EXSS 380- Central Contributions to Motor Control (pt. 1)

what are open-loop processes?

movement “signals” structured in advance and executed without conideration of feedback

what does voluntary movement involve?

complex interactions in the musculoskeletal system

what are important questions we must ask of the CNS during voluntary movement?

• How does the CNS know when to do this?

• How does the CNS know how much force to produce in each muscle?

what is unlikely in regards to complex motor control?

the use of feedback loops

what is likely involved in complex motor control?

direct involvement of higher brain centers

what are the two forms of evidence for higher brain center involvement?

• Degrees of Freedom

• Agonist-Antagonist Timing

what is the Agonist-Antagonist timing problem?

it was originally thought that central delay was associated with perception of sensory info; however with more complex movement, sensory info cannot contribute within the movement interval

what is the degrees of freedom problem?

• there are too many parameters involved in limb movement

• a large percentage of ram is taken up to process incoming sensory info and produce appropriate response

• similar responses with deafferentation

explain similar responses with deafferentation

researchers found that even when participants were numbed up and not getting as much sensory info, they were able to perform similar levels of movement

what does feedback play a role in?

refinement and adjutment only

what theory does research suggest for central control of motor functioning?

existence of theoretical structures which organize degrees of freedom

what is a motor program?

a stereotyped sequence of commands sent from the CNS to the periphery

what does a motor program produce?

a specific behavior

what does a motor program predetermine?

joint kinematics and kinetics via specific muscle activation

what does a motor program specify?

degrees of freedom to act as single unit

what are examples of multiple motor programs?

• walking

• running

• throwing

• writing

what do motor programs tell our body?

tells muscle when to “turn on,” how much force to use, and when to “turn off”

what are motor programs controlled by?

higher brain structures

what do higher brain structures do for motor programs?

• selects appropriate motor program

• prepares selected motor program for activation

• selects appropriate muscles

• activates selected motor program

what is the evidence for motor programs?

• feedback processes too low to impact rapid movements

• complex movement possible with deafferentation

• voluntary movements are preprogrammed

explain the point of no return discovered by Henry and Harrison

evidence for motor program because many people cannot stop a movement once they have started completing that action

what are the two potential problems with motor programs?

• storage problem

• novelty problem

what is the storage problem?

• how many motor programs must an individual possess to function normally? i.e. do we have a different motor programs for the same action at different speeds, etc.

• do we have limited storage capacity for motor programs?

what is the novelty problem?

• how are we able to accurately perform a novel task? i.e. how are we able to perform new tasks, maybe not the best, but without having done them before

• no two motions are exactly the same (golf swing, jump shot)