Download Basal gangla

Cortex
Thalamus
Basal ganglia
Cerebellum
Brainstem
Spinal cord
BASAL GANGLA
Other sensory
receptors
Muscle
contraction
Proprioceptors
Organization of a real-life move
Basal ganglia
• Position: telencephalon (striatum, pallidum and nucl. subthalamicus),
midbrain (substantia nigra)
• Connections: cortex, thalamus, brainstem
• Transmitters: GABA, modulating: dopamine, acetylcholine
• Functions:
– Organization of movements
– Eye movements
– motivation
– Learning (motor skills)
– emotions
• 4 nuclei:
–
–
–
–
–
Nucleus caudatus
Striatum
Putamen
Pallidum (globus pallidus és ventrális pallidum)
Substantia nigra
Nucleus subthalamicus
Functional anatomy of the basal ganglia
Anatomical parts:
• nucleus caudatus
• putamen
• globus pallidus
• pars interna (GPi)
• pars externa (GPe)
• substantia nigra
• pars compacta
• pars reticularis
Connections of the basal ganglia
Cortex→striatum
(glutamaterg)
Motor cortex
nucl. caudatus
Pallidum
Striatum
Direct pathway
(red): striatum
inhibits pallidum
pars interna &
substantia nigra
pars reticularis
Indirect pathway
(green): striatum
inhibits pallidum
pars externa &
subthalamic
nuclei
Substantia
nigra
subthalamic
Cortex – basal ganglia – thalamus –
cortex
Direct pathway
Indirect pathway
•
•
•
Cortex →striatum, activation
Striatum GABAergic → pallidum pars interna –
inhibition
• Striatum GABAergic → substantia nigra pars reticularis
– inhibition
• Pallidum pars interna & substantia nigra GABAergic →
thalamus – inhibition
• Thalamus glutamatergic →cortex – activation
Therefore the activation of cortex inhibits the inhibition of
thalamus = disinhibition
•
•
•
•
•
striatum GABAergic → substantia nigra pars
compacta – inhibition
substantia nigra pars compacta dopaminergic
→ striatum, dual effect
striatum GABAergic → pallidum pars
externa– inhibition
pallidum pars externa GABAergic →
subthalamic nuclei – inhibition
A subthalamic nuclei glutamatergic →
pallidum pars interna & substantia nigra pars
reticularis – activation
Nucleus subthalamicus glutamatergic →
pallidum pars externa - activation
Cortex – basal ganglia – thalamus –
cortex
Cortex
Figure legend:
Red: GABA (inhibition)
Blue/empty:
glutamate (activation)
Thalamus
Pallidum pars
externa
Striatum
Green: dopamine
(dual effect)
S. nigra pars
compacta
Nucl.
subthalamus
Pallidum pars S. nigra pars
interna
reticularis
Connections of the basal ganglia
Glu, glutamate;
DA, dopamine.
Acetylcholine is the
transmitter produced by
interneurons in the
striatum.
SNPR, substantia nigra, pars
reticulata;
SNPC, substantia nigra, pars
compacta;
ES, external segment;
IS, internal segment;
PPN, pedunculopontine
nuclei.
The subthalamic nucleus
also projects to the pars
compacta of the substantia
nigra
Function of the basal ganglia
Function of the basal ganglia
•
•
•
•
•
Nucleus accumbens, ventral
pallidum and ventra tegmentum:
motivation
Tegmentum: dopaminergic tracts to
nucl. accumbens
Injury of dopaminergic tracts:
„paralysis of will”, in emergency
able to perform coordinated and
fast movements, otherwise nearly
motionless
Desire, apetitive behaviour
Not consuming behaviour (injury in
animal models: do not take food,
but eat it if given into mouth)
•
•
•
•
•
Superior colliculus: optical tract (midbrain)
Retinotopic imaging
Connection to s. nigra pars reticularis
SNr: tonic inhibition
Eye movements: SNr silent
Subconscious control of learned
movements: Putamen circuit
Supplementary
motor cortex
Premotor cortex
Somatosensory cortex
Primary motor cortex
Putamen
Internal globus pallidus
Thalamus
VA, VL
nuclei
Abnormal functions:
athetosis -glob. pallidus,
ballismus -n. subthalamicus.
chorea -putamen
Subconscious execution of the learned patterns of movements
(= putting together the sequences of movements)
Subconscious cognitive control of
motor activity: Caudatus - circuit
Somatosensory
cortex
Premotor
cortex
Association cortex
(memories)
nucl.
Caudatus
Internal globus
pallidus
Cognitive control of motor activity
Immediate, several sec. long, automatic
responses („lion is coming”)
Thalamus
VA, VL
nuclei
Parkinson’s disease
Loss of dopaminergic neurons in the
substantia nigra pars compacta (SNc)
Parkinson’s disease
Parkinson’s disease
•Resting tremor
•Increased muscle tone (rigid muscles,
tilting of trunk, short steps)
•Hypokinesia (less spontaneous
movements)
•Akinesia (inhibition of initiation of
movements)
•Bradikinesia (slow execution of
movements)
•Loss of mimics, emotions can not be seen
•Monoton speech
•Increased parasympathetic tone:
salivation, sweating
Chorea
• Hyperkinetic-hypotonic
disorder
• Chorea: involuntary, sudden
movements of face and
limbs
• Basal ganglia: striatum
GABA-erg neuron injury
• Huntington
• Sydenham: rheumatic fever
• Chorea gravidarum
(pregnancy complication)
• Wilson’s disease (copper
metabolism)
• Spongiform
encephalopathias
• Neuroborreliosis
• Iatrogenic: dopamine
agonists, Parkinson’s,
schizophrenia and antiepilepsy drugs
Huntington’s disease
Symptoms:
• hyperkinesia
• chorea
• dementia
Causes of Huntington’s disease:
•Autosomal dominant genetic defect
•Deterioration of GABA-ergic neurons in the
striatum (caudate+putamen)
•Decreased inhibition over GPe
•STN won’t stimulate GPi
•VL and VA stimulates cortical motorneurons