Cerebellum and basal ganglia

An introductory lecture to the cerebellum and basal ganglia, as well as associated diseases.

1. The Cerebellum & Basal
Ganglia
Csilla Egri, KIN 306 Spring 2012
The cerebellum. Fighting the drunken stooper since
1862.

2. Outline
General function
Anatomy of the cerebellum
Functional divisions
Projections
Anatomy of the basal ganglia
Projections
Basal ganglia disorders
Parkinson’s disease
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3. General functions
3
Cerebellum
Major role in timing of motor
activities and in rapid, smooth
progression of movements
Monitors and makes corrective
adjustments to motor plan
Basal ganglia
Helps plan and control complex
patterns of movement
Relative movement intensities,
directions, and sequence
No direct projections to lower motor
neurons of skeletal muscle
Movement influenced by regulation of
activity of upper motor neurons

4. Cerebellar cortex:
functional divisions
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3 functional divisions
Vestibulocerebellum
Flocculus + nodulus
Spinocerebellum
Vermis and adjacent
intermediate zone
Cerebrocerebellum
Lateral zone
Sunderland Fig 19.1 (online access http://www.ncbi.nlm.nih.gov/books/NBK10799/
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5. Cerebellar cortex: functional
divisions
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Vestibulocerebellum
Inputs:
From vestibular nuclei in brainstem
Function:
Regulate movements underlying posture and
equilibrium
Coordination of eye and head movements
Damage:
Impairs ability to stand upright, maintain posture
and balance
Cerebellar nystagmus

6. Cerebellar cortex: functional
divisions
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Spinocerebellum
Inputs:
Directly from spinal cord
Function:
Lateral portion
Movement of distal muscle (ex. gross
movements during walking)
Central portion (vermis)
Movement of proximal muscles
Damage:
Overshoot and intension tremor
Impaired gait

7. Cerebellar cortex: functional
divisions
7
Cerebrocerebellum
Inputs:
Many areas of cerebral cortex (relayed thru pons)
Function:
Planning and timing of sequential movements
Speech
Damage:
Ataxia: incoordination of complex, purposeful movements of
hands, fingers, feet and speech apparatus
Failure of smooth progression of movement
Lesions to any division of cerebellum result in
impairments on ipsilateral side of the body

8. Cerebellum: projections
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4 deep cerebellar nuclei
receive input from
cerebellar
cortex and send projections
to thalamus
1.Fastigial
2.2 Interposed
3.Dentate
Information travels via
cerebellar peduncles
1.Superior (efferent)
2.Middle (afferent)
3.Inferior (mixed)
Sunderland Fig 19.1

9. Cerebellum:
inputs
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Receive many inputs
from periphery, spinal
cord and brain
regions
Sunderland Fig 19.3

10. Cerebellum:
outputs
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Sunderland Fig 19.6
Why would lesions to the cerebellar
cortex affect movement on ipsilateral
side of the body?

11. The basal
ganglia
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Sunderland Fig 18.1
Striatum
Receives inputs from
and projects back to
motor cortex via
thalamus
Closed loop

12. The basal ganglia:
inputs
12
Striatum is main input
center
integrates inputs from
a variety of
structures, including
substantia nigra pars
compacta
No input directly
from spinal cord
Send inhibitory
connections to two main
output centers
Sunderland Fig 18.2

13. The basal ganglia:
outputs
13
Internal globus pallidus and
substantia nigra pars reticulata
are main output centers
SN-pars reticulata mainly
projects to superior colliculus
Eye movement
Internal globus pallidus
mainly projects to thalamus
Relays output to motor
cortices
Each send tonic inhibitory signals
Sunderland Fig 18.5

14. The basal ganglia: general
circuitry
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Input: to striatum
Ouput: internal globus pallidus and
substantia nigra pars reticulata
Inhibitory connections
GABA throughout most of
basal ganglia
Excitatory connections:
Glutamate from cortex,
subthalamic nucleus and
thalamus
Dopamine from subsantia nigra
pars compacta can be either
inhibitory or excitatory
Sunderland Fig 18.1

15. The basal ganglia: general
circuitry
15
Outputs of striatum project via two
different pathways
each pathway is modulated by
dopamine from substantia nigra
pars compacta
Direct
Facilitates movement
Excited by dopamine (D1
receptors)
Indirect
Inhibits movement
Inhibited by dopamine (D2
receptors)
Kandel Figure 43-3
What effect does dopamine
release have on movement?

16. The basal ganglia: general
circuitry (supplementary slide)
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The basal ganglia enables the proper motor program to be activated via the
direct pathway and inhibits competing motor programs via the indirect pathway.
Can be
modulated by
SnC

17. The basal ganglia: direct
pathway
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Sunderland Fig 18.8
Dopamine release onto D1 = Increased
excitation of motor cortices
Cortical projections to direct pathway
result in dis-inhibition of thalamus

18. The basal ganglia: indirect pathway
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Sunderland Fig 18.8
Dopamine release onto D2 = Increased
excitation of motor cortices
Cortical projections to indirect
pathway result in dis-
inhibition of subthalamic
nucleus and inhibition of
thalamus

19. Disorders of the basal ganglia
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Parkinson’s Disease
Characterized by resting tremor,
slowed/absent movement
(hypokinesia), rigidity of the
extremities and neck, & reduced
facial expressiveness
Caused by the loss of the
dopaminergic neurons in the
substantia nigra pars compacta
Typically treated with L-Dopa
WebCT readings: Circuits within the basal ganglia system

20. Parkinson’s Disease
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Increased output of indirect
pathway, decreased output
of direct pathway
Sunderland Fig 18.10

21. Objectives
After this lecture you should be able to:
Discuss the general role of the cerebellum and basal ganglia in
voluntary movement
Describe the organization of the cerebellum
List the major inputs/outputs to and from the cerebellum
List the major functions of the three functional divisions of the
cerebellum
Describe the organization of the basal ganglia
List the major inputs/outputs to and from the basal ganglia
and their corresponding neurotransmitters
Trace the connections of both the direct and indirect pathway of
the basal ganglia and their contributions to movement
Relate how disorders of the basal ganglia such as
Parkinson’s disease affect these pathways
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22. 22
1.The globus pallidus interna primarily projects to the
______________________ whereas the substantia nigra
pars reticulata primarily projects to
______________________.
2.Inhibition of the subthalamic nucleus results in
increased or decrease motor movement?
3.The __________________________ cerebellar peduncle
is the main pathway for efferent fibers.
Test your knowledge