Please enable JavaScript.
Coggle requires JavaScript to display documents.
W3 Motor Control: Central Contributions - Coggle Diagram
W3 Motor Control: Central Contributions
4 Basic issues of motor control
Motor systems are immensely complex
neurons and muscle are stochastic (noisy), nonlinear
History and context matter
Environmental conditions are often unpredictable and dynamic
Theoretical divide
centralism
order imposed on periphery by CNS executive
a pre made command from CNS executed by muscles
Muscles , local reflex loop in the spinal cord
more to it than just reflexes
all or none of the script
: not Feedback : open loop control
address-specific control
: commands sent to specific muscles
commands: when to contract, how intently to contract and contraction duration
EX: clock study
inhibition of movement once a motor program began- all or none
if given enough time to stop. 50% chance of success
peripheralism
take basic reflexes and combine them in different ways
*Components
*: Reflex theory, S-R chaining (behaviorism and classical conditioning )
do a movement> generates sensory FB> seres as a stimulus to trigger another reflex arc
BUT this it shitty explanation bc how tf do ppl acquire novel behaviors
fundamental unit: reflex arch
Reflex chaining is how complex movements are computed
Why ppl are skeptical of this theory
didn't seem up to the task of describing complex, voluntary movements
no explanation of the deafferentation studies or results of studies on inhibition of movements
motor program: OPEN LOOP CTRL.
how long to contract
how forceful to contract
when to contract
execution error
right program but flawed execution
can correct during slower actions
selection error
picked the wrong program an involuntary responce
novelty problem
how can we make movements that we've never done before??
no 2 movements are identical
storage problem
vast majority of movements and variations. can we store it all. Is there room??
Generalized motor programs
MP are stored abstractly as a set of invariant features to which specific parameters are applies upon execution
i
nvariant features:
relative timing, relative force, order
Parameters
: overall force and duration, muscle selection
Purpose
: reduce storage demand bc this one program can be applied to most. also Solves novelty issue bc new parameters can be applied to a GMP to yield a new movement
relative timing is
preserves
when overall
duration and force
changes
Motor equivalence
: changes in muscle selection can show differences but preserve overall movement form
EX: diff. hand writings with limbs
:
Loop systems
Closed
sensory feedback
Open
Motor programs and GMP's are open
no FB needed
blocking, inhibition, deafferentation studies, rapid actions (too fast for feedback)
BUT many actions are under continual perceptual guidance (closed-loop)
Inverse model
in trajectory planning: decode a desired path into the set of muscles torques required to achieve it;
control
is open loop but
adjusted
by feed back
more current version of motor programing
Internal forward models
acts in the control of rapid movements by generating predictions about movement consequences to stand in place of (slow) feed back
Fitts law
logarithmic speed-accuracy trade off
MT depends on difficulty
trade off speed for accuracy to keep rate of info processing constant
due to bottlenecking in the CNS (limited resource)
more likely observed for CLOSED LOOP, continuous control involving corrective sub-movement
continuous, closer, correction
Schmidt's law
Linear speed-accuracy trade off
Task
: complete movement to target of fixed width located a different distances with a prescribed MT
Movement variability increases (linearly) as a function of both distance and speed
likely observed for pre-programed
OPEN LOOP
Ballistic, fast, not correction
CRITICUE OF INFORMATION PROCESSING APPROACH
j