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Cerebellum

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

  2. Cerebellar Signs Hypometria & Response delays Ataxia Incoordination/rapid alternatingmovements(disdiadocho-kinesia) PNS Fig. 42-16

  3. 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)

  4. 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

  5. Intent Exerts influence at all levels Actual Motor Hierarchy 1° Som sensory

  6. Cerebellar Functional Anatomy

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

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

  9. Spinocerebellum: Vermis Intermediate hem. Spinocerebellum (Vermis + Intermed. Hem) Cerebrocerebellum: Lateral hem. Control of limbs and trunk Cerebrocerebellum (Lateral hemisphere) Planning of movement+ Vermis Vestibulo-cerebellum (Floculo-nodular lobe) Intermediate hem. Lateral hem. Control of eye & head movements Balance Floculo-nodular lobe Cerebellar divisions IVth vent NTA Fig. 13-1

  10. Cerebellar Cortex Inputs Climbing fibers•from Inferior olive Mossy fibers Output Purkinje neurons Interneurons Granule neurons Stellate neurons Basket neurons Golgi neurons Molecular Purkinje Granular NTA Fig. 13-11

  11. Without inhibitory circuits With inhibitory circuits Inhibitionreduces size of active Purkinje neurons = Lateral inhibition Output morefocused; moreprecise Parallel fiber input to cerebellar cortex

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

  13. Spinocerebellum Vermis Intermediatehemisphere CerebrocerebellumLateral hemisphere Inter posed Dentate Fastigial Vestibulo-cerebellum To frontalmotor areas To lateral sysetms To medial sysetms To vestibular nuclei Motor Planning +++ Eye mvt & balance Functional divisions of cerebellar cortex --> Deep nuclei Spinocerebellum Vermis Intermediate hem CerebrocerebellumLateral hemisphere Vestibulo-cerebellum Floculo-nodularlobe Motor execution PNS Fig. 42-3 NTA Fig. 13-1

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

  15. Intermediate and Lateral Hemispheres Vermis & Vestibulocerebellum Planning andlimb control Thalamus and Cortical motor areas Brain stem nuclei Cerebellar cortex & Deep nuclei Brain stem nuclei Axial control PNS Fig. 42-10, 12 Ipsilateral Bilateral

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

  17. MotorLearning Before Before Prisms Prisms After After PNS Fig. 42-15

  18. Non-motor Function Passive stimulation Discriminate roughness Manipulate only Manipulate + discriminate PNS Fig. 42-14

  19. 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

  20. 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

  21. 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