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