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

Motor Programs and Sensorimotor Learning

Learning Objectives

• Explain Bernstein’s problem (a primary issue in motor control)

• Describe hierarchical learning and schema theory

• Describe stages of motor learning

• Identify factors affecting motor learning: practice and feedback

Bernstein and the Degrees of Freedom Issue

Definition and Relevance

The degrees of freedom (DoFs) problem refers to the challenge of controlling the many independent components of a motor system to produce effective action. In the human body, this means coordinating numerous muscles, joints, and movement directions.

• Degrees of Freedom: The number of independent ways a dynamic system can move.

• Example: Touching your nose with your finger can be achieved through many possible limb configurations.

Joint	Movements	DoFs	Muscles
Shoulder	Flex/extend, ab/adduct, internal/external rotation	3	~20
Elbow	Flex/extend, pronate/supinate	2	~10
Wrist	Flex/extend, radial/ulnar deviation	2	~10
Total		7	~40

The Problem of Redundancy

• How do we select and coordinate DoFs for smooth, reproducible, and quick actions?

• Redundancy allows flexibility and adaptability, but complicates control.

Research Efforts to Solve the Problem

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

• Muscle Synergies: Groups of co-activated muscles are controlled as a unit, simplifying coordination.

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

Motor Control Models

Inverse Model

An inverse model calculates the necessary feedforward motor commands from desired motor output information, using a model of the musculoskeletal system.

• Translates goals into specific muscle activations and joint movements.

Forming Motor Memories (Sensorimotor Learning)

Definition and Process

Sensorimotor learning is the improvement of motor skills through practice, resulting in long-lasting neuronal changes.

• Requires multiple repetitions under varied conditions.

• Leads to decreased time and variability in task performance.

• Assessed via performance curves, retention tests, and transfer tests.

Schema Theory

Generalized Motor Programs

During skill acquisition, individuals form a schema—a generalized motor program that can be adapted to different effectors (e.g., right hand, left hand, teeth, foot).

• Allows for variability and novelty in movement.

• Consistency arises from using the same general plan across effectors.

• Variable practice leads to better transfer to related tasks.

Hierarchical Learning

Mechanism for Schema Generation

Movements are coded in motor programs stored in long-term memory (LTM), organized at distinct levels of control.

• Enables rule-based, flexible behavior.

• Efficient storage via chunking—grouping information into meaningful units.

Example: Playing piano involves hierarchical control: overall goal, piece selection, finger movements, timing.

Chunking in Memory

Application to Motor Learning

Chunking refers to grouping individual elements into larger, meaningful units, facilitating memory and learning.

• Example: Memorizing "FBI, CIA, KGB, UPS" is easier than "FB, ICI, AKG, BUP, S" due to contact with learned chunks in LTM.

Fitts’ 3-Stage Theory of Learning

Stages of Skill Acquisition

• Cognitive Stage: Learning basic procedures; high conscious effort.

• Associative Stage: Transition from conscious to automatic control.

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

Stages of Motor Learning: Fitts & Bernstein Comparison

Fitts & Posner	Bernstein
Cognitive: Understand task, develop strategies, high attention, large improvements	Novice: Discover DoF, not energy efficient, not flexible/adaptable
Associative: Refine skill, less attention, improvements slower	Advanced: Begin to release DoF, joints coordinated, improved coordination
Autonomous: Skill is automatic, low attention, secondary tasks possible	Expert: All DoFs used, most efficient, exploitation of passive forces

• Learning is not strictly linear; can be regressive or progressive.

• Task differences affect progression through stages.

Motor Learning Paradigm

Phases of Learning

• Acquisition: Perform and practice 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 Improvement

• Y-axis: Motor performance (error, speed, accuracy)

• X-axis: Practice trial

• Improved performance is seen over repeated trials.

Stages of Motor Learning: Acquisition, Consolidation, Retention

• Acquisition: Initial improvement during practice.

• Consolidation: Gains require time to become effective; estimated 6-hour window after practice.

• Retention: Long-term maintenance of skill.

Linking Fitts’ Stages to Procedural Learning

Neuroplasticity and Memory

• Procedural learning involves changes in brain activity and connections (neuroplasticity).

• Regions show altered activity hours after initial learning.

Practice Conditions

Transfer of Learning

• Transfer depends on similarity between practice and performance environments.

• Better transfer occurs when practice tasks closely resemble performance tasks.

Constant vs Variable Practice

• Constant Practice: Only a single variation of a task is practiced.

• Variable Practice: Many variations of a class of actions are practiced; enhances schema development and future novel performance.

Random vs Blocked Practice

• Blocked Practice: Many trials on a single task practiced consecutively; low contextual interference.

• Random Practice: Practice trials on several different tasks are mixed; high contextual interference.

• Random practice leads to better learning and stronger memory representations.

Feedback in Motor Learning

Types of Feedback

• Inherent (Intrinsic) Feedback: Information from natural consequences of action.

• Augmented (Extrinsic) Feedback: Information from measured performance outcome, provided artificially.

Types of Augmented Feedback

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

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

Type	Description
Average Feedback	KR of average performance after several trials
Faded Feedback	High rate initially, then reduced
Bandwidth Feedback	Feedback only when performance is outside acceptable limits

Frequency of Feedback

• Too much feedback creates dependency; less feedback encourages use of intrinsic feedback.

• Complex tasks may require more feedback.

• Reducing feedback can facilitate learning in retention, even if it degrades acquisition performance.

Summary

• Motor learning involves complex coordination of degrees of freedom, formation of motor programs, and adaptation through practice and feedback.

• Hierarchical and schema theories explain how skills are acquired, stored, and transferred.

• Effective practice and feedback strategies enhance learning and retention of motor skills.