guide

1. cerebellum

2. Overview
• Is located behind the Medulla and Pons
• Contains only 10% of the Brain’s volume
• Situated in posterior cranial fossa
• Also has two hemispheres

4. • Receives two inputs; one from the muscles and
joints and other from the motor area of the
cerebral cortex
• After comparing it gives corrective signals to the
motor cortex for the correction of voluntary
movements

5. Functional Overview
• Basically evaluates and adjusts motor
movement while it is in progress.
• Does a lot of integration and evaluation of
incoming information.
• Is very important for balance and motor
learning

6. Anatomically
Cerebellum surface has many parallel
convolutions called Folia (leaves) that run
from side to side.
Has three distinct lobes separated by two
fissures
Anterior lobe
Middle lobe
Posterior lobe

8. Longitudinal functional divisions of
anterior and posterior lobes
• In the centre a narrow band separated
from the remainder of cerebellum by
shallow grooves is the Vermis
• Laterally on each side of the Vermis is
cerebellar hemisphere, each divided into
Intermediate and Lateral zones

9. Longitudinal functional divisions
Cerebro
cerebellum
Vestibulo
cerebellum
Spinocerebellum

10. Phylogenetic history of cerebellum
• Archicerebellum (Vestibulocerebellar) is oldest part
_flocculonodular lobe
• Paleocerebellum (Spinocerebellar)
• Neocerebellum (pontocerebellum)

11. Vermis
• Helps control the proximal muscles of the body
and limbs e.g. axial body, neck, shoulders and
hips.
• Generally governs posture, locomotion,
and gaze.

12. Intermediate Zone
Gets somatosensory information from
limbs
Helps control distal muscles of the limbs, hands
and fingers, feet and toes
Lateral zone
Responsible for planning the sequence and
timing of movements

13. Has Three Distinct Regions*
Cerebellar cortex.
• Is the outer covering
• Is composed mostly of Gray Matter
Internal White Matter
• Are Myelinated Axons/Fiber Tracts
Three pairs of Deep Nuclei
• Fastigal
• Interposed
Globose
Emboliform
• Dentate

14. Cerebellar Nuclei
• Dentate nucleus
Carries information important for
coordination of limb movements
(along with the motor cortex and
basal ganglia)
• Emboliform nucleus and
Globose nucleus
Regulates movements of ipsilateral
extremity
• Fastigial nucleus
– Regulates body posture
– Is related to the flocculo nodular
lobe

15. Three layers of grey matter
• Outer molecular or plexiform layer
• Intermediate purkinje layer
• Inner granular layer

17. Molecular or plexiform layer
• It’s the outermost layer cells are arranged in two strata
• Superficial strata contains star shaped cells called stellate cells
• Deep strata contains basket cells
• In addition this layer contains parallel fibers, terminal portion of
climbing fibers and dendrites of purkinje and golgi cells
• Basket cells and stellate cells are inhibitory, result in lateral
inhibition of purkinje cells hence sharpens the signals

18. Purkinje layer
• Thinnest layer between molecular and granular
layer
• Single layer of flask shaped purkinje cells
• Purkinje cells are the largest neurons
• Dendrites ascend and arborize in the molecular
layer to end on climbing or parallel fibers
• Axons descend into white matter and terminate
on the cerebellar nuclei
• Purkinje cells are “final common path "of
cerebellar cortex

19. Granular layer
• Innermost layer of cerebellar grey matter
• Contains Granule cells and Golgi cells
• Granule cells are the only excitatory cells in the
cerebellar cortex
• Axons of granule cells ascend into molecular
layer and form parallel fibers which synapses
with dendrites of purkinje cells, stellate cells,
basket cells and golgi cells
• Dendrites of granule cells along with axons and
dendrites of golgi cell synapse with mossy fibers
in the synaptic area called the glomerulus

21. AFFERENTS
From other
parts of
brain
From
spinal cord

22. I-From other parts of brain
a. Vestibulocerebellar Tract
Info from Semicircular Canals through
vestibular nuclei to cerebellum in
flocculonodular lobe
Maintains Upright Posture
b. Reticulocerebellar Tract
Information from reticular formation to
cerebellum

23. c. Olivocerebellar Tract
Info From Spinal Cord, basal ganglia, reticular
formation Through Olivary N to Contralateral
Cerebellar Hemisphere
Source of Climbing Fibers for Direct Input to
Cerebellum
d. Cuneocerebellar Tract
Mediate Proprioception From Upper Limbs and
Neck

24. e. Pontocerebellar tract
Info from cerebral cortex(motor and premotor
cortex and also somatosensory cortex) to
pontine nuclei
From pontine nuclei to Cerebellar Hemisphere
OTHERS; Tectocerebellar, Rubrocerebellar and
Trigeminocerebellar tract

25. II-Afferent from the spinal cord
Dorsal Spinocerebellar Tract
Unconscious Proprioception From Muscle
Spindles, Golgi Tendons and Tactile
Receptors
Ventral Spinocerebellar tract
Excited by motor signals arising in anterior
horn of spinal cord from
1. Brain through corticospinal and
rubrospinal tracts
2. Internal motor pattern generated in cord
itself

26. The Ventral spinal pathway provides efference
copy of the anterior horn motor drive .
And the dorsal Spinocerebellar tract apprise
the cerebellum of momentary status of
1. Muscle contraction
2. degree of tension in the muscle tension
3. Positions and rates of movements of different
parts of body

27. Cerebellar Afferent Pathways
mossy fibers

28. Cerebellar Inputs
Vermis
 Receives input from spinal cord
regarding somatosensory and kinesthetic
information (intrinsic knowledge of the
position of the limbs)
 Damage leads to difficulty with postural
adjustments

29. Intermediate Zone
 Receives input from the red nucleus
and somatosensory information
from the spinal cord
Damage results in rigidity & difficulty in
moving limbs

30. Lateral Zone
 Receives input from the motor and
association cortices through the Pons
 Projects to the dentate nucleus, which
projects back to primary and premotor cortex
 Damage leads to 4 types of deficits:
- Ballistic movements (cerebellar ataxia)
- Coordination of multi-joint movement
(lack of coordination: asynergia)
- Muscle learning
- Movement timing

31. Inputs to cerebellum from spinocerebellar tracts have a
somatotopic organization.
2 maps of body Primary fissure
Signals from the motor cortex, which is also arranged somatotopically,
project to corresponding points in the sensory maps of the cerebellum.

32. Cerebellar Efferent Pathways*
• From midline structures of cerebellum (vermis) to
Fastigial nuclei:
• project to the vestibular nuclei & to the pontine and
medullary reticular formation
Fibers pass in Vestibulospinal & Reticulospinal tracts
• Function: Maintains posture and equilibrium

33. Intermediate
zone
Emboliform &
Globose
nuclei
ventrolateral
and anterior
nuclei of the
thalamus
Cerebral
cortex
Midline
structures of
the thalamus
Basal ganglia
Red nucleus
Reticular
formation of
the upper
portion of the
brain stem

34. From lateral zone of cerebellar hemisphere to
Dentate nuclei:
to ventrolateral and ventroanterior nuclei of the
thalamus to motor cortex
Function: helps in coordinate sequential motor
activities initiated by the cerebral cortex

35. Cerebellar Cortical Circuits
• Inputs to the cerebellar cortex (mossy and
climbing fibers) excite the deep nuclei cells as
they enter.
• The outputs of the cerebellar cortex (Purkinje
cell axons) inhibit the deep nuclei cells.*

37. Go
P
B
Gr
Deep cerebellar
nuclei
P
Mossyfibers
Gr: Granule cells
Go: Golgi cells
P: Purkinje cells
St: Stellate cells
B: Basket cells
Excitatory
(Glutamate)
Inhibitory
(GABA)
Parallel fibers
St
Spinal cord and brainstem
Molecular
layer
Purkinje cell
layer
Granule cell
layer
White matter
SC Vestibular n.
Reticular n.
Motor cortex
(via thalamus)
Sup
Col
inferior olivary nucleus
Collaterals Collaterals

38. • Direct stimulation of deep cerebellar nuclei from
mossy and climbing fibers leads to excitation.
• Signals from purkinje fibers leads to inhibition.
• Normally balanced and output from deep
cerebellar nuclei is constant moderate level of
excitation.
• The inhibitory signal from purkinje fibers
resemble a delay line ,negative feed back signal
and is effective in damping.

39. • Turn-On/Turn-Off and Turn-Off/Turn-On Output
Signals from the Cerebellum *
• Purkinje Cells "Learn" to Correct Motor Errors-
Role of the Climbing Fibers
• The degree of motor enhancement by the
cerebellum at the onset of contraction, the
degree of inhibition at the end of contraction,
and the timing of these all are learned by
experience.

40. Function of Cerebellum
• Error Control Device - Monitor, Quality Control
– Monitors outputs to muscles from motor cortex and sensory
signals from receptors.
– Compares the efferent project plan with execution at motor
action site.
– Considers related factors and makes adjustment.

41. Vestibulocerebellum – controls tone &
movements of muscles involved in equilibrium &
posture, by receiving impulses from vestibular
apparatus.
• Vestibulocerebellum calculates in advance where
the different parts will be in a movement and uses
information from the periphery as feed back for
Anticipatory correction of postural signals to maintain
equilibrium.

42. Spinocerebellum – coordinates mainly
movements of distal parts of limbs, such as
the fast ballistic movements (in association
with cerebrocerebellum), & also coordinates
saccadic eye movements.
• It receives impulses from proprioceptors in
muscles, tendons & joints, tactile receptors,
visual receptors & auditory receptors.

43. Corticocerebellum – coordinates timing &
planning involved in fast sequential movements
like writing, running, talking etc.
• It perform its function by the intensive to & fro
connection with the cerebral cortex (cerebro-
cerebello-cerebral connections).

44. Functions of Corticocerebellum
1- Servomechanism
2- damping function
3- Coordination of ballistic movements
4- Planning and timing of Sequential Movements
5-comparator function

45. • The patterns of cerebellar activity are learned by trial
and error, over many repetitions. Many of the basic
patterns are established early in life:
1. The fine balancing adjustments you make while
standing and walking.
2. The ability to fine-tune a complex pattern of
movement improves with practice, until the
movements become fluid and automatic.

46. 1-Damping function
• Prevents exaggerated muscular activity.
• Makes voluntary activities smooth and accurate.
• Voluntary movements are initiated in motor areas of cerebral
cortex.
• Corticocerebellum receives information from motor cortex as well
as feedback signals from the muscles as soon the muscular
activity starts
• Sends information back to motor cortex to cut off extra impulses

47. 2- Coordination of ballistic movements
• Ballistic movements are the rapid alternate movements in different
parts of body while doing skilled or trained work e.g. typing,
cycling, dancing etc.
• Corticocerebellum plays an important role in preplanning these
ballistic movements during learning process.

48. 3- Planning of Sequential Movements
• Plays an important role in timing and programming the
movements during learning process
• Corticocerebellum plans the sequential movements and also time
of each movement
• All the information from corticocerebellum is communicated to
sensory motor area of cerebral cortex and stored in memory

49. 4-Comparator function
• This function is responsible for integration and coordination of
various muscular activities
• Receives messages from both cerebral cortex and
muscles(proprioceptive impulses)
• Compares the both and corrects

50. 5-Servomechanism
• It is the correction of any disturbance or interference in performing
skilled work.
• Once skilled works are learnt, the sequential movements are
performed without interruption
• However in case of disturbance corticocerebellum immediately
influences the cortex to correct.

51. 6- Extra motor Predictive Functions of the
Cerebellum
• The cerebrocerebellum (the large lateral lobes) also helps to "time"
events other than movements of the body.
• For instance, the rates of progression of both auditory and visual
phenomena can be predicted by the brain, but both of these require
cerebellar participation.
• As an example, a person can predict from the changing visual scene
how rapidly he or she is approaching an object.
• is particularly helpful in interpreting rapidly changing spatiotemporal
relations in sensory information

52. Clinical Considerations
Some Signs of Dysfunction
• Hypotonia-Reduced Muscle Tone
• Ataxia -Lack of Order and Coordination in
Activities

53. • Bradykinesia : Slow Movement
• Asthenia: Mild Muscular Weakness
• Asynergia: Inability to perform two acts
simultaneously

54. Clinical Considerations
• Dysdiadochokinesia
– Clumsiness in Alternating Movements
• Dysarthria
– Ataxic Dysarthria
– Scanning Speech
– Slurred and Disjointed Speech

55. • Dysmetria and Ataxia
– Error in Judgment of Range and Distance of
Target
– Undershooting or Overshooting (past
pointing)
• Intentional Tremor
– the movements tend to oscillate, especially
when they approach the intended mark, first
overshooting the mark and then vibrating
back and forth several times before settling on
the mark

56. • Hypotonia
– Reduced Resistance to Passive Stretch
– Due to loss of cerebellar facilitation of the
motor cortex and brain stem motor nuclei by
tonic signals from the deep cerebellar nuclei.
• Rebounding
– Inability to Predict Movement
– Cannot Hold Back Movement
• Disequilibrium
– Unsteady Gait, Body Wavering

57. •Drunken gait
•Pendular knee jerk
•Cerebellar nystagmus:
involuntary movements of eyeballs due to
lesion in flocculonodular lobe