Reaching and Manipulation Flashcards
Whats the degree of freedom in the upper limb?
including shoulder and the trunk:
37
just the hand up to the wrist:
21 + 3 = 24
What are some of the variables that changes with time during reaching?
- grip size
- hand movement velocity
size of max grip is proportional to size of object.
fingers begin to stretch and grip size increase rapidly to maximum then reduced to match object size.
What is essential for successful grasping?
- hand must be adapted to correct shape, size, and use of object
- finger movements must be timed appropriorately so that they can close on the object.
How vision play a role in grasping?
- activate the proper schemas and specify the composition of the fingers for grasping.
- determine the relative positions of the hand and the object to the grasped, so that forces during the lift can be applied.
What is the neural control of reach and grasp?
using the visual pathways
- dorsal pathways (vision for action) - spatial location
- ventral pathways (vision for perception) - discrimination of visual shapes and object
posterior parietal cortex (PPC) involved in integrating info and plan action (shaping hand for grasp)
Which descending pathways are responsible for reach and grasp?
Reaching movement - midbrain & brainstem
Grasping - pyramidal pathways (corticospinal)
What is the role of cerebellum in reaching and grasping ?
controlling hand movement during grasping and regulating the amount of force required.
What happens if there is lesion in the posterior parietal cortex and anterior parietal lobe respectively?
PPC - difficulty in reaching in the correct/planned direction
APL - difficulty with in-hand manipulation skills.
What can lead to abnormal reaching and grasping movements?
- visual deficits and object localization (including neglect)
- problems with eye-hand-head coordination
- impairment of reach (poor coordination)
- problems with grasp
- apraxia
- compensatory trunk movements.
