Reach and Grasp

Question 1

two basic questions in this lecture?

Answer 1

1. what computations must be performed during reach planning?
2. what computations change during learning?

Question 2

what computations are important for reach planning?

Answer 2

1. Retinal position of target
2. position of target in space (eye to head, head to torso, torso to object)
3. initial hand position (with respect to target)
4. motor command necessary to move hand to target

Question 3

what coordinate transformation underlie reaching?

Answer 3

visual coordinate > joint angle coordinate > hand position

Question 4

describe motor babbling

Answer 4

Babies wave seen hand more and resist a weight to SEE their hand move. Weight + prevent direct vision of either hand: babies will wave hand if they can see it on TV monitor. Observe sensory consequences of movement

Question 5

define reafference and give an example

Answer 5

definition: Sensory stimulation from self-produced movements

Crucial in development. Kitten in box does not develop important abilities (cliff avoiding, blinking at approaching object) b/c it does not observe the consequences of its own actions even though it gets the same visual input as the active kitten.

Question 6

describe basic prism google experiment

Answer 6

Ask person to reach for target. Put on prism goggles (shift view left/right), ask to reach again. Take off, ask to reach again. Big errors in reach as soon as you put goggles on and as soon as you take them off (after-effect). AFTER-EFFECT indicates there was a re-mapping in the brain due to the goggles.

Question 7

how to separate sensory (arm-independent) from motor (arm-specific) effects in prism goggle experiment? AKA where is the remapping being done?

Answer 7

1. intermanual transfer: transfer task to the other hand. If MOTOR aspect is being remapped in the brain, there will not be transfer (no after-effect). If SENSORY aspect is being remapped in the brain, there will be transfer (after-effect) with the opposite arm.
2. perception of “straight ahead” (not fully sure how this is done)

Question 8

how to figure out whether active or passive exposure matters in the prism goggle experiment

Answer 8

In the kitten experiment -
active vs. passive exposure?

visual feedback of arm:
seeing whole arm or just fingertip?
seeing arm for the whole reach or just at end?

visual feedback of error:
timing - immediate or delayed?

Question 9

how learning extends across time and different tasks?

Answer 9

“visual rotation” task:
consolidation/savings
interference
(need details)