Transcript Brain Mechanisms of Movement

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 ~

SMA
M1
S1
PM
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 (a) 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
Dorsolateral
tract
Ventral
Ventromedial
tract
Subcortical Motor Systems:
Cerebellum & Basal Ganglia
Caudate
Putamen
Cerebellum
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 joints

serial movement only
Dysmetric movements
 to wrong coordinates
 Alcohol intoxication
 depression of cerebellar circuits ~

Basal Ganglia

Caudate nucleus
Putamen
Globus Pallidus
Striatum
Substantia Nigra
 Tegmentum
 Control slow movements
 Using immediate sensory feedback ~

Parkinson’s Disease
1% of population
 Nigrostriatal pathway
 Substantia nigra neurons die
 Progressive loss
 Hypokinesia
 Rigidity
 Bradykinesia
 Akinesia ~

Parkinson’s Disease
Motor Cortex
+
Striatum
DA
+
Substantia
Nigra
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 ~
