JHU BME 580.422 Biological Systems II Adaptation of Visuomotor Maps Disorders of parietal cortex

1. JHU BME 580.422 Biological Systems II Adaptation of Visuomotor Maps Disorders of parietal cortex Reza Shadmehr

2. Schematic of the computations involved in reaching hand location in fixation coordinates Displacement vector in fixation coordinates Force (motor output) q xh q q Dq xa f xt Proprioceptive state of the body: arm, head, and eye positions Displacement vector in proprioceptive coordinates Target location in fixation coordinates

4. PPC neurons encode target of intended movement during the delay period PPC cell Somatosensory cortex cell A Control Task D Control Task 0.5 sec 0.5 sec B Delay Task E Delay Task C F Delay Task Delay Task Crammond and Kalaska 1989

5. PPC neurons encode target of intended movement even after it disappears Kalaska JF Can J Physiol Pharmacol 1996

6. Human PPC neurons code for target location in fixation centered coordinates Delayed pointing with intervening saccade Delayed pointing Right cortex Left cortex Activation area when the remembered target is to the right of fixation …left of fixation Medendorp et al. 2003

7. Opposing load No load Assisting load Deltoid muscle 500 ms Primary motor cortex cell 100 imp/s Posterior parietal cortex cell (area 5) PPC neurons encode target location and not the forces necessary to reach that target Kalaska et al. J Neurosci 1989 Kalaska JF (1988)

8. Newts show an inability to adapt to radical changes in the optics of vision Experiment: rotate each eye by 180o. After 4-5 months, no sign of adaptation. “When the piece of meat was moved back and forth in the water several centimeters above and a little to one side of the animals, they tilted their heads downward on that side and began to move toward the bottom of the aquarium. Even though the newts happened to be resting on the bottom when the lure was thus waved above them, they cocked their heads down under them and began pushing about among the pebbles of the bottom with the nose and forefeet. If the lure was placed below the animals, the head and forebody were tilted upward and the newts started toward the surface.”

9. Primates adapt to radical changes in optics of vision A Latency (s) Post- Pre- Days of reversing B C Day 3 Day 34

10. camera target xdv xt q2 xee q1 c2 c1

11. Wedge prisms: rapid adaptation and equally rapid de-adaptation indicates short-term changes in existing networks A B

12. With extensive training, throwing with wedge prisms can become a skill. This indicates formation of a new map for the prism and the ability to switch on context.

13. Patients with lesion in the right hemisphere may exhibit neglect of the left visual space Model Copy Marshall JC & Halligan PW (1995) Nature 373:521

14. Neglect of the extra-personal and personal space Test for neglect of extra-personal space: Line bisection test, figure copying, reading a sentence. Test for neglect of personal space: use a comb, use a razor to shave the face, use a lipstick. Neglect of extra-personal space: lesion of the right frontal lobe, ventral premotor cortex Neglect of personal space: lesion of the right inferior parietal cortex STG: superior temporal gyrus MFG: medial frontal gyrus WM: white mater SMG: supramarginal gyrus Committeri, G. et al. Brain 2007 130:431-441

15. Prism glasses produce after affects that improves the sense of “straight ahead” in neglect patients Rossetti Y. et al. (1998) Nature 395:166

16. Prism glasses produce after affects that reduce the neglect observed in PPC lesions Prisms Controls original pre- post- late Rossetti Y. et al. (1998) Nature 395:166

17. Apraxia Apraxia is an inability to perform skilled movements, particularly tool use, in the absence of elementary motor deficits (weakness, normal posture or tone). It is most commonly associated with damage to the parietal cortical areas of the left hemisphere. When the patient is asked to demonstrate use of a screwdriver, the patient may position his hand as if holding a pen. When given a partially driven nail into a piece of wood, and a collection of tools, they may select a scissor to drive the nail rather than a hammer. In performing a task that requires a sequence of actions, these patients may have difficulty in putting the acts in the proper order. For example, demonstrate how to prepare a letter and envelope for mailing.

18. Understanding actions of others: the mirror neuron system Social skills and theory of mind: the awareness that other people have beliefs and desires as we do, but different from our own, and that these beliefs and desires guides their actions. By observing their actions, we can guess their goals and intentions.

19. D Fogassi et al. (2005) Science 308:662-667.

20. Fogassi et al. (2005) Science 308:662-667.

21. Summary of the posterior parietal cortex Actions are planned in fixation centered coordinates: Position of the hand and the target are represented in terms of their location with respect to the fixation. Neurons combine proprioceptive information with visual information using a gain field. Movements are planned in terms of goals, not in terms of detailed forces. Lesion of the right parietal cortex can result in neglect. Lesion of the left parietal cortex can result in apraxia. Mirror neurons might provide a mechanism through which we understand the intention of others.