Central core of white matter
- Cerebellar peduncles are continued into this white matter
- White matter of the two sides is connected by a thin lamina of fibres that is closely related to the roof of the fourth ventricle.
- Superior medullary velum:
- Upper part of the lamina
- Inferior medullary velum:
- Lower part of the lamina
- Made of 2 crescentic sheets
The input to the cerebellar nuclei is derived from two sources:
- Efferents (see below)
- Afferents
- Derived from
- Three main sources:
- Cerebral cortex
- Spinal cord
- Vestibular nerve
- Minor sources
- Red nucleus
- Tectum
- Excitatory input is derived from fibers that originate in cells that lie outside the cerebellum,
- Inhibitory input is derived from fibers that arise from the Purkinje cells of the cortex.
- Cells outside the cerebellum that send afferents directly to the cerebellar nuclei include pontocerebellar, spinocerebellar, and olivocerebellar fibers, most of which give collaterals to the cerebellar nuclei, then continue on to the cerebellar cortex.
The white matter consists of two types of fibres
Intrinsic:
- Remain confined within the cerebellum
- Connect different regions of the cerebellum (either in the same hemisphere or of the two cerebellar hemispheres):
- Projection fibres:
- Cerebellar cortex → cerebellar nuclei.
- Association fibres:
- Interconnect different parts of the cerebellar cortex.
- Commissural fibres:
- Left ↔ Right cerebellar hemispheres.
Extrinsic: Two ways of sub grouping them
Via tract entrance into the cerebellum via the peduncles
Superior cerebellar peduncle: (brachium conjunctivum)
- Forms the lateral wall of the upper half of the ventricle.
- Consists predominantly of efferent fibres arising in cerebellar nuclei (mainly the dentate nucleus).
- Main afferent: Ventral (anterior) spinocerebellar tract
- Pass along the upper and lateral margin of the rhomboid fossa (Fourth ventricle).
- The fibres of the peduncle enter the midbrain and cross to the opposite side before ending in the red nucleus and the thalamus
- Fibres Entering cerebellum (afferents)
- Fibres exiting cerebellum (efferents)
- Efferents arise from
- Emboliform nuclei
- Globose nuclei
- Dentate nuclei
Tracts | Origin | Termination | Function |
Ventral (anterior) spinocerebellar tract | Secondary neurons in intermediate gray matter of lumbosacral spinal cord (Fibers cross locally and then re-cross in the pons to return to the ipsilateral side.) | Vermis and intermediate part of anterior lobe of cerebellum (ipsilateral; terminates as mossy Fibers) | Proprioception and exteroception (lower limb) |
Tectocerebellar fibres | Visual input | ||
Trigeminocerebellar fibres | Proprioception from mesencephalic nucleus | ||
Hypothalamocerebellar fibres | Hypothalamus | Somatic visceral integration | |
Coerulocerebellar fibres | Locus ceruleans | Noradrenergic modulation of cerebellar learning |
Tracts | Origin | Termination | Function |
Cerebellorubral fibres → Rubrospinal tract | Emboliform nuclei Globose nuclei Dentate nuclei | Red nucleus and thalamus | Fine motor coordination and muscle tone |
Cerebellothalamic fibres → thalamocortical → Corticospinal tract | Emboliform nuclei Globose nuclei Dentate nuclei | Fine motor coordination and muscle tone | |
Cerebelloreticular → reticulospinal trasct | Fastigial Nuclei Globose nuclei | Reticular formation and vestibular nuclei (projection is mostly contralateral) | Somatomotor and autonomic modulation |
Cerebello-olivary fibres | GABAergic feedback | ||
Cerebellohypothalamic fibres | Hypothalamus | Cerebellar autonomic modulation |
- The right half of the posterior lip of the cerebellomesencephalic fissure has been removed.
- Cerebellomesencephalic fissure
- Anterior wall
- Midline: collicular plate and lingula,
- Laterally: superior cerebellar peduncles.
- The middle cerebellar peduncle wraps around the lateral surface of the superior peduncle. The trochlear nerve arises below the inferior colliculi.
The right half of the lingula and superior medullary velum have been removed to expose the fourth ventricle.
Additional white matter has been removed below the right superior peduncle to expose the dentate nucleus in which the superior peduncular fibers arise.
- Enlarged view.
- The dentate nucleus appears to wrap around the rostral pole of the tonsil.
Middle cerebellar peduncle: (brachium pontis)
- Largest of the three peduncles
- Forms a large prominence on the lateral surface of the pons,
- It is separated from the ventricular surface by the superior and inferior cerebellar peduncles.
- The rostral surface of the middle cerebellar peduncles appear to wrap around the caudal margin of the superior cerebellar peduncles.
- Interpeduncular sulcus
- Shallow groove
- Marks the junction of the superior and the middle cerebellar peduncles.
- It continuous
- Anteriorly with the pontomesencephalic sulcus
- Transverse groove between the pons and midbrain
- Superiorly with the lateral mesencephalic sulcus
- Longitudinal fissure dorsal to the cerebral peduncle.
- Course
- Begins as a lateral continuation of the ventral part of the pons (demarcated on the surface by the attachment of trigeminal nerve)
- Fibres, which arise in pontine nuclei, cross to the opposite side. The fibres of the peduncle form a thick bundle that passes laterally and backwards to enter the white core of the cerebellum through the horizontal fissure.
- Entering the cerebellum, the fibres are placed lateral to those of the inferior peduncle (the superior peduncle being still more medial in position).
- Afferent fibres only: which transmit the impulses mainly from pontine nuclei to the opposite cerebellar hemisphere (pontocerebellar fibres).
- Fibres entering cerebellum
- The right half of the posterior lip of the cerebellomesencephalic fissure has been removed.
- Cerebellomesencephalic fissure
- Anterior wall
- Midline: collicular plate and lingula,
- Laterally: superior cerebellar peduncles.
- The middle cerebellar peduncle wraps around the lateral surface of the superior peduncle. The trochlear nerve arises below the inferior colliculi.
Tracts | Origin | Termination | Function |
Pontocerebellar fibres | Basal pontine nuclei. Relay cerebropontine to pontocerebellar projections (source of 90% of the axons in middle peduncle) | Lateral regions of posterior and anterior lobes of cerebellum (contralateral to the origin of these fibers in pons; terminate as mossy fibers; branches to dentate nucleus, also contralateral to the origin in pons) | Cortico-ponto-cerebellar pathway for motor planning |
Few serotoninergic fibres | Modulates the responses of other neurotransmitters |
Inferior cerebellar peduncle: (brachium conjuctiva)
- Forms the anterior and upper margin of the lateral recess.
- Aka restiform body + juxtarestiform body
- Connects the posterolateral part of the medulla ↔ cerebellum
- Course
- Peduncle passes upwards and laterally along the inferolateral margin of the rhomboid fossa (Fourth ventricle).
- Near the upper end of the medulla, the peduncle lies between the superior cerebellar peduncle (on its medial side) and the middle cerebellar peduncle (laterally).
- The inferior peduncle then turns sharply backwards to enter the while core of the cerebellum.
- Juxtarestiform body:
- Over the medial part of the inferior cerebellar peduncle
- Fibres that pass through the vestibular nuclei before entering the cerebellum.
- Fibres entering the cerebellum
- Fibres Exiting the cerebellum
- All efferent going through the inferior cerebellar peduncle arises from the from the fastigial nucleus
Tracts | Origin | Termination | Function |
Posterior spinocerebellar tract | Proprioception and exteroception (lower limb) | ||
Cuneocerebellar tract (posterior external arcuate fibres) | Proprioception and exteroception (upper limb) | ||
Olivocerebellar fibres | Dorsal olivary nucleus Medial accessory olivary nucleus Principle olivary nucleus | Cerebellar cortex | Climbing fibres from inferior olivary and accessory olivary nucleus for cerebellar learning |
Par-olivocerebellar fibres | Same as above | ||
Reticulocerebellar fibres | Lateral reticular nucleus Paramedian reticular nucleus | Feedback from entire central nervous system: spinal cord to cortex | |
Vestibulocerebellar fibres | Information about head position in its movement | ||
Anterior external arcuate fibres | From arcuate nuclei and pontobulbar body, both of which are displaced pontine nuclei (cortico-arcuato-cerebellar pathways and cortico-pontobulbar-cerebellar circumolivary bundle) | ||
Fibres of striae medullares | Same as above | ||
Trigeminocerebellar fibres | Trigeminal nuclei (sensory/mastication) | Exteroception (main sensory and spinal nuclei) |
Tracts | Origin | Termination | Function |
Cerebello-olivary fibres | Fastigial nucleus | GABAergic feedback | |
Cerebellovestibular fibres | Fastigial nucleus | Regulates body equilibrium | |
Cerebelloreticular fibres | Fastigial nucleus | Somatomotor modulation |
- Tela choroidea has been opened, but the choroid plexus, which arises on the inner surface of the tela in the fourth ventricle, has been preserved.
- The fringelike choroid plexus extends through the foramen of Luschka slightly below and behind the junction of the facial and vestibulocochlear nerves with the brainstem.
- The inferior cerebellar peduncle ascends on the dorsolateral margin of the medulla.
Via source of tracts
Afferent
Summary
flowchart TD A["Cerebral Cortex Brainstem<br>(descending motor pathways)"] subgraph Inhibitory B["Deep Cerebellar Nuclei"] end subgraph Stimulatory C["Purkinje Cells"] end D["Mossy Fibers Climbing Fibers"] E["Cerebral Cortex<br>(proprioceptive input)"] F["Muscles, Tendons, Joints<br>(proprioceptive input)"] G["Vestibular Nuclei<br>(input concerning equilibrium)"] E --> D F --> D G --> D D --> C C --> B B --> A
Cerebral cortex
- Corticopontocerebellar pathway
- Cerebral cortex → corona radiata → internal capsule → pontine nuclei → The cells of the pontine nuclei give rise to mossy fibers that cross the midline to reach the opposite cerebellar hemisphere via the middle cerebellar peduncle.
- Cortico-olivocerebellar pathway
- Cerebral cortex → corona radiata → internal capsule → terminates bilaterally at inferior olivary nuclei → The cells of the inferior olivary nuclei give rise to climbing fibers that cross the midline to enter the opposite cerebellar hemisphere via the inferior cerebellar peduncle.
- Corticoreticulocerebellar pathway
- Cerebral cortex → corona radiata → internal capsule → terminates bilaterally in the reticular formation of the pons and medulla → The cells of the reticular formation give rise to mossy fibers that enter the ipsilateral cerebellar hemisphere via the inferior and the middle cerebellar peduncles.
Spinal cord
- Ventral spinocerebellar tract
- Ventral and intermediate gray matter of the spinal cord → Most of its fibers cross the midline to enter the ventral spinocerebellar tract on the opposite side (a small number of fibers are uncrossed) → tract ascends bilaterally in the dorsolateral region of the lateral funiculus → ventral spinocerebellar tract enters the cerebellum via the superior cerebellar peduncle → crosses the midline for a second time → terminates as mossy fibers in the cerebellar cortex.
- Functionally, this tract carries sensory information (mainly proprioceptive) from one side of the body (lower limbs) to the same side of the cerebellum.
- Dorsal spinocerebellar tract
- Nucleus dorsalis (Clarks column) → Most of its fibers are uncrossed → The tract ascends bilaterally in the ventrolateral region of the lateral funiculus → the dorsal spinocerebellar tract enters the cerebellum via the inferior cerebellar peduncle → terminates as mossy fibers in the intermediate zone of the cerebellar cortex.
- Functionally, this tract carries sensory information (mainly proprioceptive) from one side of the body (trunk and lower limbs) to the cerebellum ipsilaterally.
- Cuneocerebellar tract
- Accessory cuneate nucleus of the medulla → Enters the cerebellar hemisphere on the ipsilateral side through the inferior cerebellar peduncle.
- It is the upper extremity equivalent of the dorsal spinocerebellar tract.
- Functionally, this tract transmits sensory (mainly proprioceptive) information from the upper limb and upper part of the thorax.
Vestibular nerve
Cerebellum
- Reciprocal (bidirectional) connection between cerebellum and vestibular system
- Cerebellar afferents from the vestibular system includes:
- First-order neurons that originate in the vestibular labyrinths (direct)
- Second-order neurons that originate in the ipsilateral vestibular nuclei (indirect)
- Inferior cerebellar peduncle
- The vestibulocerebellum, which is the part of the cerebellum that reciprocates with the vestibular system, includes the flocculonodular lobe and the vermis.
- Course
- The vestibular nerve gives rise to afferent fibers that terminate in the vestibular nuclei of the brainstem → The neurons of the vestibular nuclei in turn give rise to mossy fibers → enter cerebellum via inferior cerebellar peduncle → ipsilateral flocculonodular lobe on the same side.
- Function
- Responsible for body posture, equilibrium, and the control of eye movements.
Efferent
- The entire output of the cerebellar cortex is transmitted by the inhibitory Purkinje cells, most of which terminate on the deep cerebellar nuclei (a few Purkinje cell axons continue past the cerebellar nuclei to synapse on the lateral vestibular nucleus in the medulla).
- The cells of the cerebellar nuclei constitute the entire efferent outflow system of the cerebellum.
- Superior cerebellar peduncle
- These constitute the majority of the fibers.
- Transmits those fibers that ascend to the
- Globose and emboliform nuclei send out axons through the superior cerebellar peduncle (cross the midline) → Axons ascend and synapse in the contralateral red nucleus → red nucleus projects fibers into the rubrospinal tract that crosses the midline
- Projections from the globose and emboliform nuclei cross twice before reaching their final destination → influence motor body activity ipsilaterally
- Function
- The globose and emboliform nuclei (rubrospinal tract) influences flexor activity of the extremities (tone)
- See GCS motor flexion
- The axons of neurons in the dentate nucleus (and some from the globose and emboliform nuclei) exit the cerebellum → superior cerebellar peduncle → cross the midline in the same decussation → axons ascend to synapse in the contralateral ventrolateral, ventroposterolateral, and centrolateral nuclei of the thalamus → Thalamus project axons through the internal capsule and the corona radiata → primary motor cortex.
- Function
- The dentate nucleus thus influences the motor neurons of the cerebral cortex on the contralateral side.
- The motor cortex, however, projects descending fibers in the corticospinal tract, which cross the midline in the decussation of the pyramids. Thus, the neurons in the dentate nucleus influence motor activity on the same side of the body.
- Therefore, the dentate mainly influences coordination of the ipsilateral body.
- Inferior cerebellar peduncle
- GCS-Motor Extension
- Transmits those fibers that descend to the
- Two routes
- The axons of the neurons in the fastigial nucleus → exits cerebellum via inferior cerebellar peduncle → Axons descend to terminate bilaterally on the lateral vestibular nucleus → uncrossed descending of vestibulospinal tract
- A few Purkinje cell axons bypass the deep cerebellar nuclei → project directly on the lateral vestibular nucleus → uncrossed descending of vestibulospinal tract
- Function
- The neurons in the fastigial nucleus influence motor activity (facilitate extensor muscle tone) on the same side of the body. Fibers also synapse on the superior and medial vestibular nuclei.
- Therefore, the coordination of extensor muscles is also influenced by the cerebellum.
- Axons of the fastigial nucleus pass exit cerebellum via inferior cerebellar peduncle → Some of these axons descend to synapse with cells in the reticular formation on both sides → descending reticulospinal tract (projects both ipsilaterally and bilaterally) to the spinal gray matter
- Function: The axons of the reticulospinal tract end on interneurons and influence motor neurons indirectly through synaptic relays within the spinal cord.
Red nucleus
Abbreviation | Full Form | Abbreviation | Full Form |
ATegDec | Anterior tegmental decussation (rubrospinal fibers) | MVessp | Medial vestibulospinal tract |
CC | Crus cerebri | MVNu | Medial vestibular nucleus |
CorRu | Corticorubral fibers | OcNu | Oculomotor nucleus |
FacNu | Facial nucleus | PTegDec | Posterior tegmental decussation (tectospinal fibers) |
InfVNu1 | Inferior (or spinal) vestibular nucleus | Py | Pyramid |
LCSp | Lateral corticospinal tract | RNu | Red nucleus |
LRNu | Lateral reticular nucleus | RuSp | Rubrospinal tract |
LVNu | Lateral vestibular nucleus | SC | Superior colliculus |
LVesSp | Lateral vestibulospinal tract | SVNu | Superior vestibular nucleus |
ML | Medial lemniscus | TecSp | Tectospinal tract |
MLF | Medial longitudinal fasciculus | VesSp | Vestibulospinal tracts |
Thalamus
Vestibular
Reticular formation
Abbreviation | Full Form | Abbreviation | Full Form |
ALS | Anterolateral system | PO | Principal olivary nucleus |
ATegDec | Anterior tegmental decussation (rubrospinal fibers) | PTegDec | Posterior tegmental decussation (tectospinal fibers) |
BP | Basilar pons | Py | Pyramid |
CC | Crus cerebri | RB | Restiform body |
CRet | Corticoreticular fibers | RetNu | Reticular nuclei |
CTec | Corticotectal fibers | RetSp | Reticulospinal tract(s) |
GigRetNu | Gigantocellular reticular nucleus | RNu | Red nucleus |
LCSp | Lateral corticospinal tract | RuSp | Rubrospinal tract |
ML | Medial lemniscus | SC | Superior colliculus |
MLF | Medial longitudinal fasciculus | SN | Substantia nigra |
MVNu | Medial vestibular nucleus | SpVNu | Spinal (or inferior) vestibular nucleus |
OcNu | Oculomotor nucleus | TecSp | Tectospinal tract |
Cerebellar afferent tracts
Abbreviation | Full Form | Abbreviation | Full Form |
ACNu | Accessory (external or lateral) cuneate nucleus | PSCT | Posterior (dorsal) spinocerebellar tract |
ALS | Anterolateral system | PSNu | Principal (chief) sensory nucleus of trigeminal nerve |
AMV | Anterior medullary velum | Py | Pyramid |
ASCT | Anterior (ventral) spinocerebellar tract | RB | Restiform body |
Cbl | Cerebellum | RSCF | Rostral spinocerebellar fibers |
CblNu | Cerebellar nuclei | RuSp | Rubrospinal tract |
CCblF | Cuneocerebellar fibers | S | Sacral representation |
DNuC | Dorsal nucleus of Clarke | SBC | Spinal border cells |
FNL | Flocculonodular lobe | SCP | Superior cerebellar peduncle |
IZ | Intermediate zone | SpTNu | Spinal trigeminal nucleus |
L | Lumbar representation | SpTTr | Spinal trigeminal tract |
MesNu | Mesencephalic nucleus | T | Thoracic representation |
ML | Medial lemniscus | TriMoNu | Trigeminal motor nucleus |
PRG | Posterior (dorsal) root ganglion | VesNu | Vestibular nuclei |
Cerebella efferent tracts
Abbreviation | Full Form | Abbreviation | Full Form |
ALS | Anterolateral system | NuDark | Nucleus of Darkschewitsch |
AMV | Anterior medullary velum | OcNu | Oculomotor nucleus |
BP | Basilar pons | PO | Principal olivary nucleus |
CblOl | Cerebello-olivary fibers | PonNu | Pontine nuclei |
CblTh | Cerebellothalamic fibers | RetForm | Reticular formation |
CblRu | Cerebellorubral fibers | RNu | Red nucleus |
CC | Crus cerebri | RuSp | Rubrospinal tract |
CeGy | Central grey (periaqueductal grey) | SC | Superior colliculus |
CM | Centromedian nucleus of thalamus | SCP | Superior cerebellar peduncle |
CSp | Corticospinal fibers | SCP, Dec | Superior cerebellar peduncle, decussation |
DAO | Dorsal accessory olivary nucleus | SN | Substantia nigra |
DNu | Dentate nucleus (lateral cerebellar nucleus) | SVNu | Superior vestibular nucleus |
ENu | Emboliform nucleus (anterior interposed cerebellar nucleus) | ThCor | Thalamocortical fibers |
EWNu | Edinger-Westphal nucleus | ThFas | Thalamic fasciculus |
FNu | Fastigial nucleus (medial cerebellar nucleus) | TriMoNu | Trigeminal Motor nucleus |
GNu | Globose nucleus (posterior interposed cerebellar nucleus) | VL | Ventral lateral nucleus of thalamus |
IC | Inferior colliculus | VPL | Ventral posterolateral nucleus of thalamus |
InfVNu | Inferior (spinal) vestibular nucleus | VSCT | Ventral spinocerebellar tract |
Imu | Interstitial nucleus | ZI | Zona incerta |
LRNu | Lateral reticular nucleus | 1 | Ascending projections to superior colliculus, and possibly ventral lateral and ventromedial thalamic nuclei |
LVNu | Lateral vestibular nucleus | 2 | Descending crossed fibers from superior cerebellar peduncle |
MAO | Medial accessory olivary nucleus | 3 | Uncinate fasciculus (of Russell) |
ML | Medial lemniscus | 4 | Juxtarestiform body to vestibular nuclei |
MLF | Medial longitudinal fasciculus | 5 | Reticular formation |
MVNu | Medial vestibular nucleus | ㅤ | ㅤ |
Pontocerebellar, Reticulocerebellar, Olivocerebellar, Ceruleocerebellar, Hypothalamocerebellar, and Raphecerebellar Fibers
Abbreviation | Full Form | Abbreviation | Full Form |
AntLb | Anterior limb of internal capsule | PostLb | Posterior limb of internal capsule |
CblNu | Cerebellar nuclei | PonNu | Pontine nuclei |
CerCblF | Ceruleocerebellar fibers | PO | Principal olivary nucleus |
CPonF | Cerebropontine fibers | PPon | Parietopontine fibers |
CSp | Corticospinal fibers | PRNu | Paramedian reticular nuclei |
DAO | Dorsal accessory olivary nucleus | Py | Pyramid |
FPon | Frontopontine fibers | RB | Restiform body |
Hyth | Hypothalamus | RCblF | Reticulocerebellar fibers |
HythCblF | Hypothalamocerebellar fibers | RetLenLb | Retrolenticular limb of internal capsule |
IC | Internal capsule | RNu | Red nucleus |
LoCer | Nucleus (locus) ceruleus | RetTegNu | Reticulotegmental nucleus |
LRNu | Lateral reticular nucleus | SCP | Superior cerebellar peduncle |
MAO | Medial accessory olivary nucleus | SubLenLb | Sublenticular limb of internal capsule |
MCP | Middle cerebellar peduncle | SN | Substantia nigra |
ML | Medial lemniscus | TPon | Temporopontine fibers |
NuRa | Raphe nuclei | 1 | Nucleus raphe, pontis |
OCblF | Olivocerebellar fibers | 2 | Nucleus raphe, magnus |
OPon | Occipitopontine fibers | 3 | Raphecerebellar fibers |
PCblF | Pontocerebellar fibers | ㅤ | ㅤ |