Cerebellum John H. Martin, Ph.D. Center for Neurobiology & Behavior Columbia University

Cerebellar Signs Ataxia Hypometria & Response delays Incoordination/ rapid alternating movements (disdiadocho- kinesia) PNS Fig

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 influence at all levels Intent Actual 1° Som sensory

Cerebellar Functional Anatomy

Cerebellar Anatomy Cerebellar Cortex Deep Cerebellar Nuclei: Dentate Interposed Fastigial PNS Fig. 42-1

Input-output Organization Cerebellar cortex Fastigial Interposed Dendate Deep Cerebellar Nuclei: Vestibular nuclei Cortex Nuclei Output Extrinsic inputs: mossy fiber climbing fiber NTA Fig. 13-2,4

IV th vent Vermis Intermediate 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 movements Balance Cerebellar divisions NTA Fig. 13-1

Cerebellar Cortex Inputs Output Interneurons Climbing fibers from Inferior olive Mossy fibers Purkinje neurons Stellate neurons Granule neurons Basket neurons Golgi neurons Molecular Purkinje Granular NTA Fig

Parallel fiber input to cerebellar cortex With inhibitory circuits Inhibition reduces size of active Purkinje neurons = Lateral inhibition Output more focused; more precise Without inhibitory circuits

Cbm unfold Functional divisions of cerebellar cortex --> Deep nuclei PNS Fig. 42-2

Functional divisions of cerebellar cortex --> Deep nuclei Vermis Intermediate hem Cerebrocerebellum Lateral hemisphere Spinocerebellum Vestibulo- cerebellum Floculo-nodular lobe Cerebrocerebellum Lateral hemisphere Dentate Intermediate hemisphere Inter posed To lateral sysetms Spinocerebellum Vermis Fastigial To medial sysetms To frontal motor areas Motor Planning +++ Motor execution Vestibulo- cerebellum To vestibular nuclei Eye mvt & balance PNS Fig NTA Fig. 13-1

Medial & lateral systems Interposed nuclei Fastigial Vestibulocerebellum via vestibular nuclei NTA Fig. 10-2

Intermediate and Lateral Hemispheres Vermis & Vestibulocerebellum Cerebellar cortex & Deep nuclei Brain stem nuclei Thalamus and Cortical motor areas BilateralIpsilateral Brain stem nuclei Planning and limb control Axial control PNS Fig , 12

Functions of the Cerebellum Motor learning/adaptation Non-motor functions: –Active tactile exploration –Higher brain functions (cerebellar cognitive- affective syndrome)

Motor Learning Before Prisms After Before Prisms After PNS Fig

Non-motor Function Passive stimulationDiscriminate roughness Manipulate onlyManipulate + discriminate PNS Fig

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