Normal reach and grasp Flashcards
What does a target in our peripheral vision result in?
Neck muscles activated
Eye muscles activated
Eyes move first
Head moves: eyes reach target before head stops moving
What are the interactions between eye and hand movements when reaching?
Eye and head movements interact with and influence each other.
Proprioceptive signals from eye muscles contribute to the ability to localize targets in extra personal space
The visual system provides inputs to 2 parallel pathways for?
Perception and object recognition: visual cortex to temporal cortex
Localization: visual cortex to parietal lobe
What is role of cortex and cerebellum in reaching?
Higher centers in cortex make movement plan in relation to the movement goal.
Cerebellum receives and updates movement plan with sensory info
What two visual pathways are involved in reach and grasp?
Dorsal stream: visual to parietal, action-relevant info for reaching including object position, structure, orientation, mediates sensorimotor transformations
Ventral stream: visual to temporal, conscious visual perceptual experience, perceptual identification of objects
What are somatosensory contributions to reaching (vision, spindles, cutaneous receptors, etc)?
Somatosensory info not required for fast, simple or non-repetitive arm movement initiation or execution.
Incoordination wit complex tasks results when visual input removed.
Muscles spindles have an important role in position sense.
Cutaneous afferents also important for position sense
What are somatosensory contributions to grasping?
Cutaneous afferent input: essential for control of grip forces
Somatosensory cortex: critical for control of grasp
What are visual and somatosensory contributions to anticipatory control of reaching?
Proactive visual and somatosensory control to allow for the correct initial direction of the reach.
Update proprioceptive and visual body maps to allow reaching movement
What are motor components for reach and grasp?
Intact: primary motor cortex for precision grip, cerebellum for coordination of reach and grasp and anticipatory postural control, midbrain and brainstem for proximal muscles in reach
Appropriate muscle tone
Range of motion in hand, arm, and trunk
Muscle strength
Synergistic control of components of movement
What is classification of grasping patterns?
Power: finger and thumb pads direct force toward palm
Precision: finger and thumb direct forces to each other
What are two requirements for successful grasp?
Hand must be adapted to shape, size, and use of object
Finger movements must be timed in relation to transport
What is pregrasp hand shaping affected by?
Intrinsic properties of object (shape, size, texture): grip size changes primarily by movements of fingers, grip size is larger than width of target and scaled down just before contact with object
Extrinsic (contextual): objects location with respect to body
T/F: hand shaping begins during the transport phase of the reach and the grasp and reach are coupled?
True
What is bimanual reach skills?
When one hand performs a simple task and other performs complex task, the pattern of movement of the hand doing the simple task has some elements of the complex task.
This is more pronounced when the non dominant hand has to do the complex task
What were results of study looking at bilateral and unilateral exercise in control and hemiplegic populations?
Control unimanual: non dominant hand was slower than the dominant
Control bimanual: slower than either unimanual performance (dominant or non dominant), both reached target at same time
Hemiparesis unimanual: Impaired upper limb was slower than non impaired regardless of dominance
Hemiparesis bimanual: was slower than impaired unimanual,
