Biomedical subjects

A Brodal

Publications and source records attributed to A Brodal.

At least 37 records · Page 2Linked to original sources

PubMed1977

The olivocerebellar projection studied with the method of retrograde axonal transport of horseradish peroxidase. V. The projections to the flocculonodular lobe and the paraflocculus in the rabbit.

HRP was injected in the flocculonodular lobe and the paraflocculus in the rabbit to determine the areas of the inferior olive which project onto these cerebellar regions. Following injections in the flocculus labeled cells occurred in the dorsal cap and the rostralmost tip of the medial accessory olive. Following injections in the nodulus labeled cells were likewise found in the dorsal cap, but in addition in the rostralmost part of the dorsomedial cell column and the adjoining part of the medial accessory olive. Injections in the dorsal paraflocculus gave rise to labeling in the rostrolateral part of the medial accessory olive, while injections in the ventral paraflocculus resulted in labeling in the principal olive, mainly in the lateral part of the ventral lamella. Injections in the lateral third of the dentate nucleus gave rise to labeling mainly in the dorsal lamella of the principal olive. The results are discussed with reference to those obtained by previous authors. There are both similarities and discrepancies. It appears from what is known of afferents from areas mediating visual impulses to the inferior olive that the olivary areas projecting onto the flocculonodular lobe, and possibly the dorsal paraflocculus, may mediate visual impulses to these lobules.

Afferent Pathways↗

PubMed1977

The olivocerebellar projection in the cat studied with the method of retrograde axonal transport of horseradish peroxidase. VI. The projection onto longitudinal zones of the paramedian lobule.

Microinjections (30-50 nl) of a horseradish peroxidase (HRP) suspension of 25% (wt./vol.) were made in different folia of the paramedian lobule of cats, and the sites of occurrence of labeled cells in the inferior olive were precisely determined. In each case only a small number of cells are labeled, aggregated in a minute area. The labeled cells are found within three only of the four olivary areas previously determined (Brodal et al., '75) to project onto the paramedian lobule (fig. 1): one area in the rostral half of the medial accessory olive, another in the dorsal accessory olive (except its caudalmost part), and a third in part of the caudal half of the dorsal lamella of the principal olive. Labeled cells were never found in the fourth area, the ventral lamella. A distinct zonal pattern in the projection is demonstrated (figs. 3, 5B): a middle longitudinal zone of the paramedian lobule receives olivary afferents from the area in the medial accessory olive, a medial zone from part of the projection area in the dorsal accessory olive, a lateral zone from part of the projection area in the dorsal lamella. This zonal projection appears to extend throughout the length of the paramedian lobule (the two caudalmost folia could not be studied). tthe somatotopical pattern in the projections from the accessory olives described previously (Brodal et al., '75) is confirmed. The pattern of a zonal projection obtained with the HRP-method (fig 5B) is simpler than that deduced by Armstrong et al ('74) from recordings of antidromic potentials in the olive (fig 5A). Concerning main points there is satisfactory agreement. The phenomenon that following microinjections of HRP in superficial parts of the folia labeled cells occur within parts only of the regions of the olive which contain labeled cells following large HRP-injections in the paramedian lobule is discussed.

Afferent Pathways↗

PubMed1977

The pontine projection to the cerebellar vermal visual area studied by means of the retrograde axonal transport of horseradish peroxidase.

Following injections of horseradish peroxidase (HRP) in cerbellar vermal lobules VI, VIIA and B, VIIA and B in the cat, the distribution of labeled cells in the pontine nuclei was mapped in drawings of serial transverse and horizontal sections. The labeled pontine cells are distributed in 4 largely longitudinal columns, situated in the dorsolateral, peduncular, lateral and paramedian pontine nucleus (referred to as columns A, B, C and D, respectively). The majority of afferents to the vermal, visual areas come from colums A and B. To some extent cells projecting to the various sublobules have their preferential location within each column (Fig. 5). The majority of the fibers end in lobule VII. Available data from the literature show that only columns A, D and rostral part of B may be involved in the transmission of visual impulses to the vermal area, since these columns receive afferents from the superior colliculus, the lateral geniculate body and the visual cortex, respectively. The route via the superior colliculus-dorsolateral nucleus appears to be quantitatively the most important. As judged from data on fiber connections, impulses from various sources (inferior colliculus, cerebellar nuclei and "non-visual" parts of the cerebral cortex) are transmitted to certain parts of the 4 columns. The functional importance of this convergence and some general features in the organization of the pons are discussed.

Animals↗

PubMed1977

The olivocerebellar projection in the cat studied with the method of retrograde axonal transport of horseradish peroxidase. IV. The projection to the anterior lobe.

Following injections of horseradish peroxidase (HRP) in the cerebellar cortex of the anterior lobe of the cat, the distribution of labeled cells in the inferior olive was mapped. The findings largely confirm those made previously in studies of olivary retrograde cell loss following cerebellar ablations (Brodal, '40b). In addition, they reveal further olivary areas projecting onto the anterior lobe, and permit a more detailed analysis of the pattern in this projection. Concerning major points the results are in agreement with physiological studies by Armstrong et al. ('74). They bring supporting evidence for a longitudinal zonal pattern in the anterior lobe (fig. 6C). The middle zone of the vermis receives its fibers from a large central area in the caudal half of the medial accessory olive, a lateral zone of the vermis from the lateral half of the dorsal accessory olive. Both olivary areas project to the corresponding cerebellar zone throughout lobules V-I. The lateralmost part of the anterior lobe (lobules IV-V) receives afferents from an area in the dorsal lamella of the principal olive. The intermediate part of lobules IV-V receives afferents from the medial half of the dorsal accessory olive and from an area in the rostral half of the medial accessory olive. There is suggestive evidence that the latter projects to a middle zone, the former to a medial and a lateral zone within the intermediate part as found physiologically. Conclusions concerning projections to the intermediate part of lobules III-II could not be made. The findings in this and preceding studies with the HRP-method show that the concept of a longitudinal pattern in the cerebellum is scarcely generally valid of the entire olivocerebellar projection. Within the projections of the lateral half of the dorsal accessory olive and the area in the rostral part of the medial accessory olive there appears to be a topical relation with the folial pattern in the anterior lobe. An analysis of the findings with reference to the afferents traced anatomically to the various olivary areas permits some conclusions as to the functional role of the olivary areas. Comparison with Oscarsson's ('73) diagram of the sites of termination of two of the spinal-olivary pathways (his DF-SOCP) and VF-SOCP) permits an anatomical explanation as concerns the projections to the vermis, while correlations as concerns the intermediate part are less satisfactory.

Animals↗

PubMed1976

The olivocerebellar projection in the cat studied with the method of retrograde axonal transport of horseradish peroxidase. III. The projection to the vermal visual area.

Horseradish peroxidase (HRP) was injected separately in one of the cerebellar lobules VI, VIIA, VIIB, VIIIA or VIIIB (together corresponding to the vermal visual area) in 17 cats. After 1-3 days the distribution of labeled cells in the inferior olive was mapped. In spite of some overlapping it is clear that the various lobules of the vermal visual area receive fibers from separate parts of a horseshoeshaped region in the caudal half of the contralateral medial accessory olive (fig. 5C). The projection area of lobule VIIA is found caudomedially and overlapping with the area supplying lobule VIIB. This in addition receives a few fibers from the nucleus beta. Fibers terminating in lobule VIIIA arise caudolaterally as do fibers destined for lobule VIIIB. A central part of the total projection area projects to lobule VI. Following injections leading to a similar extent of cortical staining in lobules VI, VII or VIII the projection of labeled cells in the corresponding projection areas differ markedly. In the area of lobule VII apparently all cells are labeled, in the area of lobule VI the density of labeled cells is considerably less, and in that of lobule VIII there are rather few labeled cells. In a few cases with widespread staining of the cerebellar visual area there was spreading of HRP to the nucleus fastigii. The projection to this form the olive was therefore investigated to avoid erroneous conclusions. In the discussion it is pointed out that on most points our findings agree fairly well with the results of studies of the olivocerebellar projection undertaken with other methods (studies of retrograde cellular changes, electrophysiological methods). No support for a longitudinal subdivision of lobules VI-VIII was found. Studies of the available literature indicate that the areas in the medial accessory olive projecting onto lobules VI-VIII probably do not receive direct afferents from regions which are known to be concerned in the transmission of visually evoked impulses. Fibers to the olive from the superior colliculus appear to pass to the nucleus beta only. This projects mainly to the uvula, to a little extent only to lobule VII. However, it may be imagined that visual impulses may reach the vermal visual area via the inferior olive by way of intercalated neurons, for example in the mesencephalic RF. Major contingents of afferents to the olivary regions projecting onto the vermal area come from the spinal cord, the motor cortex and the periaqueductal gray.

Animals↗

PubMed1976

The olivocerebellar projection in the cat as studied with the method of retrograde axonal transport of horseradish peroxidase. II. The projection to the uvula.

Following injections of small quantities of horseradish peroxidase (HRP) suspension in the uvula of the cat, the distribution of labeled cells in the inferior olive has been mapped. The findings confirm the conclusion made on the basis of studies of retrograde cell loss in the olive following ablations of the uvula (Brodal, '40b) that two small olivary subdivisions, the nucleus beta and the dorsomedial cell column project heavily to the uvula. In addition the HRP-study shows that the uvula receives a smaller number of fibers from two circumscribed areas of the contralateral medial accessory olive. These areas appear to project to the lateralmost parts of the uvula (fig. 4). The findings thus support the presence of a longitudinal zonal subdivision in the uvula. Labeled cells are found in the nucleus beta and the dorsomedial cell column also following injections of the fastigial nucleus and to a lesser degree of lobulus VII of the vermis (Hoddevik et al. 76). This may be due to collateral branching of olivary efferents. There is some evidence for a topographical correlation between dorsal and ventral parts of the uvula and rostral and caudal parts, respectively, of the nucleus beta and the dorsomedial cell column. This may be related to functional differences between the two parts of the uvula.

Animals↗

PubMed1976

A note on the method of retrograde transport of horseradish peroxidase as a tool in studies of afferent cerebellar connections, particularly those from the inferior olive; with comments on the orthograde transport in Purkinje cell axons.

1. Injections of horseradish peroxidase (HRP) suspension were made in the cerebellar cortex of cats (most often the paramedian lobule). The staining of the cerebellar cortex and the ensuing labeling of neurons in the inferior olive were studied in experiments with variations of concentration of HRP, amounts of fluid injected, survival time and age of the animals. Light microscopical studies were supplemented with electron microscopical observations. The folded cerebellar cortex offers particular difficulties with regard to obtaining a predictable extent of stained tissue, and the spreading of the fluid within the cortex shows great variations even with the same amounts and concentrations of HRP suspension. Diffusion of fluid appears to occur most easily within the molecular layer. Often there are unstained parts of folia between stained parts. Staining of the cortex is barely visible after 7 days, but appreciable shrinking of the stained area does not appear to occur until after 4 days. 2. The first signs of labeling of olivary neurons are seen after 5-10 hours, after 7 days there are no labeled cells. The rate of retrograde transport in olivocerebellar fibers is calculated to be between 50 and 100 mm/day. Labeling of cells appears to require staining of the molecular layer of its projection areas in the cerebellum. 3. For studies of the olivocerebellar projection survival times of 2-3 days and injections of 0.5 mul of a 50% HRP suspension seem in general to be well suited. Best results are obtained with animals weighing 1-3 kg. There is a clearcut correlation between the site of staining of the cortex of a particular part of the cerebellum and the site(s) and extension of olivary area(s) containing labeled cells. 4. Anterograde transport in axons of Purkinje cells has been observed. Electron microscopically the axons of these fibers contain HRP labeled tubules and vesicles as do their terminal boutons in the nuclei. 5. In cases where the injected fluid has spread to the cerebellar nuclei, localized parts contain neurons which are labeled as are the cells in the injected cerebellar cortex.

Afferent Pathways↗

PubMed1975

The olivocerebellar projection in the cat studied with the method of retrograde axonal transport of horseradish peroxidase.

The distribution of labeled cells in the inferior olive of the cat has been mapped following injections of small amounts of horseradish perosidase in the paramedian lobule of the cerebellum. The distribution of labeled cells was plotted in drawings of approximately serial transverse sections. The findings in each case were transferred to a standard diagram of the olive to facilitate comparison of cases. Previous studies of the distribution of retrograde cell loss in the inferior olive following cerebellar lesions (Brodal, '40b) showed that fibers ending in the paramedian lobule come from the caudal part of the ventral lamella of the principla olive. This was confirmed with the peroxidase method, but in addition three other separate and well circumscribed area of the olive showed labeling: one in the dorsal accessory olive, another in the rostral part of the medial accessory olive, a third in the caudal part of the dorsal lamella of the principal olive (fig. 7). There is some degree of topical arrangement within the projection of each of these olivary areas to the paramedian lobule. It is particularly striking that the projection areas of the caudal one-third of the lobule are different from and overlap only little with those of the orstral two-thirds. On account of diffusion of the injected perosidase solution in the folia it could not be decided whether the different olivary areas project to particular longitudinal zones in the paramedian lobule. The main findings can be correlated with the physiological observations of Armstrong et al. ('74). Some of the "paramedian" olivary areas are labeled also following peroxidase injections in other cerebellar parts, among them the nuclei interpositus anterior and posterior. The findings are compatible with the notion that olivocerebellar fibers branch to supply more than one cerebellar region. It is confirmed that the olivocerebellar projection, including that of the nuclei, is almost completely crossed. In the discussion it is emphasized that afferents from several sources converge on all four olivary regions projecting onto the paramedian lobule. The olivocerebellar projection obviously allows for divergence as well as convergence of impulses from the olive to the cerebellum. For further insight into the anatomical organization of the inferior olive, the entire olivocerebellar projection has to be mapped with the peroxidase methods, and further studies of the afferents to the olive are needed. In such studies, as well as in physiological ones, it is essential that findings are described with meticulous reference to the topography of the olivary subdivisions.

Animals↗

PubMed1975

The reticulovestibular projection in the cat. An experimental study with silver impregnation methods.

The distribution of degeneration in the vestibular nuclei (VN) has been studied in transversely cut sections from 9 cats with stereotaxically performed lesions in the main reticular formation (RF) of the brain stem (Nauta of Fink and Heimer method). No projection was found from the mesencephalic reticular formation (R.mes.) and nucleus reticularis ventralis (R.v.). However, the reticular nuclei gigantocellularis (R.gc.), parvocellularis (R.p.c.) and pontis oralis (R.p.o.) were found to project bilaterally onto the 4 main vestibular nuclei with an ipsilateral overweight. By far the greates contribution comes from the R.gc. and R.p.c. In cases with R.gc. lesions some degeneration was found in the small cell groups x and f. The latter is also supplied from the R.p.c. The distribution of degeneration within the vestibular complex is rather diffuse, but a certain pattern can be discovered. After R.p.c. lesions the maximal terminal field in the VN is found within the superior nucleus, while the lateral and medial nuclei are preferred sites of termination of fibers from R.gc. and R.p.c. The projections of the R.gc. and the R.p.c. may be more different than appears from our findings since lesions of one of them will most likely have affected some ascending or descending fibers emanating from the other. Since the areas of RF projecting to VN receive afferents from many sources, these sources have possibilities to act on the VN even if they do not possess direct connections with this nuclear complex. These possibilities should be remembered in physiological studies of responses in the VN following stimulation of many parts of the CNS.

Animals↗

PubMed1975