Reach to Grasp Flashcards
(28 cards)
4 Key Elements for UE skill
- Locating the object
- Reaching (postural control + moving arm in space)
- Grasping (grip formation, stable grasp)
- Manipulation skills
Locating a target
- Eyes, Head and Trunk Movement
- Cenetral Eye = eye movement
- Peripheral Object Location
– Neck muscles activate, then eyes move first and focus before head stops - Amplitude of head movement
– Head will only turn 60-75% as an efficiency think, eyes will do the rest of the look.
– The bigger the accuracy requirement the more they will zone in on central vision.
How do we control the eye when locating a target?
- Maintain stable vision via corollary discharge (efference copy) to parietal areas
- Anticipatory signal is intended eye movement so vision remains stable as eye moves.
Send information to cerebellum for anticipatory control and feedback; same concept happens but with eye movement. Signal saying eyes will look right sends info to the parietal to help with stabilizing movement.
EX: Stroke in parietal; issues with stabilization to to issues with information processing.
Reaching and Grasping Curves
- Bell shape curver profile.
- Acceleration to deceleration phase.
- Prior experience and site is the preplanned phase and then the down slope is the adjustments to grab target.
- Deceleration plays a large role with reach to grasp.
Describe this in relation to reaching and grasping - motor processes
- Triphasic muscle burst for reaching (and other ballistic motions)
- Accel, decel, fine-tune (homing in)
- Acceleration is pre-planned based on experience
- Lower values are honing in on the target.
Pathway for grasp
Primary motor cortex to corticospinal tract―fine control of grasp
Pathway for reaching
Midbrain/brainstem pathway (rubrospinal tract) ―prime movers and postural control for reach
What do we need to consider with rehab and reach to grasp?
- Seperatr structures but processed in parallel and tightly coordinated
- Grasp formation must happen before reaching target.
- Ex: Cerebral A stroke lots of grasping issues, need to tie in both grasping and reaching into rehabilitation.
Reaching and grasping involves ____ joint coordination
Multi
Reaching and grasping - postural control
- Requires anticipatory postural adjustments for timing and adaptation
- Uses the cerebllum for this!
Other mechanics of the reach are considered in planning of movement - reach and grasp
- Distance to reach
- Weight to be lifted
- Inertial resistance provided by position and intrinsic stiffness of limb (think muscle tone)
- Think of functionality of movements (reaching straight arm vs bent arm)
Temporal coordination of arm and hand - reach and grasp
- Transport of hand must be coordinated with grasp (2 different pathways)
- Use vision to plane how wide to make hand.
- At 75-80% of reach, grasp is ready to go.
- Hand must be adapted to the shape, size and use of the object before making contact
Anticipatory control of Grasp
- Grip forms during transportation phase of reach
- Pre-grasp hand shaping is based on:
– Intrinsic properties of object (size, shape, texture)
– Extrinsic (contextual) properties of object (location, orientation, subsequent task)
Grasp Types - Power vs Precision Grips
- Power grasp=force directed from pads of fingers toward palm – transmit force
- Precision = forces directed from pad to pad – manipulate; Pad of finger to the thumb. Percision, most overlap of sensory information as possible.
Cerebellar contributions to grasp/manipulation
- Organizes predictive and adaptive responses via corollary discharge (efference copy)
Reaching and Grasping - Sensory Contributions
Vision:
* Important for final accuracy
* Needed for complex or repetitive movements
* Important for pre-programming based on experience
* Dorsal visual Stream primarily involved in grasp formation
* Premotor cortex has neurons that drive both eye movement as well as arm/neck movements
Somatosensory
* Muscle spindles are important for position sense – both arm and finger
What are the 4 phases of grasp/lift (manipulation)
- Finger contact (based on experience and vision)
- Generation of grip and load force
- Object movement
- Termination (decrease load and grip force)
Grip Force
- Horizontal
- Compressive
Load Force
- Vertical
- Sheer
Predictive control requires what 3 things?
Experience, cerbellum and vision
What is reactive control important for? What does this?
- Important for fine manipulation
- Cutaneous afferents (Temp, heaviness, etc) essential to position sense and to control grip force
Bimanual Coordination
focus on function and overflow concept; two hand coordination
Limb Specialization
limb is just better a certain things for things with trajectory in space and the other for stabilization. Ex: Go to write stabilize paper with left and writes with right.
Dynamic Dominance
Specialized limbs for trajectory and stabilization; body is efficient. We can use both hands.
