MC Exam 2: Central Inputs to Motor Control Flashcards
What is closed loop control?
sensory information is used to control information, using constant feedback to meet a movement goal and minimize error
What is open loop control?
ballistic movements, pre-programmed, not sensitive to feedback
no time to modify movement
What is the reflex chaining hypothesis?
sensory information initiates a movement, one movement creates a trigger for the next movement
thought to explain order of skilled movements
What were early experiments to test reflex chain theory?
monkey deafferentation, patients with deafferentation (SCI, sensory neuropathy in diabetes)
What experiments were done to lead to central pattern generators?
mesencephalic or spinal preparations of cats
What are central pattern generators?
circuits remain intact below level of lesion, circuits need a stimulus to start rhythm but not to maintain it, self perpetuating
controls frequency and pattern but not force
What clinical application was a result of CPG?
body weight support treadmill training- concept to trigger CPG and rewire CNS
results still inconclusive
What is the reflex reversal phenomenon in locomotion?
a stimulus to the foot can cause 2 different patterns of action depending upon the phase of the stepping cycle if an obstacle is introduced
What are the two actions in reflex reversal?
- flexor withdrawal during swing
2. extensor pattern during stance
How does motor system know the timing of events in rapid movements?
by turning agonist and antagonist on/off with precise timing to control moments
What is the degrees of freedom problem?
there are too many joints and muscles to control at one time during a movement
therefore led to theory of motor programs
How can we test theory of motor programs?
by inhibiting actions
can you inhibit a well known action immediately? can you interrupt a motor program
What experiment was performed by Logan?
typing experiment, subjects would type 2-3 characters after the stop tone
indication that there is a highly developed motor program for typing “the”
What was Slater-Hammel experiment?
press button at the “8” like the arcade game (75% of trials)
found 166 ms point of no return
What action did Gray study?
baseball swing, “check swing”
found similar time for point of no return at 166 ms
What is the connection between sensory information and motor programs?
you need to know the position of your other muscles and joints prior to making your movement
EX: where are you starting, what choices/effector, how many ways can it be done
What arr errors in program selection?
- error in performers choice of action- soccer goalie diving wrong way
- error due to poor perception of environment led to poor choice
this requires performer to go back to response selection stage and make new choice. very time costly
What are errors in program execution?
- unexpected perterbations in the environment( misjudging weigh of milk carton)
- neural noise- mis calibrated sensory circuits, synaptic drift
need to make adjustments to current program, can be a more rapid connection
How is neural noise connected to performance?
neurons are constantly influx and always changing connections therefore athletes need to rehearse movements before and event to re calibrate connections
What is the hierarchical levels of control?
blending both open and closed loop controls
“a higher order, open loop control system has under it a set of closed loop processes that ensure the movements intended goal in face of perturbations”
What are two motor program limitations?
- storage- an issue of retaining learned information
2. novelty- an issue of making new movements (not every tennis stroke is same)
What are generalized motor programs?
has invariant spatial and temporal parameters (ex. handwriting with different parts of the body)
don’t need a specific program for every different task
What are invariant parameters of GMP?
what is constant?
- order of events
- relative timing
- relative force
What are controlled parameters of a GMP?
what can brain control?
- overall duration
- overall force
- muscle selection
