W4b - Motor Programs Flashcards
What is the difference between open and closed loop control system?
Closed loop has an executive and an effector, but also feedback and comparator mechanisms for determining system errors. Open loop only has executive and an effector. Open loop deals with movements not under direct conscious control. These can be practiced and enhanced eg striking a baseball
What difference does it make to the open loop system, not having a feedback mechanism?
Modifications can’t be made once the action has started. The open loop system does not know whether the actions were successful eg traffic lights, microwave
How are motor tasks geneally controlled, open or closed loops?
Most are controlled by a blend of the two
Evidence for Motor Programs - Response Complexity Effects
The effect on RT of the nature of the to-be- performed movement provides evidence that at least some of the action is organized in advance, just as a motor program theory would expect. The more complex the task the longer the RT eg one handed piano chord shorter reaction time that two handed
Evidence for Motor Programs - Startled Reactions
A very interesting property of the startle response (RT) is that these movements are initiated much faster than can be accounted for by voluntary responses to a stimulus. The research is unclear at this point as to exactly why the same movement is initiated much faster on startled trials than on normal, unstartled trials, but the role of the motor program in carrying out the response is clearly implicated
Evidence for Motor Programs - deafferentation
involves cutting (via surgery one or more of) an animal’s afferent nerve bundles where they enter the cord, so the central nervous system no longer can receive information from some portion of the periphery. studies show that sensory information from the moving limb is certainly not absolutely critical for movement production, and it is clear that many movements can occur nearly normally without it. many theorists have argued that the movements must be organized centrally via motor programs and carried out in an open-loop way, not critically dependent on feedback (e.g., Keele, 1968)
Evidence for Motor Programs - Central pattern Generator
The concept of a central pattern generator is used to describe simple, genetically-defined activities such as walking, whereas motor program theory applies to learned skills such as riding a bicycle.
Evidence for Motor Programs - Action Inhibition
considerable evidence suggests that a motor program is released that is responsible for initiating the action in tasks like hitting a baseball and that serves to carry out the entire action unless a second stop-signal program is initiated in time to arrest its completion. The question often asked is when is the point of no return, at what point is the signal released to send the motor program to the muscles?
Evidence for Motor Programs - Motor Response Programs
moving a lever in the extension direction from one position to another). In the normal movement first there is a burst of the agonist (here, the triceps) muscle; then the triceps turns off and the antagonist muscle (the biceps) is activated to decelerate the limb; and finally the agonist comes on again near the end to stabilize the limb at the target area. on some trials the lever was blocked mechanically by the experimenter so that no movement was possible. the antagonist (biceps) muscle even contracted at all when the movement was blocked and that it contracted at the same time as in the normal movements
Provide an example of postural adjustments being made to support an upcoming action
you are standing with your arms at your sides and an experimenter gives you a command to raise an arm quickly to point straight ahead. What will be the first detectable EMG (muscular) activity associated with this movement? Most people would guess that the first contraction would be in the shoulder muscles that raise the arm. But, the first muscles to contract are in the lower back and legs, some 80 ms before the first muscle in that shoulder. Interestingly, these preparatory adjustments vanish when the performer leans against a support, because postural adjustments are not needed here.
understand limitations and problems in the simple motor program concept
Storage Problem - based on the motor program concept, all movements would require their own program, the storage of which is diffciult to reconcile. The Novelty Problem: How do performers produce truly novel behavior such as performing a variant of a tennis swing that you have never performed previously? The program for such an action cannot be represented in an already stored motor program. the British psychologist Sir Fredrick Bartlett (1932), in writing about tennis, said this: “When I make the stroke, I do not . . . produce something absolutely new, and I never repeat something old”
understand generalised motor programs and evidence for this expanded concept
the solution to the limitation of the simple motor program concept. It suggests that movement programs can be generalized (Schmidt, 1975). This generalized motor program (GMP) consists of a stored pattern which can be adjusted at the time of movement execution, allowing the action to be changed slightly to meet the current environmental demands.
generalized motor program (GMP) invariant features
Some features of the tennis stroke remain the same from shot to shot, and some features of the stroke are changed each time. According to GMP theory, what remains the same reflects the invariant features of a motor program—those features that make the pattern appear the same, time after time. the most important invariance concerns the temporal structuring of the pattern (or the pattern’s “rhythm” or relative timing). For example, if you compared the relative timing of two similar but different throwing movements, the ratio of the muscle contractions would be similar.
open-loop control parameterized
As determined via sensory information processed in the stimulus identification stage, a GMP for, say, throwing (as opposed to kicking) is chosen during the response selection stage. This GMP is then retrieved from long-term memory, much the same way that you retrieve your friend’s telephone number from memory. During the movement programming stage, the motor program is prepared for initiation, or parameterized, based on the environmental info just b4 action.
parameters
If the pattern represents the invariant features of a movement, then modifying what are called parameters determines how it is executed. They do not change the form of the movement just how its executed. They include movement time (speeding up and slowing down a given movement), movement amplitude (size of the movement), limb and effector system (hand, mouth, foot (able was I ere I saw Elba). For example a steroe system - change record speed, change volume, change which speakers are used.
