Motor Programs and Sensorimotor Learning: Principles, Theories, and Practice

Motor Programs and Sensorimotor Learning

Introduction

This unit explores the psychological and neuroscientific principles underlying motor control and learning. It covers foundational theories, the problem of degrees of freedom, schema theory, hierarchical learning, stages of motor learning, and the roles of practice and feedback in skill acquisition.

Bernstein and the Degrees of Freedom Issue

Definition and Importance

• Degrees of Freedom (DoFs): Components of a control system (e.g., muscles, joints) that can vary independently and are coordinated to produce effective action.

• Primary Issue in Motor Control: The human body has many muscles, joints, and directions in which joints can move, resulting in many DoFs.

• Example: Touching your nose with your finger can be achieved through many possible limb configurations, illustrating the complexity of DoF management.

Redundancy of DoFs

• Problem: How do we select and coordinate DoFs to produce smooth, reproducible, and quick actions?

• Flexibility vs. Control: While redundancy allows flexibility and adaptability, it also makes movement control a challenge.

Research Solutions

• Minimization Principles: The nervous system may minimize energy expenditure or jerkiness in movement.

• Muscle Synergies: Groups of co-activated muscles are controlled as a unit by a single neural command, simplifying control.

• Use of Physics: Exploiting muscle properties (e.g., gravity, elasticity) to aid movement.

Motor Control Models

Inverse Model

• Definition: Calculates necessary feedforward motor commands from desired motor output information, using an internal model of the musculoskeletal system.

• Application: Allows the nervous system to plan and execute complex movements efficiently.

Forming Motor Memories (Sensorimotor Learning)

Definition and Characteristics

• Sensorimotor Learning: Improvement of motor skills through practice, leading to long-lasting neuronal changes.

• Practice: Requires multiple repetitions under varied conditions.

• Performance: Involves decreased time and variability in task execution.

• Assessment: Learning is inferred from performance curves, retention tests, and transfer tests.

Schema Theory

Generalized Motor Programs

• Schema: During skill acquisition, a generalized program (schema) is formed that can be adapted to different effectors (e.g., writing with right hand, left hand, teeth, or foot).

• Flexibility: Allows for variability and novelty in movement, as parameters of the plan can be modified.

• Transfer: Variable practice leads to better transfer to new but related tasks.

Hierarchical Learning

Mechanism for Schema Generation

• Motor Programs: Movements are coded in motor programs stored in long-term memory (LTM).

• Levels of Control: Distinct hierarchical levels allow for rule-based, flexible behavior.

• Chunking: Information is stored efficiently in chunks; a motor program is an example of chunking.

• Example: Playing piano involves hierarchical organization from the overall goal to finger timing.

Chunking and Memory

Chunking Exercise

• Chunking: Grouping information into meaningful units (e.g., FBI, CIA, KGB, UPS) facilitates memory by connecting with existing chunks in LTM.

Stages of Motor Learning

Fitts' 3-Stage Theory

• Cognitive Stage: Learning basic procedures; high cognitive activity and large improvements.

• Associative Stage: Transition from conscious to automatic control; performance becomes more consistent.

• Autonomous Stage: Little conscious involvement; performance is efficient and automatic.

Bernstein's Stages

• Novice: Observes DoF to be controlled; not energy efficient; not flexible/adaptable.

• Advanced: Begins to release DoF; joints can be controlled independently; coordination improves.

• Expert: All DoF are released; most efficient and coordinated; exploitation of passive forces.

Fitts & Posner	Bernstein
Cognitive: Understand task, develop strategies, high cognitive activity, large improvements	Novice: Observe DoF, not energy efficient, not flexible/adaptable
Associative: Refine strategies, less cognitive activity, improvements slower	Advanced: Begin to release DoF, joints controlled independently, improved coordination
Autonomous: All DoF released, focus on other aspects, secondary tasks	Expert: All DoF released, most efficient, exploitation of passive forces

Additional info: Both models recognize that learning is not strictly linear; learners may move forward and backward between stages.

Motor Learning Paradigm

• Acquisition: Performing and practicing the motor skill.

• Retention: Persistence of performance; demonstrates true learning.

• Transfer: Performance gain in one task due to practice on another; tests generalizability.

Motor Learning Curves

• Performance Measurement: Y-axis = movement error, speed, or accuracy; X-axis = practice trial.

• Learning Curve: Improved performance (reduced error) over repeated trials.

Stages of Motor Learning: Acquisition, Consolidation, Retention

• Acquisition: Performance improves with practice.

• Consolidation: Not all learning is concurrent with practice; some gains require time to become effective (e.g., 6-hour window after practice).

• Retention: Gains in performance are maintained over time.

Linking Fitts' Stages to Procedural Learning

• Procedural Learning: Involves changes in brain activity and neuroplasticity, with new connections forming between brain regions after initial learning.

Practice Conditions

• Transfer: The amount of transfer from practice to performance depends on the similarity between practice and performance conditions.

• Best Transfer: Achieved when practice closely resembles the performance environment and task.

Constant vs Variable Practice

• Constant Practice: Practicing only a single variation of a task.

• Variable Practice: Practicing many variations of a class of actions; enhances schema development and future novel task performance.

Random vs Blocked Practice

• Blocked Practice: Practicing many trials of a single task consecutively; low contextual interference.

• Random Practice: Mixing practice trials of several tasks; high contextual interference, leading to better learning and stronger memory representations.

Feedback in Motor Learning

Types of Feedback

• Inherent (Intrinsic) Feedback: Information naturally available from performing an action.

• Augmented (Extrinsic) Feedback: Information provided by an external source about performance outcome.

Types of Augmented Feedback

• Knowledge of Performance (KP): Information about the movement pattern and quality of action (kinematic feedback).

• Knowledge of Results (KR): Information about the success of an action with respect to the goal.

• Feedback Schedules:

  • Average Feedback: Given after several trials.

  • Faded Feedback: High rate initially, then reduced.

  • Bandwidth Feedback: Given only when performance is outside acceptable limits.

Frequency of Feedback

• Less is More: Too much feedback creates dependency; learners may not develop intrinsic feedback use.

• Complexity Caveat: More complex tasks may require more feedback.

Summary Table: Practice and Feedback Types

Practice Type	Description	Effect on Learning
Constant	Single variation of a task	Develops specific skill, less transfer
Variable	Multiple variations of a task	Enhances schema, better transfer
Blocked	Consecutive practice of one task	Low contextual interference, weaker retention
Random	Mixed practice of several tasks	High contextual interference, stronger retention

Feedback Type	Description	Example
Inherent (Intrinsic)	Natural sensory information from movement	Feeling the ball hit the bat
Augmented (Extrinsic)	External information about performance	Coach's comments, video replay
Knowledge of Performance (KP)	Quality of movement pattern	"Your arm was too low on the swing"
Knowledge of Results (KR)	Outcome of action	"The ball landed in the target"

Additional info: Effective motor learning involves optimizing practice conditions and feedback to promote retention, transfer, and independence in skill execution.