3 - CEREBELLUM
3.1 – GROSS NEUROANATOMY OF CEREBELLUM
• The cerebellum influences movements by modifying the activity patterns of the upper motor
neurons (like basal ganglia)
• Sends prominent projections to virtually all circuits that govern upper motor neurons
• Has 2 main gray matter structures: a laminated cerebellar cortex on its surface and clusters of
cells deep in white matter (deep cerebellar nuclei)
• Pathways that reach the cerebellum from other brain regions project to both components; thus,
afferent axons send branches to both the deep nuclei and the cerebellar cortex
• Input signals are modified as they are processed before returning to circuits of upper motor
neurons in the cerebral cortex, by thalamic relays, and in the brainstem
• When this feedback loop is damaged the individual makes persistent errors when executing
movement
PRESENT THE MACROSCOPIC ANATOMY OF THE CEREBELLUM. SOME RELEVANT PARTS
TO DISCUSS ARE THE 3 FUNCTIONAL SUBDIVISIONS IN THE CEREBELLUM
• The cerebellar hemispheres can be subdivided into 3 main parts based on differences in their
sources of input
1. Cerebrocerebellum – occupies most of lateral cerebellar hemisphere, receives input indirectly from
many areas of CC
o Well developed in primates, prominent in humans
o Regulation of highly skilled movements, especially the planning and execution of complex
spatial and temporal sequences of movement
, o Projects to the dentate nucleus à primary motor cortex (with relay in thalamus)
o Speech, inhibition, motor programs
o Everything your cerebrum can contribute to your cerebellum
2. Spinocerebellum – occupies median and paramedian zone of the cerebellar hemispheres, receives
direct input form spinal cord
o Lateral (paramedial) part is primarily concerned with
movements of distal muscles
o Concerned with movements of distal muscles
o Vermis – median strip of cerebellar hemisphere along
the midline
§ Concerned with movements of proximal
muscles, regulates certain forms of eye
movements
3. Vestibulocerebellum – phylogenetically oldest part,
comprises caudal-inferior lobes of cerebellum and
includes the flocculus and nodulus
o Receives input from vestibular nuclei in the
brainstem and is primarily concerned with
regulation of movements underlying posture
and equilibrium, as well as the vestibulo-ocular
reflex
o Projects to the vestibular nuclei à vestibular
complex
The connections between cerebellum and other parts of the NS
occur by 3 pathways called cerebellar peduncles
Superior Almost entirely efferent, neurons in the deep cerebellar nuclei, their axons project to upper motor
cerebellar neurons in deep superior colliculus, and after a relay in dorsal thalamus the primary motor and pre-
peduncle motor areas of cortex
(brachium
conjectivum)
Middle Afferent path, cell bodies from the base of the contralateral pons (pontine nuclei). Pontine nuclei
cerebellar receive input from all areas of CC and superior colliculus. The axons in the pontine nuclei
peduncle (transverse pontine fibers) cross the midline and enter the cerebellum via de middle cerebellar
(brachium peduncle. One of the largest pathways in the brain (each of the 2 middle cerebellar peduncles
pontis) contains ~20 million axons)
• The prominence of the cerebral peduncles in the ventral region of the human midbrain
reflects the magnitude of the projection from the cerebral cortex that (via pontine nuclei)
enters the cerebellum
• Corticospinal projection comprises 5% of total number of axons in each peduncle
, Inferior • Smallest but most complex of cerebellar peduncles, containing multiple afferent AND
cerebellar efferent pathways
peduncle • Afferent – axons from vestibular nuclei, spinal cord, brainstem tegmentum
(restiform body) • Efferent – project to vestibular nuclei and reticular formation
CEREBELLAR OUTPUT
• The efferent neurons of the cerebellar cortex project to the deep
cerebellar nuclei and to the vestibular complex; these then project to
upper motor neurons in the brainstem and to thalamic nuclei that
innervate upper motor neurons in the motor cortex
• In each cerebellar hemisphere there are 4 major deep nuclei:
1. Dentate nucleus (largest in humans)
2. 2 interposed nuclei
3. Fastigial nucleus
• Each receives input from a different region of the cerebellar cortex
• Although borders are not distinct, in general the
o Cerebrocerebellum à primarily to the dentate nucleus
o Spinocerebellum à the interposed and fastigial nuclei
o Vestibulocerebellum à the vestibular complex
• Laminated cortex – the rest of the cerebellum
• Deep cerebellar nuclei – clusters of cells deep in white matter, neurons are the
main source of output, do not rely on income signals but output they sent is
modified
• Cerebrocerebellar pathways from the dentate nucleus are mainly destined for premotor and
associational cortices of the frontal lobe, which function in planning volitional movements
o They reach these cortical areas after relay in the ventral nuclear complex in the thalamus
§ This pathway must cross the midline (since ipsilateral)
§ Thus, the dentate axons exit the cerebellum via superior cerebellar
peduncle à cross at the decussation of the superior cerebellar
peduncle in the caudal midbrain à ascend to the thalamus
• à along path to thalamus; sends collaterals to the
parvocellular (small-celled) division of the red nucleus in the
midbrain
• à This division of the red nucleus projects to the inferior olive,
providing a means for cerebellar output to feedback upon a
major source of cerebellar input
o This feedback is crucial for the adaptive functions of cerebellar circuits
• Spinocerebellar pathways are directed towards circuits of upper motor neurons that govern the
execution of movement
3.1 – GROSS NEUROANATOMY OF CEREBELLUM
• The cerebellum influences movements by modifying the activity patterns of the upper motor
neurons (like basal ganglia)
• Sends prominent projections to virtually all circuits that govern upper motor neurons
• Has 2 main gray matter structures: a laminated cerebellar cortex on its surface and clusters of
cells deep in white matter (deep cerebellar nuclei)
• Pathways that reach the cerebellum from other brain regions project to both components; thus,
afferent axons send branches to both the deep nuclei and the cerebellar cortex
• Input signals are modified as they are processed before returning to circuits of upper motor
neurons in the cerebral cortex, by thalamic relays, and in the brainstem
• When this feedback loop is damaged the individual makes persistent errors when executing
movement
PRESENT THE MACROSCOPIC ANATOMY OF THE CEREBELLUM. SOME RELEVANT PARTS
TO DISCUSS ARE THE 3 FUNCTIONAL SUBDIVISIONS IN THE CEREBELLUM
• The cerebellar hemispheres can be subdivided into 3 main parts based on differences in their
sources of input
1. Cerebrocerebellum – occupies most of lateral cerebellar hemisphere, receives input indirectly from
many areas of CC
o Well developed in primates, prominent in humans
o Regulation of highly skilled movements, especially the planning and execution of complex
spatial and temporal sequences of movement
, o Projects to the dentate nucleus à primary motor cortex (with relay in thalamus)
o Speech, inhibition, motor programs
o Everything your cerebrum can contribute to your cerebellum
2. Spinocerebellum – occupies median and paramedian zone of the cerebellar hemispheres, receives
direct input form spinal cord
o Lateral (paramedial) part is primarily concerned with
movements of distal muscles
o Concerned with movements of distal muscles
o Vermis – median strip of cerebellar hemisphere along
the midline
§ Concerned with movements of proximal
muscles, regulates certain forms of eye
movements
3. Vestibulocerebellum – phylogenetically oldest part,
comprises caudal-inferior lobes of cerebellum and
includes the flocculus and nodulus
o Receives input from vestibular nuclei in the
brainstem and is primarily concerned with
regulation of movements underlying posture
and equilibrium, as well as the vestibulo-ocular
reflex
o Projects to the vestibular nuclei à vestibular
complex
The connections between cerebellum and other parts of the NS
occur by 3 pathways called cerebellar peduncles
Superior Almost entirely efferent, neurons in the deep cerebellar nuclei, their axons project to upper motor
cerebellar neurons in deep superior colliculus, and after a relay in dorsal thalamus the primary motor and pre-
peduncle motor areas of cortex
(brachium
conjectivum)
Middle Afferent path, cell bodies from the base of the contralateral pons (pontine nuclei). Pontine nuclei
cerebellar receive input from all areas of CC and superior colliculus. The axons in the pontine nuclei
peduncle (transverse pontine fibers) cross the midline and enter the cerebellum via de middle cerebellar
(brachium peduncle. One of the largest pathways in the brain (each of the 2 middle cerebellar peduncles
pontis) contains ~20 million axons)
• The prominence of the cerebral peduncles in the ventral region of the human midbrain
reflects the magnitude of the projection from the cerebral cortex that (via pontine nuclei)
enters the cerebellum
• Corticospinal projection comprises 5% of total number of axons in each peduncle
, Inferior • Smallest but most complex of cerebellar peduncles, containing multiple afferent AND
cerebellar efferent pathways
peduncle • Afferent – axons from vestibular nuclei, spinal cord, brainstem tegmentum
(restiform body) • Efferent – project to vestibular nuclei and reticular formation
CEREBELLAR OUTPUT
• The efferent neurons of the cerebellar cortex project to the deep
cerebellar nuclei and to the vestibular complex; these then project to
upper motor neurons in the brainstem and to thalamic nuclei that
innervate upper motor neurons in the motor cortex
• In each cerebellar hemisphere there are 4 major deep nuclei:
1. Dentate nucleus (largest in humans)
2. 2 interposed nuclei
3. Fastigial nucleus
• Each receives input from a different region of the cerebellar cortex
• Although borders are not distinct, in general the
o Cerebrocerebellum à primarily to the dentate nucleus
o Spinocerebellum à the interposed and fastigial nuclei
o Vestibulocerebellum à the vestibular complex
• Laminated cortex – the rest of the cerebellum
• Deep cerebellar nuclei – clusters of cells deep in white matter, neurons are the
main source of output, do not rely on income signals but output they sent is
modified
• Cerebrocerebellar pathways from the dentate nucleus are mainly destined for premotor and
associational cortices of the frontal lobe, which function in planning volitional movements
o They reach these cortical areas after relay in the ventral nuclear complex in the thalamus
§ This pathway must cross the midline (since ipsilateral)
§ Thus, the dentate axons exit the cerebellum via superior cerebellar
peduncle à cross at the decussation of the superior cerebellar
peduncle in the caudal midbrain à ascend to the thalamus
• à along path to thalamus; sends collaterals to the
parvocellular (small-celled) division of the red nucleus in the
midbrain
• à This division of the red nucleus projects to the inferior olive,
providing a means for cerebellar output to feedback upon a
major source of cerebellar input
o This feedback is crucial for the adaptive functions of cerebellar circuits
• Spinocerebellar pathways are directed towards circuits of upper motor neurons that govern the
execution of movement
