Chapter 6Chapter 6

Touch, Proprioception and Touch, Proprioception and VisionVision

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

IntroductionIntroduction

Sensory information is essential for all theories Sensory information is essential for all theories of motor control and learningof motor control and learning

–Provides pre-movement information Provides pre-movement information –Provides feedback about the movement in progressProvides feedback about the movement in progress–Provides post-movement information about action Provides post-movement information about action

goal achievementgoal achievement

Focus of current chapter is three types of Focus of current chapter is three types of sensory informationsensory information

–Touch, vision, and proprioceptionTouch, vision, and proprioception

Touch and Motor ControlTouch and Motor Control

Describe some ways we use touch to help Describe some ways we use touch to help us achieve action goalsus achieve action goals

Neural basis of touch Neural basis of touch [[see Fig. 6.1see Fig. 6.1]]

–Skin receptorsSkin receptorsMechanoreceptors located in the dermis layer of Mechanoreceptors located in the dermis layer of

skinskin

Greatest concentration in finger tipsGreatest concentration in finger tips

Provide CNS with temperature, pain, and Provide CNS with temperature, pain, and movement info movement info

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

Typical research Typical research techniquetechnique

–Compare performance Compare performance of task involving finger(s) of task involving finger(s) before and after before and after anesthetizing finger(s)anesthetizing finger(s)

Research shows tactile Research shows tactile sensory info influencessensory info influences::

–Movement accuracyMovement accuracy

–Movement consistencyMovement consistency

–Movement force adjustmentsMovement force adjustments

Roles of Tactile Info in Motor Control

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

Proprioception and Motor ControlProprioception and Motor Control

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

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

Neural Basis of ProprioceptionNeural Basis of Proprioception

CNS receives proprioception information from CNS receives proprioception information from sensory neural pathways that begin in sensory neural pathways that begin in specialized sensory neurons known as specialized sensory neurons known as proprioceptorsproprioceptors

–Located in muscles, tendons, ligaments, and jointsLocated in muscles, tendons, ligaments, and joints

Three primary types of proprioceptorsThree primary types of proprioceptors–Muscle spindlesMuscle spindles–Golgi tendon organsGolgi tendon organs–Joint receptorsJoint receptors

Neural Basis of Proprioception: Neural Basis of Proprioception: ProprioceptorsProprioceptors1.1. Muscle spindlesMuscle spindles

In most skeletal muscles in a capsule of specialized In most skeletal muscles in a capsule of specialized muscle fibers and sensory neuronsmuscle fibers and sensory neurons

–Intrafusal fibers Intrafusal fibers [[see Fig. 6.2see Fig. 6.2]]–Lie in parallel with extrafusal muscle fibersLie in parallel with extrafusal muscle fibers

Mechanoreceptors that detect changes in muscle fiber Mechanoreceptors that detect changes in muscle fiber length (i.e. stretch) and velocity (i.e. speed of stretch)length (i.e. stretch) and velocity (i.e. speed of stretch)

–Enables detection of changes in joint angleEnables detection of changes in joint angle

Function as a feedback mechanism to CNS to maintain Function as a feedback mechanism to CNS to maintain intended limb movement position, direction, and velocityintended limb movement position, direction, and velocity

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

2.2. Golgi-Tendon Organs Golgi-Tendon Organs (GTO)(GTO)

In skeletal muscle near In skeletal muscle near insertion of tendoninsertion of tendon

Detect changes in muscle Detect changes in muscle tension (i.e. force)tension (i.e. force)

–Poor detectors of muscle Poor detectors of muscle length changeslength changes

3.3. Joint ReceptorsJoint Receptors

Several types located in Several types located in joint capsule and joint capsule and ligamentsligaments

Mechanoreceptors that Mechanoreceptors that detect changes in detect changes in

–Force and rotation Force and rotation applied to the joint, applied to the joint,

– Joint movement angle, Joint movement angle, especially at the extreme especially at the extreme limits of angular movement limits of angular movement or joint positions or joint positions

Techniques to Investigate the Role Techniques to Investigate the Role of Propioception in Motor Controlof Propioception in Motor Control

Deafferentation techniquesDeafferentation techniquesSurgical deafferentationSurgical deafferentation

–Afferent neutral pathways associated with movements of Afferent neutral pathways associated with movements of interest have been surgically removed or alteredinterest have been surgically removed or altered

Deafferentation due to sensory neuropathyDeafferentation due to sensory neuropathy–Sometimes called “peripheral neuropathy” Sometimes called “peripheral neuropathy” –Large myelinated fibers of the limb are lost, leading to a loss of Large myelinated fibers of the limb are lost, leading to a loss of

all sensory information except pain and temperatureall sensory information except pain and temperature

Temporary deafferentationTemporary deafferentation–““Nerve block technique” – Inflate blood-pressure cuff to create Nerve block technique” – Inflate blood-pressure cuff to create

temporary disuse of sensory nerves temporary disuse of sensory nerves

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

Tendon vibration techniqueTendon vibration technique–Involves high speed vibration of the tendon Involves high speed vibration of the tendon

of the agonist muscleof the agonist muscle–Proprioceptive feedback is distorted rather Proprioceptive feedback is distorted rather

than removedthan removed

Role of Proprioceptive Role of Proprioceptive Feedback in Motor ControlFeedback in Motor ControlResearch using the deafferentation and tendon vibration Research using the deafferentation and tendon vibration

techniques has demonstrated that proprioception techniques has demonstrated that proprioception influences:influences: Movement accuracy Movement accuracy

–Target accuracyTarget accuracy–Spatial and temporal accuracy for movement in progressSpatial and temporal accuracy for movement in progress

Timing of onset of motor commandsTiming of onset of motor commands

Coordination of body and/or limb segmentsCoordination of body and/or limb segments–Postural controlPostural control–Spatial-temporal coupling between limbs and limb segmentsSpatial-temporal coupling between limbs and limb segments–Adapting to new situations requiring non-preferred movement Adapting to new situations requiring non-preferred movement

coordination patternscoordination patterns

Vision and Motor ControlVision and Motor Control

Vision is our preferred source of sensory Vision is our preferred source of sensory informationinformation

Evidence from everyday experiencesEvidence from everyday experiences–Beginning typists look at their fingersBeginning typists look at their fingers–Beginning dancers look at their feetBeginning dancers look at their feet

Evidence from researchEvidence from research–The classic “moving room experiment”The classic “moving room experiment”

The Moving Room ExperimentThe Moving Room Experiment

Lee & Aronson (1974)Lee & Aronson (1974) Participants stood in a room in Participants stood in a room in

which the walls moved toward which the walls moved toward or away from them but floor did or away from them but floor did not movenot move

Situation created a conflict Situation created a conflict between which two sensory between which two sensory systems?systems?

Vision & proprioceptionVision & proprioception

ResultsResults When the walls moved, When the walls moved,

people adjusted their people adjusted their posture to not fall, even posture to not fall, even though they weren’t though they weren’t moving off balancemoving off balance

WHY?WHY?

Neurophysiology of VisionNeurophysiology of Vision

Basic Anatomy of the EyeBasic Anatomy of the Eye

See Figure 6.6 for the following anatomical See Figure 6.6 for the following anatomical componentscomponents

–CorneaCornea–IrisIris–LensLens–ScleraSclera–Aqueous humorAqueous humor–Vitreous humorVitreous humor

Neurophysiology of Vision, Neurophysiology of Vision, cont’dcont’dNeural Components of the Eye and VisionNeural Components of the Eye and Vision

Retina Retina [[see Fig. 6.6see Fig. 6.6]]

–Fovea centralisFovea centralis–Optic diskOptic disk–RodsRods–ConesCones

Optic nerve (cranial nerve II) Optic nerve (cranial nerve II) [[Fig. 6.7Fig. 6.7]]

–From the retina to the brain’s visual cortexFrom the retina to the brain’s visual cortex

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

Eye movment recordingEye movment recording–Tracks foveal vision’s “point of gaze”Tracks foveal vision’s “point of gaze”

i.e. “what” the person is looking at i.e. “what” the person is looking at

Temporal occlusion techniquesTemporal occlusion techniques–Stop video or film at various timesStop video or film at various times–Spectacles with liquid crystal lensesSpectacles with liquid crystal lenses

Event occlusion techniqueEvent occlusion technique–Mask view on video or film of specific events or Mask view on video or film of specific events or

characteristicscharacteristics

Role of Vision in Motor ControlRole of Vision in Motor Control

Evidence comes from research investigating Evidence comes from research investigating specific issues and vision characteristics:specific issues and vision characteristics:

1.1. Monocular vs. Binocular VisionMonocular vs. Binocular Vision

Binocular vision important for Binocular vision important for depth-perceptiondepth-perception when 3-dimensional features involved in when 3-dimensional features involved in performance situation, e.g. performance situation, e.g.

–Reaching – grasping objectsReaching – grasping objects–Walking on a cluttered pathwayWalking on a cluttered pathway–Intercepting a moving object Intercepting a moving object

Role of Vision in Motor Control, Role of Vision in Motor Control, cont’d.cont’d.2.2. Central and Peripheral VisionCentral and Peripheral Vision

Central visionCentral vision–Sometimes called foveal visionSometimes called foveal vision

Middle 2-5 deg. of visual fieldMiddle 2-5 deg. of visual field

–Provides specific information to allow us to achieve Provides specific information to allow us to achieve action goals, e.g.action goals, e.g.

For reaching and grasping an objectFor reaching and grasping an object – specific – specific characteristic info, e.g. size, shape, required to prepare, move, characteristic info, e.g. size, shape, required to prepare, move, and grasp objectand grasp object

For walking on a pathwayFor walking on a pathway – specific pathway info needed to – specific pathway info needed to stay on the pathwaystay on the pathway

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

2.2. Central and Peripheral Vision, cont’dCentral and Peripheral Vision, cont’d..Peripheral visionPeripheral vision

–Detects info beyond the central vision limitsDetects info beyond the central vision limitsUpper limit typically ~ 200 deg.Upper limit typically ~ 200 deg.

–Provides info about the environmental context and Provides info about the environmental context and the moving limb(s)the moving limb(s)

–When we move through an environment, peripheral When we move through an environment, peripheral vision detects info by assessing vision detects info by assessing optical flow patternsoptical flow patterns

Optical flow =Optical flow = rays of light that strike the retina rays of light that strike the retina

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

2.2. Central and Peripheral Vision, cont’dCentral and Peripheral Vision, cont’dTwo visual systemsTwo visual systems

–Vision for perception (Vision for perception (central visioncentral vision))Anatomically referred to as the Anatomically referred to as the ventral streamventral stream – – from visual from visual

cortex to temporal lobecortex to temporal lobe

For fine analysis of a scene, e.g. form, featuresFor fine analysis of a scene, e.g. form, features

Typically available to consciousnessTypically available to consciousness

–Vision for action (Vision for action (peripheral visionperipheral vision))Anatomically referred to as the Anatomically referred to as the dorsal streamdorsal stream – – from visual from visual

cortex to posterior parietal lobecortex to posterior parietal lobe

For detecting spatial characteristics of a scene and guiding For detecting spatial characteristics of a scene and guiding movementmovement

Typically not available to consciousnessTypically not available to consciousness

Role of Vision in Motor Control, Role of Vision in Motor Control, cont’d.cont’d.3.3. Perception – Action CouplingPerception – Action Coupling

As discussed in ch. 5, refers to the “coupling” (i.e. As discussed in ch. 5, refers to the “coupling” (i.e. linking together) of a perceptual event and an linking together) of a perceptual event and an actionaction

Example of research evidence:Example of research evidence:–See experiments by Helsen et al. (1998 & 2000) See experiments by Helsen et al. (1998 & 2000)

described in textbook (pp.127 – 128)described in textbook (pp.127 – 128)

–Results show that spatial and temporal Results show that spatial and temporal characteristics of limb movements occurred together with characteristics of limb movements occurred together with specific spatial and temporal characteristics of eye specific spatial and temporal characteristics of eye movementsmovements

Role of Vision in Motor Control, Role of Vision in Motor Control, cont’d.cont’d.4.4. Amount of Time Needed for Movement Amount of Time Needed for Movement

Corrections?Corrections?Concerns vision’s feedback role during movementConcerns vision’s feedback role during movement

Researchers have tried to answer this question since Researchers have tried to answer this question since original work by Woodworth in 1899original work by Woodworth in 1899

Typical procedure:Typical procedure: Compare accuracy of rapid manual Compare accuracy of rapid manual aiming movements of various MTs with target visible and aiming movements of various MTs with target visible and then not visible just after movement beginsthen not visible just after movement begins

–Expect accurate movement with lights off when no visual Expect accurate movement with lights off when no visual feedback needed during movement feedback needed during movement

–Currently, best estimate is a Currently, best estimate is a range of 100 – 160 msec.range of 100 – 160 msec. (The (The typical range for simple RT to a visual signal)typical range for simple RT to a visual signal)

Role of Vision in Motor Control, Role of Vision in Motor Control, cont’d.cont’d.5.5. Time-to-Contact: The Optical Variable Time-to-Contact: The Optical Variable tautau

Concerns situations in whichConcerns situations in which–Object moving to person must be interceptObject moving to person must be intercept–Person moving toward object needs to contact or avoid contact Person moving toward object needs to contact or avoid contact

with objectwith object

Vision provides info about time-to-contact object which Vision provides info about time-to-contact object which motor control system uses to initiate movementmotor control system uses to initiate movement

–Automatic, non-conscious specification based on changing size Automatic, non-conscious specification based on changing size of object on retinaof object on retina

–At critical size, requisite movement initiatedAt critical size, requisite movement initiated

David Lee (1974) showed the time-to-contact info David Lee (1974) showed the time-to-contact info specified by an optical variable (specified by an optical variable (tautau), which could be ), which could be mathematically quantifiedmathematically quantifiedMotor control benefit –Motor control benefit – Automatic movement initiation Automatic movement initiation