The cerebellar peduncles are three paired bundles of

fibres Fiber (spelled fibre in British English; from ) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorp ...

that connect the

cerebellum The cerebellum (: cerebella or cerebellums; Latin for 'little brain') is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as it or eve ...

to the

brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is co ...

. *

Superior cerebellar peduncle In the human brain, the superior cerebellar peduncle (brachium conjunctivum) is one of the three paired cerebellar peduncles of bundled fibers that connect the cerebellum to the brainstem. The superior cerebellar peduncle connects to the midbrain. ...

is a paired structure of white matter that connects the cerebellum to the mid-brain. *

Middle cerebellar peduncle The middle cerebellar peduncle (or brachium pontis) is one of three paired cerebellar peduncles connecting the brainstem to the cerebellum. The connection is from the pons. It connects the pons to the cerebellum, with fibres originating from the ...

s connect the cerebellum to the pons and are composed entirely of centripetal fibers. *

Inferior cerebellar peduncle The inferior cerebellar peduncle is formed by fibers of the restiform body that join with fibers from the much smaller juxtarestiform body. The inferior cerebellar peduncle is the smallest of the three cerebellar peduncles. The upper part of t ...

is a thick rope-like strand that occupies the upper part of the posterior district of the medulla oblongata. The peduncles form the lateral border of the

fourth ventricle The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ...

, and form a distinctive diamond the middle peduncle forming the central corners of the diamond, while the superior and inferior peduncles form the superior and inferior edges, respectively.

Structural origin

Superior cerebellar peduncle

The

superior cerebellar peduncle In the human brain, the superior cerebellar peduncle (brachium conjunctivum) is one of the three paired cerebellar peduncles of bundled fibers that connect the cerebellum to the brainstem. The superior cerebellar peduncle connects to the midbrain. ...

s (bracchia conjunctiva) emerge from the cerebellum and ascend to form the lateral portion of the roof of the

, where they enter the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

below the inferior colliculi. They are bridged by the

superior medullary velum The superior medullary velum (anterior medullary velum) is a thin, transparent lamina of white matter which - together with the inferior medullary velum - forms the roof of the fourth ventricle. It extends between the two superior cerebellar ped ...

. The superior cerebellar peduncles represent the main output route from the cerebellum, and as such, most of their fibers are efferent. A relatively small afferent contribution is present. The efferent pathways include the cerebellorubral, dentatothalamic, and fastigioreticular tracts. All of them emerge from the

deep cerebellar nuclei There are four paired deep cerebellar nuclei embedded in the white matter centre of the cerebellum. The nuclei are the fastigial, globose, emboliform, and dentate nuclei. In lower mammals the emboliform nucleus appears to be continuous with t ...

; the cerebellorubral fibers from the

globose nucleus The globose nucleus is one of the deep cerebellar nuclei. It is located medial to the emboliform nucleus, and lateral to the fastigial nucleus. The ''globose nucleus'' and emboliform nucleus are known collectively as the interposed nuclei. The ...

and

emboliform nucleus The emboliform nucleus is a deep cerebellar nucleus that lies immediately to the medial side of the dentate nucleus, partly covering its hilum. It is one of the four pairs of deep cerebellar nuclei, which are from lateral to medial: the dent ...

, the dentatothalamic fibers from the

dentate nucleus The dentate nucleus refer to a pair of deep cerebellar nuclei deep within the white matter of the cerebellum of the brain with a dentate – tooth-like or serrated – edge. The dentate forms the largest pathway between the cerebellum and the r ...

, and the fastigioreticular fibers from the

fastigial nucleus The fastigial nucleus (roof nucleus-1) is located in each cerebellar hemisphere. It is one of the four paired deep cerebellar nuclei of the cerebellum. It is made up of two sections: the rostral fastigial nucleus and the caudal fastigial nucle ...

. They emerge together to ascend in the roof of the fourth ventricle and proceed anteriorly to the midbrain tegmental area medial to the

lateral lemniscus The lateral lemniscus is a tract of axons in the brainstem that carries information about sound from the cochlear nucleus to various brainstem nuclei and ultimately the contralateral inferior colliculus of the midbrain. Three distinct, primarily ...

. The cerebellorubral fibers cross over at this point to enter the contralateral

red nucleus The red nucleus or nucleus ruber is a structure in the rostral midbrain involved in motor coordination. The red nucleus is pale pink, which is believed to be due to the presence of iron in at least two different forms: hemoglobin and ferritin. ...

. The dentatothalamic fibers also cross over and ascend to synapse in the ventral intermediate, and ventral anterior nuclei of the

thalamus The thalamus (: thalami; from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter on the lateral wall of the third ventricle forming the wikt:dorsal, dorsal part of the diencephalon (a division of ...

. The fastigioreticular fibers enter the

reticular formation The reticular formation is a set of interconnected nuclei in the brainstem that spans from the lower end of the medulla oblongata to the upper end of the midbrain. The neurons of the reticular formation make up a complex set of neural networks ...

of the midbrain, pons, and medulla oblongata. Afferent pathways include the

anterior spinocerebellar tract The spinocerebellar tracts are nerve tracts originating in the spinal cord and terminating in the same side ( ipsilateral) of the cerebellum. The two main tracts are the dorsal spinocerebellar tract, and the ventral spinocerebellar tract. Both of ...

, and the tectocerebellar tract. The fibers of the anterior spinocerebellar tract originate in

Clarke's column The posterior thoracic nucleus, (Clarke's column, column of Clarke, dorsal nucleus, nucleus dorsalis of Clarke) is a group of interneurons found in the medial part of Rexed lamina VII, also known as the intermediate zone, of the spinal cord. It i ...

of the spinal cord and cross in the

anterior white commissure The anterior white commissure (ventral white commissure) is a bundle of nerve fibers which cross the midline of the spinal cord just anterior (in front of) to the gray commissure ( Rexed lamina X). A delta fibers (Aδ fibers) and C fibers carr ...

to the

lateral funiculus The most lateral of the bundles of the anterior nerve roots is generally taken as a dividing line that separates the anterolateral system into two parts. These are the anterior funiculus, between the anterior median fissure and the most lateral ...

, where they ascend to upper pontine levels before crossing back to enter the cerebellum through the superior peduncle. They terminate in the hind limb region of the cerebellar cortex. The tectocerebellar tracts emerge from the superior and inferior colliculi on both sides, terminating in the intermediate

vermis The cerebellar vermis (from Latin ''vermis,'' "worm") is located in the medial, cortico-nuclear zone of the cerebellum, which is in the posterior fossa of the cranium. The primary fissure in the vermis curves ventrolaterally to the superior s ...

(culmen, declive, folium, tuber, pyramid) and the lobulus simplex. The function of the tectocerebellar tract is not known, but it is widely believed to mediate visual and auditory reflexes.

References

Cerebellar connections {{Neuroanatomy-stub