Cerebellum

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Cerebellum module
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Cerebellum menu
Cerebellum menu
Cerebellum menu
Cerebellum
Overview of the Cerebellum The Purkinje
cell Architecture of the Cerebellum Internal
Circuitry of the Cerebellum Clinical Signs
related to the Cerebellum
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Cerebellum
Overview of the Cerebellum The Purkinje
cell Architecture of the Cerebellum Internal
Circuitry of the Cerebellum Clinical Signs
related to the Cerebellum
(next)
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Overview of the Cerebellum
Maestro Allen Robert Gross, Music director
Conductor The Santa Monica Symphony (2004)

• Orchestrates motor activity
• - coordination
• - sequencing
• Does not initiate motor activity!

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• The cerebellum does
• - monitor ongoing muscle tension (tone)
• - modulate motor activity (fine tuning)
• - preprogram movement (anticipation)
• It does NOT appreciate or perceive
• conscious sensations!

Cerebellum menu
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Cerebellum
Overview of the Cerebellum The Purkinje
cell Architecture of the Cerebellum Internal
Circuitry of the Cerebellum Clinical Signs
related to the Cerebellum
(next)
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Purkinje cell
The Purkinje cell
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Reeler mouse
The basic patterns of these synaptic contacts are
formed prenatally. If developing cells or axons
are disturbed during this period, the patterns of
synapses may not develop normally - leading to
motor problems. Toxins, trauma, or genetic
factors may lead to such disorders in humans, and
can be studied in animal models of these human
problems.

• Wobbler mouse

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A normal cerebellum also exhibits an amazing
ability to modify these synaptic contacts
postnatally - the basis for developing skilled
motor performance through practice.

• A classic experimental demonstration of this
  ability has been called the Puss n Boots
  study

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In this study, weighted booties were placed on
the feet of a cat

• and then the cat wore these boots for an
  extended time. At the end of the experiment the
  cats gait appeared normal, but there were more
  synapses made with more Purkinje cells over a
  shorter distance (increased synapse density).

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This greater density of synapses allowed the cat
to perform the motor task normally, despite the
added weight of the booties. When the booties
were removed, however, the same cat showed
exaggerated stepping. You may have had a similar
experience - athletes often train with added
resistance to improve their performance in
competition.
Cerebellum menu
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Cerebellum
Overview of the Cerebellum The Purkinje
cell Architecture of the Cerebellum Internal
Circuitry of the Cerebellum Clinical Signs
related to the Cerebellum
(next)
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Cerebellum architecture
Architecture of the Cerebellum
left lateral view
Viewed from above
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Cerebellum architecture
Architecture of the Cerebellum
left lateral view
Viewed from above
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Cerebellum architecture
Architecture of the Cerebellum
left lateral view
Viewed from above
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• Somatosensory information
• Visual information
• Information from cortex

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• Information from spinal
• cord brainstem
• Information from cortex

Somatosensory information Visual
information Information from cortex
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Internal cells of cerebellum
Efferent outputs
Afferent inputs
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• Excitatory
• Inputs!

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(axons of these cells form the parallel fibers)
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• Climbing fibers excite
• Purkinje cells
• Deep cerebellar nuclei

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• Mossy fibers excite
• Granule cells
• Purkinje cells

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• Granule cells also excite the rest of the
  internal cells

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All cerebellar outputs are inhibitory
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• This feed forward circuit allows the
  spinocerebellum to regulate body limb
  movements, the vestibulocerebellum to regulate
  eye movements, and the cerebrocerebellum to
  regulate planning and execution of cortical motor
  programs.

Cerebellum menu
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Cerebellum
Overview of the Cerebellum The Purkinje
cell Architecture of the Cerebellum Internal
Circuitry of the Cerebellum Clinical Signs
related to the Cerebellum
(next)
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Internal circuitry
Internal circuitry of the Cerebellum
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The three left-right pairs of cerebellar peduncles
contain all the input and output pathways for
the cerebellum
Left Superior Cerebellar Peduncle

• Left
• Internal Capsule

Left Middle Cerebellar Peduncle
Left Inferior Cerebellar Peduncle
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Connects medulla cerebellum
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• 2.

Connects pons cerebellum
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Red nucleus Ventral Lateral (VL) nucleus of
Thalamus Reticular formation (brainstem)
Connects midbrain cerebellum
Cerebellum menu
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Cerebellum
Overview of the Cerebellum The Purkinje
cell Architecture of the Cerebellum Internal
Circuitry of the Cerebellum Clinical Signs
related to the Cerebellum
(next)
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Cerebellar signs
Clinical signs related to Cerebellar dysfunction
Uncoordinated voluntary movements are hallmark
features of cerebellar disorders
Select a button to view the videoclip

• heel-to-shin test
• finger-to-nose test
• diadochokinesis tests
• ataxia (drunken gait)

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Cerebellum menu
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Heel-to-shin test
Play movie
More complex than it appears initially, this test
requires bilateral coordination, sequencing of
activity in multiple muscles, and postural
support - all being cerebellar functions.
Cerebellar signs menu
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Finger-to-nose test (example 1)
Play movie
Another simple-seeming but complex task - the
client is to use her fingertip to alternate
touching the clinicians fingertip, then her own
nose. Posture, proprioception, and control of
muscles in the arm as well as the eyes - all
cerebellar functions. Note she is better with
her right hand
Cerebellar signs menu
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Finger-to-nose test (example 2)
Play movie
The same client, but more severely impaired. The
EEG record to the left of the screen shows her
brains activity during the task.
Cerebellar signs menu
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Diadochokinesis test (example 1)
Play movie
The classic test - a rhythmic, alternating
movement. The fluidity of movement is
dramatically different using her right versus
left hand.
Cerebellar signs menu
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Diadochokinesis test (example 2)
Play movie
The same test performed by a different client.
Although the hand position alternates, it
requires the clinician to begin the movement and
the force of the hand contacting the leg is
excessive. Note that performing this test induces
clonus of the right leg in this individual
Cerebellar signs menu
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Ataxia (example 1)
Play movie
Balance, gait, posture, and coordination of
movements all are impaired.
Cerebellar signs menu
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Ataxia (example 2)
Play movie
A more severely impaired individual who attempts
to compensate by using visual cues and taking
smaller steps. Apparently this movie was made
before the invention of gait belts
Cerebellar signs menu
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That is the end of the Cerebellum tutorial!
Cerebellum menu