12.4 Motor Program Theory

Motor Program Theory is a key concept in understanding how our brains control movement. It suggests that our nervous system stores pre-structured sets of commands for specific movements, allowing for quick and efficient execution of well-learned skills.

This theory fits into the broader landscape of Motor Control Theories by offering an explanation for how complex movements are planned and executed. It contrasts with other theories that emphasize real-time control or environmental influences on movement.

Motor programs: Definition and role

Concept and structure of motor programs

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• Motor programs are pre-structured sets of motor commands stored in the central nervous system that are used to execute specific movements or skills
• Motor programs contain the necessary information to carry out a movement, including:
  • Sequence of muscle contractions
  • Force of muscle contractions
  • Timing of muscle contractions
• Motor programs are thought to be retrieved and executed as a whole, allowing for efficient and consistent performance of well-learned skills (playing a musical instrument, typing)

Function of motor programs in motor control

• The role of motor programs is to reduce the computational load on the central nervous system during movement execution by relying on pre-planned motor commands
• Motor programs allow for rapid execution of complex skills without the need for real-time generation of motor commands
• By storing pre-structured motor commands, motor programs enable consistent and accurate performance of well-learned movements, even in the absence of sensory feedback

Motor program theory: Key characteristics

Abstract representation and generalization

• Motor programs are considered to be abstract representations of movements, meaning they do not specify the exact muscle forces or joint angles required for execution
• Motor programs are thought to be generalized, allowing for the same program to be used for similar movements with slight variations in parameters such as force or speed (throwing a ball at different distances)

Hierarchical organization and open-loop control

• Motor programs are believed to be stored in a hierarchical manner, with higher-level programs controlling the sequencing of lower-level programs responsible for specific movement components
• According to the motor program theory, motor programs are open-loop control systems, meaning they do not rely on sensory feedback during execution
• Once initiated, motor programs are thought to run to completion without being influenced by sensory input

Evidence for motor programs

Consistency and accuracy of well-learned skills

• Studies have shown that well-learned skills can be performed consistently and accurately, even in the absence of sensory feedback, suggesting the presence of pre-planned motor commands
• Patients with deafferentation (loss of sensory feedback) can still perform learned skills with relative accuracy, supporting the idea that motor programs can operate without relying on sensory input

Reaction time experiments and rapid execution

• Reaction time experiments have demonstrated that the time required to initiate a movement is shorter for well-learned skills compared to novel movements, indicating the existence of pre-structured motor programs
• The rapid execution of complex skills, such as playing a musical instrument or typing, suggests that the movements are controlled by pre-planned motor programs rather than being generated in real-time

Limitations of motor program theory

Explaining novel movement control and learning

• The motor program theory has been criticized for its inability to fully explain how novel movements are learned and controlled, as it focuses primarily on well-learned skills
• The theory does not provide a clear explanation for how motor programs are acquired, stored, and modified through learning and experience

Role of sensory feedback and context-specificity

• The theory does not adequately address the role of sensory feedback in movement control, as it assumes that motor programs operate in an open-loop manner
• The concept of generalized motor programs has been questioned, as some studies have shown that practice of a skill in one context may not always transfer to other similar contexts (practicing a tennis serve may not improve a volleyball serve)

Motor program theory vs other theories

Dynamical systems theory and schema theory

• The motor program theory differs from the dynamical systems theory, which emphasizes the role of self-organization and the interaction between the individual, the task, and the environment in movement control
• Unlike the motor program theory, the schema theory proposes that movements are controlled by generalized motor schemas that can be adapted to different contexts and modified through practice

Ecological approach and optimal control theory

• The ecological approach to motor control, in contrast to the motor program theory, emphasizes the importance of the perception-action coupling and the direct use of environmental information in guiding movements
• The optimal control theory, unlike the motor program theory, suggests that movements are controlled by optimizing a cost function that takes into account factors such as energy expenditure and movement accuracy