Subcortical Motor Systems Cerebellum Basal Ganglia Lecture 21
Subcortical Motor Systems: Cerebellum & Basal Ganglia Lecture 21
Motor Loops Cortex Subcortex Cortex Spinal cord n Cerebellum l coordination of movement n Basal Ganglia l selection & initiation of voluntary movements ~ n
Cerebellum Nonmotor functions - memory/language n Coordination of complex movements n Programs ballistic movements l no feedback during execution l direction, force, & timing n Motor learning l shift from conscious unconscious ~ n
Cerebellum: Anatomy Folia & lobules l analogous to sulci & gyri n Vermis - along midline l output ventromedial pathway n Hemispheres l output lateral pathway n Deep cerebellar nuclei l analogous to thalamus ~ n
Motor Loop Through Cerebellum n Lateral cerebellum simplest circuit 20 million axons n Cortex pons & cerebellum l Prefrontal, Motor, PPC n Pons & Cerebellum thalamus l VLc - ventrolateral nucleus n VLc M 1 lateral pathway ~ l
Prefrontal M 2 Lateral Cerebellar Motor Loop M 1 VLc Distal Limbs PPC Pons, Cerebellum
Cerebellum: Damage Lesions - loss of motor coordination n Dysynergia l no simultaneous movement of joints n serial movement only Dysmetric movements l to wrong coordinates n Alcohol intoxiction l depression of cerebellar circuits ~ n
Basal Ganglia n Caudate nucleus Putamen Globus Pallidus Striatum Substantia Nigra l Tegmentum n Control slow movements l Using immediate sensory feedback ~ n
Striatum Substantia Nigra Globus Pallidus Thalamus
Cross section of Tegmentum Substantia Nigra
Prefrontal Basal Ganglia M 2 VLo M 1 PPC Basal Ganglia Motor Loop Distal Limbs
Basal Ganglia Movement Disorders
Parkinson’s Disease 1% of population n Nigrostriatal pathway l Substantia nigra neurons die l Progressive loss n Hypokinesia l Rigidity l Bradykinesia l Akinesia ~ n
Cortex + + Parkinson’s Disease Putamen + X SMA - Substantia Nigra Globus Pallidus (GPi) VLo - + Subthalamic Nucleus
Parkinson’s Disease: Treatment Basal Ganglia - Cholinergic n Substantia Nigra - Dopaminergic n Drug Therapy l L-DOPA n Pallidectomy n Tissue transplants ~ n
Huntington’s Disease (Chorea) n Rare l onset 30 -40 s early as 20 s Degeneration of Striatum l Caudate l Putamen n GABA & ACh neurons ~ n
Symptoms Khoros = dance n Uncontrollable, jerky movements n Dementia n Progressive eventually fatal ~ n
+ SMA Putamen X- Huntington’s Disease VLo - ++ GPe GPi - Subthalamic Nucleus
Huntington’s Disease: Cause Genetic disorder n Single dominant gene on chromosome 4 n HD mutation unstable trinucleotide repeat - CAG n # of repeats correlated w/ age of onset ~ n
Huntington’s Disease: Cause HD gene huntingtin n 3 forms l mutated form binds to protein l involved in energy production l neuron starves n Excitotoxicity contributes to degeneration l glutamate Nitric oxide (NO) l Potential treatment: : Inhibit NO synthase ~ n
Hyperkinesia Excessive movement n Ballism l violent, flinging movements n Lesions in subthalamus l less inhibition of VLo l excitation of SMA ~ n
SMA + Hyperkinesia (e. g. ballism) Striatum - VLo - Globus Pallidus + X Subthalamic Nucleus
- Slides: 22