Chapter 6- Central Contributions to Motor Control

Question 1

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open-loop control systems

Answer 1

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

Question 2

in open-loop control systems, is behavior sensitive to feedback?

Answer 2

NO
-no reference of correctness

Question 3

is there a feedback component in open-loop control systems

Answer 3

NO
-once you start doing these movements, it doesn’t matter if you are doing them well or not

Question 4

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difference between open- + closed-loop control system

Answer 4

no feedback in open-loop

Question 5

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steps for open-loop control system

Answer 5

(input) ->
executive ->
(instructions) ->
effector ->
(output)

Question 6

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response-chaining hypothesis

Answer 6

-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

Question 7

another name for response-chaining hypothesis

Answer 7

reflex-chaining hypothesis

Question 8

who created response (reflex)-chaining hypothesis

Answer 8

William James

Question 9

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deafferentation

Answer 9

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

Question 10

temporary deafferentation

Answer 10

-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

Question 11

permanent deafferentation

Answer 11

-dorsal rhizotomy
-sensory neuopathy
-joint replacements

Question 12

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dorsal rhizotomy

Answer 12

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

Question 13

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sensory neuropathy

Answer 13

complete/near-complete loss of sensory information due to regenerated afferent pathways
-can be caused by disease, due to issues with afferent pathways

Question 14

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joint replacements

Answer 14

removal of joint + joint capsule, providing no joint-receptor feedback

Question 15

how can loss of feedback/sensory information affect us

Answer 15

can have consequences to our capability to move normally

Question 16

do we always need feedback?

Answer 16

NO
-sometimes, when we are really good at a task, we don’t need feedback

Question 17

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internal model /motor program

Answer 17

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

Question 18

what does CNS use to control movement

Answer 18

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

Question 19

why do we get better at movement with practice

Answer 19

internal model

Question 21

Ian Waterman case study

Answer 21

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

Question 22

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central control mechanisms

Answer 22

explain how movements occur even in the absence of sensory feedback

Question 23

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spinal preparation

Answer 23

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

Question 24

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half-center model

Answer 24

suggests interneurons alternatives stimulate flexor + extensor motor neurons due to neural circuitry producing oscillations via central pattern generators

Question 25

who created half-center model

Answer 25

Graham Brown

Question 26

Graham Brown’s half-center model

Answer 26

-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

Question 27

what did Graham Brown’s half-center model suggest

Answer 27

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

Question 28

decerebrate

preparations

Answer 28

transection of brainstem b-b’

Question 29

spinalized

preparations

Answer 29

below the brainstem a-a’

Question 30

deafferented

preparations

Answer 30

transection of dorsal roots

Question 31

immobilized

preparations

Answer 31

fictive/imagined locomotion

Question 32

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central pattern generator

Answer 32

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

Question 34

video in class about CPG

Answer 34

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

Question 35

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where are CPGs located

Answer 35

within the spinal cord

Question 36

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describe how CPGs work

Answer 36

-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

Question 37

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what are CPG patterns controlled by

Answer 37

controlled by prewired pattern generators that can handle most details of actions in the control of gait + other

Question 38

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how are CPGs turned on/off

Answer 38

can be turned on by many sources of stimulation + continue until they are stopped by a source of input

Question 39

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is extensive modification to a basic pattern possible in CPGs

Answer 39

YES- either from higher or lower feedback centers

Question 40

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do CPGs need conscious awareness for human/animal to operate

Answer 40

NO
-this is why we walk without thinking about it

Question 41

Mike the chicken

Answer 41

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

Question 42

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generalized motor programs

Answer 42

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

Question 43

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what is required for generalized motor programs

Answer 43

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