Motor Behavior chapter 5

Motor Redundancy

-For any movement there are numerous ways the movement could be done 

Degrees of Freedom Problem

-A problem in selecting just one solution

Models

-Provide a general framework of the processes and physiological systems contributing to the formation and execution of motor acts

What two purposes do movement models serve?

-Provide conceptual framework to understand how movements are formulated and executed. Enables prediction of change following interventions.

-Provide a framework for practical use to devise more effective programs for rehab, practice, and training. 

Closed-loop models

-Explain movement as am outcome of feedback initiated reflex actions and prepatterned neural systems.

Hierarchical models

-Describes a systemic command structure from top to bottom 

• similar to open loop

Heterarchical models

-Describe a distributed and balanced command and execution system

• similar to closed loop

What is the simplest model of motor control?

-Reflex models

Reflex models

-Come together from chain and linking up of different reflex actions 

Hardwired neural circuits

-produced fixed movements 

Equilibrium point hypothesis

-Suggests the commands set stretch reflex thresholds

Uncontrolled manifold hypothesis

-Posits that the brain activates series of synergist muscle actions

Central pattern generators

-Built-in movements initiated by CNS or sensory systems.

-Run without complex commands or sensory input

-Listed as closed loop

Complex closed-loop models

-Involvement of higher brain centers but still rely on feedback loops

Synergies

-Ensembles or groupings of muscle and limbs that work together as a functional unit

Synergies involve?

-Inherent neural pathways, muscle and limb biomechanical properties, and learned behaviors

Synergistic actions reduce?

-Degrees of freedom and simplifies CNS planning

Coordinative structures

-Synergies among opposite limbs during bilateral movements 

Asymmetric movements assimilated

-The timing of one another such that each arm arrived at the target at the same time 

Movements are considered?

-Centrally programmed

The initiation of movement is purely

-Open loop because there has been no proceeding movements to produce feedback

Schema theory

-Posits a generalized motor program (GMP) and schemes 

GMP’s

-A general representation of various motor actions, or a class of actions 

Schemes

-Separate memory components in which movements are recognized and recalled 

• decision-making and learning processes for the GMP

Invariant characteristics

-Features of the GMP that do not change 

• relative force, relative timing, and sequencing

Parameters

-Features that change within the GMP

• overall force, overall duration, and specific muscles 

Blocked movement shows?

-Similar movement pattern as normal movement

Schema theory is criticized for?

-Implausibility of the brain being able to store so much information

-GMP’s do not explain how entirely new movements are created

-GMP’s rely on executive controller making never-ending rapid fire decisions

-The concepts of movement invariant charachteristics may not be so invariant

Internal model

-Emphasize that the brain sends commands to the PNS and itself through efference copy

All the models find consensus on what 3 points?

-The nervous system is most concerned with movement outcomes or effects than specific muscle actions

-The nervous system must take into account psychological, physiological, and biomechanical properties of the body, the movement goals, and the environmental context

-There exists board wired, preformed, and synergistic movements that form building blocks for more complex movements  

Constraint

-Barrier or restriction that must be used, avoided, or overcome for effective movement to take place

Task and environmental constraints are considered?

-External

Environmental constraints may be?

-Regulating, nonregulatory, physical, or sociocultural

Self-organizing properties

-Dynamic systems working as individual units and interacting with other systems

Attractor state

-Systems that tries to maintain a stable and patterned state of operation 

Control parameter

-Factors that when they change may cause a wholesale change throughout the entire system

What is an example of a control parameter?

-speed

Order parameter

-The rest of the system components that follow suit

Destabilize the system

-Promotes better functioning at a new stable state

Affordances

-Link what is perceived and what action may take place

• a process termed perception-action coupling