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Motor Systems: Lecture 4

Motor Systems: Lecture 4. Michael S. Beauchamp, Ph.D. Assistant Professor Department of Neurobiology and Anatomy University of Texas Health Science Center at Houston Houston, TX. Michael.S.Beauchamp@uth.tmc.edu. Hierarchical Organization and Functional Segregation

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Motor Systems: Lecture 4

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  1. Motor Systems: Lecture 4 Michael S. Beauchamp, Ph.D. Assistant Professor Department of Neurobiology and Anatomy University of Texas Health Science Center at Houston Houston, TX Michael.S.Beauchamp@uth.tmc.edu

  2. Hierarchical Organization and Functional Segregation of Central Motor Structures Level 4: Association Cortex Side Loop 1: Basal Ganglia (Caudate Nucleus, Putamen, GlobusPallidus, SubstantiaNigra, Subthalamic Nucleus) Level 3: Motor Cortex Thalamus (VA,VL,CM) Level 2: Brain Stem (Red Nucleus, Reticular Formation, Vestibular Nuclei, Tectum, Pontine Nuclei, Inferior Olive) Side Loop 2: Cerebellum Level 1: Spinal Cord

  3. Action Zones Aflalo & Graziano, Neuron,2007

  4. From J. Nolte (2002) The Human Brain, 5th Edition

  5. Basal Ganglia

  6. Basal Ganglia Nomenclature Nucleus accumbens Caudate Putamen Globuspallidus Subthalamic nucleus Substantianigra (Ventral Tegmental Area) Corpus striatum Striatum or Neostriatum Lenticular nucleus

  7. Ventral Tegmental Area

  8. How the striatum got its name…

  9. Basal ganglia have motor and nonmotor functions

  10. Basal Ganglia Afferents

  11. Basal Ganglia Efferents

  12. Basal Ganglia Intrinsic Connections

  13. Functions Direct Pathway: select appropriate movements Indirect Pathway: inhibit inappropriate movements

  14. Direct Pathway Direct Pathway excites motor cortex E I I Cortex  striatum  GPint  thalamus +1 x –1 x –1 = +1

  15. Direct and Indirect Pathways

  16. Direct and Indirect Pathways Direct Pathway excites motor cortex Indirect Pathway inhibits motor cortex Indirect Pathway E I I E I Cortex  striatum  GPext  Subthalamic Nucleus  GPint  thalamus +1 x –1 x –1 x +1 x –1 = –1

  17. Dopaminergic Input from SubstantiaNigra Nigrostriatal pathway excites motor cortex by (1) exciting Direct Pathway (2) inhibiting Indirect Pathway

  18. Functions of Basal Ganglia • Enable automatic performance of practiced motor acts • Gating the initiation of voluntary movements by modulating motor programs stored in the motor cortex • Cognitive functions

  19. Action Zones Aflalo & Graziano, Neuron,2007

  20. Functions of Basal Ganglia • Enable automatic performance of practiced motor acts • Gating the initiation of voluntary movements by modulating motor programs stored in the motor cortex • Cognitive functions

  21. Role of the basal ganglia in exciting one motor program via direct pathway and inhibiting competing programs via indirect pathway

  22. Dopamine neurons of substantianigra signal unexpected reward or unexpected absence of reward

  23. Dopaminergic Input from SubstantiaNigra

  24. Functions of Basal Ganglia • Enable automatic performance of practiced motor acts • Gating the initiation of voluntary movements by modulating motor programs stored in the motor cortex • Cognitive functions

  25. Striatal Neurons and Response/Habit Learning Jog et al. (1999) Building Neural Representations of Habits. Science 286: 1745-1749.

  26. Basal Ganglia Damage Impairs Probabilistic Classification Task 15% 60% 85% 40% 30% 75% 70% 25%

  27. Disorders of Basal Ganglia 1. Huntington’s Disease 2. Parkinson’s Disease

  28. From Kingsley RE (2000) Concise Text of Neuroscience, 2nd Ed.

  29. Parkinson’s Disease

  30. Parkinson’s Disease

  31. Huntington’s Disease

  32. Huntington’s Disease

  33. Hierarchical Organization and Functional Segregation of Central Motor Structures Level 4: Association Cortex Side Loop 1: Basal Ganglia (Caudate Nucleus, Putamen, GlobusPallidus, SubstantiaNigra, Subthalamic Nucleus) Level 3: Motor Cortex Thalamus (VA,VL,CM) Level 2: Brain Stem (Red Nucleus, Reticular Formation, Vestibular Nuclei, Tectum, Pontine Nuclei, Inferior Olive) Side Loop 2: Cerebellum Level 1: Spinal Cord

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