The Motor Cortex

1. The Motor Cortex April 24th 2008 Bijan Pesaran

2. Multiple motor systems Postural Voluntary Nature Reviews Neuroscience5, 532-546 (2004)

3. 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

4. Postural reflexes interact

6. Penfield’s Mapping Experiments

8. Motor cortex neurons show convergence and divergence

9. Movements have multiple representations Nature Reviews Neuroscience5, 532-546 (2004)

10. Issues in motor cortical function • Dynamics or kinematics? • Intrinsic or extrinsic? • Force or position control?

12. Activity follows instruction Tanji & Evarts, JNP 1976

13. Activity depends on type of movement Tanji & Evarts, JNP 1976

14. Activity is sustained during a delay

15. M1 reflects forces

16. Population code

17. 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

18. Kakei et al (1999)

19. Kakei et al (1999)

20. 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)

23. - - + + 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

24. 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

25. M1, Premotor Cortex and Supplementary Motor Area The Monkey knows which to press because the buttons are lit in order

26. Now examine same responses when the monkey does it from memory

27. 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)

28. 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

29. Taylor, Helms-Tillery and Schwartz Science (2002)

30. Taylor, Helms-Tillery and Schwartz Science (2002)

31. Taylor, Helms-Tillery and Schwartz Science (2002)