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Subcortical Motor Systems: Cerebellum & Basal Ganglia

Subcortical Motor Systems: Cerebellum & Basal Ganglia. Lecture 21. Motor Loops. Cortex  Subcortex  Cortex  Spinal cord Cerebellum coordination of movement Basal Ganglia selection & initiation of voluntary movements ~. Cerebellum. Nonmotor functions - memory/language

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Subcortical Motor Systems: Cerebellum & Basal Ganglia

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  1. Subcortical Motor Systems:Cerebellum & Basal Ganglia Lecture 21

  2. Motor Loops • Cortex  Subcortex  Cortex  Spinal cord • Cerebellum • coordination of movement • Basal Ganglia • selection & initiation of voluntary movements ~

  3. Cerebellum • Nonmotor functions - memory/language • Coordination of complex movements • Programs ballistic movements • no feedback during execution • direction, force, & timing • Motor learning • shift from conscious  unconscious ~

  4. Cerebellum: Anatomy • Folia & lobules • analogous to sulci & gyri • Vermis - along midline • output  ventromedial pathway • Hemispheres • output  lateral pathway • Deep cerebellar nuclei • analogous to thalamus ~

  5. Motor Loop Through Cerebellum • Lateral cerebellum • simplest circuit • 20 million axons • Cortex  pons & cerebellum • Prefrontal, Motor, PPC • Pons & Cerebellum  thalamus • VLc - ventrolateral nucleus • VLc  M1  lateral pathway ~

  6. Prefrontal M2 M1 PPC Distal Limbs Lateral Cerebellar Motor Loop Pons, Cerebellum VLc

  7. Cerebellum: Damage • Lesions - loss of motor coordination • Dysynergia • no simultaneous movement of joints • serial movement only • Dysmetric movements • to wrong coordinates • Alcohol intoxiction • depression of cerebellar circuits ~

  8. Caudate nucleusPutamen Globus Pallidus Substantia Nigra Tegmentum Control slow movements Using immediate sensory feedback ~ Striatum Basal Ganglia

  9. Globus Pallidus Thalamus Substantia Nigra Striatum

  10. Cross section of Tegmentum Substantia Nigra

  11. Prefrontal M2 M1 PPC Distal Limbs Basal Ganglia Motor Loop Basal Ganglia VLo

  12. Basal Ganglia Movement Disorders

  13. Parkinson’s Disease • 1% of population • Nigrostriatal pathway • Substantia nigra neurons die • Progressive loss • Hypokinesia • Rigidity • Bradykinesia • Akinesia ~

  14. + Subthalamic Nucleus SMA + Cortex + Parkinson’s Disease Putamen VLo - + X Globus Pallidus (GPi) - Substantia Nigra

  15. Parkinson’s Disease: Treatment • Basal Ganglia - Cholinergic • Substantia Nigra - Dopaminergic • Drug Therapy • L-DOPA • Pallidectomy • Tissue transplants ~

  16. Huntington’s Disease (Chorea) • Rare • onset 30-40s • early as 20s • Degeneration of Striatum • Caudate • Putamen • GABA & ACh neurons ~

  17. Symptoms • Khoros = dance • Uncontrollable, jerky movements • Dementia • Progressive eventually fatal ~

  18. + VLo GPi GPe SMA Putamen Huntington’s Disease - X - + + Subthalamic Nucleus -

  19. Huntington’s Disease: Cause • Genetic disorder • Single dominant gene on chromosome 4 • HD mutation - unstable trinucleotide repeat - CAG • # of repeats correlated w/ age of onset ~

  20. Huntington’s Disease: Cause • HD gene  huntingtin • 3 forms • mutated form binds to protein • involved in energy production • neuron starves • Excitotoxicity contributes to degeneration • glutamate  Nitric oxide (NO) • Potential treatment:: Inhibit NO synthase ~

  21. Hyperkinesia • Excessive movement • Ballism • violent, flinging movements • Lesions in subthalamus • less inhibition of VLo • excitation of SMA ~

  22. + VLo - Globus Pallidus + Subthalamic Nucleus SMA Striatum Hyperkinesia (e.g. ballism) - X

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