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M B Carpenter

Publications and source records attributed to M B Carpenter.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1980

Abducens internuclear neurons and their role in conjugate horizontal gaze.

Experimental evidence suggests that brain stem lesions producing paralysis of lateral gaze and dissociation of conjugate horizontal eye movements have certain common features. Both of these disturbances involve abducens internuclear neurons (Abd IN) or their projections. Attempts were made to determine the course and terminal distribution of Abd IN in the monkey by autoradiographic techniques. Tritiated amino acids injected in the abducens nucleus (Abd N) labeled: (1) root fibers ipsilaterally, and (2) fibers that ascended in medial parts of the contralateral medial longitudinal fasciculus (MLF). In the opposite oculomotor complex (OMC) silver grains were profuse over the ventral nucleus (VN, medial rectus muscle) and patchy over caudal parts of the dorsal nucleus (DN, inferior rectus muscle). Labeling of cells in the reticular formation nucleus to Abd N resulted in transport ipsilaterally, outside the MLF, to the rostral interstitial nucleus of the MLF (RiMLF), a cell group considered to be concerned with vertical eye movements. Bilateral labeling of Abd N and cells of the nucleus prepositus (NPP) resulted in bilateral: (1) transport of isotope via root fibers and the MLF, and (2) selective distribution of silver grains in the OMC. Bilateral silver grain distribution in the OMC suggested profuse terminations in VN, patchy terminations in DN and vertical, linear terminations in caudal parts of the medial nucleus (MN, superior rectus muscle). Comparisons with more discrete unilateral labeling of cells in Abd N suggested that cells of the NPP project selectively to terminations in MN, and may be related to upward eye movements. Two conclusions were drawn: (1) The paresis of ocular adduction which occurs in both anterior internuclear ophthalmophlegia and in paralysis of lateral gaze results from involvement of Abd IN or their ascending projections, and (2) the NPP appears to project selectively to parts of MN of the OMC, a cell group said to provide crossed innervation for the superior rectus muscle.

Abducens Nerve↗
PubMed1978

Transport of radioactivity from primary auditory neurons beyond the cochlear nuclei.

Transneuronal degeneration in secondary brainstem auditory nuclei has been described following cochlear lesions, and Marchi studies have revealed degeneration in the trapezoid body after such lesions. These findings support the view of some early neuroanatomists that primary auditory afferents project beyond the cochlear nuclei. Silver impregnation studies of degenerating cochlear afferents have failed to support this claim, leaving the question unresolved. Using [3H] amino acids auditory projections in the monkey were traced autoradiographically from labeled ganglion cells: (1) in all portions of the spiral ganglion, (2) in apical and middle turns of the cochlea and (3) primarily in the basal turn of the cochlea. Labeling of the entire spiral ganglion resulted in profuse transport of isotope to parts of all cochlear nuclei [anteroventral (AVCN), posteroventral (PVCN), and dorsal (DCN) cochlear nuclei]. Labeled axons entering the trapezoid body (TB) projected ipsilaterally to: (1) the lateral trapezoid nuclei (LTN), (2) the lateral superior olivary nucleus (LSO), (3) the dorsal dendritic zone of the medial superior olivary nucleus (MSO), and (4) the pericollicular or cortical nucleus of the inferior colliculus (IC). Auditory fibers crossing the midline in the TB projected contralaterally to: (1) the medial trapezoid nucleus (MTN), (2) the ventral dendritic zone of the MSO, (3) the ventral nucleus of the lateral lemniscus (VNLL), and (4) the central nucleus of the inferior colliculus (CNIC). Selective labeling of cells in the apical and middle ganglionic turns ofthe cochlea resulted in a similar pattern of centripetal transport. Selective [3H] uptake primarily by ganglion cells in the basal turn of the cochlea resulted in: (1) labeling of restricted parts of all cochlear nuclei, and (2) a considerable reduction of isotope transported beyond the cochlear nuclei. Labeled fibers in the TB were distributed sparsely in the ipsilateral LTN, LSO and dorsal dendritic zone of the MSO. Fibers in the TB were not labeled contralaterally in these animals. Interpretation of these data considers the possibility of transneuronal isotope transport. The pattern of isotope transported beyond the cochlear nuclei does not correspond to the secondary projections of any individual cochlear nucleus, although it bears some resemblance to that of the AVCN. The current study suggests that some primary auditory afferents project beyond the cochlear nuclei.

Animals↗
PubMed1977

Brain stem afferents to the fastigial nucleus in the cat demonstrated by transport of horseradish peroxidase.

Although retrograde and anterograde degeneration studies have provided important information concerning brain stem afferents to the fastigal nucleus (FN), these data may be incomplete and should be confirmed by axonal transport methods. Attempts were made to inject horseradish peroxidase (HRP) unilaterally into the FN in a series of adult cats. Animals were perfused with dextran and a fixative solution of paraformaldehyde and glutaraldehyde in 0.1 M phospate buffer. Representative sections were treated by the Graham and Karnovsky ('66) method. Selective HRP injections in one FN resulted in retrograde transport of the marker to Purkinje cells of the ipsilateral vermis and distinctive appendages of the contralateral medial accessory olivary (MAO) nucleus (nucleus beta and the dorso-medial cell column). Retrograde transport of the label was found bilaterally in cells of the medial (MVN) and inferior (IVN) vestibular nuclei, in cell group x and in the nucleus prepositus (PP). Labeled vestibular neurons, most numerous in MVN, were identified in dorsal, caudal and lateral regions, with a slight ipsilateral preponderance. Only a few neurons in caudal, dorsal and lateral regions of the IVN were labeled and none of these included cells of group f. Labeled cells in the caudal third of PP were greatest ipsilaterally. Rostral and caudal injections of FN labeled smaller numbers of cells in MVN, IVN, cell group x and PP. HRP injections of FN and portions of lobules VIII and IX resulted in bilateral retrograde labeling of larger numbers of cells in MVN, IVN and cell group x, and ipsilateral labeling of cells in group y and the interstitial nucleus of the vestibular nerve. Injections of HRP into basal folia of lobules V and VI resulted in retrograde transport of the marker to cells of the medial and dorsal accessory olivary nuclei contralaterally, and to cells of the ipsilateral accessory cuneate nucleus. Transport of label injected into portions of the pyramis was detected in parts of the contralateral MAO and bilaterally in parts of the pontine and reticulotegmental nuclei. This study suggests that the principal afferents of the fastigial nucleus arise from: (1) Purkinje cells of the ipsilateral vermis, (2) restricted portions of the contralateral MAO (nucleus beta and dorsomedial cell column), (3) portions of the MVN and IVN (bilaterally) and (4) caudal parts of the PP. Secondary vestibular inputs to the fastigial nucleus probably are relayed mainly by Purkinje cells in the cerebellar cortex.

Afferent Pathways↗
PubMed1976

Projections of the globus pallidus and adjacent structures: an autoradiographic study in the monkey.

Because the globus pallidus gives rise to the principal efferent system of the corpus striatum and is traversed by several fibers systems, attempts were made to study the projections of its cells by autoradiographic technics. Tritiated amino acids (L-leucine, L-proline and L-lysine) were injected into: (1) the medial pallidal segment (MPS), (2) the MPS and the substantia innominata (SI), (3) portions of the MPS and the lateral pallidal segment (LPS) and (4) parts of the putamen. Cells labeled by injections of the MPS transported isotope to thalamic nuclei (ventral anterior, VApc, ventral lateral, VLo and VLm, and the centromedian, CM), the pedunculopontine nucleus (PPN), and the lateral habenular nucleus (Hbl). Labeled cells of the MPS and SI transported isotope to: (1) thalamic nuclei (VLo, VLm and CM), (2) PPN, (3) Hbl, (4) lateral and posterior regions of the hypothalamus, and (5) extensive dorsal regions of the substantia migra (SN). Comparisons of label transported from uptake of isotope by cells of the MPS, and cells of both pallidal segments, suggest that the LPS projects fibers only to the subthalamic nucleus (STN). Not all regions of the STN appear to receive fibers from the LPS. Selectively labeled neurons of the putamen transport isotope to broad regions of both pallidal segments and to the pars reticulata of the SN. This study suggests that cells of the MPS project profusely and topographically to: (1) the rostral ventral tier thalamic nuclei (VApc, VLo and VLm), (2) lateral portions of CM, and (3) the PPN. Fibers of the lenticular fasciculus appear to terminate preferentially in VLo. Cells in sublenticular portions of SI, and those extending into the medullary laminae of the pallidum, appear to project to: (1) HB1 via the stria medullaris, (2) the pars compacta of SN, (3) lateral and posterior regions of the hypothalamus, and (4) the so-called nucleus of the ansa lenticularis. Some fibers from cells of SI appear to join the dorsal stria terminalis, but none enter the inferior thalamic peduncle and none project to any part of the dorsomedial nucleus of the thalamus.

Amygdala↗
PubMed1976

Nigrothalamic projections in the monkey demonstrated by autoradiographic technics.

In spite of repeated demonstrations by degeneration technics, nigrothalamic fibers have been regarded with some skepticism. Attempts were made to trace nigral efferent projections in the monkey by autoradiographic technics. Tritiated amino acids (L-leucine, L-lysine and L-proline), injected into portions of the substantia nigra (SN), labeled cells in four regions, designated as, (1) rostrolateral, (2) caudolateral, (3) rostromedial and (4) central. Rostrolateral nigral neurons transported radioactive label preferentially and abundantly to thalamic nuclei; localized isotope was found in parts of three thalamic nuclei, the medial part of the ventral lateral nucleus (VLm), the magnocellular part of the ventral anterior nucleus (VAmc), and the paralaminar part of the dorsomedial nucleus (DMpl)9 Lateral neurons in the caudal half of the SN transmitted radioactive label to the same thalamic nuclei as rostrolateral nigral neuron. Isotope transported to portions of the striatum was modest and localized. Radioactive label taken up by large cells in the caudal third of the SN was transported to portions of the striatum, but not to thalamic nuclei. Labeled nigral neurons in the medial two-thirds of the rostral half of the SN, and in the middle third of the central part of the SN, transported the label mainly to parts of the caudate nucleus and putamen. In these animals modest radioactive label was seen in VLm and VAmc, but not in other thalamic nuclei. There was no evidence that nigral neurons project to the subthalamic nucleus. No radioactive transport from nigral neurons was detected in the superior colliculus, the midbrain tegmentum, or the red nucleus, and none was transported to more caudal brain stem nuclei. Nigrothalamic fibers arise particularly from cells in rostral and lateral parts of the substantia nigra. While some cells in other parts of the nigra project to thalamic nuclei, these appear scattered and less numerous. Large cells in caudal parts of the SN do not project to thalamic nuclei. These observations confirm nigrothalamic projections to VLm and VAmc, and identify a new nigral projection to part of the dorsomedial nucleus of the thalamus (DMpl). No nigral efferent fibers project to any of the intralaminar thalamic nuclei.

Animals↗