Cerebellum

John H. Martin, Ph.D.Center for Neurobiology & BehaviorColumbia University

Cerebellar Signs

Ataxia

Hypometria &Response delays

Incoordination/rapid alternatingmovements(disdiadocho-kinesia)PNS Fig. 42-16

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

Exerts influenceat all levels

Intent

Actual

1° Som sensory

Cerebellar Functional Anatomy

Cerebellar Cortex

Deep Cerebellar Nuclei:Dentate

InterposedFastigial

PNS Fig. 42-1

Input-output Organization

Cerebellarcortex

FastigialInterposedDendate

Deep Cerebellar Nuclei:

Vestibularnuclei

Cortex

Nuclei

Output

Extrinsic inputs: mossy fiber climbing fiber

+-

+

+

NTA Fig. 13-2,4

IVth vent VermisIntermediate hem.

Spinocerebellum: Vermis Intermediate hem.Spinocerebellum

(Vermis + Intermed. Hem)

Control of limbs and trunk

Lateral hem.

Cerebrocerebellum: Lateral hem.

Cerebrocerebellum(Lateral hemisphere)

Planning of movement+

Floculo-nodular lobe

Vestibulo-cerebellum(Floculo-nodular lobe)

Control of eye & head movementsBalance

Cerebellar divisions

NTA Fig. 13-1

Cerebellar CortexInputs

Output

Interneurons

Climbing fibers•from Inferior oliveMossy fibers

Purkinje neurons

Stellate neurons

Granule neurons

Basket neurons

Golgi neuronsMolecular

PurkinjeGranular

NTA Fig. 13-11

Parallel fiber input to cerebellar cortex

With inhibitory circuits

Inhibitionreduces size of active Purkinjeneurons

= Lateral inhibition

Output morefocused; moreprecise

Without inhibitory circuits

Functional divisions of cerebellar cortex --> Deep nuclei

PNS Fig. 42-2

Functional divisions of cerebellar cortex --> Deep nuclei

VermisIntermediate hem

CerebrocerebellumLateral hemisphere

Spinocerebellum

Vestibulo-cerebellumFloculo-nodularlobe

CerebrocerebellumLateral hemisphere

Dentate

Intermediatehemisphere

Interposed

To lateralsysetms

Spinocerebellum

Vermis

Fastigial

To medialsysetms

To frontalmotor areas

MotorPlanning +++

Motorexecution

Vestibulo-cerebellum

To vestibular nuclei

Eye mvt &balance PNS Fig. 42-3

NTA Fig. 13-1

Medial & lateral systems

Interposednuclei

Fastigial

Vestibulocerebellumvia vestibular nuclei

NTA Fig. 10-2

Intermediate and LateralHemispheres

Vermis & Vestibulocerebellum

Cerebellar cortex & Deep nuclei

Brain stem nuclei

Thalamus and Cortical motor areas

BilateralIpsilateral

Brain stem nuclei

Planning andlimb control

Axial control

PNS Fig. 42-10, 12

Functions of the Cerebellum

• Motor learning/adaptation• Non-motor functions:

– Active tactile exploration– Higher brain functions (cerebellar cognitive-

affective syndrome)

MotorLearning

Before

Prisms

After

Before

Prisms

After

PNS Fig. 42-15

Non-motor Function

Passive stimulation Discriminate roughness

Manipulate only Manipulate + discriminatePNS 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