Chapter 16 Flashcards
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 does feedback control involve?
information from sensory (visual or proprioceptors)
What does feedforward control involve?
takes advantage of prior experience to PREDICT consequences of sensory information
Steps in eye-head-trunk coordination in object location:
Eye movements alone needed if the target is in the central or near peripheral visual field;
Eye-head movements required if in the further periphery
Eye, head and trunk movements combined together, if in the far periphery
Objects in periphery”
- eyes first (low inertia)
- head
- hand
Movement to reaching and pointing an object:
acceleration is longer than deceleration phase
Movement to reaching and grasping an object
acceleration is shorter than deceleration phase
Visual systems contributing to grasp and reach:
dorsal stream pathway
ventral stream pathway
dorsal stream pathway:
from visual to parietal cortex; information about action and localization
ventral stream pathway
from visual to temporal lobe; information on conscious perception
Somatosensory contribution to position sense
Muscle spindle
Cutaneous afferents
Joint receptors: at the extremes of joint motion;
Somatosensory contribution to the control of grip force
Cutaneous afferents
What do cutaneous afferents do?
activate pathways to increase activity in finger muscles to increase grip force in shoulder and elbow muscles to slow acceleration of the hand
Visual and somatosensory inputs
Used to plan movement proactively;
Used reactively for error corrects during the execution of movement;
Midbrain (red nucleus) and brainstem (reticular nuclei) pathways
control the proximal muscles involved in reaching
Pyramidal pathways
fine motor control of grasping movements
Power grip:
finger and thumb directed toward palm to transmit a force to an object
Precision grip:
forces directed between thumb and finger
Types of Power grip
Cylindrical
Spherical
Hook
Lateral prehension
Types of precision grips:
pinch grips
What is power or precision grip determined by?
intrinsic or extrinsic factors
Intrinsic:
object size, shape, texture
Extrinsic:
orientation, distance and location
Phase 1 of grasp and lift:
contraction between fingers and object to be lifted
Phase 2 of grasp and lift:
grip force and load force starting to increase
Phase 3 of grasp and lift:
load force has to overcome weight of the object and start its move
Phase 4 of grasp and lift:
decrease in grip and load force
What is parameter of grip force determined by?
previous experience, perception of the characteristics of the object to be grasped using information from visual & somatosensory (cutaneous afferent)
Reaction time (RT)
the duration between the stimulus (auditory or visual cues) and the onset of voluntary movement
Reflex latency:
40 – 50 ms in response to somatosensory cues
RT:
80-120 ms;
Choice RT:
RT varies according to the amount of information to be processed,
increasingly slowed by adding choices
Fitts’ Law
describes relationship between movement time (speed), distance and accuracy
What does movement time increase with in Fitt?s Law?
the increase of movement distance
the increase of arm-movement precision
What is a critical aspect of manipulatory function?
locate a target
maintain gaze
What can a central lesion affect?
the processing of visual signals can cause target-location problems
Gaze stabilization problems can result from
Disruption of visually driven eye movements because of damage within the oculo-motor system
Disruption of vestibulo-ocular reflex control of eye movements in response to head movements
Inability to adapt the vestibulo-ocular reflex (VOR) to changes in task demands
What can a lesion on either side of posterior parietal area cause?
marked eye-hand coordination impairment or “optic ataxia
Loss of somatosensory information leads to
Impaired regulation of grip and lift forces
Problems in fine motor control of the hand
Regulation of forces in response to slips during object lift task and an ongoing grip
The majority of recovery of reach and grasp occurred during
first 90-days
Greatest proportion of inputs from the cortico-spinal tracts goes:
to the motor neuron pools of the distal upper segments
In CP, there is a lack of what?
LACK OF ANTICIPATION in hand grasp formation.
What is dependent on cutaneous input?
Forces for gripping (GF) and lifting (LF in graph)
tactile sensation
In what pathology is problems with adaption shown?
cerebellar
Motor Activity Log (MAL)
assess the amount and quality of hemiparetic arm use post-stroke and children with hemiplegic CP
Pediatric Evaluation of Disability Inventory
for children 6 months to 7.5 years of age; to assess the skills a child can perform independently or with assistance
School of Functional Assessment
for children in kindergarten to 6th grade pertinent to school-related functional tasks
Functional Independence Measure (FIM
used to measure basic ADL scales
WeeFIM
normative data for children 6 months to 7 years of age; evaluation on self-care, sphinctor control, transfer, locomotion and cognition
Wolf Motor Function Test
used to quantify single- or multiple-joint UE movement and functional tasks
Jebsen-Taylor Hand Function Test
designed to simulate to hand function common to ADL tasks
Advantages of Functional Performance-based Tests
quantification of functional performance and comparison with established norms
Limitations of Functional Performance-based Tests
Do not always examine the quality of movement used;
Do not provide insight into why patient is unable to perform a functional skills
Visual Regards
Eye-head Coordination
Target localization and Gaze stabilization
Reaching and Grasping behaviors may reveal underlying problems
planning and anticipatory control
The problems in patients with impaired reach are
(1) increased movement time and
(2) an inefficient hand trajectory
Dexterity
ability to manipulate various objects using different prehension patterns quickly and efficiently.
