of the flocculus project to central regions of SVN, while PC in the nodulus and uvula appear to project mainly to dorsal peripheral regions of SVN. SVN receives sparse projections from the ipsilateral INC, the contralateral central cervical nucleus (CCN) and virtually no projections from the reticular formation. SVN projects via the medial longitudinal fasciculus (MLF) to the ipsilateral trochlear nucleus (TN), the inferior rectus subdivision of the OMC, the INC, the nucleus of Darkschewitsch (ND) and the rostral interstitial nucleus of the MLF (RiMLF). Contralateral projections of SVN cross in the ventral tegmentum caudal to most of the decussating fibers of the superior cerebellar peduncle and terminate in the dorsal rim of the TN and the superior rectus and inferior oblique subdivisions of the OMC; sparse crossed projections enter the INC and the ND. Cerebellar projections of SVN end as mossy fibers in the ipsilateral nodulus, uvula and in medial parts of the flocculus bilaterally. Retrograde transport from unilateral injections of the OMC indicate that afferents from SVN arise ipsilaterally from central and dorsal regions and contralaterally from dorsal peripheral regions. Ventral cell group 'y' receives small numbers of afferent fibers from caudal central parts of the ipsilateral flocculus. No fibers from ventral 'y' could be traced to other vestibular nuclei, the OMC or the cerebellum.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1984

Distribution of primary vestibular fibers in the brainstem and cerebellum of the monkey.

Attempts were made to determine the central projections of ganglion cells innervating individual semicircular ducts in the monkey by implanting or injecting tritiated amino acids (leucine and/or proline), or horseradish peroxidase (HRP), selectively into a single ampulla. Central transport via the vestibular ganglion in animals receiving isotope implants or injections fell into three categories: (1) transport from ganglion cells innervating all receptive elements of the labyrinth, (2) transport from ganglion cells innervating the three semicircular ducts, and (3) transport from cells of the inferior vestibular ganglion innervating the posterior semicircular duct. Transneuronal transport of isotope was observed in secondary vestibular fibers in animals where proline was used and survival exceeded 12 days. Transneuronal labeling of secondary auditory fibers was independent on the [3H]amino acid used, and occurred with survivals of 10 or more days. HRP implanted into the ampulla of the lateral semicircular duct in several animals produced retrograde transport to efferent vestibular and cochlear neurons, but did not result in transganglionic labeling of primary vestibular or auditory fibers. Primary vestibular fibers terminate throughout the superior (SVN) and medial vestibular nuclei (MVN). Within SVN, terminals are most pronounced in its central large-celled portion, but extend into peripheral parts of the nucleus, except for a small medial area near its junction with the oral pole of MVN. Primary projections to MVN are homogenously distributed throughout the nucleus excepting a small circular area of sparse terminals along its ventral margin. Primary vestibular afferents terminate mainly in rostral and caudal portions of the inferior vestibular nucleus (IVN), but do not reach cell group 'f'. Projections to the lateral vestibular nucleus (LVN) are restricted to its ventral part. Primary projections to the accessory vestibular nuclei reach the interstitial nucleus of the vestibular nerve (NIVN) and cell group 'y'. Fibers project beyond the vestibular nuclei (VN) to terminate ipsilaterally in the accessory cuneate nucleus (ACN), the subtrigeminal lateral reticular nucleus (SLRN), and well-defined portions of the reticular formation (RF). Projections to SVN and MVN are derived primarily from ganglion cells innervating the semicircular ducts, while projections to caudal IVN, cell group 'y' and ACN are related mainly to macular portions of the vestibular ganglion. NIVN receives both macular and duct afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1983

Afferent and efferent connections of the medial, inferior and lateral vestibular nuclei in the cat and monkey.

Attempts were made to determine the afferent and efferent connections of the medial (MVN), inferior (IVN) and lateral (LVN) vestibular nuclei (VN) in the cat and monkey using retrograde and anterograde axoplasmic transport technics. Injections of HRP and [3H]amino acids were made selectively into MVN, IVN and LVN and into: (1) MVN and IVN, (2) LVN and IVN and (3) all 4 VN. Contralateral afferents to MVN arise from (1) the nuclei prepositus (NPP) and intercalatus (NIC), (2) all parts of MVN and cell group 'y' and (3) parts of the superior vestibular nucleus (SVN), IVN and the fastigial nucleus (FN). Ipsilateral projections to MVN arise from: (1) a central band of the flocculus and the nodulus and uvula, (2) the interstitial nucleus of Cajal (INC), and (3) visceral nuclei of the oculomotor nuclear complex (OMC). Efferent projections of MVN are to: (1) the ipsilateral supraspinal nucleus (SSN), and (2) the contralateral central cervical nucleus (CCN), MVN, SVN, cell group 'y', the rostroventral region of LVN, the trochlear nucleus (TN) and the INC. Projections to the abducens nuclei (AN) and the OMC are bilateral. Some ascending fibers in the cat cross within the OMC. In the monkey fibers from MVN end in a central band of the ipsilateral flocculus. Afferents to IVN arise ipsilaterally from SVN, the nodulus, the uvula and the anterior lobe vermis. Contralateral afferents arise from: (1) parts of CCN, MVN, SVN, IVN and cell group 'y' and (2) the central third of the FN. IVN receives bilateral projections from the perihypoglossal nuclei (PH) and the visceral nuclei of the OMC. Efferents from IVN project: (1) ipsilaterally to nucleus beta of the inferior olive, (2) contralaterally to parts of MVN, SVN and cell group 'y' and (3) bilaterally to the paramedian reticular nuclei. No commissural fibers interconnect cell groups 'f' and 'x'. Ascending fibers from IVN terminate contralaterally in the TN and the OMC. In the monkey fibers from IVN terminate in the ipsilateral nodulus, uvula and anterior lobe vermis; no fibers project to FN in either the cat or the monkey. Afferents to the LVN arise primarily from the ipsilateral anterior lobe vermis and bilaterally from rostral parts of the FN. No commissural fibers interconnect the LVN. Projections of the LVN are primarily to spinal cord via the vestibulospinal tract (VST); collaterals of the VST terminate in the lateral reticular nucleus (LRN). Ascending uncrossed projections from LVN in the cat terminate in the medial rectus subdivision of the OMC.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1983

Comparison of vestibular and abducens internuclear projections to the medial rectus subdivision of the oculomotor nucleus in the monkey.

Comparisons were made of projections from the vestibular nuclei (VN) and abducens internuclear neurons (AIN) to cell group A of the medial rectus subdivision (MRS) of the oculomotor nuclear complex. Cell group A, the major component of the MRS, receives projections only from the ipsilateral VN and the contralateral AIN. Neither ipsilateral vestibular projections to cell group A, arising from the medial vestibular nucleus, nor projections from MVN to the opposite abducens nucleus, match the massive projection of AIN to the MRS.

Abducens Nerve↗
PubMed1981

Connections of the subthalamic nucleus in the monkey.

Attempts were made to determine the afferent and efferent connections of the subthalamic nucleus (STN) in the monkey using retrograde and anterograde axoplasmic transport technics. Following HRP injections limited to the STN, label was transported to arrays of cells adjacent, and parallel, to the lateral medullary lamina in the rostral two thirds of the lateral pallidal segment (LPS). Only sparse label was transported to cells of the pedunculopontine nucleus (PPN) and the locus ceruleus (LC). No enzyme was transported across the midline, or to the striatum, medial pallidal segment (MPS), thalamus, substantia nigra (SN) or dorsal nucleus of the raphe (DNR). HRP injected into portions of both the STN and SN produced retrograde transport of the enzyme to cells in parallel arrays in the LPS related rostrocaudally to the injection site. Additional enzyme transport was seen in cells of the striatum, the DNR and the PPN. Only a few isolated cells were labeled in the sensorimotor cortex. Efferent connections of the STN were studied in monkeys in which [3H]amino acids were injected hydraulically or iontophoretically into the STN. Isotope traced in serial autoradiographs was distributed to: (1) both segments of the globus pallidus (GP) in arrays parallel to the medullary laminae, and (2) the pars reticulata of SN (SNpr). The greatest number of terminals was found in the MPS. Fibers from the rostral part of the STN descended along the dorsal border of the SN and projected ventrally to terminations in the SNpr. No isotope was transported across the midline, or to the striatum, thalamus, DNR or PPN. Isotope injected into both the STN and SN produced similar transport to the GP and transport via nigral efferent fibers to: (1) portions of the striatum, (2) specific thalamic nuclei (VAmc, VLm, DMpl), (3) deep and middle gray layers of the superior colliculus and (4) PPN. Control studies indicated that [3H]amino acids injected only into the SN were transported to PPN. HRP injected into PPN produced profuse retrograde transport in cells of the MPS and SNpr and distinct label in a few cells of the zona incerta and STN. These data suggest that the STN receives its major subcortical input from cell of the LPS arranged in arrays which have a rostrocaudal organization. No cells of the MPS or SN project to the STN. The output of the STN is to both segments of the GP and SNpr. Major subcortical projections to PPN arise from the MPS and SNpr, but afferents also arise from other sources. The major projection of PPN is to SN.

Animals↗