Chapter 5: Motor Learning and Motor Control

John Hughlings Jackson

"Father of British neurology", wrote on neural control of movement

What did Sherrington recognize about postural control?

"posture follows movements like its shadow"

applied motor control physiologists

PTs, OTs, speech language therapists, ATs

what did studies of cat locomotion confirm?

Sherrington's suggestion and a similar role for receptors in the tendons that signal when the leg is no longer bearing any body weight so the other leg can be lifted

What does motor learning show?

a change in the capability for movement, occurs from a change in motor performance

what does the activation of intact areas attempting to move serve as?

a signal that calls out to axons so they can be targeted

Brain plasticity

ability of the brain to show modification in response to experience or injury

anticipatory postural control

activation of postural muscles in a feed forward manner in anticipation of destabilizing forces by the movement

What is needed for an accurate movement?

additional information from our sensory systems (state of body, state of surroundings)

What can drugs that affect the electrical excitability of the brain do?

affect motor learning

base of support

area of our body that contacts a support surface

postural tone

basic activation of our antigravity muscles

Gustav Theodor Fritsch and Julius Eduard Hitzig

began the study of the brain's electrophysiology by testing on dogs

What did Fritsch and Hitzig prove?

brain areas thought to be involved in thought and emotion participated in movement production

how was controlling forward and backward sway studied?

by using a platform that the person stands on that can unexpectedly move forward or backward

Sir David Ferrier

confirmed the concept of cerebral cortical maps

What influences the activation of our muscles?

continuous flow of sensory signals from receptors to our muscles and tendons back to neurons in our spinal cord

What is sensory information crucial in?

correcting small errors, holding a steady posture

Roles of Sensory information for Motor Control

correcting/compensating errors, specifying locations of objects that we intended to contact or avoid, initial condition of body and environment, springiness of muscles, signaling when next movement can start

What causes the brain to adapt?

demands placed upon us by our environment and the reorganization of the cortical areas in response

Paul M. Fitts

described fundamental reactions between movement duration, movement size, and movement accuracy in rapid, aimed movements

Ghez and his colleagues

did an experiment with the clicking of a mouse to see accuracy

What do seizures result from? (Jackson)

excessive electrical activity beginning in one area of the brain then spreading

What does the cerebral cortex do? (Jackson)

generates movement

how does translating motor memory into performance occur?

gradually and may consist of stages involving different brain areas

motor learning

how skilled movements are acquired, optimal conditions for learning new motor skills

retention test

how we can estimate what we retained from the previous practice session

Effects of visual imagery

increased performance on retention tests

What do the receptors tell us?

inform our motor system of the state and the surroundings of our body

What has research demonstrated about strokes?

intense, repetitive practice sessions for several hours a day can improve motor function even years after a stroke

How should one practice?

intervening a new task once they can perform the previous one in a basic way

Distributed practice

long intervals during a session, better retention when tested, better motor learning

deafferented

loss of sensory signals due to an injury or disease

what can a retention test show?

maintaing performance after a rest period or improving performance after a rest period

example of how postural control is required when moving a body segment

maintaining a stable shoulder position while moving the forearm at the elbow

example of maintaining postural control with external forces

maintaining balance in the face of gravity

Which tasks or better for massed and distributed practice?

massed: learning a discrete task distributed: continuous tasks with possibility of fatigue

What does feedback at the end of a task do?

more effective in producing motor learning

Law of Practice

more practice=more learning, change is rapid early in practice then slows as performance improves

sway

motion around the vertical axis of the body

What do neural networks that plan and execute our movements interact with?

motivation, attention, sensory information about the state of environment, state of your body, emotional/strategic factors

research in the post war period

motor learning, optimal training methods, optimal design of equipment to minimize human-user errors

Feed forward predictive control

movement with accurate information about starting the configuration of limb and target

Where do skilled movements come from?

nervous system, musculoskeletal system, and the environment

Nikolai Bernstein

observed how the body interacts with the environment, theorized functional movement is the result of control distributed across many levels of the nervous system and among neuromuscular and mechanical systems of the body

What do extensive experiments in animal locomotion indicate?

patterns of rhythmic changes in muscles results from neurons within the spinal cord that function as a central pattern generator

How do we learn the best?

performing movements under our own power

center of mass

point at center of our total body mass

Dendrites

portions of neurons important for receiving information from other neurons

What facilitates adaptive rewiring?

post-injury behavioral response

what are processes that help learning associated with?

practice or experience

Random practice schedule

practicing a different skill during each session, better performance on retention test

Constant practice

practicing the same skill in the same conditions

Variable practice

practicing the same skill under varying conditions, poor performance during training, good performance on retention test, helps children

Blocked practice schedule

practicing the same skill until you are proficient, better performance during training

predictive muscle command

predicts consequences of movement

motor control

processes that underline the production of movement in health and disease

reactive muscle command

reacts to movement

Nervous system

receives sensory signals that carry information for planning and executing movements

Where do the sensory signals come from?

receptors in muscles, tendons, skin, vestibular system, joints, and ligaments

Mott and Sherrington

reported a monkey couldn't use its limb after the sensory nerve was severed, revealed sensory signals are essential (false)

"springiness" of muscles

resistance to lengthening

Law of Effect (Thorndlike)

rewarded responses are repeated and responses that are not rewarded are not repeated

What did Bernstein recognize?

same motor command will produce different results depending on the starting position of the limb

What did the mouse test reveal?

sensory information about the initial body condition is crucial to generate accurate motor commands

Schmidt and Lee's definition of motor learning

set of processes associated with practice or experience leading to relatively permanent changes in the capability for movement

Massed practice

short rest intervals during a practice session

what are therapeutic practices based upon?

site and size of lesion

World War II scientists

studied critical questions for the war effort (how to select and rapidly train pilots, bombarders, and gunners)

Franklin Henry

studied motor behavior in a PE setting, trained a generation of scientists

R.S. Woodworth

studied principles of rapid hand movements

E.L. Thorndlike

studied processes that underline skill learning, came up with "Law of Effect"

motor behavior

study of human movement or action (themes: motor control, motor learning)

What did Sanes and his colleagues realize?

the brain does not store complete, well-formed actions that are replayed from memory

What does central representation require?

the initial condition

What does a systemic body map show? (Jackson)

the muscles of the body represented in the cerebral cortex

K.J.W. Craik

theorized that information processing in the brain occurs in bursts rather than continuosly

A.T. Welford

theorized that information processing in the nervous system is delayed because the information is processed in single channels

relationship between center of mass and base support

to stand upright we need to keep the vertical projection of our center of mass within our base of support

Feedback control

used for making corrections based on current condition

How does motor learning occur?

visual imagery or physically practicing using the same brain regions

What did individuals deprived of sensory information through disease/injury tell us?

voluntary movements can be performed without sensory information

Theory of Contextual Interference

we learn better when we aren't "in the groove"

what does controlling sway require?

we predict the direction and amount of sway from sensory information then select the actions that will minimize the sway

Sir Charles S. Sherrington

won a Nobel Peace prize for his study of reflexes and their role in the brain's control of movement and posture