The pontocerebellar fibers are the

second-order neuron Second-order may refer to: Mathematics * Second order approximation, an approximation that includes quadratic terms * Second-order arithmetic, an axiomatization allowing quantification of sets of numbers * Second-order differential equation, a d ...

fibers of the corticopontocerebellar tracts that cross to the other side of the

pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other mammals, lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of ...

and run within the middle cerebellar peduncles, from the

to the contralateral

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 ...

. They arise from the pontine nuclei as the second part of the corticopontocerebellar tract (the first part being the corticopontine fibers which synapse in the pontine nuclei), and

decussate Decussation is used in biological contexts to describe a crossing (due to the shape of the Roman numeral for ten, an uppercase 'X' (), ). In Latin anatomical terms, the form is used, e.g. . Similarly, the anatomical term chiasma is named aft ...

(cross-over) in the pons before passing through the middle cerebellar peduncles to reach and terminate in the contralateral posterior lobe of the cerebellum (neocerebellum). It is part of a pathway involved in the coordination of voluntary movements. The middle cerebellar peduncle consists entirely of pontocerebellar fibers and is the largest pathway of the cerebellum.

Anatomy

The fibers are horizontally oriented, forming bundles which pass dorsally through the pons among the pontine nuclei and interweave with the perpendicularly oriented corticospinal fibers.

Termination

The pontocerebellar fibers terminate throughout the cerebellar cortex except the flocculonodular lobe in an arrangement corresponding to the cortical origin of the pathway: efferents of the

primary motor cortex The primary motor cortex ( Brodmann area 4) is a brain region that in humans is located in the dorsal portion of the frontal lobe. It is the primary region of the motor system and works in association with other motor areas including premotor c ...

project to the

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 ...

and paravermal zone; efferents of the premotor,

somatosensory The somatosensory system, or somatic sensory system is a subset of the sensory nervous system. The main functions of the somatosensory system are the perception of external stimuli, the perception of internal stimuli, and the regulation of bod ...

, and association cortex project to the

cerebellar hemisphere The cerebellum consists of three parts, a median and two lateral, which are continuous with each other, and are substantially the same in structure. The median portion is constricted, and is called the vermis, from its annulated appearance which ...

cortex. Additionally, the fibers also issue collaterals to 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 ...

Pathway

The entire pathway begins and ends in the cerebral cortex, and its entire course is the following: (Motor and sensory areas of)

cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. It is the largest site of Neuron, neural integration in the central nervous system, and plays ...

→ corticopontine fibers → (ipsilateral) nuclei pontis (synapse) → pontocerebellar fibers (decussation within

) →

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 ...

→ (contralateral) (

cerebellar cortex 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 e ...

and (collaterals)

of) posterior lobe of cerebellum (synapse) → cerebellothalamic tract →

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. ...

→ mesencephalon (midbrain) (decussation of tract at level of

inferior colliculus The inferior colliculus (IC) (Latin for ''lower hill'') is the principal midbrain nucleus of the Auditory system, auditory pathway and receives input from several peripheral brainstem nuclei in the auditory pathway, as well as inputs from the aud ...

) → (ipsilateral) (

ventral lateral nucleus The ventral lateral nucleus (VL) is a nucleus in the ventral nuclear group of the thalamus. Inputs and outputs It receives neuronal inputs from the basal ganglia which includes the substantia nigra and the globus pallidus (via the thalamic fas ...

of)

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 ...

→ (ipsilateral) motor (cerebral) cortex (predominately

premotor cortex The premotor cortex is an area of the motor cortex lying within the frontal lobe of the brain just anterior to the primary motor cortex. It occupies part of Brodmann's area 6. It has been studied mainly in primates, including monkeys and human ...

and

)

Clinical significance

Damage to the pontocerebellar fibers (or pontine nuclei) will result in contralateral

ataxia Ataxia (from Greek α- negative prefix+ -τάξις rder= "lack of order") is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in e ...

: due to the double decussation of the pathway along its entire course, it terminates in the motor cortex of the same cerebral hemisphere in which it began; the motor

lateral corticospinal tract Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

then decussates once during its descent to control movement of the opposite side of the body.

References

External links

* https://web.archive.org/web/20130330093937/http://www.neuroanatomy.wisc.edu/virtualbrain/BrainStem/16Pontine.html * https://web.archive.org/web/20080221222726/http://isc.temple.edu/neuroanatomy/lab/atlas/pmjdc/ * http://www.sylvius.com/index/p/pontocerebellar_fibers.html Pons Cerebellar connections Central nervous system pathways {{Neuroanatomy-stub