Brain Mechanisms of Movement

Lesson 21

Hierarchical Control of Movement

Association cortices & Basal Ganglia strategy : goals & planning based on integration of sensory info

Motor cortex & cerebellum tactics: activation of motor programs

Spinal cord execution: activation of alpha motor

neurons ~

Cortical Control of Movement M1 - Precentral Gyrus

Frontal Lobe somatotopic organization

M2 - Secondary Motor Cortex SMC - Supplementary Motor Cortex PM - Premotor Cortex

Somatosensory cortex S1 - postcentral gyrus PPC - Posterior Parietal Cortex ~

M1

SMA

S1PM

PPC

Sensorimotor Integration

Somatosensory cortex provides spatial coordinates

Motor Cortex executes movements

Results in meaningful behavior ~

Motor Association Cortex (M2)

Premotor & Supplemental Motor Cortex input from S1 & PPC output to M1

Active during preparation for movement Planning of movements

Stimulation - complex movements motor programs ~

Brain to Spinal Cord Upper motor neurons

communication with lower () motor neurons

Dorsolateral pathway distal limbs

Ventromedial pathway trunk, neck & proximal limbs ~

The Dorsolateral Pathway

Voluntary movement contralateral control distal limbs

Corticospinal tract M1 spinal cord about 1 million axons

Rubrospinal tract 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

Parallel processing Cortex Subcortex Cortex

Spinal cord Cerebellum

coordination of movement Basal Ganglia

selection & initiation of voluntary movements ~

Cerebellum Coordination of complex movements Programs ballistic movements

no feedback during execution direction, force, & timing

Motor learning shift from conscious unconscious Long-term depression (LTD) inhibits incorrect movements ~

Cerebellum: Damage Lesions - loss of motor coordination Dysynergia

no simultaneous movement of jointsserial movement only

Dysmetric movements to wrong coordinates

Alcohol intoxication depression of cerebellar circuits ~

Basal Ganglia

Caudate nucleus Putamen

Globus Pallidus Substantia Nigra

Tegmentum Control slow movements

Using immediate sensory feedback ~

Striatum

Parkinson’s Disease

1% of population Nigrostriatal pathway

Substantia nigra neurons die Progressive loss

Hypokinesia Rigidity Bradykinesia Akinesia ~

Motor Cortex

SubstantiaNigra

DA

+

Striatum

+

Parkinson’s Disease

Parkinson’s Disease: Treatment

Basal Ganglia - Cholinergic Substantia Nigra - Dopaminergic Drug Therapy

L-DOPA Pallidectomy Tissue transplants ~

Huntington’s Disease (Chorea)

Rare genetic disorder Single dominant gene on

chromosome 4 onset 30-40s

Symptoms Uncontrollable, jerky movements dementia Progressive ~

Huntington’s Disease (Chorea)

Degeneration of Striatum Caudate & Putamen GABA & ACh neurons

Loss of inhibition over-stimulation of motor cortex ~