Module 5 Flashcards
Generalized Motor Program
Theory that states movements can be varied along certain dimensions
Motor Programs
Pre-made set of movement commands that defines and shapes the movement
What are the two parts of an open loop control system?
Executive
Effector
What does the open loop control system not have?
Feedback or comparator mechanisms to determine system errors
Process of the open loop control system
Input
Executive
Effector
Output
How long is the open loop control system “over”?
Until the executive is activated again
What is the open loop control system not sensitive to?
Whether or not the output produced in the environment was effective in meeting the goal
Characteristics of open loop control system
Effective as long as things go as expected
Inflexible
In situations that do not have high demand in modifications
When are open loop control systems important?
In a predictable and stable environment
When does the feedback process dominate control?
In very slow movements
When do open loop portions dominate control?
Very fast and brief movements
What kind of motor behavior is typical in most tasks?
Complex blend of open and closed
Programmed Action
Appears to be organized in advance
Happens without much change from sensory feedback
Central Movement Organization
Movement details are determined by CNS and sent to muscles
Not controlled by peripheral processing
Does not involve feedback
Reaction Time Evidence for Motor Programs
Processing not natural
More info = slower RT
What does RT determine?
Slowness of the stimulation of S.I. and R.S
What happens when more limbs are included?
Reaction time increases
Why is RT sometimes longer?
More time is needed to organize the motor system before the initiation of an action
Startled Reactions
RT can be dramatically shortened under certain conditions
Movements are initiated much faster than can be accounted for by a voluntary response to a stimulus
How does one hasten the release of a startle response?
Speeding up the executive’s processing
Bypassing the executive altogether
Both
Deafferentation
Cutting an animal’s afferent nerve bundles where they enter the cord making the CNS unable to receive info from some portion of the periphery (no sensory)
What is not affected by deafferentation?
Motor pathways because they pass through the uncut ventral side of the cord
Example of deafferentation
Monkeys with cut nerve bundles are still able to physically move around (climb, chase, jump, groom), but cannot successfully complete fine motor control tasks
What happens if a movement is quick enough?
The motor program controls the entire action
What does deafferentation support?
The idea that movements can be organized centrally in motor programs
Why was the central pattern generator developed?
To explain certain features of locomotion in animals
Where is genetically defined central organization established?
Brainstem or spinal cord
What does the central pattern generator produce?
Commands to the musculature when initiated by a brief triggering stimulus from brain and they still occur if sensory nerves are cut
What does the central pattern generator involve?
More genetically-defined activities
What do motor programs involve?
Learned activities that are centrally controlled
Inhibiting Actions
Subjects are required to inhibit or stop a movement after having initiated the process of making the action
Point-of-no-return
At what point after starting the processing stages that lead to a movement is one committed to making the action?
What is a muscle response pattern of a normal movement?
Triple burst (agonist, antagonist, agonist) Typical of quick movements
What is a muscle response pattern of a blocked movement?
Even though the limb doesn’t move at all, it displays a similar pattern of muscular organization to the normal movement
Agonist/antagonist onset occurring at same time as normal movement
Movement activities are organized in ________ and run off __________ sensory information
Advance
Unmodified
What are the major roles of open-loop organizations? (4)
To issue commands to musculature
Organize the many degrees of freedom into a single unit
Postural adjustments
Modulate the many reflex pathways
What do commands to the musculature do?
Determines when, how forcefully, and how long muscles are to contract and which ones do
Anticipatory Adjustments
Motor system compensates before the movement through “knowing” what postural modifications will soon be needed
What is a major source of motor control?
Central organization of movements
Reflex-Reversal Phenomenon
Alterations in the reflex
Reversing its effect from extension to flexion
Challenges our usual conceptualizations of a reflex
Temporary Reflexes (definition)
They exist only in the context of performing a particular part of a particular action
Temporary Reflexes (laymen’s terms)
Ensuring the goal is achieved even if a disturbance is encountered
What is the critical goal for motor system?
Ensure that the intended action is generated
Why does open-loop occur?
To allow the motor system to organize an entire action without having to rely on the slow info processing from the closed loop system
Novelty Problem In Motor Program Theory
Failure to account for how novel movements are produced
System would need a separate program for every movement
Storage Problem In Motor Program Theory
Lack of efficiency that would be required to store the large number of motor programs that are required to move
Concerns how all separate programs could be stored in memory
Generalized Movement Programs
Consists of a stored pattern that is thought to be adjusted at the time of movement execution
What does the GMP allow?
The action to be changed slightly to meet the current environment demands
Invariant Features
What remains the same
Makes the pattern appear the same, time after time
Example of Invariant Features
The reason our unique writing styles appear
Surface Features
Things that change in a movement
Parameters
Type of surface feature
Is what gets modified
What do parameters determine?
How a movement is executed
What happens when a parameter is changed?
Does not alter the invariant features of GMP, but rather how the GMP is expressed at any given time
Parameterized
Initiated
Process of movements being produced
Determined in sensory identification stage
Movement chosen in response selection
GMP retrieved from long term memory
Motor program is prepared for being parameterized
When can the movement be initiated and carried out?
Once the parameters have been selected and assigned
Invariance
Constance value
What is the most important concern of a GMP?
Temporal structuring of the patterns (rhythm)
Relative Timing
Change time, but process stays the same
Set of ratios of the durations of several intervals within the movement
Independent of its overall speed/amplitude
Invariant features of a GMP (2)
Invariance
Relative timing
Parameters added to GMP (3)
Movement time
Movement amplitude
Effectors
Movement Time
When changed, the new movement preserves the important temporal-pattern features of the old movement
Movement Amplitude
Easy to increase by uniformly increasing the accelerations applied, while preserving their temporal patterning
Effectors
A given pattern can be produced even when different
Parameter that must be selected prior to action
Example of effectors keeping a pattern
Writing on a chalkboard vs in a notebook will have the same style but the way it got there was different
How does GMP provide a solution to the storage problem?
Only one program needs to be stored for each class of movement vs an infinite number
How does GMP provide a solution to the novelty problem?
Suggests the use of a schema
Theoretical structure responsible for supplying parameters needed at time of movement execution
Schema
Can be thought of as a mechanism responsible for selecting the parameters for the chosen GMP
What gets preplanned? (5)
Particular muscles Order in which muscles are involved Force of muscles Relative timing Duration of muscle contraction
Rhythm
Feature of many daily activities
When is relative timing invariant?
Actions are produced at different speeds or amplitudes
Degrees of Freedom
Controlled independently
Can be high or low
