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Motor Cortex
1. Upper Motor neurons2. Primary Motor area (M1)3. Pre-motor area (PMA)4. Supplementary Motor area (SMA)5. Frontal eye field (area 8)
Cortical Motor System
Primary motor cortex
Execution of movement• Somatopically organized
• Massive descending projections to spinal
cord
• Damage => pronounced weakness in
affected body parts
• Stimulation => simple mov’t in small
muscle groups
Two major descending
pathwaysPyramidal vs. extrapyramidal
Striated muscles
Lower motor neurons
(brain stem and spinal cord)
Brain stem
centers
Motor cortex
Pyramidal
system Extrapyramidal
system
• Pathway for
voluntary movement
• Most fibers originate
in motor cortex (BA
4&6)
• Most fibers cross to
contralateral side at
the medula
• Pathways for postural
control/certain reflex
mov’t
• Originates in brainstem
• Fibers do not cross
• Cortex can influence
this system via inputs to
brain stem
Somatotopy in M1
Motor Cortex Homunculus
• Columnar organization:
• Thumb adduction ● Thumb abduction ■
* Mirror Neurons
Sensory Motor Cortex → Betz Neurons
Direct cortico-spinal synapse
Motor Cortex Symptoms
Upper Motor Neurons Diseases:
• ↑ Pyramid × contra-lateral paralysis
Hypertonocity, Spasticity
• Babinski Sign : Plantar reflex
• ↓ Pyramid × ipsi-lateral paralysis,
Knee jerk reflex absent, passive
movement, clonus (rythmic contraction
of flexor muscles)
• Corticobulbar lesion► contralateral
lower facial muscles paralysis
• Intensive physiotherapy
Frontal Eye Field
Voluntary Eye Movement
• Frontal eye field (caudal area 8)
• Stimulation FEF → eye conjugate deviation to opposite side
• (L) FEF → pontin reticular formation (R) → abducens (R. Lat.Rectus)
• R. abducens → L. oculomotor → (L. Med. Rectus)
Sensory Motor Cortex