Lecture14_basalganglia - Basal Ganglia and dopamine...

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Basal Ganglia and dopamine pathways
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Modulation of the Pyramidal Motor System Motor Cortex Spinal/Cranial Motoneurons Ventral Thalamic Nuclei Cerebellar Cortex Muscles D2 D1 Globus Pallidus external Ventral Thalamic Nuclei Globus Pallidus internal Subthalamic nucleus SNpc Deep Cerebellar Nuclei BASAL GANGLIA SYSTEM CEREBELLAR SYSTEM proprioception efference copy dopamine Excitatory Connection Inhibitory Connection PYRAMIDAL MOTOR PATHWAY The pyramidal motor pathway is modulated by two main extrapyramidal motor systems: the basal ganglia and cerebellar systems. Dorsal Striatum
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Cerebellar System Motor Cortex Spinal/Cranial Motoneurons Ventral Thalamic Nuclei Cerebellar Cortex Muscles Deep Cerebellar Nuclei CEREBELLAR SYSTEM proprioception efference copy PYRAMIDAL MOTOR PATHWAY The pyramidal motor pathway is modulated by two main extrapyramidal motor systems: the basal ganglia and cerebellar systems. Motor cortex sends an efference copy of outgoing motor commands to the cerebellum, informing the cerebellum of what the intended motion is Cerebellum receives proprioceptive input from the muscles, informing the cerebellum of what the actual motion is Cerebellum determines what adjustments need to be made to correct any errors (differences between the intended and actual movement) Cerebellum corrects the movement by projecting back to motor cortex to modify the original command, and by projecting to spinal motoneurons (via the red nucleus) to alter their activity
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Closed-loop control system The cerebellum plays an important role in closed loop control of motor behaviors The cerebellum is an adaptive controller that improves its own performance through error driven learning Spinal Motor Neurons Proprioceptors Brain Motor Neurons Cerebellum Efference Copy Muscle Contraction & Limb Movement
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Modulation of the Pyramidal Motor System Motor Cortex Spinal/Cranial Motoneurons Ventral Thalamic Nuclei Cerebellar Cortex Muscles D2 D1 Globus Pallidus external Ventral Thalamic Nuclei Globus Pallidus internal Subthalamic nucleus SNpc Deep Cerebellar Nuclei BASAL GANGLIA SYSTEM CEREBELLAR SYSTEM proprioception efference copy dopamine Excitatory Connection Inhibitory Connection PYRAMIDAL MOTOR PATHWAY The pyramidal motor pathway is modulated by two main extrapyramidal motor systems: the basal ganglia and cerebellar systems. Dorsal Striatum
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Inhibitory gating of motor output by the Basal Ganglia Motor cortex neurons must receive “permission” from the basal ganglia to produce motor output The “permission signal” comes through excitatory feedback inputs to motor cortex from the motor thalamus: the ventral thalamic nuclei (VTN) The ventral thalamic nuclei are tonically inhibited by GABAergic neurons in the internal segment of the globus pallidus (GPi) To initiate a movement, GPi neurons must be phasically inhibited, which disinhibits the VTN permission signal Motor Cortex Spinal/Cranial Motoneurons Muscles Ventral Thalamic Nuclei Globus Pallidus
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