Mod 2 Theories of Motor Control Flashcards
What is a theory of motor control?
a group of abstract ideas about the control of movement
What is a theory?
a set of interconnected statements that describe unobservable structures or processes and relate them to each other and to observable events
What is the blueprint analogy?
- just as a blueprint provides structure that transforms stones into a house, theory gives meaning to facts
- just as the same stones can be used to make different houses, the same facts are given different meanings/interpretations by different theories
How do theories of motor control influence rehab?
- framework for interpreting behavior
- guide for clinical action/intervention
- new ideas and approaches to assessment and intervention
- working hypotheses for assessment and intervention
What is reflex theory?
the integrative power of the CNS is due to a set of reflexes coordinating the activities of different organs
What are reflexes considered as?
the building blocks and most basic functional units of complex behavior
Individual reflexes _______ give rise to complex behavior
chained together
_________ to one stimulus serves as the _______ for the next
response; stimulus
What is an example of complex inter limb coordination being mediated reflexively?
frog has paper placed on forelimb and back limb makes an upward wiping motion trying to wipe away stimulus
- when forelimb is placed in different location, back limb responds with different movement
Different movement trajectories and muscle synergies depending on ________________ not just the stimulus in frogs
position of forelimb
How do we see reflex theory in humans?
flexor withdrawal - crossed extension reflex
What does flexor withdrawal - crossed extension reflex provide a building block for in humans?
pattern formation in human gait
extension of support limb results in stretch of hip flexors which is stimulus for switching to swing phase
What are limitations of reflex theory?
does not account for
- voluntary movements not “activated by outside agent”
- movements that occur in absence of sensory input
- fast movements that occur to rapidly for sensory feedback
- same stimulus can result in different responses depending on context
- novel movements: unique combos of stimuli and responses
How is reflex theory used to interpret patient’s behavior and serve as guide of treatment?
- test reflexes to predict function
- motor behavior attributed to presence/absence of reflexes
- interventions focused on enhancing or reducing effects of reflexes
What is hierarchical theory?
- nervous system is top down, segments at top control next segment below
How is the nervous system organized in hierarchy?
higher(association areas)
middle (motor cortex)
lower (spinal)
What is important to remember about the direction of hierarchical theory?
no bottom up control
What did Hughlings Jackson find about hierarchical theory?
- NS compose of phyiologically discrete organs, with single function each
developed somatotopic representation
- claimed NS is evolutionary hierarchy
What did Rudolf Magnus propose about hierarchical theory?
- reflexes controlled in lower levels of neural hierarchy are present only when cortical areas are damaged
- higher centers typically inhibit reflexes
What is reflex/hierarchical theory?
motor control emerges from reflexes that are nested within hierarchically organized levels of nervous system
What did Georg Schaltenbrand use hierarchical theory for?
used Magnus’s concepts to explain motor development
What did Shaltenbrand conclude about hierarchical theory?
appearance and disappearance of hierarchically organized reflexes can determine neural age of child and damage to the brain could result in re-appearance of primitive reflexes
What did Stephan Weisz use hierarchical theory to tell us about development?
hierarchical organized reflexes as bases for balance and maturation corresponds to developmental progression from sit to stand to walk
What did Gesell and McGraw suggest by using hierarchical theory?
normal motor development due to increasing corticalization of CNS
emergence of higher levels over control over lower level reflexes
What is neuromaturational theory of development?
assumption that maturation of central nervous system is primary driver of motor development
What are the current concepts of hierarchical theory?
- elements of hierarchical organization but not strict top down manner
- each level of NS can act on other levels depending on tasks
- reflexes not considered sole determinant of motor control, but one of many processes
What are the limitations of reflex hierarchical theory?
- can’t explain dominant reflex behaviors that occur in intact adult
- low level reflexes are not all primitive and high level behaviors are not all mature
How might reflex hierarchical theory be used in clinic to guide treatment?
- abnormalities in reflex organization used to explained disordered motor control
What is motor programming theory?
- focus on actions rather than reactions: movement patterns occur in absence of stimulus or afferent input
motor program
What are central pattern generators in motor programming theories?
when sensory nerves cut, nervous system could generate movement with no sensory input(slow movement)
sensory input not essential but still important in modulating action
What was found in studying CPGs in cats?
spinal neural networks could produce locomotor rhythm without sensory input
changing intensity of spinal cord stimulation could change pattern from walk to trot to gallop
What is a motor program considering CPGs?
neural connections that are hardwired and produce stereotyped behaviors
What is a generalized motor program (GMP) considering motor programming theories?
goal to explain motor control in absence of feedback and how motor programs could generate novel movements
What does generalized motor program define?
how a specific movement will be performed by specifying the parameters
What does generalized motor program suggest?
- muscle activation pattern has been internally programmed and is run off without sensory feedback
Are GMP hierarchical?
yes, hierarchically organized motor programs store rules for generating movements so we can perform the tasks with a variety of effector systems
What are the limitations of motor programming theories?
CPGs: not intended to replace importance of sensory input, but show that it is not always needed
central motor program cannot be sole determinant of action
gravity acts differently on limb and can modify the movement
How can motor programming theories be used in clinic?
explanations for abnormal movement go beyond reflex, include abnormalities in CPGs and motor programs
help patients relearn correct rule for action
focus on retraining movements important to functional task, not just reeducating specific muscles or movements in isolation(in context of functional tasks)
What is systems theory?
you cannot understand neural control movement without understanding the system itself, must understand characteristics
Has is the body viewed under systems theory?
mechanical system with mass and subject to external forces
How does the same central command result in different movements in systems theory?
due to interplay between external forces and initial conditions
In systems theory, the body is a mechanical system with __________ that need to be controlled
degrees of freedom
What is the concept of levels of movement construction in systems theory?
each level solves particular class of movement problem
higher levels take advantages of functional capabilities of lower levels and reduce involvement of higher levels
In system theory what how is language like movement?
letters: tonus
words: synergies
sentences: actions
What are synergies?
group of muscles that are constrained to act together as a unit, that serve key role in solving degrees-of-freedom problem
What is dynamic systems theory?
- principle of self organization
- motor control distributed throughout many interacting systems working cooperatively to achieve movement
What does dynamic systems theory seek?
mathematical descriptions of self organizing systems
nonlinear properties: critical feature of dynamic systems
When a _______ reaches a _______ there is a shift in behavior
control parameter
critical point
Instead of emphasizing the commands from CNS on controlling movement, dynamic systems theory does what?
seeks physical explanations that contribute to movement characteristics as a whole
How does variability play a role in dynamic systems theory?
seen as proper of complex nonlinear systems that are critical to function
How does the view of variability compare between motor program theory and dynamic systems theory?
MPT: considered consequence of errors
DST: considered necessary condition of optimal function
What are attractor states?
highly stable preferred patterns of movement
What is attractor well?
characterizes amount of flexibility to change a preferred movement pattern
It is easier to change unstable movement pattern that has _______ attractor well than stable movement pattern with ________ attractor well
shallow; deep
What does a deep attractor well represent?
pattern of movement with low variability
What does a shallow attractor well represent?
pattern of movement high variability
Stable movement patterns become _______ or unstable just prior to transition to new movement pattern
more variable
What are the limitations of systems theory?
- lack of consensus on terminology and definitions
- emphasis on mathematical models make it difficult to translate into clinic
What are the clinical implications of systems theory?
movement not just output of NS but output of NS filtered through movement system
- impairments occur among multiple systems
- there’s also physical principles not just neural structures
- variability is normal to movement
What is ecological theory of motor control?
motor system allows us to interact with environment to perform goal-oriented behavior
- how we use perception to guide action
What is affordance in ecological theory?
possibility of an action on an object or environment
What is an example of affordance?
different surfaces afford infants with new opportunities to learn motor skills
What is the relationship between perception and action in ecological theory?
actions require perceptual information
What are the limitations of ecological theory?
- less emphasis on organization and function of NS
- research provides less clinal insight into nervous system injury, disease, and recovery processes
What are the clinical implications of ecological theory?
changes in personal and contextual factors can dictate how an individual interacts with their environment and there are multiple ways to achieve a functional activity
What is the integrated approach of motor control?
combination of elements from all theories of motor control
What is the parallel development of the theories of motor control within clinical practice?
researchers identify scientific basis for movement and disorders, clinicians develop applications of research
Clinical practice develops ________ with scientific theory
in parallel
What are some near-facilitation approaches in clinical practice?
bobath (NDT), brunnstrom, PNF, and sensory integration theory
What do neuro-faciliation approaches seek to do?
retrain motor control through techniques designed to facilitate or inhibit different movement patterns
What is a facilitation technique?
technique that increases patient’s ability to move in way considered appropriate by a clinician
What is an inhibitory technique?
technique to decrease patient’s use of moevemtn pattern considered to be abnormal
What are neurons-faciliation approaches based on?
reflex-hierarchical theory:
- that normal movement results from reflexes organized hierarchically in CNS
- abnormal movement is the result of a lesion causing release of inhibition over reflexes at lower levels
- recovery: higher centers must regain control of lower centers
What are the key assumptions of neurons-faciliation approaches?
functional skills will automatically return once abnormal movement is inhibited and normal is facilitated
repetition of normal patterns will automatically transfer to functional tasks
What are the clinical applications of neuron-faciliation approaches?
- identify presence of normal/abnormal reflexes
- intervention modify CNS through sensory stimulation
- intervention towards regaining normal movement pattern
What is the task oriented approach?
includes systems approach, motor control or motor learning approach, based on systems theory
What is normal movement under task oriented approach?
emerges as interaction among many different systems, each with different aspects of control
What is abnormal movement under task oriented approach?
- result from impairments in one or more systems controlling movement
- may not due to lesion itself but efforts from remaining systems
What are the clinical applications of task oriented approaches?
- work on identifiable functional tasks rather than movement pattern
- patients learn by attempting tasks rather than practicing normal movement patterns
- focus on adaptations to environment
What is a control parameter in systems theory?
variable that regulates change in behavior of entire system
