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The Motor Cortex. April 24 th 2008 Bijan Pesaran. Multiple motor systems. Postural. Voluntary. Nature Reviews Neuroscience 5 , 532-546 (2004). Postural system is reflexive. Vestibulo-cervical reflex Stabilize head on body Vestibulo-spinal reflex Stabilize limbs on body

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the motor cortex

The Motor Cortex

April 24th 2008

Bijan Pesaran

multiple motor systems
Multiple motor systems

Postural

Voluntary

Nature Reviews Neuroscience5, 532-546 (2004)

postural system is reflexive
Postural system is reflexive
  • Vestibulo-cervical reflex
    • Stabilize head on body
  • Vestibulo-spinal reflex
    • Stabilize limbs on body
  • Cervico-cervical reflex
    • Stretch reflex also exists for trunk and limbs
  • Cervico-spinal reflex
    • Adjust limb extension based on head angle
movements have multiple representations
Movements have multiple representations

Nature Reviews Neuroscience5, 532-546 (2004)

issues in motor cortical function
Issues in motor cortical function
  • Dynamics or kinematics?
  • Intrinsic or extrinsic?
  • Force or position control?
activity follows instruction
Activity follows instruction

Tanji & Evarts, JNP 1976

activity depends on type of movement
Activity depends on type of movement

Tanji & Evarts, JNP 1976

muscles and movements kakei et al 1999
Muscles and movements (Kakei et al 1999)
  • Dissociate coordinate frames
    • Extrinsic: Direction of movement in space
    • Joint: Angle of wrist joint
    • Muscle: Activity of individual or groups of muscles
slide20
Muscle-like cell responses
    • Modulated by wrist
  • Extrinsic cell responses
    • Modulated by wrist or not
  • Muscle activity follows muscle-like cell responses
    • Modulated by wrist

Kakei et al (1999)

multiple reference frames

-

-

+

+

Multiple reference frames

Direct Transformation

Eye-centered

hand location

  • Direct visuomotor transformation
    • Supports Area 5 data (Buneo et al 2002)

Nonlinear

3D geometry and muscle dynamics

Eye-centered

target location

Hand-centered

target location

Motor output

Serial Transformation

Head-on-body

position

Body-centered

hand position

Eye-in-head

position

Head-centered

target location

Nonlinear

3D geometry and muscle dynamics

Eye-centered

target location

Body-centered

target location

Hand-centered

target location

Motor output

slide24

Encoding relative position

Nonlinear

3D geometry and muscle dynamics

T

Nonlinear muscle dynamics

T-H

T-E

H

H-E

E

E-H

  • Coordinating the hand and the eye
  • Eye-centered
  • Hand-centered
  • Relative hand-eye position
  • Vectors in abstract space

Batista et al 1999

MIP

PMd

PMv

Graziano et al 1997

slide25

M1, Premotor Cortex and

Supplementary Motor Area

The Monkey knows which to press because the

buttons are lit in order

slide26

Now examine same responses when

the monkey does it from memory

paralysis 2 28 million in u s
Paralysis: 2.28 million in U.S.
  • Stroke

75,000 per year (2000)

  • Cervical spine injuries

203,000-255,000 total (2002)

  • Multiple Sclerosis

250,000-350,000 total (2002)

  • ALS (Lou Gehrig’s Disease)

30,000 total (1999)

locked in patients
Locked in Patients
  • Constellation of:
  • quadriplegia
  • lower cranial nerve paralysis
  • mutism
  • preserved consciousness and
  • cortical function

Midbrain or pons injury due to:

  • stroke
  • trauma
  • tumors