Touch, Proprioception and Vision

1
Chapter 6

• Touch, Proprioception and Vision

Concept Touch, proprioception and vision are
important components of motor control
2
Introduction

• Sensory information is essential for all theories
  of motor control and learning
• Provides pre-movement information
• Provides feedback about the movement in progress
• Provides post-movement information about action
  goal achievement
• Focus of current chapter is three types of
  sensory information
• Touch, vision, and proprioception

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Touch and Motor Control

• Describe some ways we use touch to help us
  achieve action goals
• Neural basis of touch see Fig. 6.1
• Skin receptors
• Mechanoreceptors located in the dermis layer of
  skin
• Greatest concentration in finger tips
• Provide CNS with temperature, pain, and movement
  info

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Touch and Motor Control, contd
Roles of Tactile Info in Motor Control

• Typical research technique
• Compare performance of task involving finger(s)
  before and after anesthetizing finger(s)

• Research shows tactile sensory info influences
• Movement accuracy
• Movement consistency
• Movement force adjustments

See an example of research for typing A Closer
Look, p. 109
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Proprioception and Motor Control

• Proprioception The sensory systems detection
  and reception of movement and spatial position of
  limbs, trunk, and head
• We will use the term synonymously with the term
  kinesthesis

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Neural Basis of Proprioception

• CNS receives proprioception information from
  sensory neural pathways that begin in specialized
  sensory neurons known as proprioceptors
• Located in muscles, tendons, ligaments, and
  joints
• Three primary types of proprioceptors
• Muscle spindles
• Golgi tendon organs
• Joint receptors

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Neural Basis of Proprioception Proprioceptors

• 1. Muscle spindles
• In most skeletal muscles in a capsule of
  specialized muscle fibers and sensory neurons
• Intrafusal fibers see Fig. 6.2
• Lie in parallel with extrafusal muscle fibers
• Mechanoreceptors that detect changes in muscle
  fiber length (i.e. stretch) and velocity (i.e.
  speed of stretch)
• Enables detection of changes in joint angle
• Function as a feedback mechanism to CNS to
  maintain intended limb movement position,
  direction, and velocity

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Neural Basis of Proprioception Proprioceptors,
contd

• 2. Golgi-Tendon Organs (GTO)
• In skeletal muscle near insertion of tendon
• Detect changes in muscle tension (i.e. force)
• Poor detectors of muscle length changes

• 3. Joint Receptors
• Several types located in joint capsule and
  ligaments
• Mechanoreceptors that detect changes in
• Force and rotation applied to the joint,
• Joint movement angle, especially at the extreme
  limits of angular movement or joint positions

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Techniques to Investigate the Role of
Propioception in Motor Control

• Deafferentation techniques
• Surgical deafferentation
• Afferent neutral pathways associated with
  movements of interest have been surgically
  removed or altered
• Deafferentation due to sensory neuropathy
• Sometimes called peripheral neuropathy
• Large myelinated fibers of the limb are lost,
  leading to a loss of all sensory information
  except pain and temperature
• Temporary deafferentation
• Nerve block technique Inflate blood-pressure
  cuff to create temporary disuse of sensory nerves

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Techniques to Investigate the Role of
Propioception in Motor Control, contd

• Tendon vibration technique
• Involves high speed vibration of the tendon of
  the agonist muscle
• Proprioceptive feedback is distorted rather than
  removed

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Role of Proprioceptive Feedback in Motor Control

• Research using the deafferentation and tendon
  vibration techniques has demonstrated that
  proprioception influences
• Movement accuracy
• Target accuracy
• Spatial and temporal accuracy for movement in
  progress
• Timing of onset of motor commands
• Coordination of body and/or limb segments
• Postural control
• Spatial-temporal coupling between limbs and limb
  segments
• Adapting to new situations requiring
  non-preferred movement coordination patterns

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Vision and Motor Control

• Vision is our preferred source of sensory
  information
• Evidence from everyday experiences
• Beginning typists look at their fingers
• Beginning dancers look at their feet
• Evidence from research
• The classic moving room experiment

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The Moving Room Experiment

• Lee Aronson (1974)
• Participants stood in a room in which the walls
  moved toward or away from them but floor did not
  move
• Situation created a conflict between which two
  sensory systems?
• Vision proprioception

• Results
• When the walls moved, people adjusted their
  posture to not fall, even though they werent
  moving off balance
• WHY?

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Neurophysiology of Vision

• Basic Anatomy of the Eye
• See Figure 6.6 for the following anatomical
  components
• Cornea
• Iris
• Lens
• Sclera
• Aqueous humor
• Vitreous humor

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Neurophysiology of Vision, contd

• Neural Components of the Eye and Vision
• Retina see Fig. 6.6
• Fovea centralis
• Optic disk
• Rods
• Cones
• Optic nerve (cranial nerve II) Fig. 6.7
• From the retina to the brains visual cortex

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Techniques for Invesigating the Role of Vision in
Motor Control

• Eye movment recording
• Tracks foveal visions point of gaze
• i.e. what the person is looking at
• Temporal occlusion techniques
• Stop video or film at various times
• Spectacles with liquid crystal lenses
• Event occlusion technique
• Mask view on video or film of specific events or
  characteristics

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Role of Vision in Motor Control

• Evidence comes from research investigating
  specific issues and vision characteristics
• 1. Monocular vs. Binocular Vision
• Binocular vision important for depth-perception
  when 3-dimensional features involved in
  performance situation, e.g.
• Reaching grasping objects
• Walking on a cluttered pathway
• Intercepting a moving object

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Role of Vision in Motor Control, contd.

• 2. Central and Peripheral Vision
• Central vision
• Sometimes called foveal vision
• Middle 2-5 deg. of visual field
• Provides specific information to allow us to
  achieve action goals, e.g.
• For reaching and grasping an object specific
  characteristic info, e.g. size, shape, required
  to prepare, move, and grasp object
• For walking on a pathway specific pathway info
  needed to stay on the pathway

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Role of Vision in Motor Control, contd.

• 2. Central and Peripheral Vision, contd.
• Peripheral vision
• Detects info beyond the central vision limits
• Upper limit typically 200 deg.
• Provides info about the environmental context and
  the moving limb(s)
• When we move through an environment, peripheral
  vision detects info by assessing optical flow
  patterns
• Optical flow rays of light that strike the
  retina

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Role of Vision in Motor Control, contd.

• 2. Central and Peripheral Vision, contd
• Two visual systems
• Vision for perception (central vision)
• Anatomically referred to as the ventral stream
  from visual cortex to temporal lobe
• For fine analysis of a scene, e.g. form, features
• Typically available to consciousness
• Vision for action (peripheral vision)
• Anatomically referred to as the dorsal stream
  from visual cortex to posterior parietal lobe
• For detecting spatial characteristics of a scene
  and guiding movement
• Typically not available to consciousness

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Role of Vision in Motor Control, contd.

• 3. Perception Action Coupling
• As discussed in ch. 5, refers to the coupling
  (i.e. linking together) of a perceptual event and
  an action
• Example of research evidence
• See experiments by Helsen et al. (1998 2000)
  described in textbook (pp.127 128)
• Results show that spatial and temporal
  characteristics of limb movements occurred
  together with specific spatial and temporal
  characteristics of eye movements

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Role of Vision in Motor Control, contd.

• 4. Amount of Time Needed for Movement
  Corrections?
• Concerns visions feedback role during movement
• Researchers have tried to answer this question
  since original work by Woodworth in 1899
• Typical procedure Compare accuracy of rapid
  manual aiming movements of various MTs with
  target visible and then not visible just after
  movement begins
• Expect accurate movement with lights off when no
  visual feedback needed during movement
• Currently, best estimate is a range of 100 160
  msec. (The typical range for simple RT to a
  visual signal)

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Role of Vision in Motor Control, contd.

• 5. Time-to-Contact The Optical Variable tau
• Concerns situations in which
• Object moving to person must be intercept
• Person moving toward object needs to contact or
  avoid contact with object
• Vision provides info about time-to-contact object
  which motor control system uses to initiate
  movement
• Automatic, non-conscious specification based on
  changing size of object on retina
• At critical size, requisite movement initiated
• David Lee (1974) showed the time-to-contact info
  specified by an optical variable (tau), which
  could be mathematically quantified
• Motor control benefit Automatic movement
  initiation