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Featured researches published by Per Brodal.


Neuroscience Research | 1992

Organization of the pontine nuclei

Per Brodal; Jan G. Bjaalie

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.


Experimental Brain Research | 1968

The corticopontine projection in the cat. I. Demonstration of a somatotopically organized projection from the primary sensorimotor cortex.

Per Brodal

SummarySmall lesions (in some cases bilateral) were made in the cerebral primary sensorimotor region in altogether 21 adult cats and the ensuing degeneration in the pontine nuclei was studied with the silver impregnation methods of Nauta and Glees. Using thermocoagulation it was possible to obtain lesions restricted entirely to particular cortical regions (for example the “hindlimb region” in the posterior sigmoid gyrus). The main results are as follows:1.All parts of the primary sensorimotor region send fibres to the pontine nuclei. The projections from the posterior part of the posterior sigmoid gyrus and the posterior part of the coronal gyrus are relatively scanty.2.The cortical “motor” area (the anterior sigmoid gyrus and the anterior part of the coronal gyrus) and the “sensory” area (the posterior sigmoid gyrus and the posterior part of the coronal gyrus) do not project to identical pontine regions, although both projections are organized in principally the same way.3.The “motor” and “sensory” areas both project in a somatotopical manner onto two longitudinally oriented sharply delimited columns. In both projections one column is located medial and one lateral to the longitudinal fibre bundles of the corticospinal and corticobulbar tracts. Within the medial columns the “hindlimb” is represented ventrally with “face” most dorsally, within the lateral columns the “hindlimb” is located most caudally, with “forelimb” and “face” successively more rostrally.4.The present results are in agreement with physiological observations on the cerebrocerebellar relations, but show that the pontine projection from the primary sensorimotor cortex is organized in a more complex manner than hitherto assumed.


Brain Research | 1983

Is lectin-coupled horseradish peroxidase taken up and transported by undamaged as well as by damaged fibers in the central nervous system?

Per Brodal; Espen Dietrichs; Jan G. Bjaalie; T. Nordby; Fred Walberg

Uptake and transport of horseradish peroxidase-wheat germ agglutinin conjugate (HRP-WGA) in intact and damaged passing fibers were studied by injections of the medulla and pons in 11 cats. Injections with evidence of damage to olivocerebellar fibers and cranial nerve fibers invariably lead to retrograde labeling of neurons in the inferior olive and cranial motor nuclei. With staining around--but apparently no damage of--cranial nerve root fibers, no labeling was found in their motor nuclei. Injections limited to the medullary pyramid with slight fiber damage and limited staining lead to faint retrograde labeling of a small number of cells in the ipsilateral sensorimotor cortex. More extensive staining and fiber damage of the pyramid gave a higher number of labeled cells in the ipsilateral sensorimotor cortex. From these experiments we conclude that HRP-WGA is taken up and transported retrogradely with subsequent significant cell labeling in damaged but not in intact fibers. Anterograde transport of HRP-WGA in fibers passing through the injected area was found to take place only for a very short distance, as judged from cases with injections of either the pons or the medullary pyramid interrupting many corticospinal fibers.


Brain Research | 1967

The cerebral cortical projection to the lateral reticular nucleus in the cat, with special reference to the sensorimotor cortical areas

Per Brodal; Joseph Marsˇala; Alf Brodal

Abstract Maturation of evoked cortical responses to visual and auditory stimulation was investigated in normal as well as in acute and chronically starved cats. In normal rats the most prominent changes occur at 14 days of age, i.e., decreased latencies and the appearance of all components of the evoked response. In rats acutely starved (24h) the most marked changes were observed in early periods of postnatal life. Increased latencies and absence of the first positive component were typical modifications of the responses. Chronic starvation (daily for 10–12 h, from 5 to 10 days) was followed by a significant increase in latencies lasting as long as 45 days of age. Some probable mechanisms of these changes are discussed.


Progress in Brain Research | 1997

Chapter 13 Salient anatomic features of the cortico-ponto-cerebellar pathway

Per Brodal; Jan G. Bjaalie

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 quantities of such connections in relation to those from more clearly motor-related parts of the cortex need to be more precisely determined, however. Furthermore, the anatomic data on origin of corticopontine fibers needs to be supplemented with physiological experiments to clarify their functional properties at the single-cell level. For example, nothing is known of the functional role of the large input from the cingulate gyrus, nor is the input from the posterior parietal cortex physiologically characterized. Finally, the scarcity of corticopontine connections from the prefrontal cortex in the monkey (and probably also in man) may not seem readily compatible with a prominent role of the neocerebellum in certain cognitive tasks. We discuss data--in particular from three-dimensional reconstructions--indicating that both corticopontine projects and pontocerebellar neurons are arranged in a lamellar pattern. 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 more fuzzy and exhibit gradual overlap of neuronal populations projecting to different targets. In spite of the sharpness of the corticopontine projection, there may be many opportunities for convergence of inputs from different parts of the cortex. Thus, the wide divergence of corticopontine projections produces many sites of overlap, and extensive interfaces between different terminal fields enabling convergence of inputs onto each neuron. We suggest that the lamellar arrangement of corticopontine terminal fields and of pontocerebellar neurons serve to create diversity of pontocerebellar neuronal properties. Thus, each small part of the cerebellar cortex would receive a specific combination of messages from many different sites in the cerebral cortex. The spatial arrangement of cerebrocerebellar connections have to be understood both in terms of fairly simple large-scale, gradual topographic relationships and an apparently highly complex pattern of divergence and convergence. Developmental studies of corticopontine and of pontocerebellar projections together with three-dimensional reconstructions in adults suggest that the highly complex adult connectional pattern may be created by simple rules operating during development.


Brain Research | 1972

The corticopontine projection from the visual cortex in the cat. I. The total projection and the projection from area 17.

Per Brodal

Summary Large lesions of the whole visual cortex (areas 17, 18 and 19) and small lesions (in most cases bilateral) of area 17 were made in adult cats, and the ensuing degeneration in the pontine nuclei was studied with the silver impregnation methods of Nauta and of Fink and Heimer. Most of the lesions were made by thermocoagulation. The main results are as follows. (1) The visual cortex as a whole projects onto several sharply delimited, mainly transverse bands in the rostral half of the pontine nuclei. The exact localization of these bands has been compared with the terminal areas of the corticopontine fibers from other cortical regions as determined by the present author. Only a modest degree of overlap is possible between the projection areas of the visual cortex and of the sensorimotor cortex. (2) All parts of area 17 project onto the pontine nuclei. The projection from middle parts (representing roughly the central visual field) is sparse, whereas it is heavy from rostral and caudal parts (representing peripheral parts of the visual field). (3) The total projection from area 17 covers the same pontine region as does the projection from the visual cortex as a whole (areas 17, 18 and 19). (4) A topical localization is present within the pontine projection from area 17. Rostral parts (representing the lower visual field) project more laterally within the pontine nuclei than do caudal parts (upper visual field). Medial and lateral parts of area 17 also project differently onto the pontine nuclei.


Experimental Brain Research | 1969

Electronmicroscopic observations on the structure of the pontine nuclei and the mode of termination of the corticopontine fibres an experimental study in the cat

Horstmar Holländer; Per Brodal; Fred Walberg

SummaryThe electron microscopical changes occurring in the pontine nuclei following unilateral lesions of the primary sensorimotor cortex have been studied in 7 cats with a survival time from 2–23 days. A description is also given of the fine structure of the pontine regions in receipt of the fibres. These regions are shown in Fig. 1.The study shows that the boutons are practically only in synaptic contact with dendrites. The bouton density on these is only 16%. The boutons are of the en passage and terminal type, with the latter as the most common (Figs. 4a-e). The synaptic vesicles are rounded or elongated. The formaldehyde fixed material had 17.8% boutons with vesicles of the elongated type; the material fixed with a mixture of formaldehyde and glutaraldehyde had only 11.5% of such boutons.The degenerating boutons show the dark type of reaction and the majority of the corticopontine fibres are of the type shown in Figs. 4d and 4e. Astrocytes and microglial cells participate in the removal of degenerating boutons and terminal fibres. Degenerating boutons are present even at the 23 day stage and some have apparently only started to degenerate.


Brain Research | 1972

The corticopontine projection from the visual cortex in the cat. II. The projection from areas 18 and 19.

Per Brodal

Small lesions (in most cases bilateral) were made of the cerebral cortical areas 18 and 19 in adult cats, and the ensuing degeneration in the pontine nuclei was studied with the silver impregnation methods of Nauta and of Fink and Heimer. The lesions were made by transdural thermocoagulation. Since large parts of areas 18 and 19 are buried in sulci, isolated lesions of these parts have not been achieved. The main results are as follows. (1) All parts of area 18 studied (rostral part, related to the lower visual field) project onto the pontine nuclei. (2) The fibers from area 18 terminate within mainly transverse bands in the rostral half of the pontine nuclei in the pontine regions that receive afferents from area 17. At least certain corresponding parts of areas 17 and 18 project onto identical pontine areas, and the projections from the two areas are about equally heavy. (3) There is suggestive, but not conclusive, evidence for a topical localization within the pontine projection from area 18. (4) It appears likely that all parts of area 19 situated on the convexity of the hemisphere project onto the pontine nuclei. Middle parts of area 19 (representing the central visual field) seem to project less heavily than more rostral parts. The fibers terminate mainly within a transverse band in the rostralmost part of the pontine nuclei. (5) The projections from areas 19 and 18 terminate in different parts of the pontine nuclei. No topical localization has been found within the pontine projection from area 19, but the material is inadequate to resolve this question. (6) A zone of cortex surrounding area 19 (the suprasylvian and the cingulate gyri) projects onto the same (but somewhat more extensive) pontine region as does area 19. (7) The results of the present and the preceding studies10 are discussed with regard to physiological data on the relations between the visual cortex and the cerebellum.


Brain Research | 1975

Demonstration of a somatotopically organized projection onto the paramedian lobule and the anterior lobe from the lateral reticular nucleus: An experimental study with the horseradish peroxidase method

Per Brodal

Using the retrograde axonal transport of horseradish peroxidase, the projection from the lateral reticular nucleus (NRL) to the cerebellar anterior lobe and paramedian lobule has been studied in 13 cats. Both the anterior lobe and the paramedian lobule receive a somatotopically organized projection from the NRL. The projection to the paramedian lobule is nearly exclusively ipsilateral and originates mainly in the dorsal part of NRL, while the projection to the anterior lobe is bilateral (with ipsilateral predominance) and takes origin from all parts of the NRL. The lateral part of the NRL (closely coinciding with the parvocellular nucleus) projects to the rostral part of the anterior lobe and caudal parts of the paramedian lobule (both representing the hindlimb), while the medial part of the NRL (magnocellular nucleus) projects to the caudal parts of the anterior lobe and rostral parts of the paramedian lobule (representing the forelimb). The small subtrigeminal nucleus projects onto the anterior lobe as well as the paramedian lobule, but apparently mainly to their forelimb areas.


Experimental Brain Research | 1980

The projection from the nucleus reticularis tegmenti pontis to the cerebellum in the rhesus monkey.

Per Brodal

SummaryFollowing injections of horseradish peroxidase in various parts of the monkey cerebellum, the distribution of labelled cells in the nucleus reticularis tegmenti pontis (NRT) has been studied. As a rule, labelled cells are found at all rostrocaudal levels of the NRT regardless of the injection size and site. The densest projection from NRT seems to reach the vermal visual area (lobulus VII), a less dense projection supplies the anterior lobe while the paramedian lobule receives a more sparse projection than the anterior lobe. Very few labelled cells were found in the NRT after injections of crus I and II. The projection is topographically organized so that the dorsomedial part of the NRT supplies lobulus VII, a large central region sends fibres to the anterior lobe (and the cerebellar hemispheres), while the lateral extension of NRT (processus tegmentosus lateralis) is connected with the paramedian lobule.The results of the present study are compared with those of a preceding one of cortical afferents to NRT. It is concluded that the cortical areas projecting to the NRT seem likely to exert their influences on largely different parts of the cerebellum via the NRT. The present results are also discussed inrelation to termination of other afferent contingents in the NRT, and it is concluded that the NRT is not homogenous anatomically, and consequently different parts of the nucleus would be expected to play somewhat different functional roles.

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Erik Fosse

Oslo University Hospital

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Örjan Smedby

Royal Institute of Technology

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