1. Movement and the Changing Senses Chapter 9 McGraw-Hill/Irwin © 2012 McGraw-Hill Companies. All Rights Reserved.

2. 9-2 The communicative link between the human organism and the environment is in part made possible by the senses: vision, proprioception, touch, taste, smell, and hearing.

3. 9-3 Understanding the Mechanics of Vision Light rays converge and meet at a focal point The cornea and the fluids in the eye refract (bend) the light rays The lens can adjust the focal point by changing shape Relaxation of the ciliary muscles causes the lens to flatten Contraction of the ciliary muscles causes the lens to become more spherical

4. 9-4 Understanding the Mechanics of Vision Accommodation is the adjustment of the eye to variations in distance The retina contains two photoreceptors Rods are responsible for vision in low illumination (night vision) Cones are responsible for color vision and visual acuity

5. 9-5 Understanding the Mechanics of Vision Macula lutea: an oval yellow spot at the center of the retina Fovea centralis (point of best vision) is located here Cone cells are concentrated There is an absence of rod cells

6. 9-6 McGraw-Hill Copyright © 2011 Retina 6

7. 9-7 McGraw-Hill Copyright © 20117

8. 9-8 Understanding the Mechanics of Vision

9. 9-9 Physical Development of the Eye The eye develops as an outgrowth of the forebrain Part of the central nervous system 6 cranial nerves govern vision At birth The eye is hyperopic (light focuses behind the retina) The retina contains mostly rod cells

10. 9-10 At birth

11. 9-11 Physical Development of the Eye At 1 month postnatal Cone cells appear At 8 months postnatal Macula is mature

12. 9-12 Development of Selected Visual Traits and Skilled Motor Performance

13. 9-13 Visual Acuity Static visual acuity Target and performer are stationary 20/20 vision means that you see at 20 ft. what a person with normal vision sees at 20 ft. 20/100 means that you see at 20 ft. what a person with normal vision sees at 100 ft.

14. 9-14 Visual Acuity Degree of detail that can be seen in an object A Snellen eye chart is used to determine visual acuity

15. 9-15 Visual Acuity This Snellen eye chart is used with children in grades K-1 who may not be capable of letter recognition

16. 9-16 Visual Acuity Birth20/200 and 20/400 6 months20/200 1 yr.20/50 4-5 yr.20/20

17. 9-17 Visual Acuity Dynamic visual acuity Ability to see the detail in moving objects Ability of the central nervous system to estimate an object’s direction Ability of the ocular-motor system “to catch” and “to hold” an object’s image on the eye’s fovea long enough to see detail

18. 9-18 Visual Acuity and Motor Performance Both static and dynamic visual acuity play keys roles Dynamic visual acuity is highly correlated with success in Free throw shooting Ball catching

19. 9-19 Visual Acuity and Exercise Aerobic activities appear to improve visual acuity for up to two hours post-exercise Increase in acuity due to increase in blood flow and oxygenation to the eye

20. 9-20 Visual Acuity and Aging Age-related eye diseases (ARED) are the leading cause of loss of visual acuity Conditions/diseases Age-related macular degeneration Glaucoma Cataracts Senile miosis Diabetic retinopathy Presbyopia

21. 9-21 AREDs Age-related macular degeneration (AMD) Loss of central vision Dry form Breakdown of light sensitive cells in the macula Central vision affected Not allowed to drive and will have trouble reading No problem with general movement Wet form New blood vessels form behind the retina, leak, and destroy the macula

22. 9-22 AREDs Normal AMD Amsler Grid

23. 9-23 AREDs Glaucoma Leading cause of loss in visual acuity and blindness High pressure in eye Loss of peripheral vision Eventual loss of central vision

24. 9-24 AREDs Cataracts Clouding of the eye’s lens Initial symptoms include complaints of glare, colors that seem faded, and increased need for light when reading Senile miosis Normal loss of light restriction to the eye with age Decrease in resting diameter of the pupil

25. 9-25 AREDs Diabetic retinopathy Complication of diabetes Vessels in the retina may hemorrhage Normally clear vitreous humor discolors Detached retina can occur Presbyopia Inability to focus clearly on near objects as one ages

26. 9-26 Binocular Vision and Depth Perception Binocular vision ~ coordinated eye movements Strabismus ~ misaligned eyes Common at birth, but diminishes during the first week Depth perception A cerebral function based upon information sent by the eye to the brain

27. 9-27 Binocular Vision and Depth Perception The Visual Cliff Note the mother attempting to coax the infant into crossing the apparent deep (cliff) side Infants are capable of depth perception Gibson & Walk’s (1960) classic experiment

28. 9-28 Field of Vision Refers to the entire extent of the environment that can be seen without a change in fixation of the eye Normal lateral peripheral vision = 90 degrees from straight ahead (180 degrees total) Normal vertical peripheral vision = 47 degrees above and 65 degrees below visual midline

29. 9-29 Field of Vision David’s 1987 experiment examining peripheral vision processing during the performance of a catching task

30. 9-30 Aging and Depth Perception and Field of Vision Both disease (AMD) and anatomical facial changes may cause a loss of depth perception/field of vision with age Change in facial structure Senile ptosis Drooping of the eyelid Loss of fat tissue around orbital socket

31. 9-31 Eye Dominance Refers to the ability of one eye to lead the other in tasks involving visual tracking and visual fixation Hole-in-card test

32. 9-32 Eye Dominance Unilateral dominance Right-eyed and right-handed Left-eyed and left-handed Crossed-laterals dominance Right-eyed and left-handed Left-eyed and right handed

33. 9-33 Tracking and Object Interception Tracking an object allows the performer to gain important information about the flight path of the object Smooth pursuit system Matching of eye movement speed and speed of a projectile Saccadic eye-movement system Corrects differences between projectile location and eye fixation

34. 9-34 Tracking and Object Interception 40-52 weeks Can track a 180 degree arc 5-6 yr.Can track objects in horizontal plane 8-9 yr.Can track balls that travel in arc

35. 9-35 Tracking and Object Interception Bassin anticipation time Coincidence- anticipation Process involving object interception

36. 9-36 Motor Development of Children with Visual Impairments

37. 9-37 Blindness A definition of blindness is based upon distance vision Ranges from 20/200 (80% loss of vision) to total blindness Because visual curiosity elicits movement, the unsighted child is not visually motivated to explore the unseen world

38. 9-38 Blindness Head and trunk control Curiosity encourages lifting head and trunk in sighted children Unsighted child fusses when in a prone position – parent places child on the back which does not help with head and trunk control Independent sitting Occurs in sighted children between 4 and 8 months An unsighted child can perform this task at the same time if the parents have prepared the child

39. 9-39 Blindness Creeping By 10 months a sighted child can support him/herself on hands and knees to creep and explore An unsighted child has no enticement to explore Noise making toys help the unsighted child to creep Independent walking Both sighted and unsighted children are able to walk independently at the same time However, this task is usually delayed in unsighted children

40. 9-40 Blindness Prehension Vision is extremely important in performing the task of prehension The unsighted child exhibits a delay Play For the sighted child, play is spontaneous The unsighted child is inactive and shows no desire to experiment with the environment

41. 9-41 Bayley Scale Items

42. 9-42 Nonvisual Senses

43. 9-43 Proprioceptive System The ability to be aware of location and movements in space without visual references A factor contributing to the development of body awareness, spatial awareness, and directional awareness

44. 9-44 Proprioceptive System Mechanoreceptors Muscle spindles Golgi tendon organs Joint receptors Vestibular apparatus

45. 9-45 Proprioceptive System Muscle spindles Can gauge the amount of tension within the muscle Senses how the muscle is stretched Golgi tendon organs Monitors tension in the muscle Joint receptors “Limit detectors”

46. 9-46 Classic Knee Jerk

47. 9-47 Proprioceptive System Vestibular apparatus Located in the inner ear Rotational motion Semicircular canals (angular accelerometers) Linear acceleration Otolith organs (utricle and saccule)

48. 9-48

49. 9-49 Cutaneous System Tactile sensitivity (skin) Responses to tactile stimulation Reflex response Babinski reflex Withdrawal response Move away from unpleasant or painful object Approach response Response to kisses and hugs

50. 9-50 Key Terms