Chapter 6- Central Contributions to Motor Control Flashcards
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open-loop control systems
you know the entirety of all movements you need to produce in advance
-instructions for a movement are structured in advance -> executive processing (brain) has a program/instructions to send to the effectors
-movements are executed without regard to the effects on the environment -> the effector carries out the program without possible modification
in open-loop control systems, is behavior sensitive to feedback?
NO
-no reference of correctness
is there a feedback component in open-loop control systems
NO
-once you start doing these movements, it doesn’t matter if you are doing them well or not
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difference between open- + closed-loop control system
no feedback in open-loop
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steps for open-loop control system
(input) ->
executive ->
(instructions) ->
effector ->
(output)
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response-chaining hypothesis
-assumes a movement begins with a muscular contraction caused by an external/internal signal -> this generates a sensory response-produced feedback
-feedback is just stimulus information, serving as a trigger for the next contraction in the chain (every time you complete a contraction, that completion itself is what triggers the next muscle contraction within the list of instructions)
-continued until all contractions in a sequence are completed
-response could be in same or different limbs
another name for response-chaining hypothesis
reflex-chaining hypothesis
who created response (reflex)-chaining hypothesis
William James
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deafferentation
method for interrupting the flow of sensory information to the spinal cord; involves the lack of afferent signals
-very common method for evaluating sensory information coming into system
-can be temporary or permanent
temporary deafferentation
-ex: local anesthetics injected at the dentist
-ex: blood pressure cuff- stops blood flow to a particular region so that it becomes numb + loss of sensation; once you release the cuff, regain sensation
permanent deafferentation
-dorsal rhizotomy
-sensory neuopathy
-joint replacements
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dorsal rhizotomy
removal/cutting of dorsal roots but leaves the efferent intact
-subject is still able to do motor movements but doesn’t have sensory coming upstream
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sensory neuropathy
complete/near-complete loss of sensory information due to regenerated afferent pathways
-can be caused by disease, due to issues with afferent pathways
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joint replacements
removal of joint + joint capsule, providing no joint-receptor feedback
how can loss of feedback/sensory information affect us
can have consequences to our capability to move normally
do we always need feedback?
NO
-sometimes, when we are really good at a task, we don’t need feedback
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internal model /motor program
a brain network that can adapt to practice + contain a skill representation
-basically, any time I do a movement I create a file + every time I do that movement AGAIN, I can pull out that file + reference it
-humans + animals have this
what does CNS use to control movement
internal model
-when I send instructions to muscles to do a movement, I also send copies of instructions to other parts of the brain -> the internal model will take that set of instructions sent to the brain to plan out trajectory
-this is why we get better at a movement with practice
why do we get better at movement with practice
internal model
Ian Waterman case study
19 year old male with flu-like virus which caused damage to dorsal nerves + therefore loss of proprioception
-he learned to move based on visual information to deliberately plan movements in response-chaining method
-he had to see his feet to walk- using this visual feedback even though he couldn’t sense things himself, he was able to control his locomotion
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central control mechanisms
explain how movements occur even in the absence of sensory feedback
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spinal preparation
spinal cord cut at a level below the brain so that supraspinal centers cannot influence lower ones
-stimulation shows efferent fiber activity, capable of producing a rhythmic output from motoneurons
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half-center model
suggests interneurons alternatives stimulate flexor + extensor motor neurons due to neural circuitry producing oscillations via central pattern generators
who created half-center model
Graham Brown
Graham Brown’s half-center model
-Graham Brown created the first demonstration of a half-center model- he recognized you can isolate different parts of motor control + study aspects of their nervous/muscular systems
-he was one of the first people to publish on spinal preparations- he demonstrated a spinal cord cut below the brain, where the brain was no longer able to communicate with the lower nervous system
-in studies like this, there was an external stimulation that occurs that triggers a set of information
-ex: you shock the nerve at the calf muscles to get a plantarflexion action
what did Graham Brown’s half-center model suggest
suggested there were interneurons (in spinal cord) that would stimulate the flexor/extensor muscles -> even in preparations that had no information from brain centers + no feedback from sensory neurons, there was still signaling to extensors/flexors that allowed for walking
decerebrate
preparations
transection of brainstem b-b’
spinalized
preparations
below the brainstem a-a’
deafferented
preparations
transection of dorsal roots
immobilized
preparations
fictive/imagined locomotion
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central pattern generator
a neural circuit can produce a rhythmic motor pattern without sensory feedback or descending control
-demonstrated in all animals for rhythmic movements that are essential for survival
video in class about CPG
cat doesn’t have signals coming from hindlimbs but is somehow able to respond to different speeds on treadmill- this demonstration shows there are CPGs
-we can move without feedback from the environment even with removed sensory feedback/descending control
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where are CPGs located
within the spinal cord
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describe how CPGs work
-center of control sends signals to spinal cord (where CPGs are) -> CPGs send signals to effectors which causes some output -> if system allows for feedback, then we can get feedback of different aspects
-if the feedback goes all the way to brain, it takes longer because we have to dissect that feedback
-if the feedback goes to spinal cord, we experience a reflex, which happens faster
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what are CPG patterns controlled by
controlled by prewired pattern generators that can handle most details of actions in the control of gait + other
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how are CPGs turned on/off
can be turned on by many sources of stimulation + continue until they are stopped by a source of input
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is extensive modification to a basic pattern possible in CPGs
YES- either from higher or lower feedback centers
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do CPGs need conscious awareness for human/animal to operate
NO
-this is why we walk without thinking about it
Mike the chicken
longest surviving chicken without a head; successful because he had all the aspects of the lower brainstem to allow for him to still breathe, consume, defecate, move, etc.
-this is all because of CPGS- don’t need supraspinal centers (above spine) descending signals to survive + move
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generalized motor programs
general, contain abstract information about the order of events, relative timing of events, + relative force of events
-motor program for a particular class of actions stored in memory; these are the files you have stored for things like muscle contractions you will experience, relative timing of different contractions, + how much force you must produce with each contractions
-ex: swinging a tennis racquet- a file can be pulled for any sport with this swinging motion
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what is required for generalized motor programs
certain parameters must be supplied to execute a program- details that apply to life
-the file/equation itself is fixed- swinging a racquet is fixed
-the inputs are modifiable- what type of racquet I am using
