ch 8a- motor learning Flashcards
motor learning
a change in a person’s ability to perform a skill; relatively permanent improvement in performance due to experience/practice
two categories of motor learning
- Sensorimotor adaptation
- Skill learning
Sensorimotor adaptation
sensorimotor systems respond to altered environmental (or body) conditions by reducing errors to regain previous performance level
Ex. recovery after a neurological injury
Research paradigms: prism goggles, force fields, split-belt treadmills…
Skill learning
New muscle activation patterns used to achieve better performance
Ex. learning to ride a bicycle
Research paradigms: Skilled movements, sequence learning paragdims
motor learning is possible because of
brain neuro-plasticity
brain plasticity
-the brain “rewires” and adapts based on experience
brain plasticity gives rise to
motor memory
motor memory
the ability to recall a previously learned motor (muscle) coordination
NOT called muscle memory
use dependent learning
repeating a movement can lead to learning. once error is reduced, repetition can reinforce learned behaviour
5 characteristics of successful skill learning
- Improvement: performance improves over a period of time
- Consistency: performance becomes more consistent
- Stability: internal (eg. stress) and external (eg. obstacles, weather) perturbations have less of an influence on performance
- Persistence: as learning progresses, improvements persist
- Adaptability: performance is adaptable to a variety of different performance contexts (emotional state, weather, location)
Assessing learning
Performance curves, retention tests, transfer tests
Performance curves
-Linear= proportional increase over time
-Negatively accelerated= large amount of improvement in early practice, less later
-Positively accelerated= slight performance gain early w large increase later in practice
-S-shaped= combination of all 3 (depends on individual and tasks)
Retention Tests
= assesses learned skill performance after a period of time following practice
–> measures the PERSISTENCE of improved performance
Transfer Tests
-what do they measurein terms of skill?
person must adapt the skill characteristics to a new situation
–> measures ADAPTABILITY and STABILITY of learned skill
Transfer tests:
-novel context
-novel skill variation
Novel context= changes in physical environment/change in stress level of person
Novel skill variation= try skill in a different way (e.g. new skis)
How can practice performances misrepresent learning
- early/later practice scores may not be correlated
- may overestimate/underestimate learning
- performance plateaus
-new strategy being developed
-fatigue or lack of motivation
-ceiling effect= test is too easy
-floor effect= test is too hard
coefficient that indicates complete adaptation
1
adaptation can be divided into
explicit component and implicit component
explicit component resembles a
fast process
implicit component resembles a
slow process (contributes more and more throughout adaptation)
Explicit learning
a person chooses to move in a certain way to counter the perturbation
-there is a CONSCIOUS cognitive component
Implicit learning
=updating of internal models (driven by sensory prediction error)
-WITHOUT conscious awareness
someone with a damaged cerebellum…
-would only be able to use the explicit aiming strategy
-would not get worse over repeated trials due to sensory prediction error because they do not have an implicit component
Which experiment demonstrates how attention can affect the rate of adaptation?
The split-belt treadmill:
-The conscious correction group had much more step symmetry that the distracted group
-all groups adapted but the conscious correction group adapted faster
Persistence in motor learning
“what is learned is retained”
relearning
=participants relearn the perturbation again at some later time
“savings”
relearning occurs much faster than learning
(learning is “saved”)
consolidation
resistance to interference over time
ex. learn a sequence and then learn another right after; first sequence is disrupted (not consolidated)
ex. learn a sequence and then learn another a few hours later; fist sequence is not disrupted (it is consolidated/encoded into memory)
consolidation requires
time and sleep
anterograde interference (AI)
learning of one behaviour interferes with the learning of another behaviour in the future
retrograde interference (RI)
learning of a second behaviour interferes with the consolidation of a previously learned behaviour
mapping: AA
AA= no interfering map
person learns map A and is later exposed to it again
ABA
-learns map A, map B is introduced after learning map A
-learning map B causes Anterograde Interference (AI) so the error is larger during initial trials of B than they would have been if person had not learned A previously
-reintroduced to A; small error during relearning therefore A was consolidated before B
How to determine if results were due to Retrograde Interference (RI)?
Eliminate AI. Add washout trials.
Fitts and Posner Three-stage Model
- Cognitive stage= large # errors
- Associative stage= “refining” stage
- Autonomous stage= habitual/automatic skill
during walk, is there consolidation with or without washout trials?
BOTH
consolidation occurs with and without the use of washout trials
Gentile’s Two-stage model
- Initial stage
- Later stages: closed skills, open skills, and modifying movement
Gentile’s model:
Goals of initial stage?
-get a movement coordination pattern
-learn to discriminate between regulatory (relevant) and non-regulatory (irrelevant) conditions
Regulatory conditions
characteristics of the environment that directly determine the movement characteristics the person must use
-ex. size or shape of object being grasped
Non regulatory conditions
do not directly influence movement characteristics
-ex. colour of object
Gentile’s model:
Goals of Later stage?
- fixation and diversification
- movement modification requirements
closed skills (stable environment) require
FIXATION of the basic movement coordination pattern learned in the initial stage of practice
-the learner practices so that the coordination pattern is fixed (constant)
open skills (varying environment) require
DIVERSIFICATION of the basic movement coordination pattern learned in the initial stage of practice
-learner must be able to modify their movements based on environmental context
-“practice variability”
Modifying movement
-changing movement parameters (muscles) and/or the invariant features depending on the skill
–> for closed skills= changes in the movement parameters
–> for open skills= changes in the invariant features or the parameters (ex. goalie might have to prepare for low shot but might have to change to block a different shot)
Schmidt’s Schema Theory of motor learning
-there are 4 types of information available to the learner after program is selected
-information of stored long enough in the brain to develop two schemas:
1. recall schema
2. recognition schema
4 types of information available to the learner after the program is selected and the movement is made?
- initial body conditions (initial limb position)
- Parameters assigned (muscles used)
- Augmented feedback about outcome of movement (knowledge of what happened/results)
- Sensory feedback
Recall Schema:
what info is stored?
-stores info about the relationship between parameters of motor program and movement outcome based on initial conditions (initial limb position)
Recall Schema:
what is the x axis?
movement outcomes (basically errors)
Recall Schema:
How does it work?
-with each trial, learner pairs the outcome with the parameters used to achieve it
-learner “maps” a relationship that is based on initial limb position
-can use this to achieve a movement goal in the future
Recall Schema:
Example of spot on the wall
-movement outcome= reaching down to a spot on the wall
-initial conditions= current arm/shoulder position
-select appropriate parameters (e.g. B might represent the correct muscles)
-the parameters are added to the invariant features of the action to form the motor program and achieve the desired outcome
Recognition Schema:
What info does it store?
-relationship between initial conditions, movement outcomes, and sensory consequences (feedback)
Recognition Schema:
How does it work?
-we can use expected sensory consequences to help with learning
-sensory consequences are related to the movement outcome
-we can use sensory consequences as an error tracker
Recognition Schema:
Example of basketball player
professional basketball player can perform a jump shot and turn around to celebrate before it actually goes in because the SENSORY FEEDBACK from the movement MATCHED what they expected for them to succeed
How do both schemas work together?
A learner forms a recall schema, which they can eventually use to determine how to move to achieve desired outcome. They can use the recognition schema to CONFIRM that they moved as they intended to or to identify what went wrong.
Skill Learning “De Novo Learning”
learning a new skill by learning new ways to respond to incoming sensory info by selecting the correct motor response
Lab based paradigms to study skill learning
learning arbitrary visuomotor associations:
-learn relationship between set of stimuli and actions
-performance is based on speed accuracy trade off
Learning phases of skill learning
- Learn associations between stimuli and actions
- Practice so that reaction time decreases/speed increases and less likely to get interference from a secondary task
“Off-line” gains
improvement between testing sessions with no additional practice
–> if there is retrograde interference from learning another skill, then no off-line gains will be made
Mirror reversal learning example
a continuous arbitrary skill that requires development of a new internal model
-performance improves with practice, reaction time decreases across blocks of trials
-off line gains
Changes across learning
-rate of improvement
-movement coordination (DOF problem)
-muscles used to perform the skill (become more efficient)
-changes in attention (decrease in conscious attention)
-error detection (better at detecting)
-activity across different brain areas
Power of Law of Practice
large amount of improvement in early practice and then the rate of improvement decreases
How does the CNS solve the DOF problem to produce coordinated movements?
Nervous system must determine appropriate muscle activation pattern, limb configurations, trajectories, and how to control joints
-strategy= “freeze” joints
-example= a person learning to skate; knee joint is usually locked up to reduce DOF. As the person improves, they learn to bend their knees and coordinate the DOF better
How do people use their muscles inappropriately in different stages of practice?
-greater number of muscles used than needed
-inefficient activation timing (poor sequencing)
-co-contraction of muscles to help stabilize a limb
Co-contraction
activation of both agonist and antagonist muscles around the joint that causes it to become stiffer
Changes in visual selective attention when learning a new skill?
beginner= fixate on too many/inappropriate things
-learning leads to an increased ability to direct vision to relevant environmental features
-fixate where you expect the object/regulatory features to be
Gaze fixation:
soccer player example
experts made fewer (but longer duration) gaze fixations to fewer areas of the scene compared to beginners
Prism adaptation task
reaching or pointing
Prism adaptation: role of cerebellum and PPC
-AIP in PPC is active in early phases (high error)
-cerebellum has progressive increase in activity and is active for longer than PPC
-cerebellum is involved in sensory prediction error
Patient has a cerebellar lesion, can they do prism adaptation?
No, not compared to a healthy individual
Cerebral stimulation —– adaptation during split-belt treadmill walking
improves
tDCS (transcranial direct current stimulation) is applied over the cerebellum during split belt treadmill:
Describe what happens to the 3 groups receiving different types of stimulation
- Anodal stimulation increases excitability
- Cathodal stimulation decreases excitability
- Sham= fake stimulation (control group)
tDCS (transcranial direct current stimulation) is applied over the cerebellum during split belt treadmill:
Describe what happens to the 3 groups receiving different types of stimulation
- Anodal stimulation increases excitability= faster adaptation
- Cathodal stimulation decreases excitability= slower adaptation
- Sham= fake stimulation (control group)
what does a split belt treadmill measure?
step symmetry
Cerebellum and force field reaching tasks:
results of cathodal vs. anodal stimulation (tDCS)
-cathodal tDCS over cerebellum reduces the rate of adaptation in the task
-anodal tDCS stimulation increases the rate of adaptation
RESULTS= cerebellum has a role in error correction
TMS over PPC during learning results in
more error at the end of the learning phase
-suggests that PPC is involved in the adaptation process
Reaching to a target in a velocity-dependent force field during learning and retention phases:
What is M1 involved in?
M1 (primary motor cortex) is involved in storage of motor memory
-evidence= no effect of rTMS in learning phase but decreased performance on retention tests
How are basal ganglia involved in motor learning?
long term memory retention
Individuals with Parkinson’s disease have cell death in basal ganglia, how would they perform in visuomotor rotation tasks compared to healthy individuals?
-similar rates of adaptation “learning” between groups
-PD shows impairs “savings”
—> no basal ganglia= no memory retention
Potential role of SMA (supplementary motor cortex) in motor learning
sequence learning involves learning a temporal pattern of actions (like playing the piano)
Give example evidence that SMA is involved in learning sequences
-rTMS over SMA interferes with accuracy of complex sequences
