The Cerebellum & Basal GangliaCsilla Egri, KIN 306 Spring 2012

The cerebellum. Fighting the drunken stooper since 1862.

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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General functions3

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 sequenceNo direct projections to lower motor

neurons of skeletal muscleMovement influenced by regulation of

activity of upper motor neurons

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/ use search function to browse chapter contents)

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

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

Cerebellar cortex: functional divisions

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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

Cerebellum: projections8

4 deep cerebellar nucleireceive input from

cerebellarcortex and send projections to thalamus1. Fastigial

2. 2 Interposed

3. Dentate

Information travels viacerebellar peduncles1. Superior (efferent)

2. Middle (afferent)

3. Inferior (mixed)Sunderland Fig 19.1

Cerebellum: inputs

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Receive many inputs from periphery, spinal

cord and brain regions

Sunderland Fig 19.3

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?

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

The basal ganglia:inputs

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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

The basal ganglia:outputs

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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

The basal ganglia: general circuitry

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Input: to striatumOuput: 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

The basal ganglia: generalcircuitry

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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?

The basal ganglia: generalcircuitry (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

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

The basal ganglia: indirect pathway18

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

Disorders of the basal ganglia19

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

Parkinson’s Disease20

Increased output of indirect pathway, decreased output

of direct pathwaySunderland Fig 18.10

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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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