Transcript Neural Mechanisms: Contributions And Control

Neural Mechanisms: Contributions
And Control
Chapter 4
Nervous System
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Movement prep, execution, and control occur here
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CNS vs. PNS
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CNS - Brain and spinal cord
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PNS - nerves that extend off of the brain and spinal cord; ;link
body and CNS
Afferent vs. Efferent (PNS)
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Afferent - conducts nerve impulses from sensory receptors to the
CNS
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Efferent - transmits impulses from CNS to limbs, muscles, etc.
Sensory Receptors: Stimuli Detection
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Exteroceptors: located at or near surface of body
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Detect stimuli outside the body
Provide information about the environment: What’s
happening? Do I feel pain?
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Interoceptors: hunger
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Detect stimuli from the internal viscera
Provide information about the internal environment
Proprioceptors
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Provide information regarding body position and
movement: muscle tension, joint position
Vision
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Dominant sensory system
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70% of sensory receptors are in the eyes
Information from other sensory receptors may
be ignored in favor of visual information
Two Visual Systems in Motor
Control
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Visual information is delivered from the retina
along two separate pathways to two different
places
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Focal vision, specialized for object identification
Ambient vision, specialized for movement control
Although separate, these systems function in
parallel
Focal Vision
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Functions to identify objects primarily located in
the central region of the visual field
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Answers the question “What is it?”
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Voluntary; strongly linked to consciousness
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Function hampered in low light conditions
Ambient Vision
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Involves both the central and peripheral visual fields
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Not affected by changes in light strength
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Provides information about our own movements in
relation to other objects
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Answers questions “Where is it”; “Where am I in relation to it?”
Often functions at subconscious level
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Fine motor control may occur without us knowing it
Parallel Processing
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Ambient vision processes the broader
environment
Focal vision processes the environment
immediately in front
Comparison of the two systems
Feature
Focal Vision
Ambient Vision
Visual Field
Location
Central Only
Central and
Peripheral
Awareness
Conscious
Subconscious
Effect of low
Illumination
Degradation
Very Little
General Question
Resolved
What is it?
Where is it?
Focal Vision and Movement Control
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Since focal vision is at the conscious level, visual
information is processed through the information
processing stages
Vision is a source of exteroceptive information about
the environment
Movement control only occurs as information is
processed through the stages
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Focal vision helps one accurately ID a pencil from a pen
Is it as easy to make the ID in low light situations?
Ambient Vision and Movement
Control
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The flow of light and changes in that flow across the
retina provide a person with the following information
about their movement
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Stability and balance
Velocity of the movement through the environment
Direction of movement relative to the position of fixed objects
in the environment
Movement of environmental objects relative to the person
Time until contact between the person and an object in the
environment
Time to Contact
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As an object approaches the size of the object
will increase in the retinal image
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Faster the enlargement, the faster the object is
approaching
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Used to determine when an action should be
initiated
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Ambient vision is used to detect last moment
changes
Ambient Vision and Movement Control
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Because ambient information functions at the
subconscious level, it is relatively fast
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However this information is sent to lower levels of the CNS
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Not at the same level as where the CNS selects and initiates
movement
Therefore, ambient vision operates to make minor adjustments
to already programmed actions
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Ie. Compensate for a head movement when getting ready to
swing a golf club or a change in posture when walking with
crutches
Vision and Performance
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The performer must be able to make quick and
accurate decisions with focal vision
The performer must also be able to anticipate
someone else’s movement or their own in relation to an
object or a person through ambient vision
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Anticipation helps to decrease the information processing time
Visual search strategies will assist in the development
of this ability
Visual Search Strategies
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Directs learner to information rich areas where critical
cues occur
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Provide extensive practice opportunities in situations
that contain common task relevant cues
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Later in development/experience: Design situations
with high variability while still requiring the learner to
search for same cues each attempt
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Helps prepare learner to generalize visual search strategies for
performance or game situations
Visual Dominance
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Vision exerts a strong influence on motor
control, but it may not always be positive
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One may need to use other modes on control
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For example, monitor the sound of the engine rather than
rely only on gauges in the car
Over-reliance on vision may create ineffective
performance
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The firefighter who only notices the flames in front and fails
to listen to the cracking of timber to the right or left may be
injured
Practical Application
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Visual Dominance
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Trace between the lines looking through the mirror.
Describe how you performed. What difficulties did you
experience? What conflicts existed between your visual
information and your proprioceptor information?
Describe the link between visual and proprioceptive feedback
in the execution of visuomotor tasks.
Based on your findings, summarize different ways you might
help learners in your content field learn to link visual and
proprioceptive feedback.
Turn in your results at our next class.
Proprioceptor Information
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Golgi tendon organs; protects tendons & muscles from
excessive tension
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Muscle spindles;tells CNS how much and how fast a
muscle is changing length
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Joint kinesthetic receptors; info about movements being
too slow, fast or in the wrong direction
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Vestibular apparatus; info about posture and balance
Proprioception & motor control
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Proprioceptors send info on initial conditions & limb
position to the generalized motor program (recall
schema)
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Proprioceptors evaluate for correctness to the intended
goal (recognition schema)
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How does this information supplement the focal and
ambient vision information?
Implications for learning how to
interpret proprioceptive information
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Help beginners develop their frame of
reference about a movement (How does it
feel?; How should it feel?)
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Explore various possibilities to begin to develop
their reference
Gain information through proprioceptors as well as
vision
Manual assistance with cues
What do you think?
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A middle-aged man wants to learn to rope jump for
fitness. Unfortunately, he is visually impaired having
lost most sight in a work-related accident. Explain how
the man would control the movement. Then describe
how you would assist the man in achieving the goal.
Discuss some things you might do to encourage the
use of other sensory information. Provide supporting
rationale for your suggestions.
CNS and Memory
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Processes required to plan movement in some
way are stored in the CNS
Use of perception, making decisions on
movement response and production often
come from some type of information that is
stored from previous experiences
Storage of information from previous attempts
is in memory
Memory
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Ability to store and recall information
WORKING MEMORY
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Refers to short-term
Working memory serves as interactive workspace
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Duration
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Use information or lose it
Hold information for only 20-30 seconds
Capacity
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Seven +/- 2 items
Increased size of item depends on chunking
WORKING MEMORY
Processing Activities
 Use information to solve a specific movement
problem
 Use information to perform the goal of movement
 Use information in preparing the information for
storage
LONG-TERM MEMORY
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Permanent storage of information
Duration of information storage is permanent
Forgetting occurs when we cannot find a
memory, or it is a retrieval problem
Capacity of information storage is unlimited
Subsystems of Long-term Memory
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Episodic memory
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Semantic memory
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Contains information about personal experiences
and events that are associated with a specific time
and context
Represents general knowledge that is developed by
our experiences but is not associated with time
Procedural memory
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Retains information regarding how to do something
The memory of skills, operations and actions
Relating LTM to motor control
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Episodic memory retrieves information
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Used as a guidance for what to do from past
experiences
Semantic memory relays what you have
learned to do previously (concepts)
Procedural memory puts the plan into motion
(blueprint)
GMP provides the ‘blueprint’
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Motor program and schema are in procedural
memory
In a specific situation, episodic & semantic systems
help to determine ‘what to do’
Information interacts with info in procedural memory
Motor program is selected with parameters
Skill is executed
Forgetting
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Decay theory
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Interference theory
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Proactive interference
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Retroactive interference
CAUSES OF FORGETTING
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Trace decay—time is a factor in working
memory
Proactive interference—activities that occur
prior to the presentation of information that is to
be remembered
Retroactive interference—interfering activity
occurs during retention
Forgetting—this is greatest when there is
similarity between what is remembered and the
interfering activity
Proactive Interference in working
memory
Info not to be
recalled
Time
New
Info
Recall
Why does proactive interference
impact forgetting?
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Confusion
Similarity of movements mixes up the encoding
of information
Ways to decrease impact
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Active rehearsal (talk to yourself, visualization)
Retroactive interference and
working memory
Information
to be
remembered
Recall
Time
Info not to be
remembered
Why does retroactive interference
impact forgetting?
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Too much similarity between the goal
movement and other interfering activity
Perhaps the number of movements to be made
or observed during retention interval exceeds
attention capacity
Ways to decrease impact
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When giving info, avoid showing improper techniques after
proper technique until practice has occurred
FORGETTING AND
LONG-TERM MEMORY
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Working memory ‘forgets’ more than long-term
memory
Certain types of motor skills are remembered more
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Continuous versus serial discrete skills (more cognitive
processing or procedural knowledge)
Procedural skills deteriorate over time (use it or lose it)
Long-term memory forgetting may be due to
misplacing information or a retrieval problem
STRATEGIES THAT ENHANCE MEMORY
PERFORMANCE
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Increase the movement’s meaningfulness
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Imagery (powerful rehearsal strategy)
Verbal labeling; critical element cue, ‘elbows in’
Inform one about information to be tested
(intention to remember)
Group or organize information into ways that are
meaningful (subjective organization)
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Skilled person seems to organize information as result of
practice; “chunks remembered”
STRATEGIES THAT ENHANCE MEMORY PERFORMANCE
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If the context of practice and test are similar,
memory is enhanced
This relationship between practice and test
context is called the encoding specificity
principle
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Important that practice conditions are similar to how
skills will be used in game or real life
Practical Application
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Generate a list of tips that practitioners could use to
help a learner to ‘remember’.