Motor Control IV Flashcards
prehension
-what is required to perform this?
know target location
reach
grasp
manipulation
prehension: reach
- what is it?
- how is it done?
- guided by…
transport hand to target so digits align with target
- produced primarily by proximal musculature
- guided extrinsically by target (distance, location)
prehension: grasp
- what is it?
- how is it done?
- guided by…
pre-shaped digits; opens them to match target size
- produced primarily by distal muscles of hand and fingers
- guided by intrinsic properties of target (size and shape)
manipulation
-what is it
carrying out target’s intended use
role of vision in prehension
vision is key for accurate prehensino
- determines environment regulatory conditions in which the action with occur: distance/location; size, orientation
- person needs to look directly at object for grasp = point of gaze
- enables corrections that occur just before grasp
- binocular vision aids grip size and force of grip
reach (at normal speed) is under _____ loop control
-why?
closed
-visual information (feedback) is used constantly during reach and grasp
Two-Stream Hypothesis
- composed of two…
- -what are they?
composed of 2 distinct visual systems
- ventral stream
- dorsal stream
ventral stream
- what part of brain?
- function
- vision for…
- described as the _____ pathway
visual cortex --> temporal lobe provides relevant information about physical properties of the object being reached for -shape, size, orientation vision for perception described as the "what" pathway
dorsal stream
- what part of brain
- function
- vision for…
- describes as the _____ pathway
visual cortex –> posterior parietal cortex
provides action-relevant information about all phases of reaching movement
vision for action
describes as the “where” and “how” pathway
perception vs. action
-size extimation vs. grasp of 2 circles with different external areas that make them appear to be different sizes
discs estimated to be different sizes
grip aperture equal
reach
-FMRI data suggests existence of…
-
a map related to movement planning in posterior parietal cortex (PPC)
reach FMRI data
-separate sensorimotor transformation areas for…
smooth pursuit eye movements
reach
grasp
reach: PPC
- involved in…
- output to…
involved in encoding goals for movement
output to premotor and primary motor cortex
what computation does the brain need to make for accurate reach?
coordinates of hand and object
-object coded relative to eyes (visual)
-hand coded relative to body (somatosensory)
timing of postural response (APA)
inertial properties of the limb
encode kinematics and kinetics of movement (permotor and primary MC)
-efference copy to cerebellum
first sign of voluntary reach and grasp is at what age?
around 4 months
postural support of reaching
- key brain structure
- requirements or _____ dependent
- -explain
key brain structure for learning of anticipatory postural adjustments during bimanual task is the cerebellum
task-dependent
-requirements in supported sitting are < standing and postural demands for stand and reaching are greater and require greater activation of LE and trunk musculature to prevent instability
-postural demands can affect speed and accuracy of UE
EMG during prehension (reach and grasp)
- order of muscle firing
- head moves _____% of way to target
neck muscles fire first (20-40 ms) before (due to increased inertia of head) eyes, and then arm (eyes can move alone if target is within central visual field)
- in a coordinated movement of eyes and arm - we look to the target that is selected to grasp
- typically, head moves 60-70% of the way to target
arm has _____ muscle program
-brief explanation
tri-phasic
-agonists-antagonists for breaking and then agonist
pointing vs. reaching to grasp
-control of UE movements
pointing
-segments controlled as a unit
reach to grasp
-hand controlled independently of arm, with arm carrying out transport; hand carries out grasp and manipulation
pointing vs. reaching to grasp
-velocity profile and movement duration
reaching movement duration > pointing movement duration
grasp an object; acceleration phase < deceleration
hit a target: acceleration phase > deceleration
reach transport phases
-what are the phases
acceleration and deceleration
perhension is different from pointing/aiming task because…
person intends to use the object to achieve some type of goal
reach has acceleration and deceleration phases
prehension: reach and grasp
- requires coordination of what components?
wrist/hand transport
grip aperture: pre-shaping and closure
hand orientation
grasping kinematics
- hand preshaped during…
- max grip aperture (distance between thumb and index finger tip) occurs within _____ of movement completion
- scaling of max grip aperture traces correlated to…
hand preshaped during movement to target (object)
max grip aperture occurs within 60-80% of movement completion
scaling of max grip aperture traces correlated to object size
factors that affect grip aperture size
faster reach-grasp movements –> larger maximum grip apertures
-grasp at normal speed vs. grasp “as fast as possible” without dropping the object
–376 ms for fast speed
–735 ms for normal speed
larger maximum apertures were observed for the faster movements
-reach-grasp movements that start with an open grip aperture show a tendency of the hand grip to partially close before achieving its maximum aperture
2 requirements for successful grasp
hand adapted to size, shape,a nd use of object (pre-shaping)
finger movements must be times appropriately for open/closure
2 primary grasp/grip patterns
power
precision
power grasp pattern
- explain
- types of grasps
finger and thumb pads directed toward palm to exert force on object types -hook -spherical -cylindrical
precision grasp pattern
- forces directed between…
- allows for _____ that power does not
forces directed between the thumb and fingers
allows movement of object relative to hand and with the hand (power does not)
precision grasp pattern
-types of grips
3-jaw chuck (tripod)
pinch (pad to pad, tip to tip)
lateral pinch
sensation and grasp
- what are of brain is responsible for cutaneous input?
- what would happen without this?
primary sensory cortex
without it –> uncoordinated grip and uncoordinated forces
with slippery objects, cutaneous receptors detect…
- as a result…
- what patients will have difficulty with this response
detect slip
-activate motor activity to increase grip force in finger muscles
patients with sensory neuropathy
control of hand posture relation to regulation of contact force
separate but not independent because hand must be shaped properly so the correct set of fingers makes contact with the object
fMRI study of brain regions demonstrate that ____ and _____ signal level of grip force prediction through _____
caudate and anterior putamen signal level of grip force prediction through
-cortex, ventral thalamus, cerebellum (efference copy/corollary discharge/reafference)
slippage
-_____ sensation
cutaneous sensation
evolution of normal and tangential forces with finger pad contact on glass
increased grip forces
“stick” decreases with increased tangential forces
adaptation of grip forces
- with age
- with loss of sensation
aging
-decreased manual dexterity with larger grip forces
loss of sensation
-larger grip forces, no matter the weight or texture of the material
application to prosthetic hand
a five-fingered prosthetic hand consisting of digits driven by DC motors
- force sensor resistors (FSR) placed at fingertip and potentiometers attached at proximal and middle joints
- information from FSR can detect level of normal force exerted and also slippage between fingers and object
development of prehension
-phases
phase 1
-infant reaches with one hand when they see an object
-once infant makes manual contact with object, vision facilitates hand closure (grasp)
phase 2
-infant uses 2 hands to acquire an object; child attempts different type of grasps
-role of vision in grasp to close hand decreases; switches to tactile stimulation
infants reaching for rattle in dark and light
-effect on prehension
prehension enhanced if infant views their own hands
prehension in infants (at 1 week)
-when does grasp formation develop
can reach for and intercept moving object, but hand is wide open - grasp formation which develops around 10-22 weeks
prehension at 4 months
prehension controlled proximally; poor contact with object
prehension at 5 months
prehension controlled distally; contact orients hand to object
prehension at 6 months
squeeze emerges (fingers close around object)
prehension at 9 months
prehension controlled by thumb and 1 finger (pincer grip); hand orients before contact
pre-shapes for object size
poor adjusting grip force
prehension at 13 months
fingers oppose action of thumb without hand being stabilized
prehension at 18 months
child can release the object
if object is scaled to hand size, grasp is similar to adult pattern as early as age…
6-7 years
age and prehension
-characteristics of young
infant can intercept moving objects; able to predict where an object will be which is anticipators
thumb opposition at 7 weeks
children open hands wider
children have increased variability
grip formation not mature until around 7 years
age and prehension
-characteristics of elderly
30% decrease in speed of reach
more time in target deceleration phase
accuracy is about the same for drawing tasks, just slower
20-40% increase in time to do fine manipulation skills by age 70
most decrements are reversible with practice
neural subsystems contributing to reach and grasp
- function of peripheral receptors
- visual input divided into…
tells you what’s happening around you, where you are in space, and where your joints are relative to each other
-visual input is divided into 2 parallel paths
neural subsystems contributing to reach and grasp: function of…
- higher cortical centers
- basal ganglia
- cerebellum
- descending paths
higher cortical centers make movement plan
basal ganglia plans forces to grasp
cerebellum refines movement
descending paths activate spinal cord neurons to muscles
prehension open loop control
- when is it used
- this control takes advantage of…
anticipate requirements of task and obstacles that might perturb arm trajectory and correct for effects of perturbation
anticipatory control takes advantage of previous experience to predict consequences - occurs before sensory receptors are stimulated and reduces reliance of feedback
prehension closed loop control
feedback from vision and proprioception needed at end of movement to ensure hitting target accurately
systems theory
-predicts…
predicts specific neural and musculoskeletal subsystems that contribute to control for reach, grasp and manipulation
patient application: reaching across body for object
- difficulty
- how might this effect your treatment plan
visual processing is more complex
-reaching a target on opposite side is slower and less accurate than movements to target on same side as arm
when you
when you examine a patient, consider where you have the target and for your intervention, you may want to begin ipsi reaching prior to progressing to contra reaching
