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Jan G. Bjaalie - One of the best experts on this subject based on the ideXlab platform.
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Chapter 13 Salient anatomic features of the cortico-ponto-cerebellar pathway
Progress in brain research, 1997Co-Authors: Per Brodal, Jan G. BjaalieAbstract:Publisher Summary This chapter focuses on the cerebrocerebellar pathway, synaptically interrupted in the pontine nuclei. Recent studies of the primate Corticopontine projection show that the neocerebellum—in addition to connections from motor and sensory areas—receives connections from various association areas of the cerebral cortex, some of which are thought to be primarily engaged in cognitive tasks. The anatomic data on the origin of Corticopontine Fibers needs to be supplemented with physiological experiments to clarify their functional properties at the single-cell level. The scarcity of Corticopontine connections from the prefrontal cortex in the monkey may not seem readily compatible with a prominent role of the neocerebellum in certain cognitive tasks. Corticopontine and pontocerebellar lamellae have similar shapes and orientations but appear to differ in other respects. Corticopontine terminal fields are sharply delimited, apparently without gradual overlap between projections from different sites in the cortex, whereas pontocerebellar lamellae are fuzzier and exhibit gradual overlap of neuronal populations projecting to different targets.
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Topographical organization in the early postnatal projection: A carbocyanine dye and 3‐D computer reconstruction study in the rat
The Journal of comparative neurology, 1995Co-Authors: Trygve B. Leergaard, Egbert A. J. F. Lakke, Jan G. BjaalieAbstract:We have explored basic rules guiding the early development of topographically organized projections, employing the rat Corticopontine projection as a model system. Using anterograde in vivo tracing with 1,1′, dioctadecyl-3,3,3′,3′ -tetramethylindocarbocyanine perchiorate (DiI), we studied the distribution of labelled Fibers in the pontine nuclei in relation to cortical site of origin during the first postnatal week. Labelled Corticopontine Fibers enter the pontine nuclei in distinct, sharply defined zones. The putative terminal Fibers typically occupy lamella-like subspaces. Related to changes in cortical site of origin, we describe mediolateral, internal to external, and caudorostral distribution gradients in the pontine nuclei. Fibers originating in the anterolateral cortex occupy an internal central core, while implantations at increasing distance from the anterolateral cortex produce (1) more externally located lamellae, and (2) a caudal to rostral shift in fiber location. Previous investigations have shown that pontocerebellar neurons migrate into the ventral pons in a temporal sequence (Altman and Bayer [1987] J. Comp. Neurol. 257:529). The earliest arriving neurons occupy the central core and later arriving neurons settle in more externally and rostrally located subspaces. We hypothesize that the earliest arriving corticopon tine Fibers grow into the then only available zone of pontocerebellar neurons (central core), attracted by a diffusible chemotropic cue. Later arriving Fibers grow into correspondingly later and more externally and rostrally located contingents of pontocerebellar neurons. Thus, we propose that the topographical organization in the early postnatal Corticopontine projections determined by simple temporal and spatial gradients operative within source cerebra cortex and target region (pontine nuclei). © 1995 Wiley-Liss, Inc.
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organization of the pontine nuclei
Neuroscience Research, 1992Co-Authors: Per Brodal, Jan G. BjaalieAbstract:The pontine nuclei provide the cerebellar hemispheres with the majority of their mossy fiber afferents, and receive their main input from the cerebral cortex. Even though the vast majority of pontine neurons send their axons to the cerebellar cortex, and are contacted monosynaptically by (glutamatergic) Corticopontine Fibers, the information-processing taking place is not well understood. In addition to typical projection neurons, the pontine nuclei contain putative GABA-ergic interneurons and complex synaptic arrangements. The Corticopontine projection is characterized by a precise but highly divergent terminal pattern. Large and functionally diverse parts of the cerebral cortex contribute; in the monkey the most notable exception is the almost total lack of projections from large parts of the prefrontal and temporal cortices. Within Corticopontine projections from visual and somatosensory areas there is a de-emphasis of central vision and distal parts of the extremities as compared with other connections of these sensory areas. SubCorticopontine projections provide only a few percent of the total input to the pontine nuclei. Certain cell groups, such as the reticular formation, project in a diffuse manner whereas other nuclei, such as the mammillary nucleus, project to restricted pontine regions only, partially converging with functionally related Corticopontine connections. The pontocerebellar projection is characterized by a highly convergent pattern, even though there is also marked divergence. Neurons projecting to a single cerebellar folium appear to be confined to a lamella-shaped volume in the pontine nuclei. The organization of the pontine nuclei suggests that they ensure that information from various, functionally diverse, parts of the cerebral cortex and subcortical nuclei are brought together and integrated in the cerebellar cortex.
Deepak N. Pandya - One of the best experts on this subject based on the ideXlab platform.
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Course of the fiber pathways to pons from parasensory association areas in the rhesus monkey.
The Journal of Comparative Neurology, 1992Co-Authors: Jeremy D. Schmahmann, Deepak N. PandyaAbstract:The course of the fiber pathways to pons from parasensory association areas in the rhesus monkey was investigated by injection of tritiated amino acids and the technique of autoradiography. Results confirm the projection to pons from parasensory association areas in the temporal, parietal, and occipital lobes and extend these observations to include the posterior parahippocampal gyrus. The findings reveal that the white matter of the posterior limb of the internal capsule above the midpoint of the lateral geniculate nucleus, and at the medical aspect of the lateral geniculate nucleus, comprise common regions through which these Corticopontine Fibers lead to the basis pontis. The Fibers demonstrate a certain degree of topographic organization in the posterior limb of the capsule above the lateral geniculate nucleus and also in the cerebral peduncle. Taken together with previous observations concerning the termination patterns of these associative Corticopontine projections, it would appear that the Corticopontine system consists of segregated and partially overlapping pathways, which are to some extent distinguishable anatomically at each stage of their trajectory from origin to destination. Furthermore, the existence of a common area through which all parasensory associative input to pons is transmitted suggests that a precisely located lesion in this part of the corticopontocerebellar circuit may disrupt the cerebellar access to higher order information derived from the parasensory associative regions. © 1992 Wiley-Liss, Inc.
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Course of the fiber pathways to pons from parasensory association areas in the rhesus monkey.
The Journal of comparative neurology, 1992Co-Authors: Jeremy D. Schmahmann, Deepak N. PandyaAbstract:The course of the fiber pathways to pons from parasensory association areas in the rhesus monkey was investigated by injection of tritiated amino acids and the technique of autoradiography. Results confirm the projection to pons from parasensory association areas in the temporal, parietal, and occipital lobes and extend these observations to include the posterior parahippocampal gyrus. The findings reveal that the white matter of the posterior limb of the internal capsule above the midpoint of the lateral geniculate nucleus, and at the medial aspect of the lateral geniculate nucleus, comprise common regions through which these Corticopontine Fibers lead to the basis pontis. The Fibers demonstrate a certain degree of topographic organization in the posterior limb of the capsule above the lateral geniculate nucleus and also in the cerebral peduncle. Taken together with previous observations concerning the termination patterns of these associative Corticopontine projections, it would appear that the Corticopontine system consists of segregated and partially overlapping pathways, which are to some extent distinguishable anatomically at each stage of their trajectory from origin to destination. Furthermore, the existence of a common area through which all parasensory associative input to pons is transmitted suggests that a precisely located lesion in this part of the corticopontocerebellar circuit may disrupt the cerebellar access to higher order information derived from the parasensory associative regions.
Jeremy D. Schmahmann - One of the best experts on this subject based on the ideXlab platform.
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Course of the fiber pathways to pons from parasensory association areas in the rhesus monkey.
The Journal of Comparative Neurology, 1992Co-Authors: Jeremy D. Schmahmann, Deepak N. PandyaAbstract:The course of the fiber pathways to pons from parasensory association areas in the rhesus monkey was investigated by injection of tritiated amino acids and the technique of autoradiography. Results confirm the projection to pons from parasensory association areas in the temporal, parietal, and occipital lobes and extend these observations to include the posterior parahippocampal gyrus. The findings reveal that the white matter of the posterior limb of the internal capsule above the midpoint of the lateral geniculate nucleus, and at the medical aspect of the lateral geniculate nucleus, comprise common regions through which these Corticopontine Fibers lead to the basis pontis. The Fibers demonstrate a certain degree of topographic organization in the posterior limb of the capsule above the lateral geniculate nucleus and also in the cerebral peduncle. Taken together with previous observations concerning the termination patterns of these associative Corticopontine projections, it would appear that the Corticopontine system consists of segregated and partially overlapping pathways, which are to some extent distinguishable anatomically at each stage of their trajectory from origin to destination. Furthermore, the existence of a common area through which all parasensory associative input to pons is transmitted suggests that a precisely located lesion in this part of the corticopontocerebellar circuit may disrupt the cerebellar access to higher order information derived from the parasensory associative regions. © 1992 Wiley-Liss, Inc.
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Course of the fiber pathways to pons from parasensory association areas in the rhesus monkey.
The Journal of comparative neurology, 1992Co-Authors: Jeremy D. Schmahmann, Deepak N. PandyaAbstract:The course of the fiber pathways to pons from parasensory association areas in the rhesus monkey was investigated by injection of tritiated amino acids and the technique of autoradiography. Results confirm the projection to pons from parasensory association areas in the temporal, parietal, and occipital lobes and extend these observations to include the posterior parahippocampal gyrus. The findings reveal that the white matter of the posterior limb of the internal capsule above the midpoint of the lateral geniculate nucleus, and at the medial aspect of the lateral geniculate nucleus, comprise common regions through which these Corticopontine Fibers lead to the basis pontis. The Fibers demonstrate a certain degree of topographic organization in the posterior limb of the capsule above the lateral geniculate nucleus and also in the cerebral peduncle. Taken together with previous observations concerning the termination patterns of these associative Corticopontine projections, it would appear that the Corticopontine system consists of segregated and partially overlapping pathways, which are to some extent distinguishable anatomically at each stage of their trajectory from origin to destination. Furthermore, the existence of a common area through which all parasensory associative input to pons is transmitted suggests that a precisely located lesion in this part of the corticopontocerebellar circuit may disrupt the cerebellar access to higher order information derived from the parasensory associative regions.
Martin E. Schwab - One of the best experts on this subject based on the ideXlab platform.
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Functional Recovery and Enhanced Corticofugal Plasticity after Unilateral Pyramidal Tract Lesion and Blockade of Myelin-Associated Neurite Growth Inhibitors in Adult Rats
The Journal of Neuroscience, 2018Co-Authors: Werner J. Z’graggen, Michaela Thallmair, Gerlinde A S Metz, Gwendolyn L Kartje, Martin E. SchwabAbstract:After a lesion of the mature CNS, structural plasticity and functional recovery are very limited, in contrast to the developing CNS. The postnatal decrease in plasticity is correlated in time with the formation of myelin. To investigate the possible role of an important myelin-associated neurite growth inhibitor (NI-250; IN-1 antigen), one pyramidal tract of adult Lewis rats was lesioned (pyramidotomy), and the rats were treated with the antibody IN-1, a control antibody, or no antibody. Functional recovery was studied from postoperative day 14 until day 42 using a food pellet reaching task, rope climbing, and a grid walk paradigm. The corticofugal projections to the red nucleus and basilar pontine nuclei were analyzed after survival times of 2 and 16 weeks. Treatment with the monoclonal antibody IN-1 resulted in almost complete restoration of skilled forelimb use, whereas all the control groups showed severe and chronic impairments. This functional recovery was paralleled by sprouting of the corticorubral and the Corticopontine Fibers across the midline, thus establishing a bilateral, anatomically specific projection.
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Compensatory Sprouting and Impulse Rerouting after Unilateral Pyramidal Tract Lesion in Neonatal Rats
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2000Co-Authors: Werner J. Z’graggen, Gerlinde A S Metz, Martin E. Schwab, Karim Fouad, Olivier Raineteau, Gwendolyn L KartjeAbstract:After lesions of the developing mammalian CNS, structural plasticity and functional recovery are much more pronounced than in the mature CNS. We investigated the anatomical reorganization of the corticofugal projections rostral to a unilateral lesion of the corticospinal tract at the level of the medullary pyramid (pyramidotomy) and the contribution of this reorganization and other descending systems to functional recovery. Two-day-old (P2) and adult rats underwent a unilateral pyramidotomy. Three months later the corticofugal projections to the red nucleus and the pons were analyzed; a relatively large number of corticorubral and Corticopontine Fibers from the lesioned side had crossed the midline and established an additional contralateral innervation of the red nucleus and the pons. Such anatomical changes were not seen after adult lesions. Intracortical microstimulation of the primary motor cortex with EMG recordings of the elbow flexor muscles were used to investigate possible new functional connections from the motor cortex of the pyramidotomy side to the periphery. In rats lesioned as adults, stimulation of the motor cortex ipsilateral to the pyramidotomy never elicited EMG activity. In contrast, in P2 lesioned rats bilateral forelimb EMGs were found. EMG latencies were comparable for the ipsilateral and contralateral responses but were significantly longer than in unlesioned animals. Transient inactivation of both red nuclei with the GABA receptor agonist muscimol led to a complete loss of these bilateral movements. Movements and EMGs reappeared after wash-out of the drug. These results suggest an important role of the red nucleus in the reconnection of the cortex to the periphery after pyramidotomy.
Per Brodal - One of the best experts on this subject based on the ideXlab platform.
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Chapter 13 Salient anatomic features of the cortico-ponto-cerebellar pathway
Progress in brain research, 1997Co-Authors: Per Brodal, Jan G. BjaalieAbstract:Publisher Summary This chapter focuses on the cerebrocerebellar pathway, synaptically interrupted in the pontine nuclei. Recent studies of the primate Corticopontine projection show that the neocerebellum—in addition to connections from motor and sensory areas—receives connections from various association areas of the cerebral cortex, some of which are thought to be primarily engaged in cognitive tasks. The anatomic data on the origin of Corticopontine Fibers needs to be supplemented with physiological experiments to clarify their functional properties at the single-cell level. The scarcity of Corticopontine connections from the prefrontal cortex in the monkey may not seem readily compatible with a prominent role of the neocerebellum in certain cognitive tasks. Corticopontine and pontocerebellar lamellae have similar shapes and orientations but appear to differ in other respects. Corticopontine terminal fields are sharply delimited, apparently without gradual overlap between projections from different sites in the cortex, whereas pontocerebellar lamellae are fuzzier and exhibit gradual overlap of neuronal populations projecting to different targets.
-
organization of the pontine nuclei
Neuroscience Research, 1992Co-Authors: Per Brodal, Jan G. BjaalieAbstract:The pontine nuclei provide the cerebellar hemispheres with the majority of their mossy fiber afferents, and receive their main input from the cerebral cortex. Even though the vast majority of pontine neurons send their axons to the cerebellar cortex, and are contacted monosynaptically by (glutamatergic) Corticopontine Fibers, the information-processing taking place is not well understood. In addition to typical projection neurons, the pontine nuclei contain putative GABA-ergic interneurons and complex synaptic arrangements. The Corticopontine projection is characterized by a precise but highly divergent terminal pattern. Large and functionally diverse parts of the cerebral cortex contribute; in the monkey the most notable exception is the almost total lack of projections from large parts of the prefrontal and temporal cortices. Within Corticopontine projections from visual and somatosensory areas there is a de-emphasis of central vision and distal parts of the extremities as compared with other connections of these sensory areas. SubCorticopontine projections provide only a few percent of the total input to the pontine nuclei. Certain cell groups, such as the reticular formation, project in a diffuse manner whereas other nuclei, such as the mammillary nucleus, project to restricted pontine regions only, partially converging with functionally related Corticopontine connections. The pontocerebellar projection is characterized by a highly convergent pattern, even though there is also marked divergence. Neurons projecting to a single cerebellar folium appear to be confined to a lamella-shaped volume in the pontine nuclei. The organization of the pontine nuclei suggests that they ensure that information from various, functionally diverse, parts of the cerebral cortex and subcortical nuclei are brought together and integrated in the cerebellar cortex.
