Multiple zonal projections of the basilar pontine nuclei to the cerebellar cortex of the rat

Abstract

This study revealed a sagittal zonal pattern of projections to the cerebellar cortex after hydraulic or iontophoretic injections of anterograde tracers (tritiated leucine, wheat germ agglutinin-horseradish peroxidase, or biotinylated dextrane amine) in the basilar pontine nuclei of Wistar rats. The zonal pattern of projection was observed only after injections of small size, whereas large injections labeled diffusely wide areas of the cerebellar cortex, masking the zonal projection because the fusion of contiguous stripes. Diverging projections to discrete sets of sagittal stripes in the two sides of the cerebellar cortex arose from single injections. The stripes of fiber terminals were sharply delimited on both sides by areas, interstripes, either virtually void of labeling or with a much lower density of labeling. Thus, the areas of the cerebellar cortex were parceled in sets of sagittal compartments, stripes and interstripes, by the pontine projections. Up to five compartments (three stripes and two interstripes) were observed in the paraflocculus, in the copula pyramidis, and in vermal lobule IX. Up to nine compartments (five stripes and four interstripes) were found in the crus I, the lobulus simplex, the paramedian lobule, and vermal lobules VI-VIII. Up to seven compartments (four stripes and three interstripes) were found in the crus II. Single injections into the basilar pontine nuclei usually labeled symmetric areas of the cerebellar cortex, which, in some cases, showed similar number of stripes. When this was not the case, the stripes were usually more numerous in the contralateral than in the ipsilateral side. All areas of the cerebellar cortex were projected upon, with zonation patterns from different regions of the basilar pontine nuclei. The projections of the basilar pontine nuclei to the cerebellar cortex were arranged according to a fixed pattern specific for each cortical area, independently of the number of stripes labeled within. The mean width of the stripes visualized in the single cortical areas of different rats was similar, despite the different size of the injections. The length of the stripes ranged widely in the various areas of different rats. The data collected in this study are consistent with the idea that all the mossy afferents to the cerebellar cortex are arranged with a zonal pattern.

Precise Spatial Relationships between Mossy Fibers and Climbing Fibers in Rat Cerebellar Cortical Zones

“…On the one hand, mossy fiber input is usually characterized by multiple representations of the same body parts distributed as a mosaic of patches within the cerebellar cortex [the fractionated somatotopy of Welker (1987)]; however, note that some aspects of mossy fiber organization have also been described in terms of longitudinal strips (Ekerot and Larson, 1980;Serapide et al, 2001). In contrast, climbing fiber inputs with similar receptive field characteristics adhere to parasagittally arranged zones in which finer microzonal subdivisions can be recognized (Oscarsson, 1979;Apps and Garwicz, 2005).…”

“…They originate from many parts of the CNS such as the pontine nuclei, trigeminal complex, lateral reticular nucleus, dorsal column nuclei, and the spinal cord (Yatim et al, 1996;Alisky and Tolbert, 1997;Serapide et al, 2001;Odeh et al, 2005). Individual mossy fibers are characterized by a divergent pattern of projections (i.e., they distribute collaterals along both the rostrocaudal and mediolateral axes) (Mihailoff, 1993;Wu et al, 1999;Sultan, 2001;Ruigrok, 2003).…”

Current source density correlates of cerebellar Golgi and Purkinje cell responses to tactile input

“…The 2nd peak (at ϳ20 ms) has been attributed to a corticopontocerebellar projection (Morissette and Bower 1996;Vos et al 2000) relayed via the somatotopy-preserving basal pontine nuclei (Leergaard et al 2000;Serapide et al 2001). This origin is supported by the disappearance of the 2nd peak by lidocaine inactivation of area S1 (Morissette and by isoflurane anesthesia and paired-pulse stimulation in the present study.…”

Sensory-motor Integration and Synaptic Plasticity in Cerebellar Córtex

“…At last, the cerebrocerebellum which begins in the frontal, parietal and occipital areas of cerebral cortex projects them to the nucleus' basis and from the nucleus' basis to the lateral hemispheres of the cerebellum. (SERAPIDE, 2001). This pathway is involved in planning and coordinating the most complex movements, integrating sensorial data to mental commands (cognitive and emotional).…”