Motor control

What is motor control

• regulation of mechanisms that control movement

• process by which the nervous system coordinates muscle activity to produce movement

movement is constrained by

1. demands of the task

2. resources of the individual

3. characteristics of the environment

demands of the task

• discrete (task has a clear beginning and end?) or continuous task (ongoing)

• closed or open task (is task performed in a predictable environment or changing)

• stability or mobility (holding position vs moving)

• manipulative or not (interaction with objects or not)

Individual resources

• cognitive system

• motor system

• sensory and perception system

characteristics of the environment

• closed/predictable environment vs open/unpredictable environment

• stable surface or moving surface?

process of motor control

• Motivation/Intention to Move

  • The desire or goal to perform a movement originates in higher brain areas.

  • Prefrontal cortex is involved in decision-making and planning the movement.

• Planning of Movement

  • The movement is conceptualized, sequenced, and prepared.

  • Involves premotor cortex and supplementary motor area (SMA).

  • These areas decide what the movement will be and how it will be executed.

• Initiation of Movement

  • Once planned, movement commands are sent to the primary motor cortex (M1), which generates the signals that initiate voluntary movement.

• Coordination and Regulation

  • The cerebellum fine-tunes movement, ensuring smooth and coordinated actions.

  • The basal ganglia help regulate movement initiation, intensity, and suppression of unwanted movements. Also responsible for repetitive movement without conscious control of initiating and performing activity.

• Transmission to Muscles

  • Signals travel down through the corticospinal tract in the spinal cord.

  • Lower motor neurons in the spinal cord or brainstem relay the signal to the target muscles.

• Execution and Feedback

  • Muscles contract and the movement is performed.

  • Sensory feedback (proprioception, touch, vision) from the somatosensory cortex and cerebellum helps adjust ongoing movements.

reflex theory (sherrington - late 1800s) (NATURE)

assumptions:

• peripheralist approach

• reflexes are basis of all movement

• external stimulus leads to movement

• nervous system - triggers, coordinates, and activates muscles

practical implications:

• use sensory input to control motor output

• stimulate good reflexes

• inhibit undesirable (primitive) reflexes

• relies heavy on feedback

limitations:

• doesn’t explain voluntary movements

• reflex cant be basic unit of behaviour

• doesn’t explain how single stimulus results in varying responses

Hierarchical theory (Gessel, 1950s) (NATURE)

assumptions:

• centralist / top down, unidirectional flow

• voluntary movements initiated by “will” (higher levels)

• reflexive movements dominate only after CNS damage

practical implications:

• identify and prevent primitive reflexes

• reduce hyperactive stretch

• normalize tone

• facilitate “normal” movement patterns

• developmental sequence

limitations:

• doesn’t explain the dominance of reflexive behaviours in normal adults

• everyone’s developmental pattern is different.

Ecological theory (gibson - 1960s) (NURTURE)

assumptions:

• perception-action system

• perception focuses on detecting information in the environment that will support the actions necessary to achieve the goal.

practical implications:

• explore multiple ways in achieving functional task and discovering best solution for patient, given the set of limitations

limitations:

• gives less emphasis on the nervous system

Motor programming theory

assumptions:

• higher-level motor programs store rules for generating movements

• central motor pattern without sensory stimulus / reflex

• central pattern generators (CPGs) - spinal motor programs that can produce movement without cortical or sensory input.

practical implications:

• correction of abnormal movement requires changes in central pattern generators or higher level motor programs.

• retrain for functional task and just re-educate muscles in isolation.

limitations:

• importance of sensory input in controlling movement

• doesn’t explain interaction with other variables (such as environment)

Dynamic systems theory (Bernstein - early 1900s)

practical implications:

• identifiable, functional tasks

• practice under a variety of conditions

• modify environmental contexts

• GOAL DIRECTED

limitations:

• very broad with different systems

reflex in short

action - reaction

—→ generate basic movement

hierarchical in short

top-down control of reflex activity

—→ CNS pathology involves reflex patterns

motor programme in short

stored movements

—> relearn rules and generate movements

dynamic systems theory in short

movement in association with multiple systems

—→ promotes variability

ecological systems in short

in relation to the demands of the environment.

—→ adaptation to the different environment and may vary between individuals.

What is Motor Learning?

• processes leading to relatively permanent changes in the producing skilled movement

  • brain tries to accomodate and learn repetitive activity, skills required, when learning new skill or recovering from neurological dysfunction

• applicable in:

  • learning a new skill

  • recovery of movement/function

• basic concepts:

  • process of acquiring capability for skill

  • results from experience/practice

  • cannot be measured/quantified directly - but inferred from output

  • produces relatively permanent changes - no short-term alterations

degrees of freedom concept

1 d.o.f = e.g. flex and extended

2 d.o.f = e.g. wrist flex / extend / ulnar and radial deviation

3 d.o.f = e.g shoulder flex/extension, abduction/adduction, and internal/external rotation

problem with d.o.f concept

multiple joints and muscles make the total number of possible movements vast, making movement coordination complex.

• redundancy = many ways exist to achieve the same motion

• coordination = the brain must decide which joints and muscles to activate while maintaining stability

• variability = movements are not always identical; small variations occur even in repeated actions

nervous system simplifies d.o.f. concept by …

• synergies: group of muscles and joints work together as functional units to reduce computational complexity

• motor primes: predefined/learnt movement patterns help generate smooth and efficient actions

• learning and adaptation: with practice, movements become more automatic and efficient, reducing unnecessary degrees of freedom.

procedural stages of motor learning

1. cognitive

2. associative

3. autonomous

cognitive stage of motor learning

• The learner is trying to understand the movement or task.

• Performance is inconsistent and full of errors.

• Requires high attention and conscious effort.

• Relies heavily on verbal instructions, demonstrations, and feedback.

associative stage of motor learning

• Associate input with output for future wanted outcomes

• The learner begins refining the movement.

• Errors become fewer and less severe.

• The movement becomes smoother and more coordinated.

• Less reliance on external feedback, more use of internal cues.

• More focused on improving accuracy, timing, and efficiency.

influencing variables in motor learning

Individual -

• interest

• attention

• preferred learning method

Practice -

• part or whole

• blocked or random or combination

• physical or mental

Feedback -

• intrinsic or extrinsic

• intermittent or continuous

• concurrent or post-performance

clinical application of motor learning - rehabilitation

Manipulate task or environment so it becomes challenging for patient so they are built and developed further to bring them back to recovery.