1. The Motor Cortex April 24 th 2008 Bijan Pesaran

2. Nature Reviews Neuroscience 5, 532-546 (2004) Multiple motor systems PosturalVoluntary

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. Nature Reviews Neuroscience 5, 532-546 (2004) Movements have multiple representations

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)

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

23. Multiple reference frames Direct visuomotor transformation –Supports Area 5 data (Buneo et al 2002) Direct Transformation Serial Transformation Head-on-body position Eye-in-head position Eye- centered target location Head- centered target location Body- centered target location Hand- centered target location Body-centered hand position + - Motor output Eye- centered target location Hand- centered target location Eye-centered hand location + - Nonlinear 3D geometry and muscle dynamics Motor output Nonlinear 3D geometry and muscle dynamics

24. MIP PMd Nonlinear muscle dynamics Encoding relative position Nonlinear 3D geometry and muscle dynamics Batista et al 1999 Graziano et al 1997 H T E T-E E-H H-E T-H PMv Coordinating the hand and the eye Eye-centered Hand-centered Relative hand- eye position Vectors in abstract space

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)