Week 10 Flashcards
motor learning –>
behavioral component
What does motor learning emphasize?
the brain’s role in acquiring, planning, initiating, and modifying movement
motor control –>
physioloigcal component
motor control is an are of study dealing with:
the understanding of the physiological and neural aspects of movement (may also be described as neuromuscular control)
Motor control includes the Interaction of CNS, PNS and musculoskeletal systems that execute:
movement and monitor/ integrate sensory information.
Why do we study the cognitive map?
it is a group of abstract ideas that help to describe the control of movement and how a movement can be learned by an individual
What does a cognitive map usually include?
contains underlying assumptions:
• interaction of central or peripheral control mechanisms
(• what variables determine the organization of control?)
What framework does a cognitive map provide??
- explains the key variables around which movement is organized
- predicts movement control outcomes based on manipulation of these variables
- guide for hypothesis-driven clinical action ( results in active problem solving by the clinician)
What is one important characteristic of all motor control theories?
Include an explanation of how we control coordination (ie what variables is the nervous system trying to control and command?)
What is coordination?
patterning of head/body/limbs relative to patterning of environment and objects (this definition holds, regardless of the skill of the performer)
When we have multiple solutions possible it is called:
motor redundancy or motor adbundance
Degrees of freedom =
describes the number of ways in which a given unit (part of the body) is capable of moving
What is degrees of freedom related to?
• # of joints moving
• number of muscles/motor units activated
(Example: consider # of joints needed to pick up the cup of coffee)
In the degrees of freedom problem, under normal circumstance, ________________________________ exists between a motor problem (task) and a motor solution.
NO ONE-TO-ONE CORRESPONDENCE
In the degrees of freedom problem, you have what redundancies?
• redundant anatomical df’s (diff mms/joints)
• redundant kinematics df’s
(diff trajectories, velocities, acceleration / can still achieve same goal)
• redundant neuruophysiological df’s (multiple neurons for same mm)
(mental framework) There are 2 predominant theoretical approaches to explain how skilled movement is coordinated and controlled, they are:
- top-down
2. dynamic interaction
(mental framework) top-down =
existence of a command center in brain that makes all decisions regarding movement
(mental framework) dynamic interaction =
- command center can’t account for all variations of skilled movement
- skilled movement emerges from dynamic interaction of variables in body, environment, and skill
open loop control (feed-forward) =
- downplays feedback in initiation and execution
- suggests top-down hierarchy
(** discrete)
(*** relies on central command / almost a pre-packaged program)
closed-loop (feedback) =
- explain movement as outcome of feedback-initiated reflex actions and pre-patterned neural systems
- error detection & correction maintain desired goal
(** serial & continuous)
what is the fundamental difference between closed-loop and open-loop control?
fundamental difference = presence of feedback to modify motor demand during the movement
Open-loop control mechanisms include a two-level hierarchy:
- executive (command center generates action plan that contains all necessary information to complete motor response
- effectors = mm and limbs; carry out command without modification
input –> [perception–> decision making –> motor command]–> output
What is the role of feedback in an open-loop control?
- feedback constantly present, but comes too late to adjust the ongoing movement
- once pre-structured commands are initiated, command must run as planned
- feedback received can be used only to modify subsequent attempts
When is open loop control most effective?
for controlling movement that occurs in stable, predictable environments where need for modification is LOW
- advance instructions are given that specify what is to be performed, as well as sequence and timing (including movements of accuracy in short duration movements and rapid movement (
In the closed-loop controlled feedback system, the command center needs only to generate action plans that intiate movement:
- sensory feedback continually compared to desired movement
- detected discrepancies sent back to command center for correction
- note the difference in the content of the instructions in closed vs. open-loop (open = full command / closed = command to initiate)
Give a common/ everyday of a closed-loop controlled feedback system:
- thermostat in house
- stretch reflex (nervous system
- slack-lining (functional activity)
What are 4 key components of closed-loop control mechanisms:
- executive - decision maker
- effector - enacts the decisions
- feedback - reference of correctness/goal
- comparator ( = cerebellum)
in a closed-loop control system, executive =
- stimulus identification
- response selection
- response programming
in a closed-loop control system, effector =
spinal cord, mm, motor programs
in a closed-loop control system, feedback =
- interoceptive = inside of the body
* exteroceptive = outside of body (i.e. visual, auditory)
in a closed-loop control system, comparator =
- slow movements: feedback fine tunes mm force patterns
* fast movements: visual checking after completetion of movement
Describe the “steps” of close-loop control mechanisms:
- system goal is defined
- sensory information is compared to actual information about movement
- executive is informed about an error
- executive sends command to the effector
- match is made, error is corrected to = 0
(if error = 0, executive sends command to “turn OFF the furnace,” or command for action. If error exists, executive sends command to “turn ON the furnace”)
What are the 4 theories of motor control?
- reflex theory
- hierarchical theory
- motor program theories
- dynamical systems theory
Reflex theory =
(based off the work of sir charles sherringtion)
• Basic assumptions = reflexes are the building blocs of all movement / events in EN served as stimulus for action
• Complex behaviors result from CHAINING of reflexes = individual is a passive recipient of externally-produced sensory input that excites motor systems
• sensory –> motor–> sensory (feedback) (monkey unilateral UE deafferentation (DRG cut) - lost mvmt. / this went unchallenged for over 60 years)
• closed-loop in nature
What are the limitations of the reflex theory?
CAN’T EXPLAIN:
• Spontaneous or voluntary movements
• fast sequential movements (e.g typing)
• reflexes can be modulated (a single stimulus can trigger various responses)
• novel movements can be carried out
• Taub (1980) - deafferented monkeys
(-bilateral deaffentation: monkeys able to move arms - unilateral deafferentation: monkeys relearned movement while “good” arm constrained)
Hierarchial theory =
motor control emerges from reflexes nested w/in hierarchically organized level in CNS
• higher centers always in control of lower centers
• higher centers inhibit reflexes control by lower
• reflexes control by lower centers present only when higher centers are damages
• neuro-maturational theory of development (brain determines infant behavior)
What are some current opinions on hierarchical models?
- each level of motor system can act on other levels
* reflexes are only one of many motor control processes
What are some limitations of the hierarchical theory?
- can’t explain dominance of reflex behavior in certain adult situations (flexor withdrawal)
- Environment and other non-CNS factors can affect infant movement (infant stepping reflex)
What is the influence of hierarchical theory on treatment paradigms (neurorehabilitation) ?
- “When the influence of higher centers is temporarily or permanently interfered with, normal reflexes become exaggerated and so called pathological reflexes appear”
- “The release of motor responses integrated at lower levels from restraining, influences of higher center, especially that of the cortex, leads to abnormal postural reflex activity”
