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Motor Programs
Motor Programs notes
67
Anatomy
Graduate
10/01/2014

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Term
what is a closed loop system of motor control?
Definition
a system of motor control that requires feedback for accurate movement
Term
what is the path of the closed loop?
Definition
you have a reference for movement that is sent from the executive to the effector to create the movement. Feedback about the movement is sent back up to be compared to the reference
Term
is balancing on one foot an open or closed loop and why
Definition
closed loop because you use the feedback from your body to maintain your balance
Term
what does your feedback come from when standing on one foot
Definition
vision, proprioception, sensory receptors, vestibular system
Term
what are the open and closed loop parts of reaching out to grab a cup
Definition
you initially use open loop to reach. When you get close to the cup, you need vision and sensation to be sure you touch the cup and grasp it correctly
Term
is using a cursor on the computer open or closed loop?
Definition
closed: you use visual input to guide movement
Term
what is the path of the open loop?
Definition
executive issues commands, effectors produce movement
Term
is the open loop a feedforward or feedback system
Definition
feedforward
Term
is the closed loop a feedback or feedforward system
Definition
feedback
Term
do feedforward systems depend on sensory feedback for accuracy?
Definition
no
Term
can feedback be available to a feedforward system?
Definition
yes, it's just not used
Term
what are examples of feedforward systems
Definition
boxing jab, jumping off a box, baseball bat swing
Term
how is running a hybrid open/closed loop?
Definition
when you execute your program for running, it's open loop. If you intermittently sample the environment for visual, somatosensory = closed loop. If you start to fall, you will have reactions/reflexes enclosed loop to respond
Term
what is a motor program?
Definition
a stored set of commands that, when executed, produce movement that does not depend on feedback
Term
is a motor program open or closed loop?
Definition
open loop: feedforward. You just do it
Term
does a motor program require feedback
Definition
no
Term
describe the storage limitation for motor programs
Definition
you have an unlimited potential number of motor programs to store. Do we have enough capacity in the CNS for this many motor programs?
Term
describe the novelty limitation for motor programs
Definition
what about movement that you've never been exposed to? You don't already have a motor program for that?
Term
what is a general motor program?
Definition
a motor program for one type of movement that can be varied for different environments
Term
what are some features that make a generalized motor program clearly a part of a gmp?
Definition
order of events, timing, relative force
Term
what are parts of a GMP that can vary?
Definition
overall force, overall duration, muscles used
Term
if you write a sentence with your dominant hand, non-dominant hand, pen gripped with teeth, pen taped to foot, are you still using the same generalized motor program
Definition
yes: there are features that are the same for each task
Term
what does it mean that phasing is the same in a GMP
Definition
each muscle has the same proportion of movement to other muscles
Term
are running and walking the same motor program and why/why not?
Definition
no: they are different because your relative support pattern is different. The phasing is different
Term
what is an impulse
Definition
a force acting over time
Term
how do motor programs work according to the impulse timing theory?
Definition
the motor program tells the muscles when to come on, when to shut off, how many muscles to recruit, how much force to use
Term
what evidence do we have that motor programs work according to the impulse timing theory?
Definition
measurements of onset, duration, and magnitude of EMG activity during movement
Term
what is a central pattern generator
Definition
an isolated 2-3 segments of the spinal cord that can produce a rhythmical output in flexor/extensor nerves in a locomotor pattern
Term
is the CPG model a model of impulse timing
Definition
yes
Term
what is necessary for the system according to impulse timing
Definition
the system must know where the limb is at the start of movement and must specify appropriate durations and intensities of the muscular impulses
Term
in a force vs time graph, what is the area under the curve?
Definition
impulse
Term
how can you decrease impulse?
Definition
decrease force, decrease time
Term
what are degrees of freedom as applied to human movement?
Definition
independent states that have to be controlled at the same point during a motor at
Term
what is the degrees of freedom problem
Definition
humans have so many degrees of freedom that it would be impossible to control them all individually
Term
is movement optimal or just good enough
Definition
movement is just good enough. Habit is strong.
Term
does the brain maintain and use a currently accurate model of the musculoskeletal plant?
Definition
no. it tries to activate damaged muscles.
Term
Are motor programs computed by optimization or learned and recalled?
Definition
learned and recalled
Term
what is good about motor programs?
Definition
keeps the executive from having to worry about all of the degrees of freedom. Oversimplifies the many degrees of freedom.
Term
what are some innate motor programs
Definition
reflexes that we are born with: sucking, swallowing, grasp, stepping, breathing rooting
Term
how are innate motor programs activated?
Definition
by a stimulus or by central processing
Term
describe rapid movements as evidence for motor programs
Definition
some movements can be faster than the time to process information. Example = study in which people were told to start a motor program, then stop it. If told to stop too late, they can't stop because they've initiated their motor program
Term
why is "reaction time is longer when you're going to do a complex task" evidence for motor programs?
Definition
because the programming is more complicated, it takes longer to load the programming.
Term
how are blocked movements evidence for motor programs?
Definition
if you try to lift a lever that you've lifted before, you will recruit the same muscles at the same times to try to lift the lever even if the lever is blocked and won't move.
Term
how is deafferentation evidence for motor program?
Definition
can still perform the same tasks even without sensory information coming back
Term
how are anticipatory postural adjustments evidence of motor programs?
Definition
EMG shows that muscles are activated prior to movement because the motor program is pre-programmed
Term
what are some things that the motor program theory does not account for?
Definition
biomechanical properties of limbs, such as springiness in muscles; changes in mechanics such as if you change the starting position, environment effects, task characteristics and constraints
Term
are we as focused on reflexes with motor programming as we were initially
Definition
no
Term
what are the clinical implications of motor programming
Definition
we know that movement can occur without sensory feedback. We can focus on learning and creating new programs through practice, associations.
Term
what is the speed-accuracy relationship?
Definition
slower is more accurate
Term
what are the 2 phases of aiming movements?
Definition
initial open loop movement, final closed loop to use feedback to reach the target
Term
what is Fitts Law?
Definition
movement time is related to task (distance, target size, effector)
Term
what is fitts tapping task?
Definition
varied target width and distance between targets
Term
what is the mathematical relationship for fitts law
Definition
Movement time = a + b[log2(2A/W)]
Term
what is log2 (2A/W)
Definition
index of difficulty
Term
fitts law says that more processing takes more or less time for movement
Definition
more
Term
what determines the slope of the relationship in the fitts law graph?
Definition
effector
Term
what is on the y axis of the fitts law graph
Definition
movement time
Term
what is on the x axis of the fitts law graph
Definition
index of difficulty
Term
what are the units for the index of difficulty
Definition
bits/second
Term
what does the difficulty depend on?
Definition
the ratio of A:W
Term
what does A stand for?
Definition
amplitude
Term
what does w stand for?
Definition
width
Term
can fitts law be generalized to other situations?
Definition
yes
Term
describe the relationship between force and force variability
Definition
linear: the more force, the greater the variability of the force
Term
how does force variability explain fitts law
Definition
the more force we try to generate with our muscles, the more variable we are. As we move faster, there is more force and more force variability, hence more error.
Term
what are exceptions to speed-accuracy trade off?
Definition
faster movements can be more consistent and more accurate, BUT this is still different from the spatial accuracy tasks examined by fitts law
Term
why does moving slower make you more accurate?
Definition
you can use sensory feedback to improve spatial accuracy
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