Inferior Cerebellar Peduncle (Restiform Body)
The inferior cerebellar peduncle contains the following fiber systems:
Posterior spinocerebellar tract and cuneocerebellar tract (A).The fibers of theposterior spinocerebellar tract (Flechsig’stract) (A1) originate from cells of the poste-rior thoracic nucleus (Clarke’s column) (A3),in which the afferent fibers of the proprio-ceptive sensibility terminate (tendon or-gans, muscle spindles, pp. 312, 314). The re-gion supplied by this tract is restricted to the lower extremity and the lower trunk. The fibers of the posterior spinocerebellar tract terminate as mossy fibers in the ver-mis and intermediate zone of the anterior lobe and in the pyramid. The corresponding fibers for the upper extremity and the upper part of the trunk collect in the lateralcuneate nucleus (Monakow’s nucleus) (A4)and extend as cuneocerebellar tract (A2) to the same areas. The anterior spinocerebellar tract reaches the cerebellum via the supe-rior cerebellar peduncle (brachium con-junctivum).
Vestibulocerebellar tract (B).The cerebel-lum receives primary and secondary vesti-bular fibers. The primary fibers (B5) origi-nate from the vestibular ganglion (B6) (pre-dominantly from the semicircular ducts) and run to the cerebellum without synaps-ing. The secondary fibers (B7) synapse in the vestibular nuclei (B8). Nearly all fibers terminate in the nodulus, flocculus (B9), and fastigial nucleus (B10) but some termi-nate in the uvula. The connection with the vestibular nuclei also contains cerebellofu-gal fibers (cerebellovestibular tract), which originate from the terminal areas just men-tioned and from the vermis of the anterior lobe. Some of them synapse in the lateral vestibular nucleus and extend in the vesti-bulospinal tract to the spinalcord.
Olivocerebellar tract (A).The olive (A11),which may be regarded as a cerebellar nu-cleus transposed ventrally, sends all its fibers to the cerebellum. The olive and its accessory nuclei receive ascending fibers from the spinal cord (spino-olivary tract) (A12), fibers from the cerebral cortex and from extrapyramidal nuclei (centraltegmental tract, p. 144, A). The fibers syn-apse in specific segments of the olive to form the olivocerebellar tract (A13), which crosses to the opposite side and extends to the contralateral half of the cerebellum. The fibers of the olivary complex terminate as climbing fibers in the cerebellar cortex: the fibers of the accessory nuclei (termination zone of the spino-olivary tract) run to the cortex of vermis and intermediate zone of the anterior lobe, while the fibers of the main nucleus (termination zone of cortical fibers and tegmental tract) run to the cere-bellar hemispheres.
Reticulocerebellar tract, nucleocerebellar tract, and arcuatocerebellar tract (C).Thelateral reticular nucleus (C14) receives ex-teroceptive sensory fibers which ascend to-gether with the spinothalamic tracts. The postsynaptic fibers run as reticulocerebellartract (C15) through the ipsilateral cerebellarpeduncle to the vermis and the hemisphere. The nucleocerebellar tract (C16) transmits tactile impulses of the facial area primarily from the trigeminal nuclei (C17) to the cere-bellum. The fibers of the arcuatocerebellartract (C18) originate in the arcuate nucleus(C19) and run to the floor of the fourth ven-tricle, where they form the medullary striae. They run crossed and uncrossed and are thought to terminate in the flocculus.
The uncinate fasciculus of cerebellum, a cere-bellospinal tract originating in the con-tralateral fastigial nucleus, has not been un-equivocally demonstrated in the human brain.