Control Systems: How Do We Control Movements? (Response Programming Stage)

Closed-Loop Control System Four Components Executive--For decision making and error correction Effector System--For carrying out decisions Feedback about error--Information about error that executive acts on Reference mechanism--Feedback is compared to this to define error

Closed-Loop Control Allows for error detection and correction Self-regulating--All components are contained within system Works well with slow movements Response Produced Feedback Information from a variety of sources about movement (from teacher, vision, proprioceptors)

Closed-Loop Control Examples Central heating or AC Traffic light that takes into account the traffic patterns

Closed-Loop Control Advantages Used for fine motor control Can be utilized to produce unpracticed movements Error determination Flexibility in movement Not dependent on advance information Used for fine motor control Threading a needle

Closed-Loop Control Disadvantages Execution of corrections is very attention demanding Movement to small target vs. a large target System is very slow Uses Information Processing stages (Need one RT) to correct 5 to 7 corrections per second

Open-Loop Control Two components Self-initiating Executive Effector Self-initiating Works well with rapid actions Planned in advance Not under conscious control Based on motor program idea

Motor Program Plan of action for movement Stored in long-term memory Details are determined by CNS and sent to muscles for action Practice leads to new programs More stable or precise Longer programs Analogous to a computer program

Open-Loop Control Examples Room Air Conditioner Traffic light that doesn't account for traffic flow

Open-Loop Control Advantages Disadvantages Can produce rapid movement when feedback is absent or disrupted Attention can be focused on other components of movement Disadvantages No ability to detect/correct errors Not effective in open skills

Hierarchical Control Combination of open and closed loop control Higher level is responsible for monitoring feedback Lower level is responsible for carrying out adjustments Control could be a result of practice or strategic decision

Errors in Movement Errors in Response Selection Made the wrong choice Need a new program for movement Requires 120-200 ms to initiate a movement correction Involve higher centers Requires attention

Errors in Movement Errors in Response Execution Made the correct choice, but performed movement wrong Doesn't require new program Only requires 30-80 ms to initiate a correction in the movement Mechanism for correction is reflexive closed-loop control Attention is not needed

Feedforward Control Advance information to prepare system FB prior to movement Example Postural Adjustments

Are these closed loop systems?

Factors Contributing to Motor Control Mechanical Factors Force resulting from a contraction is greatest when muscle is at optimal length Elastic properties of muscles Physical properties can enhance movement control Environmental properties Body's own properties

Factors Contributing to Control Neurological-Reflex Factors Reciprocal Inhibition Inhibition of flexors when extensors are stimulated Central pattern generators In animals, rhythmic activity in flexors/extensors for walking Synergies Functional linkage of muscle groups across joints

Factors Influencing Movement Production After-contraction Phenomenon Contraction temporarily biases later contractions Magnitude of contraction is related to magnitude of bias Tonic Neck Response When head is turned to one side, ipsilateral arm extends, contralateral arm flexes Hand grip measures

Theories of Motor Learning Adam's Closed-Loop Theory Utlilizes feedback (KR, vision, proprioception) Composed of two components Perceptual Trace--memory of past movement Memory Trace--selects and initiates response; Open-loop motor program

Adam's Closed-Loop Theory Problems with theory Slow & fast movements develop error detection differently Predicts that variability in practice is harmful to learning

Schmidt's Schema Theory (1975) Schema--rule or concept Theory has open-loop dependency; rapid actions Two states of memory Recall Memory Movement production MP structured in advance Recognition Memory Response evaluation

Schema Theory KR and sensory consequences are important Errors are not detrimental Variability in practice is beneficial for rule formation Novel movements are not a problem because of rule-based learning Error detection in fast actions