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PHTH 7303 Neuro > Exam 3 Week 12 ppt 12 and 13 Reach and Grasp > Flashcards

Exam 3 Week 12 ppt 12 and 13 Reach and Grasp Flashcards

1
Q

what are 2 types of grip?

A

~precision

~power

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2
Q

When do you use a precision grip?

A

when grabbing a pen or needle

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3
Q

what mediates a precision grip?

A

~primary motor cortex

~very specific activation of individual cortical motor neuron projections

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4
Q

when do you use a power grip?

A

holding a hammer or climbing a rope

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5
Q

what mediates a power grip?

A

both cortical motor and noncortical motor projections

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6
Q

Visuomotor transformations are mediated by

A

the PPC (posterior parietal cortex) and premotor cortex

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7
Q

vasomotor transformation areas- damaged

A

exhibit impaired preshaping of the hand during goal-directed grasping

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8
Q

What are some key elements to reach, grasp, and manipulate? (5)

A

~Locating the target; also called visual regard
~Coordination of eye and hand motions
~Reaching (Translocation of arm & hand in space and Postural support)
~Grasping including grip & release
~In hand manipulation of object

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9
Q

Feedforward control in reach and grasp (general)

A

anticipation of the requirements of the task

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10
Q

Feedback control in reach and grasp (general)

A

response to errors in performance of the task

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11
Q

Feedforward control in reach and grasp (detailed)

A

~necessary for the Anticipation of events & resultant actions based upon previous experiences
~new task, Visual information updates previous experiences
~Muscle activation preceding the event which decreases the reliance on only feedback control

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12
Q

Feedback control in reach and grasp (detailed)

A

~feedback mechanisms are used to react to the perturbation particularly if it deviates from the anticipated characteristics of the ball (weight, velocity, etc)
~Represented by the short latency (approx 50 msec) reflex response following impact

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13
Q

Eye-head coordination

A

~when object in peripheral sequence of events
~when vision of object needed, head moves 60-75% distance to target
~when greater accuracy needed full head and eye simultaneous movement to target
**3 distinct conditions

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14
Q

Details on eye-head coordination: peripheral vision sequence of events

A

~Eye movement – shortest latency & begins before head movement
~Head movement – EMG activation of neck musculature 20-40 msec BEFORE eye muscles but inertia of head > eyes so eyes move first
~Eyes focus on object before head stops moving – so eyes must maintain that position and focus as the head is still moving

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15
Q

Details on eye-head coordination: 3 distinct conditions

A

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

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16
Q

Details on control of reaching and grasping: Visual pathways and movement in the parietal cortex

A

~need to keep a Stable visual image with eye movement
~anticipates the amount of eye & head movement and update brain’s representation of the visual field based upon anticipated movement
~visual saccades “catches up” to the brain’s updated image
~can be seen with the Parietal neurons beginning to firing 80 msec prior to visual saccades
~Parietal neurons have corollary discharges to other brain regions such as the pre-motor cortex & frontal eye fields

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17
Q

Details on control of reaching and grasping: pre-motor cortex and frontal eye fields

A

~Neurons driving both saccadic movements & UE movements are both located adjacent to UE 1° motor cortex in the frontal eye fields and pre-motor cortex respectively

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18
Q

Details on control of reaching and grasping: eye-hand coordination

A

~Hand movements are more accurate when accompanied by eye movements
~Increased gain & decreased latency of visual pursuit movements when hand is following the target
~linkage between hand and eye movement are through afferent copy or corollary discharge rather than proprioceptive feedback because it is too fast to rely upon feedback
~Proprioceptive feedback does assist in accuracy of visual & manual pursuit

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19
Q

Kinematics of reach and grasp

A

~Arm and hand is controlled as unit when arm used to point to an object
~reaching to grasp: hand is controlled independently of rest of arm
~reaching alone as in pointing and reaching for grasp are two separate processes controlled by different sets of neurons
~Velocity profiles different depending upon task (Point & touch versus Grasp)
~grasp in different contexts

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20
Q

Velocity when reach and grasp: normal grasp

A

acceleration phase < duration than deceleration phase

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21
Q

Velocity when reach and grasp: point and hit

A

acceleration phase > duration than deceleration phase

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22
Q

kinematics of reach and grasp: in different contexts

A

Grasp & throw longer acceleration phase and shorter deceleration phase than grasp & fit object into box

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23
Q

implications for rehab for reaching and grasping

A

***Patients should do a variety of different reaching tasks:
~Reach & point
~Reach & grasp
~Reach, grasp & throw
~Reach, grasp & manipulate
~Reach, grasp & place in box or remove from box

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24
Q

Ebbinghus illusion

A

~the brain that cognates and recognizes sizes involves what is called the ventral visual stream where you cognitively recognize the relative size of objects
~pathway to the temporal lobe

(the ebbinghus illusion is illustrated by the red and blue dot diagrams. The red dot in the middle is actually the same size in both pictures, but when surrounded by many small blue dots it appears bigger than when surrounded by a few large blue dots.)

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25
Q

Visual feedback and reaching

A

~visual feedback- important kinematic effects on reaching
~Reaching with visual feedback showed longer duration but greater accuracy than without visual feedback
~Cortically blind individuals have visual behaviors showed significant correlation between pointing and target position mediated by superior colliculus

26
Q

visual feedback and grasp

A

~Visual Feedback’s role in grasp studies have shown that there is No difference in the kinematics of the grasp component with or without visual feedback
~vision is used to enhance grasp accuracy, the thumb position in relation to wrist is the key to visual feedback of grasp

27
Q

reaching across midline

A

Slower & less accurate than reaching on the same side

28
Q

Loss of somatosensory input & reaching

A

~Problems in reaching immediately after loss of sensation
~Gradually skills return but only for simple reaching movements that are well learning
~New or complex movements are impaired.

29
Q

Loss of somatosensory input & grasp

A

~essential for grip
~Loss of cutaneous sensation prevents control of slip of objects within grasp
~abnormal Increase in the force of muscles of grasp to compensate for lack of “slip” information
~elevated force of grip is often decreased over a 20-30 sec period & 7 of 10 subjects dropped objects at least once
~Neurons in somatosensory cortex that are both slowly adapting & fast adapting neurons which respond to slipping objects

30
Q

Neural Basis for reaching and grasping involves what 2 parts of the brain?

A

~PPC (posterior parietal cortex)

~PMA (premotor cortex)

31
Q

details on the neural basis for reaching and grasping: supplementary motor cortex

A

~the supplementary motor cortex initiates the concept of reaching and grasping

32
Q

details on the neural basis for reaching and grasping: anterior cingulate gyrus

A

~the anterior cingulate gyrus provides the motivation to accomplish the act

33
Q

details on the neural basis for reaching and grasping: posterior parietal cortex

A

~the posterior parietal cortex provides numerous descriptions of objects for manipulation & multiple strategies to grasp objects

34
Q

details on the neural basis for reaching and grasping: premotor cortex

A

~the premotor cortex chooses the best strategies for reaching & grasp

35
Q

are there 2 separate motor pathways for reaching and grasping?

A

YES

36
Q

when does reaching occurs in development?

A

1 week

37
Q

when does grasping occurs in development?

A

10 week

38
Q

Are the same motor cortex neurons active in precision grip and in power grip?

A

no the motor cortex neurons active in precision grip are inactive in power grips

39
Q

details on the neural basis for reaching and grasping: role of the cerebellum

A

~More active during reaching and grasp than just gripping an object
~Play a role in anticipatory postural adjustments for reaching tasks – particularly those for which the person had not been previously trained

40
Q

postural support and reaching tasks

A

~Task dependence with the interaction between postural support and reaching tasks.
~Reaching tasks when standing requires more postural support than when sitting
~Postural demands can effect speed & accuracy of reaching tasks
~External support of trunk decreasing postural demands movements are faster & more accurate

41
Q

reaching and grasping coordination

A

~In reaching as hand is transported toward the object the hand opens to maximum grasp size
~occurs at about 75-80% of movement time no matter how fast or slow the movement
~Size of the grasp then decreases to match object size
~Thumb & index finger distance is usually largest during this last phase of approach to decrease at contact

42
Q

Reach and grasp coordination- perturbed (reach)

A

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

43
Q

Reach and grasp coordination- perturbed (grasp)

A

~If grasp is perturbed, the transport phase is also disrupted

44
Q

Reach and grasp coordination- perturbed (functional link?)

A

~there is a strong Functional link of timing of two processes

45
Q

Reach and grasp coordination- perturbed (implications for rehab)

A

~implication In rehabilitation. The therapist can retrain each component separately & then both components need to be retrained together

46
Q

what are 2 hypotheses for reach and grasp for target distances?

A

~joint angle

~distance point

47
Q

joint angle hypothesis

A

select proper joint angle to reach the point

48
Q

distance point hypothesis

A

select point in space to reach

49
Q

what are two forms of feedback used in reaching tasks?

A

~proprioceptive

~visual

50
Q

proprioceptive feedback in reaching tasks

A

helps in joint angle

51
Q

visual feedback in reaching tasks

A

helps tell where you are in space

52
Q

2 theories for targeting

A

~distance programming theory
~location programming theory

**Both strategies are used dependent upon the task and context

53
Q

Distance programming theory

A

~Individual perceiving the distance to target

~Programs the activation of muscles at level & pattern to propel hand/arm that distance

54
Q

location programming theory

A

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

55
Q

slow movements= ____ theory

A

Slow movements are accomplished by distance strategy

56
Q

ballistic movement= ___ theory

A

Ballistic movements are accomplished by a combination of both distance & location strategies

57
Q

what is visual regard?

A

locating the target

58
Q

what does the ventral visual stream do in regard to reach and grasping?

A

It cognates and recognizes sizes

59
Q

what is the role of the ventral visual stream in reaching and grasping?

A

it cognates and recognizes sizes

60
Q

what is the role of the dorsal visual stream in reaching and grasping?

A

Grip size is controlled through the dorsal visual stream to the posterior parietal cortex

61
Q

what is the significance of the roles in reaching and grasp that the ventral visual stream and dorsal visual stream have?

A

You can be fooled by the ebbinghus illusion when the ventral visual stream cognates and recognizes size, but you will still properly position hand grip size because that is controlled by the dorsal visual stream

PHTH 7303 Neuro (89 decks)

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