Reaching and Grasp part 2

Question 1

Compared to reaching on the same side, reaching across midline is what?

Answer 1

slower and less accurate

Question 2

What happens to reaching when there is a loss of somatosensory input?

Answer 2

there are problems reaching immediately after loss of sensation

Question 3

When there is a loss of somatosensory input, what will occur over time with reaching?

Answer 3

gradually skills might return but only for simple reaching movements that are well learned
new or complex movements are impaired

Question 4

Is somatosensory input important for grip?

Answer 4

yes, it is essential

Question 5

What happens with grip when there is a loss of cutaneous sensation?

Answer 5

it prevents control of slip of objects

Question 6

What compensates when there is a loss of somatosensory input (loss of grip)?

Answer 6

There is typically an increase in force of muscles of grasp to compensate for the lack of “slip” information

Question 7

How long do people typically maintain the increased muscle force for compensation of grip?

Answer 7

It often decreased over a 20-30 second period

Question 8

Neurons in somatosensory cortex that are slow and fast adapting both respond to what?

Answer 8

slipping objects

Question 9

What corticies are involved in reaching and grasp?

Answer 9

posterior parietal cortex and premotor cortex

Question 10

Which cortex involves initiating the concept of reaching and grasp?

Answer 10

supplementary motor cortex

Question 11

What area provides the motivation to accomplish the act?

Answer 11

anterior cingulate gyrus

Question 12

What does the posterior parietal cortex do for grasp?

Answer 12

it provides numerous descriptions of objects for manipulation and multiple strategies to grasp objects

Question 13

What does the premotor cortex do for reaching and grasp?

Answer 13

it helps choose the best strategy for reaching and grasp

Question 14

How many motor pathways are involved in reaching and grasp? (child development evidence)

Answer 14

two

Question 15

in an infant, when does reaching occur?

Answer 15

1 week

Question 16

in an infant, when does grip appear?

Answer 16

after 10 weeks

Question 17

What neurons are active in precision grip and inactive in power grip?

Answer 17

Motor cortex (cortical) neurons

Question 18

What is the role of the cerebellum during reaching and grasp?

Answer 18

(more active during reaching and grasp rather than just gripping an object)
It also seems to play a role in anticipatory postural adjustments for reaching tasks (particularly untrained people)

Question 19

What requires more postural support than reaching when sitting?

Answer 19

reaching when standing

Question 20

How can postural demands effect reaching tasks?

Answer 20

it can effect the speed and accuracy

Question 21

What could decrease postural demands and make movements more accurate and faster?

Answer 21

if there is external support of the trunk

Question 22

What happens in the reaching hand as it is transported toward the object?

Answer 22

the hand opens up to maximum grasp size

Question 23

How much of the movement time does hand opening occur?

Answer 23

75-80% of movement time no matter how fast or slow the movement is

Question 24

After the hand opens up during transportation of the hand to the object, what happens?

Answer 24

The size of the grasp decreases to match object size

Question 25

What distance is the largest during the last phase of reaching and grasping? why?

Answer 25

thumb and index finger distance

to decrease the size at contact

Question 26

How does a perturbation of the reach affect grasp?

Answer 26

if reach (transport phase) is perturbed, grasp is affected with a brief interruption of the grip aperture formation

Question 27

What happens if grasp is perturbed ?

Answer 27

the transport phase will also be disrupted

Question 28

Are timing of the reach and the grasp correlated?

Answer 28

yes, there is a functional link of the timing of the two processes

Question 29

Since reaching and grasping are highly correlated, how could we plan therapy?

Answer 29

we could work on retraining each component separately and then both components need to be retrained together

Question 30

What are the two hypotheses in targeting distances?

Answer 30

Joint angle hypothesis

Distance point hypothesis

Question 31

What is the joint angle hypothesis?

Answer 31

select proper joint angle to reach the object

Question 32

what is the distance point hypothesis?

Answer 32

select a point in space to reach

Question 33

What two types of feedback are used in reaching tasks?

Answer 33

visual

proprioceptive

Question 34

What is visual feedback in reaching tasks?

Answer 34

point in space

Question 35

what is proprioceptive feedback in reaching tasks?

Answer 35

joint angle

Question 36

What is the distance programming theory?

Answer 36

• individual perceives a distance to target

- programs the activation of muscles at level & pattern to propel hand/arm that distance

Question 37

What is the location programming theory?

Answer 37

-nervous system programs the relative activation of antagonistic muscles to move limb to a certain position in 3D space

Question 38

Which movements are accomplished by the distance theory?

Answer 38

slow movements

Question 39

What movements are accomplished by the distance and location programming theory?

Answer 39

ballistic movements