Reaching Grasp 1

Question 1

What are the two types of grasps?

Answer 1

Precision grip

Power grip

Question 2

What is an example of a precision grip?

Answer 2

grasping a pen or needle

Question 3

What is the precision grip mediated by?

Answer 3

primary motor cortex

Question 4

What specifically activates with a precision grip?

Answer 4

individual cortical motor neuron projections

Question 5

What is an example of a power grip?

Answer 5

when holding a hammer or climbing a rope

Question 6

What is the power grip mediated by?

Answer 6

both cortical and non cortical motor projections

Question 7

What are visuomotor transformations mediated by?

Answer 7

PPC and premotor cortex

Question 8

What happens when there is damage to the PPC and premotor cortex?

Answer 8

impaired preshaping of the hand during goal directed grasping

Question 9

What are some key elements to reach, grasp, and manipulate tasks?

Answer 9

• locating target (visual regard)
• coordination of eye and hand
• reaching (translocation of arm and hand AND postural support)
• grasping including grip and release
• in hand manipulation of object

Question 10

What is feedforward?

Answer 10

anticipation of the requirements of the task and resultant actions based upon previous experiences

Question 11

What is feedback control?

Answer 11

need for response to errors in performance of the task

Question 12

For feedforward, what happens with a new task?

Answer 12

visual information updates previous experiences

Question 13

What happens after the visual information is updated during feedforward?

Answer 13

muscle activation

Question 14

Once the task is complete, what happens to react to the perturbation?

Answer 14

feedback mechanisms

Question 15

What is feedback control represented by?

Answer 15

the short latency reflex response following impact

Question 16

What is the first step in reaching and grasping?

Answer 16

target location (head eye location)

Question 17

When there is an object in peripheral vision sequence of events during reaching and grasping, what happens?

Answer 17

eye movement (shortest latency)
head movement (EMG activity in neck is before eyes but inertia of head is large so our eyes move first)
-eyes focus on object before head stops moving

Question 18

When there is vision of the object needed, which moves more the head or eyes?

Answer 18

head moved 60-75% distance and eyes completed motion

Question 19

When do you use full head and eye simultaneous movement?

Answer 19

when greater accuracy is needed

Question 20

What are the 3 distinct conditions in the target location?

Answer 20

eye movement alone
control of eye movement and head movement
locate in far periphery, eye, head and trunk movement together

Question 21

What does the parietal cortex do to your eyes and head when reaching and grasping?

Answer 21

it anticipates the amount of eye and head movement that is needed and updates the brain’s representation of the visual field based upon the anticipated movement

Question 22

How do we know that through visual saccades, the eyes catch up to the brain’s updated image?

Answer 22

because parietal neurons begin to fire 80 msec prior to the visual saccade

Question 23

How does the parietal neurons communicate with the premotor cortex and the frontal eye fields?

Answer 23

through corollary discharges

Question 24

Where are neurons that drive saccadic movements and UE movement located?

Answer 24

adjacent to the UE primary motor cortex in the frontal eye fields (saccadic movements) and the pre motor cortex (UE movement)

Question 25

Hand eye coordination: Hand movements are more accurate when accompanied by?

Answer 25

eye movements

Question 26

There is an _____ gain and _____ latency of visual pursuit movements when the hand is following the target.

Answer 26

increased gain and decreased visual pursuit

Question 27

The link between hand and eye movement is not through proprioceptive feedback (movement is too fast to rely on feedback), so what is the linkage between?

Answer 27

afferent copy or corollary discharge

Question 28

With hand eye coordination, what does proprioceptive feedback assist in?

Answer 28

accuracy of visual and manual pursuit

Question 29

When used to point at an object, the arm and hand is controlled as what?

Answer 29

a unit

Question 30

when reaching to grasp, the hand and arm are controlled how?

Answer 30

hand is controlled independently of the rest of the arm

Question 31

What are the details of velocity with grasp?

Answer 31

acceleration phase < deceleration phase

Question 32

What are the details of velocity with point and hit object?

Answer 32

acceleration phase > deceleration phase

Question 33

velocity of grasp and throw

Answer 33

longer acceleration phase

Question 34

velocity of grasp and fit object into box

Answer 34

shorter acceleration phase than grasp and throw

Question 35

What are the different tasks that a patient should be able to do?

Answer 35

``` reach and point reach and grasp reach, grasp, and throw reach, grasp, and manipulate reach, grasp, and place in box or remove from box ```

Question 36

What is the illusion called when there is a small object surrounded by larger object and the same small object surrounded by another small object would look bigger?

Answer 36

Ebbinghaus illusion

Question 37

What two visual pathways does the Ebbinghaus illusion separate well?

Answer 37

dorsal and ventral visual streams

Question 38

what is the ventral visual stream?

Answer 38

site where you cognitively recognize the relative size of objects

Question 39

Where is the ventral visual stream going?

Answer 39

it is a pathway to the temporal lobe

Question 40

What does the dorsal visual stream control?

Answer 40

grip size. positioning hands properly to pick up an object

Question 41

Where is the dorsal visual stream going?

Answer 41

to the posterior parietal cortex

Question 42

Duration of reaching with visual feedback?

Answer 42

longer duration but greater accuracy

Question 43

What helps mediate cortically blind but visual behaviors when talking about pointing and target position?

Answer 43

superior colliculus

Question 44

What role does visual feedback have on grasp?

Answer 44

no difference in the kinematics of grasp with or without feedback

Question 45

What can be noted when using visual feedback when grasping?

Answer 45

the thumb position in relation to the wrist is the key