EXSS 380- Central Contributions to Motor Control (pt. 2)

what is a motor program responsible for?

a class of actions

what is specified to govern movement characteristics for a given trial/

parameters

discuss grasping as a generalized motor program

• when we know the object properties, we know the appropriate grip force and lifting force

• changes in the motor output occur with changes in the objects parameters, 2lbs. v. 25lbs.

define invariant features

what aspects of the movement pattern remain constant from trial to trial

define parameters

what aspects can vary while still allowing for the same overall pattern

what are the three invariant features we discussed?

• order of events

• relative force

• phasing

describe order of events

no matter what is influencing the movement, the muscles will fire/activate/deactivate in the same order

describe relative force

no matter what influences the movement, the ratio of muscle forces in comparison to one another will remain the same; i.e. if lifting a light then heavy weight, the ratio of bicep to tricep force will remain 2:1 despite the weight

describe phasing

relative temporal organization (proportional); i.e. no matter the speed of a motion the muscles will still fire at the same percentage of time; whether slowly walking or speed walking one muscle is still going to fire for 45% of the total time it takes

what are the three parameters we discussed?

• overall duration

• overall force

• muscle selection

describe overall duration

with invariant features held constant, a motor program can be performed quickly or slowly

what does faster movement do?

compresses movement time; each component compressed proportionally

describe overall force

proportional changes in muscle forces; throwing 2lbs. ball v. 5 lbs. ball

describe muscle selection

muscles used to perform a movement are not housed within the motor program; think about the handwriting example

describe the phonograph analogy

• a song can be recognized by its invariant features

• expression of invariant features may change based on the established parameters

what is the execution of motor programs integrated with?

sensory/afferent input

what functions within the other to monitor movement characteristics?

closed-loop processes function within open-loop circuits to monitor movement characteristics; back-up plan to ensure intended movement execution

what are the three sources of sensory info crucial to control voluntary movement?

• visual input

• somatosensory

• vestibular apparatus (postural control)

what happens prior to movement?

• determination of appropriate parameters

• sensory cues about the initial state of the motor system

• functional tuning

what are common sensory cues about the initial state of the motor system?

• location in space

  • what is the appropriate action

what is function tuning?

the appropriate overall force; think about force when working against gravity ot biarticulate muscle

what happens during movement?

• monitoring and adjustments (long duration)

• feedback not necessarily used unless errors occur (may lead to reflexive correction)

what happens following movement?

• assessment of previous movement

• was environmental goal achieved?

• appropriate force?

• leads to motor learning

summarize central control of motor learning

• voluntary movements controlled by motor programs

• motor programs can be generalized to fit a class of movements

• generalized motor programs display invariant features, the expressions of which are determined by parameters

• feedback is used

what is feedback used for?

• set motor program parameters prior to execution

• account of unanticipated perturbations

• augment parameteres for subsequent trials