Brain Mechanisms of Movement Lecture 19

Hierarchical Control of Movement n Association cortices & Basal Ganglia l strategy : goals & planning l based on integration of sensory info n Motor cortex & cerebellum l tactics: activation of motor programs n Spinal cord l execution: activation of alpha motor neurons ~

Cortical Control of Movement n M1 - Precentral Gyrus l Frontal Lobe l somatotopic organization n M2 - Secondary Motor Cortex l SMC - Supplementary Motor Cortex l PM - Premotor Cortex n Somatosensory cortex l S1 - postcentral gyrus l PPC - Posterior Parietal Cortex ~

M1 SMA S1 PM PPC

Sensorimotor Integration n Somatosensory cortex l provides spatial coordinates n Motor Cortex l executes movements n Results in meaningful behavior ~

Motor Association Cortex (M2) n Premotor & Supplemental Motor Cortex l input from S1 & PPC l output to M1 n Active during preparation for movement l Planning of movements n Stimulation - complex movements l motor programs ~

Brain to Spinal Cord n Upper motor neurons communication with lower (  ) motor neurons n Dorsolateral pathway l distal limbs n Ventromedial pathway l trunk, neck & proximal limbs ~

The Dorsolateral Pathway n Voluntary movement l contralateral control l distal limbs n Corticospinal tract l M1  spinal cord l about 1 million axons n Rubrospinal tract l M1  red nucleus  spinal cord ~

Descending Motor Pathways Dorsal Ventral Ventromedial tract Dorsolateral tract

Caudate Putamen Cerebellum Subcortical Motor Systems: Cerebellum & Basal Ganglia

Subcortical Motor Loops n Parallel processing n Cortex  Subcortex  Cortex  Spinal cord n Cerebellum l coordination of movement n Basal Ganglia l selection & initiation of voluntary movements ~

Cerebellum 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 l Long-term depression (LTD) l inhibits incorrect movements ~

Cerebellum: Damage n Lesions - loss of motor coordination n Dysynergia l no simultaneous movement of joints serial movement only n Dysmetric movements l to wrong coordinates n Alcohol intoxication l depression of cerebellar circuits ~

Basal Ganglia n Caudate nucleus Putamen Globus Pallidus n Substantia Nigra l Tegmentum n Control slow movements l Using immediate sensory feedback ~ Striatum

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

Motor Cortex Substantia Nigra DA + Striatum + Parkinson’s Disease

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

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

Huntington’s Disease (Chorea) n Rare genetic disorder l Single dominant gene on chromosome 4 l onset 30-40s n Symptoms l Uncontrollable, jerky movements l dementia l Progressive ~

Huntington’s Disease (Chorea) n Degeneration of Striatum l Caudate & Putamen l GABA & ACh neurons n Loss of inhibition l over-stimulation of motor cortex ~