In the

human brain The human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brain consists of the cerebrum, the brainstem and the cerebellum. It controls most of the activities of the ...

, the superior cerebellar peduncle (brachium conjunctivum) is a paired structure of

white matter White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribution ...

that connects the

cerebellum The cerebellum (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 or even larger. In humans, the cerebel ...

to the

midbrain The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation. The name comes from the Greek ''mesos'', " ...

. It consists mainly of

efferent fibers Efferent nerve fibers refer to axonal projections that ''exit'' a particular region; as opposed to afferent projections that ''arrive'' at the region. These terms have a slightly different meaning in the context of the peripheral nervous syste ...

, the

cerebellothalamic tract The cerebellothalamic tract or the ''tractus cerebellothalamicus'', is part of the superior cerebellar peduncle. It originates in the cerebellar nuclei, crosses completely in the decussation of the superior cerebellar peduncle, bypasses the red nu ...

that runs from a cerebellar hemisphere to the contralateral thalamus, and the cerebellorubral tract that runs from a cerebellar hemisphere to the

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. ...

. It also contains afferent tracts, most prominent of which is the

ventral spinocerebellar tract The spinocerebellar tract is a nerve tract originating in the spinal cord and terminating in the same side (ipsilateral) of the cerebellum. Origins of proprioceptive information Proprioceptive information is obtained by Golgi tendon organs and ...

. Other afferent tracts are the trigeminothalamic fibers, tectocerebellar fibers, and noradrenergic fibers from the

locus coeruleus The locus coeruleus () (LC), also spelled locus caeruleus or locus ceruleus, is a nucleus in the pons of the brainstem involved with physiological responses to stress and panic. It is a part of the reticular activating system. The locus coerule ...

. The superior peduncle emerges from the upper and medial parts of the

of each

hemisphere Hemisphere refers to: * A half of a sphere As half of the Earth * A hemisphere of Earth ** Northern Hemisphere ** Southern Hemisphere ** Eastern Hemisphere ** Western Hemisphere ** Land and water hemispheres * A half of the (geocentric) celes ...

and is placed under cover of the upper part of the cerebellum.

Structure

Superior cerebellar peduncles are connected together by the anterior medullary velum, which can be followed upward as far as the

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

, under which they disappear. Below, they form the upper lateral boundaries 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 ve ...

, but as they ascend they converge on the dorsal aspect of the ventricle and thus assist in forming its roof.

Decussation

The decussation of superior cerebellar peduncle is the crossing of fibers of the superior cerebellar peduncle across the midline, and is located at the level of the

. It comprises the

, which arises from the

dentate nucleus The dentate nucleus is a cluster of neurons, or nerve cells, in the central nervous system that has a dentate – tooth-like or serrated – edge. It is located within the deep white matter of each cerebellar hemisphere, and it is the largest sin ...

(therefore also known as

dentatothalamic tract The dentatothalamic tract (or dentatorubrothalamic tract) is a tract which originates in the dentate nucleus and follows the ipsilateral superior cerebellar peduncle, decussating later on and reaching the contralateral red nucleus and the contrala ...

), as well as the cerebellorubral tract, which arises from the

globose A sphere () is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. A sphere is the set of points that are all at the same distance from a given point in three-dimensional space.. That given point is the ce ...

and emboliform nuclei and project to the

contralateral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

to eventually become the

rubrospinal tract The rubrospinal tract is a part of the nervous system. It is a part of the lateral indirect extra-pyramidal tract. Structure In the midbrain, it originates in the magnocellular red nucleus, crosses to the other side of the midbrain, and desce ...

. It is also known as horseshoe-shaped commissure of Wernekinck. It is important as an anatomical landmark, as lesions above it cause contralateral cerebellar signs, while lesions below it cause ipsilateral cerebellar signs.

Additional images

Image:Gray677.png, Scheme showing the connections of the several parts of the brain. Image:Gray682.png, Superficial dissection of brain-stem. Lateral view. Image:Gray701.png, Axial section of the pons, at its dorsal (superior) part. Image:Gray707.png, Sagittal section through right cerebellar hemisphere. The right olive has also been cut sagittally. Image:Gray745.png, Dissection showing the course of the cerebrospinal fibers. Image:Gray792.png, Upper part of medulla spinalis and hind- and mid-brains; posterior aspect, exposed in situ.

References

External links

* * * https://web.archive.org/web/20080518232033/http://isc.temple.edu/neuroanatomy/lab/atlas/micn/ * http://www.neuroanatomy.wisc.edu/Bs97/TEXT/P18/sum.htm
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