Movement Science Week 6 - Transcripts

Introduction to Motor Control

• Motor control is the dynamic ability to regulate or direct the mechanisms essential to movement and posture.
• The human movement system has the ability to reorganize movement and strategies to adapt to constantly changing tasks and environmental constraints.
• Understanding motor control requires knowledge of the motor systems, including the neuromuscular and biomechanical systems.
• Sensation and perception are vital for functional movement control.
• Cognitive processes are essential for motor control.
• Regulatory features of the environment shape movement, while non-regulatory features affect performance.

Movement Task Classifications

• Discrete movements have a recognizable beginning and end, such as kicking a ball or standing up from a chair.
• Continuous movements lack an inherent end and continue until the person chooses to stop, like walking or running.
• Closed movements occur in predictable environments, such as walking on a level surface in a room.
• Open movements demand adaptation in changing environments, such as playing basketball or soccer.
• Stability tasks are performed with a non-moving base of support, like sitting in a chair.
• Mobility tasks require the base of support to move, such as walking or crawling.
• Manipulation tasks involve upper extremity movements, like picking up a glass.
• Non-manipulation tasks do not involve specific upper extremity movements, such as walking.

Theories of Motor Control

• Theories help understand patient behavior and guide clinical interventions.
• Theories expand possibilities for clinical practice.

Classic Reflex Theory

• Reflexes are the building blocks of complex behaviors, according to this theory.
• Limitations:
  • Requires external stimulus for activation.
  • Cannot explain movements without sensory stimulus.
  • Doesn't explain fast movements without sensory feedback.
  • Fails to explain the ability to produce new movements.
• Clinical implications:
  • Focus on enhancing or reducing reflexes during motor tasks.

Hierarchy Theory

• The nervous system is organized hierarchically with control flowing top-down.
• Lower levels can also influence higher levels.
• Clinical implications:
  • Interventions based on integrating reflexes into functional movement patterns.
• Limitations:
  • Cannot explain dominant reflex behavior in certain situations.

Motor Programming Theories

• Motor programs can be activated by peripheral receptors or the central nervous system.
• Generalized motor programs represent broad representations for movements with features like order, timing, and relative force.
• Allows for variations in movement performance.
• Limitations:
  • Central motor programs are not the sole determinant of actions.
  • Does not consider musculoskeletal and environmental variables.

Systems Theory and Dynamic Systems Theory

• Movement emerges from interaction of multiple systems: nervous, musculoskeletal, gravity, and inertia.
• Bernstein emphasized the importance of integrating these systems.
• Levels of movement include: Tonus (muscle language), Synergies (muscle coordination), Space (purposeful movement), and Action (movement organization).
• Dynamic systems theory emphasizes change over time and highlights constraints on movement arising from individual, task, and environment interactions.
• Limitations:
  • Nervous system plays a less crucial role than mathematical formulas and body mechanics.
• Clinical implications:
  • Focus on understanding the body as a mechanical system.
  • Recognize movement as an interaction between multiple elements.

Key Concepts in Systems Theory

• Degrees of Freedom: The body's numerous ways to move.
• Synergies: Muscles working together for adaptable, flexible movement.
• Self-Organization: Emergent movement without specific commands.
• Non-linear Behavior: Sudden, rapid changes in movement configuration when parameters reach a critical value.
• Variability: Inherent variability in human movement is crucial for optimal function.
  • Variability in movement arises from variations in space and time.
  • Optimal variability allows for flexible, adaptive strategies.
  • Too little variability can lead to injury.
  • Too much variability can impair performance.
• Clinical implications:
  • View variability as a necessary component of normal function.
  • Encourage patients to explore different movement patterns.

Ecological Theory

• Actions require perceptual information specific to the goal and context.
• Focuses on the interaction between individuals and their environment.
• Emphasizes the role of perception in guiding action.
• Limitations:
  • Less emphasis on the nervous system's organization and function.
• Clinical implications:
  • Individuals actively explore their environment.
  • Adapt movements based on perceptual information.
  • Encourage exploration of tasks and environments to achieve optimal performance.

Integrated Theory

• No single theory is comprehensive.
• An integrated approach combining elements from all theories is optimal for understanding motor control.
• Researchers strive to develop a unified theory of motor control.

Motor Learning

• Motor learning is the acquisition of knowledge or ability, and memory is the outcome of learning, including the retention and storage of that knowledge or ability.
• Memory can be divided into two categories: implicit and explicit.
• Implicit memory operates unconsciously and automatically.
• Explicit memory operates consciously, for example, in the memory of people, places, and objects.
• Motor learning happens non-linearly, depending upon the task, conditions, and characteristics of the learner.
• Motor learning involves learning new strategies for sensing and moving.
• Motor learning, like motor control, emerges from a combination of perception, cognition, and action processes.
• We will use motor learning to talk about both the acquisition and the re-acquisition of movement.
• Learning is defined as a relatively permanent change.
• Performance is defined as a temporary change in motor behavior seen during practice sessions, or set of processes associated with practice or experience leading to relatively permanent changes.
• True learning of a motor skill is demonstrated when performance and practice of the motor scroll during acquisition results in persistence of that performance at a later time or later retention phase.

Attentional Processing

• During real life situations, information needs to be processed from multiple sensory inputs in order to adapt to the changing conditions.
• Attentional processing is used to detect and select the central information from the environment during memory storage and during the process of competitive selection, or when selecting the domain that will be accessed by the working memory.
• The interaction between the cognitive and motor requires processing from multiple sensory inputs in order to adapt to the changing conditions, thus increasing attentional processing.

Memory

• Learning reflects the process by which we acquire knowledge, and memory is the product of that process.
• Memories is often divided into two components, short-term memory and long-term memory.
• Short-term memory refers to the working memory, which has a limited capacity for information and only lasts for a few moments.
• Short-term memory reflects a momentary attention to something, such as when we remember a phone number only long enough to dial it and then we forget it.
• Long-term memory is related to the process of learning.
• Long-term memory can be seen as a continuum.
• Initial stages of long- term memory formation reflect functional changes in the efficiency of the synapses.
• Later stages of memory formation reflect structural changes in your synaptic connections.
• These memories are less subject to disruption.
• The two basic forms of long-term memory are nondeclarative or implicit and declarative or explicit.

Nondeclarative Learning:

• Nondeclarative forms of learning include nonassociative, associative, and procedural learning.
• Nondeclarative or implicit learning is more reflexive, automatic, or habitual and requires frequent repetition for its formation.
• Nonassociative Learning includes:
  • Habituation: decreased responsiveness that occurs because of a repeated exposure. We use a habituation exercises to treat patients who are dizzy with certain types of vestibular dysfunction. The patients are asked to repeatedly move in ways that provoke their dizziness and that results in a decrease of that dizziness response.
  • Sensitization: increased responsiveness following a threatening or noxious stimulus. So if we would put a painful stimulus on my skin and then a light touch, I'm going to react more strongly than normal to that light touch or I will have increased responsiveness. So when we think of this, sensitization can counteract the effects of habituation.
• Associative Learning includes:
  • Classical Conditioning: an initially weak stimulus, such as a bell, becomes effective when at producing a response when it becomes associated with a stronger stimulus. For example, in Pavlovian experiments, dogs were associated with food and a bell. We might use this in therapy by giving a patient a verbal cue and physical assistance when moving. Hopefully, they can eventually make the movement with only a verbal cue.
  • Operant Conditioning: Behaviors followed by a reward will be repeated, and behaviors followed by an aversive stimulus will be less likely to be repeated. We might use this in therapy. For example, if someone leaves their home and experiences a fall, they might be less likely to repeat that activity. The decrease in activity results in declining physical function, which in turn could increase the likelihood of a fall.
• Procedural Learning: learning tasks that can be performed automatically or without attention or conscious thought, like a habit. Procedural learning develops slowly through repetition of an act over many trials. It is expressed through improved performance of the task that was practiced. For example, moving from a chair to a bed.

Declarative Memory

• Declarative learning results in knowledge that can be consciously recalled and thus requires processes, such as awareness, attention, and reflection.
• We often use declarative learning when helping patients reacquire functional skills like buttoning a shirt.
• Since declarative learning requires the ability to express the process to be performed, it cannot easily be used with patients who have cognitive and/or language deficits that impair their ability to recall and express the knowledge.
• Teaching movement skills declaratively, however, does allow patients to rehearse movements mentally, increasing the amount of practice available to them when a physical condition such as fatigue might limit them.
• Constant repetition can transform declarative into nondeclarative or procedural knowledge.
• Declarative learning requires four types of processing: Encoding, Consolidation, Storage, and Retrieval.
  • Encoding: requires attention. The extent of encoding is determined by the level of motivation, the extent of attention to the information, and the ability to associate it meaningfully with information that is already in the memory.
  • Consolidation: includes the process of making information stable for a long-term memory storage and involves structural changes in the neurons.
  • Storage: involves a long-term retention of memories and has a vast capacity compared to the limited capacity of short-term or working memory.
  • Retrieval: involves a recall of the information from different long-term storage sites.

Motor Learning Theories

• Schmidt's Schema Theory: Proposed that motor programs do not contain the specifics of movements, but instead they contain generalized rules for specific groups of movements. The center of this theory is the concept of a schema. The schema is information stored in the short-term memory that is used to create two other schemas:
  • Recall Schema: This schema is used to select a specific response. Each time a person makes a movement with a goal in mind, they use a particular movement parameter such as a certain amount of force and then they receive input about the accuracy of that movement. The nervous system creates a relationship between the parameter and the movement outcome. This rule is retained in the recall schema.
  • Recognition Schema: This schema is used to evaluate the response. In this case, the sensory consequences and the outcomes of previous similar movements are combined with the current conditions to make a representation of the expected sensory consequences. This is then compared to the sensory information of the current movement to evaluate the efficiency of the response.
• Newell's Ecological Theory: States that motor learning is a process that increases the coordination between perception and action in a way that's consistent with the task and the environment. The theory proposes that during practice, there's a search for optimal strategies to solve the task. Part of that search involves not only finding the appropriate motor response, but also finding the most appropriate perceptual cues.
• Fitts and Posner's 3-Stage Model: This model suggests that there's three main phases involved in learning a new skill.
  • Cognitive Phase: The learner is concerned with understanding the task, developing strategies that could be used to carry out the task, and determining how the task is going to be evaluated. Performance tends to be variable, inefficient, and with error. However, the improvements in this stage of learning are large.
  • Associative Phase: The person selects the best strategy for the task and now begins to try to improve that skill. There's less variability in performance, and improvement also occurs more slowly. It's proposed that the cognitive aspects of learning are not as important in this stage because a person focuses more on refining that particular movement pattern.
  • Autonomous Phase: The skill is now automatic, with very few errors and needing less attention for its performance. The person can devote their attention to other aspects of the skill, like scanning the environment for obstacles, or they might choose to focus on a secondary task, like talking to a friend while walking.
• Bernstein 's 3-Stage Approach: In this theory, the emphasis is on controlling the degrees of freedom of the body segments involved in the movement as a central component to learning a new skill.
  • Novice Stage: There's a reduction of the number of degrees of freedoms of the joints to be controlled to a minimum. For example, a newly standing infant might freeze the degrees of freedom to the leg and trunk and only sway about the ankle joints in response to the threats of balance.
  • Advanced Stage: More degrees of freedom are released to improve efficiency.
  • Expert Stage: Learner can execute the skill in a relaxed and efficient manner.

Motor Skill Learning: Stages of Motor Development

• Advanced Stage: Performer begins to release additional degrees of freedom by allowing movements at more joints involved in the task.
• Expert Stage: Individual utilizes all available degrees of freedom to perform the task efficiently and in a coordinated manner.
• Clinical Implications:
  • Co-activation of muscles during early stages of learning a new motor skill can be explained by the theory.
  • Co-activation stiffens joints and constrains degrees of freedom.
  • Providing external support during early phases of learning can help constrain degrees of freedom for patients with coordination problems.
• Limitations:
  • Limited research on the autonomous or expert stages of learning.
  • Reaching these stages requires significant time and effort.
  • Gentile's 2-Stage Theory:
    • Stage 1: Understanding Task Dynamics:
      • Learner focuses on grasping the task requirements, including the goal, movement strategies, and environmental features.
      • Distinguishing relevant from non-relevant environmental features is crucial.
    • Stage 2: Fixation or Diversification:
      • Learner focuses on adapting movement to different demands for both closed and open skills.
      • Closed Skills: Minimal environmental variation, consistent movement pattern.
      • Open Skills: Changing environmental conditions, requires adaptation.
• Motor Program Formation: Development of motor programs for complex behaviors by combining programs for smaller units.

Motor Learning & Feedback

• Intrinsic Feedback: Sensory information received from the body during movement; visual, somatosensory.
• Extrinsic Feedback: Supplementation to intrinsic feedback, often verbal or tactile cues.
• Concurrent Feedback: During the task (e.g., manual guidance).
• Terminal Feedback: At the end of the task (e.g., "push harder next time").
• Knowledge of Results (KR):
  • Terminal feedback about the outcome of the movement in relation to the goal.
  • Important for learning motor tasks.
• Knowledge of Performance (KP):
  • Feedback regarding the movement pattern used to achieve the goal.
  • Intrinsic feedback is sufficient for some tasks, where KR has minimum effect.
• Feedback Frequency:
  • Fading Schedule: More feedback early, gradually reducing as the patient progresses.
  • Constant Feedback:
    • Leads to better performance during acquisition.
    • May hinder delayed retention, creating dependency on feedback.
  • Summary Feedback:
    • Less feedback during acquisition.
    • Better delayed retention.
• Feedback Timing:
  • Simple Tasks: Immediate feedback for best immediate performance, but delayed feedback for better retention (after 15 trials).
  • Complex Tasks: Feedback after 5 trials found to be most effective.
• Feedback Precision:
  • Adults: Quantitative KR (with units of measure) is most effective.
  • Children: Unfamiliar or precise KR can be confusing.
• Mental Practice:
  • Performing the skill in one's mind without muscle activity.
  • Enhances learning, especially when physical practice isn't possible.
  • Less effective than physical practice.
• Guidance Condition:
  • Physically guiding the learner through the task.
  • May not be more effective than unguided discovery learning.
  • Best used when learning a new task.

Practice Conditions

• Massed Practice:
  • Practice time exceeds rest time.
  • Can decrease performance due to fatigue in continuous tasks.
• Distributed Practice:
  • Rest time is equal to or greater than practice time.
  • Better than massed practice for continuous tasks.
• Constant Practice:
  • Practicing a task in constant conditions (e.g., standard stairs with a rail).
  • Ideal for tasks performed under constant conditions.
• Variable Practice:
  • Practicing a task in a variety of conditions (e.g., different types of stairs).
  • Best for tasks performed under variable conditions.
• Random Practice:
  • Practicing different tasks in a random order.
  • Leads to better learning than blocked practice, despite lower performance during acquisition.
• Blocked Practice:
  • Practicing one task until completion, then moving to the next.
  • Might be better for initial learning before transitioning to random practice.
  • Contextual Interference:
    • Occurs when multiple skills are practiced within a session.
    • Interferes with performance during practice, but benefits learning in the long run.
• Whole Practice:
  • Practicing the entire task together.
• Part Practice:
  • Breaking down the task into its steps to allow mastery before combining them into a whole.
  • Task components must be practiced in the same context, not in isolation.
  • Less effective than whole practice for developing functional motor programs.
• Transfer:
  • Extent to which learning in one environment transfers to another.
  • Influenced by the similarity of neural processing demands.
  • Encourage variations of the task to promote transfer.

Recovery of Function

• Function:
  • The recovery of a skilled action (e.g., holding a fork).
• Recovery:
  • Restoration of a damaged structure or function.
  • Includes clinical improvements regardless of how they occurred.
• Compensation:
  • An alternative strategy used to complete a task (e.g., using a different grip).
• Sparing of Function:
  • A function is maintained despite injury (e.g., incomplete spinal cord injury with partial leg function).
• Stages of Recovery:
  • Spontaneous Recovery: Recovery without intervention.
  • Forced Recovery: Improvement achieved through specific interventions.
• Factors Affecting Recovery:
  • Age:
    • Brain responds differently to injury at different stages of development.
    • Mature areas may be more susceptible to similar damage in infants and adults.
    • Immature areas may compensate for injured areas.
  • Injury Severity:
    • Generally, more severe injuries lead to more impaired outcomes.
    • Variability exists within even severe injuries.
  • Speed of Injury:
    • Slowly developing lesions (e.g., stroke) often cause less functional loss than acutely developed lesions.
  • Pre-Injury Factors:
    • Exercise, environmental factors, and nutrition are neuroprotective.
  • Medications:
    • Can reduce the nervous system's reaction to injury and promote recovery.
  • Post-Injury Factors:
    • Exercise and training can impact recovery.
    • Timing, frequency, and intensity depend on the site of injury.
• Neuroplasticity:
  • The brain's ability to change, ranging from short-term synaptic modifications to long-term structural reorganizations.
  • Occurs at multiple levels: brain, cellular, biochemical, and genetic.
• Sensitive or Critical Periods:
  • Enhanced plasticity in the nervous system, making it more open to modification.
  • Neurological changes are often associated with lasting effects.

Neuroplasticity and Recovery of Function

• Neural Plasticity is the brain's ability to adapt and change in response to experience and learning.

• Short-term Changes in neural plasticity involve changes in synaptic efficiency.

• Long-term Changes involve structural changes in the brain, such as the creation or elimination of synapses.

• Habituation leads to a decrease in synaptic potentials, resulting in fewer synapses over time.

• Sensitization leads to an increase in synaptic potentials, resulting in more synapses over time.

• Recovery of function after an injury or stroke also involves a continuum of short-term and long-term changes.

• Associative Learning is a type of learning where a person learns to predict the relationship between two stimuli or between a behavior and its consequence. It uses common cellular processes involving protein modification.

• Cortical Mapping refers to the different brain areas responsible for various motor and sensory functions.

• Research shows that cortical reorganization occurs in response to activity, behavior, and learning new skills.

• Cortical Reorganization can also occur after nerve injury, suggesting a window of increased plasticity where recovery may be possible.

• Critical Periods are periods of increased neuroplasticity in the developing brain, where specific learning experiences have a greater impact.

Principles of Experience-Dependent Neuroplasticity

• Use it or lose it: Neural circuits not actively engaged begin to degrade.
• Use it and improve it: Training can protect and enhance neural networks.
• Specificity: Practice related to the specific skill being learned is most effective.
• Repetition: Repetition is necessary for lasting neural changes.
• Intensity: Training must be intense enough to stimulate neuroplasticity.
• Time matters: The timing of interventions can affect their effectiveness.
• Salience: Training must be functionally relevant and meaningful to the individual.
• Age matters: Neuroplasticity decreases with age, but it still occurs.
• Transference: Plasticity in one neural circuit can promote plasticity in others.
• Interference: Plasticity in one response can interfere with the acquisition of other behaviors.

Test your understanding of motor control in human movements with this quiz. Explore the components of movement, the role of perception, and various theories of motor control. Answer questions about key characteristics and limitations in the control of movement.