Cerebellum Cerebellum • The anatomy of the cerebellum and its The anatomy of the cerebellum and its gross divisions • Its principal input and output pathways • Its principal input and output pathways • The organization of the cerebellar t cortex • Role of climbing vs. mossy fibre input • The parallel-fibre/Purkinje cell model of learning learning • Roles of the cerebellum in motor control Oct-09 RCM - BMedSci Neuro III 1 of 36 Cortico-cerebellar Premotor, Sensory motor P tP itl loop Post. Parietal Inputs: Sensory – motor cortex, assocation (PPC) assocation (PPC), spinal, vestibular, everything but primary sensory, Outputs: to all areas it receives from, via thalamus (to cortex) Cerebellum and red n. (to spine) Oct-09 RCM - BMedSci Neuro III 2 of 36 Cerebellum: “little brain” Oct-09 RCM - BMedSci Neuro III 3 of 36 Cerebellum • Massive cortical area, but much simpler th t than neo-cortex • Exerts influence on movement via influence motor and pre-motor cortex • Also connects with reticular formation • Also connects with reticular formation and spinal cord • Adds coordination, fine control, skill to basic movement patterns basic movement patterns • A powerful learning machine Oct-09 RCM - BMedSci Neuro III 4 of 36
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CerebellumCerebellum
• The anatomy of the cerebellum and itsThe anatomy of the cerebellum and its gross divisions
• Its principal input and output pathways• Its principal input and output pathways• The organization of the cerebellar
tcortex• Role of climbing vs. mossy fibre inputg y p• The parallel-fibre/Purkinje cell model of
learninglearning• Roles of the cerebellum in motor control
P ki j ll i• Purkinje cell inputs:from Parallel fibres 200,000from Climbing fibres 1from Climbing fibres 1
Oct-09 RCM - BMedSci Neuro III 18 of 36
Fractured somatotopy
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Topographical output
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Saggital in-out organizationgg g
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Climbing fibre induced
+LTD
Purkinjecell
Inhibitoryinterneurons
- +
Cerebellar l i
+-
climbing fibres nuclei
+
climbing fibres
thalamus mainly to motor & premotor cortex
red nucleus to spinal t ti l
inputsoutputs
red nucleus to spinal cord sensory-motor cortical
areas, parietal cortex, spinal cord
Oct-09 RCM - BMedSci Neuro III 22 of 36
Cerebellar learninggVOR gain:• head velocity via mossy fibres error signal viahead velocity via mossy fibres, error signal via
climbing fibres• LTD reduces P-cell inhibition of nuclei, disinhibition of
direct pathwaydirect pathway• “push-pull” mechanism in bilateral cerebellum• Combines to fine tune direct pathway gainCombines to fine tune direct pathway gain• Fast pathway – 14 ms latencyEye-blink:Eye blink: • CS via mossy fibres; US via climbing fibres• LTD selects out specific inputs, disinhibits nuclear
llcells• Important role in timing of CR• Slow: controls blink at ~500 ms after CSOct-09 RCM - BMedSci Neuro III 23 of 36
Slow: controls blink at 500 ms after CS
Complex LTD induction (!!)p ( )Parallel fibres: excitation f P ki j llof Purkinje cell
Climbing fibres: gstrong excitation leads to opening of VGCCsCa++ combined with mGluR activation triggers protein kinase Cprotein kinase CPhosphorylation of AMPA receptors LTDreceptors …LTD
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LTD and learning of VOR gaing g
Input : vestibular
P ki j I hibit
+- +
Input : vestibular signal of head motionOutput : Purkinje
cellInhibitory
interneurons
-
+Output : modulation of direct path to ocular motor
Vestibular nucleus
+neurons
Semi-circ
+Training signal :retinal slip signal on Semi circ.
canalsOMNsp g
climbing fibres
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parallel fibres & granule cellsVOR gain
PurkinjeParallel fibre-Purkinje cell j
LTD
CF: retinalslip (H-E) MF: vestibular
head velocityLTD –modulated
+head velocity
+
modulated inhibition -
Lateral vestibular nuclei
ocular motor
“push-pull” from bilateral circuits
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neurons
Simple/complex spike codes
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Complex spike event detection
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parallel fibres & granule cellsEye blink CC
PurkinjeLTD driven selection of
inputs
CS : tone, light, touch etc
+
US :
touch etc
air puffPremotor neurons
Eyelid motor
neurons
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neurons
Skill learning
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Visuo-motor recalibration• Prism glasses distort visual inputs – need to adjust
movement output to recalibratep• Short term learning• Blocked by cerebellar lesiony
(Martin et al, 1996)
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Eye-hand coordination
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CEREBRAL FRONTAL LOBE
Cerebello-cerebral processing
PRE-FRONTALCORTEX
MOTOR CORTEX
MANIPULATION OF MANIPULATION OFMANIPULATION OFINFORMATION
MANIPULATION OFMUSCLES
CEREBELLAR DENTATE NUCLEUS
VENTRAL DORSAL PARTVENTRAL DORSAL PART
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Cerebellar-cerebral processingp g
CEREBRAL FRONTAL LOBE
PRE-FRONTAL MOTOR CORTEXPRE FRONTALCORTEX
MOTOR CORTEX
MANIPULATION OFINFORMATION
MANIPULATION OFMUSCLESINFORMATION MUSCLES
CEREBELLAR DENTATE NUCLEUS
VENTRAL DORSAL PART
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Summaryy• Cerebellar cortex: big and (relatively!) simple• Important for all skilful movement• Huge numbers of parallel fibres bringingHuge numbers of parallel fibres bringing
diverse sensory-motor input to Purkinje cells• Climbing fibres induce parallel fibre : P cell• Climbing fibres induce parallel fibre : P-cell
LTD – the main (but not only) mechanismAdj t VOR i t l i l• Adjusts VOR gain, supports classical conditioning of eye-blink (& other reflexes)
• Predictive control
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Hand outs
• PDF file (~1Mbyte) of these powerpoint slides available from:powerpoint slides available from: prism.bham.ac.uk/courses p