Normal Control of Reach, Grasp and Manipulation Flashcards
What are 6 concepts related to reach and grasp?
- Movement control principles
- Locating a target
- Characteristics of reach and grasp
- Systems contributing to reach and grasp
- Grasping patterns
- Neural control of reach and grasp
What type of control mechanisms (1) contribute to the control of upper extremity movement? (for example catching a ball)
Both feedforward (anticipatory) and feedback
What does feedback control involve?
Input from sensory receptors (visual or somatosensory) being compared to a reference signal, representing a desired state of the system (e.g., a position of the arm)
What does feedforward or anticipatory control take advantage of?
prior experience to predict consequences of sensory information
Because of feedforward control there is ___ reliance on feedback control
less
When dropping a ball the initial input is ______ (using vision), while final input is _____ (using somatosensory inputs).
feedforward
feedback
In order to reach for an object successfully, what must wee do first?
locate the object in space (2)
Describe the sequence of events that occur when locating a target
1) Eye movements
2) Head movements
3) Trunk movements
When working with a patient having problems with functional grasp what may clinicians consider for treatment? Why?
Training the different control systems separately, as the patient’s problem may be related to the eye movements with little head movement, or eye-head movements for visual regards
What do kinematic studies show once an object appears in the peripheral visual field?
Eye movement begins first due to low inertia; then head movements and followed by hand movement
EMG studies indicate that muscle responses are activated _____ rather than sequentially.
synchronously
What are 2 ways in which eye and hand movements interact and influence each other?
- hand movement becomes more accurate when accompanied by eye movement
- there is an increase in gain during smooth pursuit if the hand is also following the target
When patients are asked to reach and grasp an object the movement duration is of the reach was much ______ than if the subject was asked to grasp the object
longer
When preparing to grasp an object, the acceleration phase of the reaching movement is much ______ than the deceleration phase.
shorter
When asked to point at an object, the acceleration phase of the reaching movement is much ______ than the deceleration phase.
longer
True or False
Reach and Grasp are controlled by different neural mechanisms.
True
In helping patients with problems related to reach and grasp, movements need to be practiced in a variety of task conditions. What are a few examples?
- reach and point
- reach and grasp
- reach, grasp and manipulate
What are 3 areas of the cerebral cortex are critical to the control of reach and grasp(4)?
- primary motor cortex
- premotor cortex
- areas of the posterior parietal lobe
What are the 2 pathways in which sensory inputs from the visual system go through during goal-directed reaching?
- dorsal stream pathway
- ventral stream pathway
What is the dorsal stream pathway related to?
Where the object is in extrapersonal space (localization) and the action systems involved in object manipulation
Therefore, the dorsal stream pathway is aka what?
localization and action pathway
The localization and action (dorsal stream) pathway transmits information from the visual cortex to the _____ cortex
parietal
What is the ventral stream pathway related to?
What is being reached for (perception and object recognition)
Therefore, the ventral stream pathway is aka what?
The perceptual pathway
The perceptual (ventral stream) pathway transmits information from the visual cortex to the _____ cortex
temporal
What are 3 somatosensory receptors that contribute to position sense?
- muscle spindles
- cutaneous afferents
- joint receptors (at the extremes of joint motion)
What is the major somatosensory input contribution to grasping?
control of grip forces
______ _____ receptors contribute to the control of grip force
cutaneous afferents
What are the 2 contributions that visual and somatosensory inputs (in combination) provide for reaching and grasping?
- Used to plan movement proactively
- Used reactively for error corrects during the execution of movement
What are the 2 separate descending pathways for reach and grasp?
- midbrain (red nucleus) and brainstem (reticular nuclei) pathways
- pyramidal pathways
What do the midbrain (red nucleus) and brainstem (reticular nuclei) pathways control?
the proximal muscles involved in reaching
What do the pyramidal pathways control?
fine motor control of grasping movements
Reaching also involves a complex interaction of what musculoskeletal and neural system components?
- Joint ROM
- Spinal flexibility
- Muscle strength, tone and coordination
- Biomechanical relationship among limb segments
- Postural support of reaching (task-dependent control)
What are the 2 classifications of grasping patterns (5)?
- Power or Precision grip
- Grasp and Lift task
What types of factors determine power or precision grip?
- intrinsic factors such as object size, shape, and texture
- extrinsic factors such as orientation, distance and location
What are 4 types of power grips?
- Cylindrical
- Spherical
- Hook
- Lateral prehension
A precision grip the forces are between what?
the thumb and fingers
What does a precision grip allow?
in-hand control
What are the parameters for grip force based on?
- previous experience
- perception of the characteristics of the object to be grasped (using information from visual & somatosensory)
Define reaction time
the duration between the stimulus and the onset of voluntary movement
Reaction time is ____ than reflex latency
longer
Reflex latency = approximately __ ms in response to somatosensory cues, whereas reaction time = __-__ ms
40
80-120
Reaction time varies according to what? What is this called?
the amount of information to be processed
choice RT
Choice reaction time is increasingly ____ by adding choices
slowed
What describes relationship between movement time, distance and accuracy?
Fitt’s Law
According to Fitt’s law, movement time _____ with the increase of movement distance
increases
According to Fitt’s law, movement time _____ with the increase of arm-movement precision
increases
What is the clinical implication of Fitt’s law?
It is an effective way to increase the level of difficulty of a task while objectively monitoring the patients’ progress
True or False
Reach and Grasp are two distinct components that appear to be controlled by different mechanisms.
True
Based on research concerning the control mechanisms of reach and grasp, what is the suggested intervention paradigm for a client with upper extremity paresis complicated by spasticity?
a. Train only reach and grasp together.
b. Begin by practicing the reach component without actually grasping/lifting an object.
c. Begin by practicing grasp of objects of varying sizes.
d. Train only the reach and lift components together.
B
