Download Basal ganglia

Basal ganglia
Basal ganglia
• Basal ganglia regulate
–
–
–
–
muscle contraction
muscle force
multijoint movement
Sequencing of movement
• The output of the basal ganglia is via
– Motor area of the cerebral cortex
– Pendunculopontine nucleus (elicits rhythmical
behaviors such as locomotor patterns) : located in
the brain stem
Caudate
Putamen
Globus pallidus
Subthalamic nucleus
Substantia nigra
Corpus
straitum
straitum
Caudate nucleus
putamen Leniform
nucleus
Globus pallidus
The function of caudate : cognitive, not motor
The function of the ventral striatum : limbic
Basal ganglia : no direct connections with
lower motor neurons
(1) Motor planning areas of the cerebral cortex
(2) Pedunculopontine nucleus of the midbrain
• Subthalmic nucleus : inferior to the thalamus
and lateral to the hypothalamus
• Substantia nigra : a nucleus in the midbrain
named for the color of its cells
 Compacta (provide essential dopamine to the
striatum)
 Reticularis
• Substantia nigra reticularis and globus palidus
internus : output nuclei of the basal ganglia
system
– Output nuclei : inhibit the motor thalamus and the
pedunclopontine nucleus of the midbrain
(1) Motor planning areas of the cerebral cortex
• a major basal ganglia circuit connects motor
and somatosensory areas of the cerebral
cortex-> the putamen-> the output nuclei->
the motor thalamus-> motor areas of the
cerebral cortex ; corticofugal tracts
(2) Pedunculopontine nucleus of the midbrain
• From the globus pallidus internus to the
pedunclopontine nucleus, thence to the
reticulospinal and to the vestibulospinal tracts
Basal Ganglia Connections
Input Portion
STRIATUM
(Caudate Nucleus and Putamen)
Output Portion
1. PALLIDUM (Globus Pallidus)
2. SNr (Substantia Nigra, Pars Reticulata)
Basal Ganglia Connections
STRIATUM
Afferents from
1. Cerebral Cortex [Corticostriatal Projection]
2. Thalamus [Thalamostriatal Projection]
3. SNc (Substantia Nigra, pars compacta),
Ventral Tegmental Area (VTA, A10)
and A8(Retrorubral Area) [Nigrostriatal Projection]
4. Dorsal Raphe Nucleus (B6, B8) [Raphestriatal Projection]
5. Amygdaloid Nuclear Complex [Amygdalostriatal Projection]
Efferents to
1. Pallidum (GPi & GPe) [Striopallidal Projection]
2. SNr [Strionigral Projection]
3. SNc from striosome
Afferent Connections of Basal Ganglia
Input-Output
Relationship
of Basal Ganglia
1. striopallidal fiber
2. strionigral fiber
3. strionigral fiber
from striosome
to SNc
4. ventrostrioventro-pallidal fiber
Basal Ganglia Connections
PALLIDUM (Globus Pallidus)
Afferents from
1. Striatum [Striatopallidal Projection]
2. STN <GPi & GPe> [Subthalamopallidal Projection]
Efferents to
1. Thalamus (VLo, VApc, CM) <GPi> [Pallidothalamic Projection]
2. STN <GPe> [Pallidosubthalamic Projection]
SNr (Substantia Nigra, Pars Reticulata)
Afferents from Striatum [Striatonigral Projection]
Efferents to
1. Thalamus (VLm, VAmc, MD) [Nigrothalamic Projection]
2. Brain Stem Nucleus: Tectum (Superior Colliculus) &
Pedunculopontine Nucleus (PPN)
Efferent Connections of Basal Ganglia
Connections of the Basal Ganglia
amygdaloid body
Cerebral
Cortex
raphe
STRIATUM
Thalamus
STN
SNc
Pallidum
SNr
habenular
nucleus
tectum
PPN
(superior colliculus)
(pedunculopontine nucleus)
Basal Ganglia (Main Motor Circuit)
Connections
Primary
Motor Area
(M I)
Supplementary
Motor Area
(SMA)
STRIATUM
(Putamen)
pyramidal
tract
THALAMUS
(VLo, VApc, CM)
LMN
ansa
lenticularis
lenticular
fasciculus
PALLIDUM
(GPi)
Basal Ganglia (Prefronatal Complex Loop)
Connections
Primary
Motor Area
(M I)
Prefrontal
Association
Cortex
STRIATUM
(Caudate
Nucleus)
THALAMUS
SNr
pyramidal
tract
(VLm, VAmc, MD)
LMN
(Substantia Nigra,
pars reticulata)
Basal Ganglia (Limbic Loop)
Connections
Orbitofrontal Cortex
Anterior Cingulate Gyrus
Hippocampal Formation
THALAMUS
(VAmc, MD)
Ventral Striatum
Caudate Nucleus
Ventral Pallidum
GPi, SNr
Basal Ganglia (Oculomotor Loop)
Connections
Primary
Motor Area
(M I)
Frontal
Eye Field
(area 8)
STRIATUM
(Caudate
Nucleus)
THALAMUS
SNr
pyramidal
tract
(VLm, VAmc, MD)
LMN
Tectum
(Substantia Nigra,
pars reticulata)
Basal Ganglia and Pyramidal Tract
SMA
(supplementary motor area)
upper motor neuron
UMN
pyramidal
tract
lower motor neuron
LMN
BASAL
GANGLIA
CIRCUIT
Function of the basal ganglia
• Sequencing movements and regulating
muscle tone and muscle force
• Select and inhibit specific motor
synergies;
- from putamen to the output nuclei :
select synergies (direct path)
- via the globus pallidus externus and
subthalamic nucleus : inhibit synergies
(indirect path)
Pathology of the basal ganglia
• Movement disorders
- hypokinetic disorders
 parkinson’s disease
- hyperkinetic disorders
 Huntington’s disease
 Dystonia
 Subtype of cerebral palsy
• Difference in abnormal movements are due to
dysfunction in specific parts of the basal gangliathalamocortical motor circuit and in the basal
ganglia-pedunculopontine nucleus
• The basal ganglia inhibit the motor thalamus and the
pedunculopontine
 Excessive inhibition : hypokinetic disorder
 Inadequate inhibition : hyperkinetic disorders
Parkinson’s disease:
•
Muscular rigidity
Shuffling gait
Drooping posture
Rhythmical muscular tremors
Masklike facial expression
Parkinson’s disease interferes with both voluntary and
automatic movements
• Pathology : the cause of cell death is unknown
- the death of dopamine-producing cells in the
substantia nigra compacta and acetylcholineproducing cells in the pedunculopontine nucleus
• The loss of dopamine in the basal ganglia direct
pathway : reduces activity in the motor areas of the
cerebral cortex, decreasing voluntary movements
• The loss of pedunculopontine cells, combined with
increased inhibition of the pedunculopontine nucleus :
disinhibits the reticulospinal and vestibulospinal tracts,
producing excessive contraction of postural muscles
• People with parkinson’s disease : difficulty coming to
standing from sitting, flexed posture, shuffling of the
feet, decreased or absent arm swing
Signs of parkinson’s disease
• Rigidity : increased resistance to movement in all
muscles; causes active muscle contraction, directly
• Hypokinesia : decreased ranges of active motion and
in the lack of automatic movements, including facial
expression and normal arm swing during walking,
decreased ability to control the force output of
muscles
• Resting tremor : pill-rolling tremor; tremor is
prominent when the hand is at rest and diminishes
during voluntary movement
• Freezing during movement : when their movements
abruptly cease (interrupts gait)
• Visuoperceptive impairments : deficit in using visual
information to guide movements (ex: a walker)
• Postural instability : secondary to the
extreme stiffness of postural flexor and
extensor.
• Parkinson’s dementia :
– Autonomic dysfunction
– Interfere with the ability to plan, to maintain
goal orientation, and to make decision.
• Dopamine (L-dopa) : initially effective in
reducing signs of the disease
• However, tolerance to L-dopa, side effects
(hallucinations, delusions, psychosis,
dyskinesia) and progression of the disease
with involvement of other cells
• Disknesia : involuntary movements
- chorea: brisk, jerky movements
- dystonia : involuntary sustained postures or
repetitive movements
• Surgical procedure
• Physical and occupational therapy : improve
movement and functional abilities ; moderate
level of activity
parkinsonism
• Collective name for disorders that cause signs similar
to parkinson’s disease
• disorders that cause the signs seen in parkinson’s
disease and encompasses disorders of toxic,
infectious, or traumatic etiology
• Lesions of the lentiform nucleus are associated with
parkinsonism
• Side effect of drugs that treat psychosis or digestive
problems
• Phenothiazine, thioxanthine, antiemetics and other
drugs that block CNS dopamine receptor
Multiple system atrophy
• Multiple system atrophy(MSA) :
– progressive degenerative disease affecting
the basal ganglia, cerebellar, and
autonomic systems and cerebral cortex
– MSA is characterized by;
• Parkinsonism
• Cerebellar signs
• Autonomic dysfunction
 Parkinsonism : slow movements and rigidity
 Cerebellar aspects : dysarthria
(uncoordinated speech), truncal and gait
ataxia (narrow-based)
 Autonomic aspects : postural hypotension,
bladder and bowel incontinence, abnormal
respiration, decreased sweating, tears, saliva,
impotence in men
 A decrease in goal-oriented cognitive ability
and difficulty with directing attention
 In men : usually impotence
 In women : difficulty urinating
Diagnosis
• Pure parkinsonism : if no autonomic or cerebellar signs are
present
• Pure autonomic failure : orthostatic hypotension and other
autonomic signs occur without signs of basal ganglia or
cerebellar involvement
- affects postganglionic neurons of the sympathetic system
- MSA : both the preganglionic and postganglionic neurons in the
sympathetic and parasympathetic systems
• In MSA : autonomic neurons :
- lost from brain stem nuclei and from the spinal cord
- Parkinson’s disease is the most common misdiagnosis, and
one third of people with MSA die while still misdiagnosed
- poor response to L-dopa, orthostatic hypotension, difficulty
with urination, rapid progression of functional limitations, lou
• MSA

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



poor response to L-dopa
orthostatic hypotension
difficulty with urination
rapid progression of functional limitations
Loud breathing
impotence
• MSA is synonymous
 Olivopontocerebellar atrophy : incoordination,
dysarthria, balance deficits
 Striatonigral degeneration : rigidity and
bradykinesia
 Shy-Drager syndrome : autonomic dysfunction
• Treatment
 drugs
 Decrease orthostatic hypotension
-
slow position changes
avoiding prolonged standing
eating smaller meals
use of elastic garments
avoidance of warm temperature
 Exercise programs to maintain strength and
physiologic fitness
Hyperkinetic Disorders
• Abnormal involuntary movements
 Huntington’s disease
 Dystonia
 Some type of cerebral palsy
Huntington’s disease
• Autosomal dominant hereditary disorder
• Causes degeneration in many areas of the brain,
most prominently in the striatum and cerebral cortex
• Decrease in signals from the output nuclei, resulting
in disinhibition of the motor thalamus and
pedunculopontine nucleus -> disinhibition of the
motor thalamus and pedunculopontine nucleus ->
excessive output from the motor area of the cerebral
cortex
• Signs : chorea, consisting of involuntary, jerky, rapid
movements, dementia
• Onset : 40~ 50 age
• Progressive, resulting in death about 15 years after
signs first appear
• Prevalence : 5~10 cases per 100,000 people
Dystonia
• Genetic, usually nonprogressive
• Movement disorders : involuntary sustained muscle contractions
causing abnormal postures or twisting, repetitive movements
• Focal dystonias: limited to one part of the body (writer’s cramp,
musician’s cramp) ; reduced reciprocal inhibition due to
decreased descending inhibition
• Treatment
 Avoidance of heavy gripping of instruments
 Sensory retraining
 Mental rehearsal of the target movement without overt
body movement
 Motor control
 Heat, cold and exercise
 Medications : acetylcholine, GABA, dopamine
 Surgical lesion of the motor thalamus or injection of
botulinum toxin into the affected muscles
• Segawa’s dystonia : interfere with walking and may mimic the
appearance of cerebral palsy; progress slowly and can be
effectively treated with medications
Choreoathetotic cerebral palsy
• Abnormal involuntary movements
• People with choreoathetosis, a type of
cerebral palsy
• Chorea : abrupt, jerky movements
• Athetosis : slow, writhing, purposeless
movements
summary
• Basal ganglia disorders
 interfere with voluntary and automatic
movements
 Produce involuntary movements
 Hypokinesia : decrease in the amount of
and speed of voluntary and automatic
movements (Parkinson’s disease)
 Hyperkinesia : abnormal excessive
movement (huntington’s disease, dystonia,
choreoathetotic palsy)