Transcript Cerebellum - Columbia University

Cerebellum
John H. Martin, Ph.D.
Center for Neurobiology & Behavior
Columbia University
Cerebellar
Signs
Hypometria &
Response delays
Ataxia
PNS Fig. 42-16
Incoordination/
rapid alternating
movements
(disdiadochokinesia)
Research Points to Several
Key Cerebellar Functions
• Comparison of intent and action (ie.,
errors) and generates corrective signals
• Motor learning and adaptation
• Plays a role in automating and
optimizing behavior
• Motor cognition and general cognition &
emotions (new evidence; controversial)
Goal: Cerebellar function
• Overview of motor system hierarchy
• Cerebellar anatomy
• Principal pathways out of the cerebellum-How the cerebellum impacts the motor
pathways
• Experimental approaches to reveal:
– Motor learning
– Mental processes underlying movement control
– Role in cognition and emotions
Motor Hierarchy
1° Som sensory
Intent
Actual
Exerts influence
at all levels
Cerebellar Functional Anatomy
Cerebellar Cortex
Deep Cerebellar Nuclei:
Dentate
Interposed
Fastigial
PNS Fig. 42-1
Input-output Organization
Cerebellar
cortex
Deep Cerebellar
Nuclei:
Fastigial
Interposed
Dendate
+
Cortex
+ +
Nuclei
Output
Vestibular
nuclei
Extrinsic inputs:
mossy fiber
climbing fiber
NTA Fig. 13-2,4
Cerebellar divisions
Spinocerebellum:
Vermis
Intermediate hem.
Spinocerebellum
(Vermis + Intermed. Hem)
Cerebrocerebellum:
Lateral hem.
Control of limbs
and trunk
Cerebrocerebellum
(Lateral hemisphere)
Planning of movement+
Vestibulo-cerebellum
(Floculo-nodular lobe)
Control of eye &
head movements
Balance
NTA Fig. 13-1
IVth vent
Vermis
Intermediate hem.
Lateral hem.
Floculo-nodular lobe
Cerebellar Cortex
Inputs
Climbing fibers
•from Inferior olive
Mossy fibers
Output
Purkinje neurons
Interneurons
Granule neurons
Stellate neurons
Molecular
Purkinje
Granular
NTA Fig. 13-11
Basket neurons
Golgi neurons
Without inhibitory circuits
With inhibitory circuits
Inhibition
reduces size of
active Purkinje
neurons
= Lateral
inhibition
Parallel fiber input to cerebellar cortex
Output more
focused; more
precise
Functional divisions of cerebellar cortex --> Deep nuclei
PNS Fig. 42-2
Functional divisions of cerebellar cortex --> Deep nuclei
Spinocerebellum
Vermis
Intermediate
hemisphere
Cerebrocerebellum
Lateral hemisphere
Spinocerebellum
Vermis
Intermediate hem
Cerebrocerebellum
Lateral hemisphere
Inter
Dentate posed
Fastigial
Vestibulocerebellum
To frontal
motor areas
Motor
Planning
+++
To
lateral
sysetms
To
medial
sysetms
Motor
execution
Vestibulocerebellum
Floculo-nodular
lobe
To
vestibular
nuclei
Eye mvt &
balance
PNS Fig. 42-3
NTA Fig. 13-1
Medial & lateral systems
Interposed
nuclei
Fastigial
Vestibulocerebellum
via vestibular nuclei
NTA Fig. 10-2
Intermediate and Lateral
Hemispheres
Planning and
limb control
Vermis & Vestibulocerebellum
Thalamus and
Cortical motor areas
Brain stem nuclei
Cerebellar cortex
& Deep nuclei
Brain stem nuclei
Axial control
Ipsilateral
PNS Fig. 42-10, 12
Bilateral
Functions of the Cerebellum
• Motor learning/adaptation
• Non-motor functions:
– Active tactile exploration
– Higher brain functions (cerebellar cognitiveaffective syndrome)
Motor
Learning
Before
Before
Prisms
After
PNS Fig. 42-15
Prisms
After
Non-motor Function
Passive stimulation
Discriminate roughness
Manipulate only
Manipulate + discriminate
PNS Fig. 42-14
Cerebellar Motor Functions
• Implemented via lateral and medial pathways,
especially the corticospinal tract
• Incorporated into motor programs via frontal motor
areas (SMA, premotor cortex…)
• Becomes part of motor strategy via prefrontal cortex
Cerebellar Cognitive Affective
Disorder
• Lesions of the posterior cortex and vermis
• Impairment of executive functions
– Planning, verbal fluency, abstract reasoning
• Difficulties with spatial cognition
– Visuo-spatial organization, visual memory
• Personality changes
– Blunting of affect, inappropriate behaviors
• Language disorders
– Agrammatism
Conclusions
• Cerebellar lesions produce
– Incoordination & errors not weakness
– Lose ability to anticipate errors
– Lose ability to correct
• Motor learning
– Requires sensory awareness
– Implemented via the descending cortical and
brain stem pathways
• Cognitive and emotional disturbances
– Anatomical connections to prefrontal and
cingulate cortex (via thalamus)
• No single function
– Clearly mostly motor; learning, optimizes
– Functions may apply to cognitive and emotional
behaviors