Transcript 56 Cerebellum and Basal Ganglia

Cerebellum and Basal Ganglia
in Motor Control
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The cerebellum and its motor functions
Based on cerebral intent and external conditions
The cerebellum tracks and modifies millisecond-tomillisecond muscle contractions,
to produce smooth, reproducible movements
Cerebellum and Its Motor Functions
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It helps to sequence motor activities

And makes adjustments in the body’s motor activities while
they are being executed so that they will conform to the motor
signals directed by the cerebral motor cortex and other parts of
the brain

The cerebellum also aids the cerebral cortex in planning the
next sequential movement
Cerebellum and Its Motor Functions

The intermediate zone is concerned with controlling muscle
contractions in the distal portions of the upper and lower limbs

The lateral zone is involved in overall planning of sequential
motor movements
Topographical Representation of the Body in
the Vermis and Intermediate Zones
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Axial portions of the body lie in the vermis
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Limbs and facial regions lie in the intermediate zones
Neuronal Circuit of the Cerebellum
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Input Pathways to the Cerebellum:
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Afferent pathways from the other parts of the brain:
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Corticopontocerebellar pathway: originates in the cerebral
motor and premotor areas and also in the somatosensory cortex
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It passes pontile nuclei and pontocerebellar tracts mainly to the
lateral divisions of the cerebellar hemispheres
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Olivocerebellar tract: is excited by fibers from the motor
cortex, basal ganglia, reticular formation and spinal cord
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Vestibulocerebellar fibers:
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Reticulocerebellar fibers:
Neuronal Circuit of the Cerebellum
Neuronal Circuit of the Cerebellum
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Afferent pathways from the periphery:
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Dorsal spinocerebellar tract: comes mainly from the muscle
spindles, and to a lesser extent from other somatic receptors
such as Golgi tendon organs
– Muscle contraction
– Degree of muscle tension
– Positions and rates of movement of the body parts
– Forces acting on the surfaces of the body

Ventral spinocerebellar tract: is excited mainly by motor
signals arriving in the anterior horns of the spinal cord
(efference copy of the anterior horn motor drive)
Neuronal Circuit of the Cerebellum
Output Signals from the Cerebellum
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Deep cerebellar nuclei and the efferent pathways
– Dentate
– Interposed
– Fastigial nuclei

All these deep cerebellar nuclei receive signals from
– The cerebellar cortex
– Deep sensory afferent tracts to the cerebellum
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Excitatory signals to the deep nuclei and corresponding
cerebellar cortex areas
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Immediately after that, an inhibitory signal is sent by the
cerebellar cortex to the deep nucleus
Output Signals from the Cerebellum
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From the deep nuclei, output signals leave the cerebellum:
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A pathway originates in the midline structures (vermis) and to
medullary and pontile areas of the brain stem (equlibrium)
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A pathway originates in
– Intermediate zone
– Interposed nucleus
– Ventrolateral and ventroanterior portions of the thalamus
– Basal ganglia
– Red nucleus and reticular formation of the upper brain stem
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This pathway helps coordinate reciprocal contractions of agonist
and antagonist muscles in the limbs
Output Signals from the Cerebellum
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A pathway originates that begins in the cerebellar cortex of the
lateral zone, then to dentate nucleus, thalamus and then to the
cerebral cortex
Functional Unit of the Cerebellar Cortex
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The Purkinje cell and deep nuclear cell
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Afferent input is carried by climbing fibers and mossy fibers
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The output from the functional unit is from the deep nuclear cell
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This is under both excitatory and inhibitory influences
Functional Unit of the Cerebellar Cortex
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The Purkinje cells and deep nuclear cells fire continuously
under normal resting conditions
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Balance between excitation and inhibition at the deep cerebellar
nuclei
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Other inhibitory cells in the cerebellum: basket and stellate cells
in the cerebellum provide additional inhibitory signals
– Their role in lateral inhibiton
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Turn-On/Turn-Off and Turn-Off/Turn-On output signals from
the cerebellum: typical function of the cerebellum is to provide
rapid turn-on signals for the agonist muscles and simultaneous
reciprocal turn-off signals for the antagonist muscles
Functional Unit of the Cerebellar Cortex
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The Purkinje cells learn to correct motor errors: role of
climbing fibers
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Timing and force of muscle contractions must be
learned by the cerebellum
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Failure of actual movement to match the intended
movement at first attempt
Function of the cerebellum in overall
motor control
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The nervous system uses the cerebellum to coordinate motor
control functions at three levels:
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Vestibulocerebellum: it provides neural circuits for body’s
equlibrium movements
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Spinocerebellum: It provides circuitry for coordinating
movements of mainly distal limbs
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Cerebrocerebellum: Lateral portions of the cerebellum, signal
transduction with the cerebral cortex
Functional Divisions-cerebellum
• Vestibulocerebellum (flocculonodular lobe)
The vestibulocerebellum
input-vestibular nuclei
output-vestibular nuclei
The vestibulocerebellum
Function:
The control of the equilibrium and postural movements.
Especially important in controlling the balance between
agonist and antagonist M. contractions of the spine, hips,
and shoulders during rapid changes in body positions.
Method
Calculate the rates and direction where the different parts of
body will be during the next few ms.
The results of these calculations are the key to the
brains’s progression to the next sequential movement.
• Spinocerebellum (vermis & intermediate)
•Spinocerebellum (vermis & intermediate)
–input-periphery & spinal cord:
–output-cortex
• Spinocerebellum (vermis & intermediate)
Functions:
-- Provide the circuitry for coordinating mainly the movements of
the distal portions of the limbs, especially the hands and fingers
-- Compared the “intentions ” from the motor cortex and red
nucleus, with the “performance” from the peripheral parts of the
limbs,
--Send corrective output signals to the motor neurons in the anterior
horn of spinal cord that control the distal parts of the limbs (hands
and fingers)
--Provides smooth, coordinate movements of the agonist and
antagonist M. of the distal limbs for the performance of acute
purposeful patterned movements.
Cerebellar Control of Ballistic Movements
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Sequential control of rapid movements, such as movements of
the fingers in typing
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Or saccadic movements of the eyes when reading
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When the cerebellum is removed, these changes occur in
ballistic movements:
– Movements are slow to develop
– The force is weak
– Movements are slow to turn off (intentional tremor)
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Biphasic nature of ballistic movements: first excitatory and then
delayed inhibitory function is required
• Cerebrocerebellum (lateral zone)
input-pontine N.
output- premotor cortex and primary and association
somatosensory areas
(no direct output to the primary motor area)
• Cerebrocerebellum (lateral zone)
 Receives
all its input from the motor cortex, adjacent
pre-motor and somatic sensory cortices of the brain.
Transmits its output information back to the brain.
 Functions in a “feedback” manner with all of the
cortical sensory-motor system to plan sequential
voluntary body and limb movements,
 Planning these as much as tenths of a second in
advance of the actual movements (mental rehearsal of
complex motor actions)
• Vestibulocerebellum (flocculonodular lobe)
Balance and body equilibrium
• Spinocerebellum (vermis & intermediate)
Rectify voluntary movement
• Cerebrocerebellum (lateral zone)
Plan voluntary movement
Clinical Abnormalities of the Cerebellum
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Failure of progression:
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Dysdiadochokinesia: When the motor system fails to predict
where the different parts of the body will be at a given time, it
loses perception of the parts during motor movement
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Succeeding movement may begin too early or much too late
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Dysarthria: Failure of orderly succession of individual mucle
movements in talking
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Intention tremor (or action tremor)
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Cerebellar nystagmus
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Hypotonia
The motor functions of basal ganglia
The motor functions of basal ganglia
Caudate nucleus, Putamen, Globus Pallidus, Substantia Nigra
and Subthalamic Nucleus
Neuronal Circuitry of the Basal Ganglia
Putamen circuit
Caudate circuit
Basal Ganglia
Connections
• Circuit of connections
–cortex to basal ganglia to
thalamus to cortex
–Helps to program
automatic movement
sequences (walking and arm
swinging or laughing at a
joke)
• Output from basal
ganglia to reticular
formation
–reduces muscle tone
–damage produces
rigidity of Parkinson’s
disease
The Putamen Circuit
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One of the principal roles of the basal ganglia in motor control is to
function in association with the corticospinal system to control
complex patterns of motor activity
– Writing letters of alphabet
– Cutting paper with scissors, hammering nails, most aspects of vocalization
and any other skilled movements
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Neural pathways of the putamen circuit:
– Beginning in premotor and supplementary areas of motor cortex and
somatosensory areas of the cortex
– Putamen
– Internal portion of the globus pallidus
– Ventoanterior and ventrolateral relay nuclei of the thalamus
– And then back to the primary motor cortex and supplementary cerebral areas
associated with the primary motor cortex
The Putamen Circuit
Abnormal function of the putamen circuit
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Athetosis: continuous writhing movements of hands, arms,
neck or the face
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Hemiballismus: A lesion in the subthalamus often leads to
sudden unilateral wild, large amplitude flinging movements
of the arm and leg, normally causing falls and preventing
postural maintenance
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Chorea
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Parkinson’s disease
The Caudate Circuit
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Role of basal ganglia for cognitive control of sequences of
motor patterns
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The caudate nucleus plays a major role in cognitive control
of motor activity
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The caudate nucleus receives large amounts of its input from
the assoaiction areas of the cerebral cortex processing
different types of sensory and motor information into usable
thought patterns
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Cognitive functions and rapid control of motor activity
The Caudate Circuit
Components of Basal Ganglia
Caudate
Putamen
GPe
GPi
1. Corpus Striatum
Striatum ----- Caudate Nucleus & Putamen
Pallidum ----- Globus Pallidus (GP)
Components of Basal Ganglia
2. Substantia Nigra
Pars Compacta (SNc)
Pars Reticulata (SNr)
STN
3. Subthalamic Nucleus (STN)
SN (r & c)
Function of the basal ganglia to change the
timing and to scale the intensity of movements
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To determine how rapidly the movement is to be performed
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To control how large the movement will be
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In patients with severe lesions of the basal ganglia, these
timing and scaling of the movements are poor
Functions of Specific Neurotransmitter
Substances in the Basal Ganglial System
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Dopamine pathways from SN to caudate nucleus and putamen
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GABA pathways from the caudate nucleus and putamen to the
globus pallidus and SN
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ACh pathways from the cortex to the caudate nucleus and
putamen
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Multiple general pathways from the brain stem:
– Norepinephrine
– Serotonin
– Enkephalin

Glutamate
Functions of Specific Neurotransmitter
Substances in the Basal Ganglial System
Clinical Syndromes Resulting from Damage to
the Basal Ganglia
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Aside from athetosis and hemiballismus
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Parkinson’s disease
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Huntington’s disease (chorea)
Parkinson’s
Disease
PD
Disease of mesostriatal
dopaminergic system
Muhammad Ali in Atlanta Olympic
normal
Parkinson’s Disease
Substantia Nigra,
Pars Compacta (SNc)
DOPAminergic Neuron
Clinical Feature (1)
Slowness of Movement
- Difficulty in Initiation and Cessation
of Movement
Parkinson’s Disease
Clinical Feature (2)
Resting Tremor
Parkinsonian Posture
Rigidity-Cogwheel Rigidity
HUNTINGTON’S CHOREA
Clinical Feature
- Predominantly autosomal dominantly
inherited chronic fatal disease
(Gene: chromosome 4)
- Insidious onset: Usually 40-50
- Choreic movements in onset
- Frequently associated with
emotional disturbances
- Ultimately, grotesque gait and severe
dysarthria, progressive dementia
ensues.
Principal Pathologic Lesion:
Corpus Striatum (esp. caudate nucleus)
and Cerebral Cortex
HEMIBALLISM
Clinical Feature
Lesion: Subthalamic
- Usually results from CVA
(Cerebrovascular Accident)
involving subthalamic nucleus
- sudden onset
- Violent, writhing, involuntary
movements of wide excursion
confined to one half of the body
- The movements are continuous
and often exhausting but cease
during sleep
- Sometimes fatal due to exhaustion
- Could be controlled by
phenothiazines and stereotaxic
Nucleus surgery