Sources of Sensory Information

1
Sources of Sensory Information
2
2 basic sources

• First from the environment, called exteroception
  (from the outside)
• Second from your body, called interoception
  (comes from inside)

3
Exterceptive Information

• Chief of these sources is your vision
• Defines the physical structure of the environment
• Second of these sources is audition- your hearing
• Very important in sports and activities requiring
  a good sense of sound for direction, speed, etc.,
  and for those who are visually impaired

4
Interoceptive Information

• Also called kinesthetic information
• More relevant to us for motor control
• More commonly called proprioception (from within
  the body)
• Includes information on positions of the joints,
  forces produced by muscles, orientation of the
  body in space

5

• Kinesthesis- sense or awareness we have of
  movements of our joints and muscles during motor
  activity
• Kinesthesis and proprioception are often used
  interchangeably
• This information critical in sports such as
  gymnastics, diving, figure skating- all those
  that require information about how your body
  moves through space

6

• Vestibular apparatus in the inner ear critical to
  posture and balance
• Muscles spindles provide the nervous system with
  information about changes in muscle length
• Golgi tendon organs (junction of muscle and
  tendon) give information about level of force in
  muscle
• Cutaneous receptors are in most skin areas, give
  information about pressure, temperature and touch
  (haptic information)

7
Closed-Loop Control Systems

• How does a heating-cooling system work in your
  home?
• Comparator- (thermostat) senses difference
  between goal and actual room temperature
  (action/no action)
• If an error occurs (action) sends a signal to the
  executive, which is the command or control center
• The executive issues a command to the effector,
  which is responsible for carrying out the action
• Sensory information is carried back to the
  comparator, called feedback, and the loop starts
  over again

8
When do we use this model?

• Driving a car
• Walking
• Sitting
• When else?

9
Conceptual Model

• We have already worked with the information
  processing model
• Stimulus identification, response selection,
  response programming
• This is the executive part of the conceptual
  model
• The motor program in the brain, the spinal cord
  and muscles are the effector- they are the parts
  that carry out the actions

10

• The output- product- performance- provides the
  feedback
• And the comparator is the desired state vs. the
  actual state of performance based on the feedback
• The desired state is determined by the look, the
  sound and the feel of the movement
• When input arrives the desired state is
  determined and represents the feedback you should
  get if you perform the movement correctly

11
Conceptual Model and Continuous Long-Duration
Skills

• Useful for maintaining balance and posture
  (throwing darts, casting a lure, etc.)
• Continuous tracking skills require attending to a
  constantly changing target, such as driving a
  car, running a 10K race- these type of activities
  require using exteroceptive information as well
  as kinesthetic feedback

12
Limitations of Closed-Loop Systems

• Although the system has flexibility in movement
  control and allows for a variety of movement
  options and strategies, its biggest disadvantage
  is that control is very slow particularly in the
  response programming stage. Although you are
  getting feedback, you have to wait for that
  feedback before you can make changes

13
The Conceptual Model
Input
Error
Stimulus Identification
Executive
Response Selection
Response Programming
Desired state
Comparator
Motor Program
Actual state
Effector
Proprioceptive feedback
Spinal Cord
Muscle force, length, joint position, body
position
Muscles
Exteroceptive feedback
Output
Vision, audition
14
Chapter 4 Continued

• Sources of Sensory Information

15
Rapid Tracking Behavior

• Remember that the information processing model
  stages require time and attention so closed-loop
  systems that include these stages are slow as
  well
• In the model corrections occur a few hundred
  milliseconds after an error occurs
• Error processed (stimulus-ID stage)
• Movement Correction (Response selection stage)
• Modification organization/initiation (response
  programming stage)
• Adequate if only 2-3 changes required per second

16
Discrete Tasks of Brief Duration

• Closed-loop system also inadequate when it comes
  to such brief skills as hitting, striking
  throwing, catching common in sport (the actual
  action itself, not the preparation phase)
• If too much time elapses between when the
  movement is initiated and when correction can be
  made, success may not occur
• Therefore, the first few hundred milliseconds of
  a brief, rapid movement occur more or less
  without modification
• Finally, scientists have determined that there is
  an all or nothing point where a go signal is
  initiated and the movement proceeds without
  interruption (Slater-Hamel experiment)

17
Reflexive Modulations in Movement Skills

• To this point we have been talking about
  consciously controlled movement adjustments based
  on sensory information. However, there are other
  adjustments, called reflexes, that occur at the
  spinal cord and brain stem level that go on at
  the same time as controlled movement.

18
Types of Compensation

• M1 Response
• One of the most rapid underlying limb control,
  prompted when and unexpected load is added to a
  limb. 30-50 ms, involves 1 synapse, is
  non-conscious and automatic
• M2 Response
• 50-80 ms after the load comes the functional
  stretch reflex, which also travels to the spinal
  cord, but then moves on to the brain stem. Here
  muscles are activated to help with the load
  (knee-jerk reflex). Not affected by SR
  alternatives, but we can adjust the amplitude of
  the response

19

• Triggered Reaction
• 80-120 ms too fast to be voluntary, but too slow
  for M1 or M2. This is the little slip of the
  glass (called wineglass effect) made before you
  are even aware the glass is slipping, caused by
  awareness of slippage against the cells of your
  skin
• Voluntary Reaction-Time Response (M3)
• 120-180ms, voluntary response, powerful and
  sustained, can affect all muscles in the body,
  not just those being stretched. This response is
  sensitive to Hicks Law.
• Coordinating compensations
• If more flexibility is needed more sources of
  sensory information must be taken into account
  before the action is defined, so more time is
  needed to process information

20

• Reflexes in the conceptual Model
• M1 and M2 occur in the effector stage
• Final common path and loops within loops
• Role of Movement Time- the amount of time that
  elapses from beginning to end of a persons
  movement
• Only when the action takes longer than 300 ms is
  there potential for all responses to be active
• Choices among modes of control
• If performer can choose then the system can be
  preprogrammed
• We do this when we tell a student to
  concentrate or focus on a particular source
  of feedback
• Voluntary feedback leads to over-control- when
  perhaps preprogrammed operation corrected by
  inner feedback loops would be best

21
Role of Two Visual Systems in Movement Control

• We have two different visual systems
• Focal vision for object identification and
  ambient vision for movement control

22
Focal Vision

• Used to identify objects in the center of your
  visual field
• Answers the question what is it?
• It is conscious
• It is biased by movement
• It is diminished by dim light

23
Ambient Vision

• Uses both central and peripheral portions of the
  visual field
• Not degraded by dim light
• Believe it is specialized for movement control,
  to detect motion as well as the position of
  objects in the environment
• Answers the questions where is it? and where
  am I in relation to it?
• Contributes to fine control of movement

24
Visual Control of Movement Skills

• Focal Vision and Movement Control
• Vision processed as another source of
  exteroceptive information
• Particularly important when we fail to accurately
  identify objects in our environment, such as
  during night driving

25

• Ambient vision and movement control
• Optical flow- movement of patterns of light rays
  from the environment over a persons retina,
  allowing the person to perceive motion, position
  and timing
• Aids in stability and balance, velocity of
  movement through the environment, direction of
  movement relative to fixed objects, movement of
  environmental objects relative to the observer,
  time until contact between observer and object
• Visual proprioception- information about movement
  of your body in space

26

• Concept of Tau
• As objects approach us, the retinal image
  expands. That rate of expansion (how fast or
  slow) tells us the speed of the approaching
  object. So, images that expand on our retina are
  approaching more quickly.
• This is important for people who perform
  interceptive actions (catching a ball) or
  coincident-timing tasks (preparing the body for
  entry into the water at the proper time of a
  springboard dive)

27

• Balance
• Strongly affected by varying the visual
  information presented to the person (spotting on
  a wall)
• Vision in the Conceptual Model
• Focal system is exteroceptive
• Ambient system is more non-conscious

28
Visual Dominance and Visual Capture

• Visual dominance
• Tendency for visual information to supersede
  information coming from other senses
• Visual capture
• Tendency for visual information to attract a
  persons attention more easily than other forms
  of information