©2007 mcgraw-hill higher education. all rights reserved chapter 6 touch, proprioception and vision...

©2007 McGraw-Hill Higher

Education. All rights reserved

Chapter 6Chapter 6

Touch, Proprioception and Vision

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



IntroductionIntroduction

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



Touch and Motor ControlTouch 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 tipsProvide CNS with temperature, pain,

and movement info



Touch and Motor Control, cont’dTouch and Motor Control, cont’d

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

Roles of Tactile Info in Motor Control

See an example of research for typing – A Closer Look, p. 109



Proprioception andMotor ControlProprioception andMotor Control

Proprioception: The sensory system’s detection and reception of movement and spatial position of limbs, trunk, and head

•We will use the term synonymously with the term “kinesthesis”



Neural Basis of ProprioceptionNeural 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



Neural Basis of Proprioception: ProprioceptorsNeural 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



Neural Basis of Proprioception: Proprioceptors, cont’dNeural Basis of Proprioception: Proprioceptors, cont’d

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



Techniques to Investigate the Role of Propioception in Motor ControlTechniques 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



Techniques to Investigate the Role of Propioception in Motor Control, cont’dTechniques to Investigate the Role of Propioception in Motor Control, cont’d

Tendon vibration technique•Involves high speed vibration of the

tendon of the agonist muscle•Proprioceptive feedback is distorted

rather than removed



Role of Proprioceptive Feedback in Motor ControlRole 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



Vision and Motor ControlVision 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”



The Moving Room ExperimentThe 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 weren’t moving off balance

WHY?



Neurophysiology of VisionNeurophysiology of Vision

Basic Anatomy of the Eye See Figure 6.6 for the following

anatomical components•Cornea•Iris•Lens•Sclera•Aqueous humor•Vitreous humor



Neurophysiology of Vision, cont’dNeurophysiology of Vision, cont’d

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 brain’s visual cortex



Techniques for Invesigating the Role of Vision in Motor ControlTechniques for Invesigating the Role of Vision in Motor Control

Eye movment recording•Tracks foveal vision’s “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



Role of Vision in Motor ControlRole 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



Role of Vision in Motor Control, cont’d.Role of Vision in Motor Control, cont’d.

2. Central and Peripheral Vision Central vision

•Sometimes called foveal visionMiddle 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




2. Central and Peripheral Vision, cont’d. Peripheral vision

•Detects info beyond the central vision limitsUpper 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




2. Central and Peripheral Vision, cont’d Two visual systems

•Vision for perception (central vision)Anatomically referred to as the ventral stream –

from visual cortex to temporal lobeFor fine analysis of a scene, e.g. form, featuresTypically 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 movementTypically not available to consciousness




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




4. Amount of Time Needed for Movement Corrections?

Concerns vision’s 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)




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



Chapter 6Chapter 6

Touch, Proprioception and Vision

©2007 mcgraw-hill higher education. all rights reserved chapter 6 touch, proprioception and vision...

Documents

movement info touch

proprioception information

joint movement angle

reception of movement

sensory neuropathysometimes

muscle tension

muscle spindlesin

motor controlsee