TOUCH, HAPTICS & PROPRIOCEPTION
Touch <ul><li>The oldest perceptual modality </li></ul><ul><li>The most social sense </li></ul><ul><li>The most closely li...
Receptive Field <ul><li>Mechanoreceptors  detect skin deformations Tactile acuity is determined by how close the mechanore...
Receptive Field
Receptive Field The two-point threshold for any part of the body is determined by the size of the receptive fields and the...
Receptive Field The two-point threshold for any part of the body is determined by the size of the receptive fields and the...
Types of Fibers <ul><li>Rapidly Adapting (RA) -respond to changes in stimulation, but do not continue to respond to consta...
The nerve fibers enervate four receptor types <ul><li>Receptors </li></ul><ul><li>Meissner Corpuscles (RA-punctate) respon...
Four Receptor Types <ul><li>Merkel Receptor SA Punctate </li></ul><ul><li>Meissner Corpuscle RA Punctate </li></ul><ul><li...
Cross Section of the Skin
Peripheral Pathways of Touch <ul><li>Proprioceptors </li></ul><ul><li>Mechanoreceptors </li></ul><ul><li>Two pathways for ...
Peripheral Pathways for Touch
Peripheral Pathways For Touch
Cortical Pathways of Touch
Sensation of Touch <ul><li>Adjacent portions of skin surface tend to be represented by adjacent portions of cortex </li></...
Cortical Magnification <ul><li>The receptive fields and cortical representations give more acuity to fingers, mouth, nose ...
Cortical Magnification corresponds to greater acuity
Cortical Plasticity for Touch
Faculties of Touch <ul><li>1)  Object identification </li></ul><ul><li>2) Proprioception </li></ul><ul><li>3) Object local...
Object Identification <ul><li>Haptics provide abstract, 3-D information about object form </li></ul><ul><li>Spatial Freque...
Haptics <ul><li>Active touch is a mode of perceptual explorarion (c.f., visual search) </li></ul><ul><li>Haptics can detec...
Haptics
Spatial Frequencies <ul><li>Spatial frequencies correspond to the rate of minute deformation which determine texture (i.e....
Proprioception <ul><li>All muscles have nerve fibers which detect the amount the muscle is stretched </li></ul><ul><li>All...
Proprioception
Prioprioception Includes  The Vestibular Sense Ocular Motor
Haptics, Proprioception and Object Location <ul><li>Prioprioceptors allow you to determine the position of every part of y...
Interactions of Touch  & Vision
 
Thermal Conductance  <ul><li>A uniquely tactile object property  </li></ul><ul><li>The rate at which heat is gained or los...
Pain <ul><li>Pain Pathway </li></ul>Somatosensory Cortex Thalamus Spinal Cord Dorsal Horn Nerve Free Nerve Ending
Pain <ul><li>Sharp Pain Reflex </li></ul><ul><li>Limb is pulled toward the body out of harms way </li></ul><ul><li>Normal ...
Pain: The Reflex Arc
Gaiting Pain <ul><li>Gate control theory of pain - pain is actively suppressed in emergency situations by messages sent fr...
Gating Pain: Dorsal Horn (Root) Back Chest
Spino-Thalamic Pathway:  Temperature & Pain
Medial Lemniscal Pathway:  Mechanoreceptors &  Proprioception
Phantom Pain <ul><li>After surgical removal of a limb, sensations resume in the limb </li></ul><ul><li>In 90% of patients,...
Phantom Pain:  Strange Facts <ul><li>Stimulating certain areas of skin (e.g., face) may aggrevate phantom pain. </li></ul>...
Phantom Pain:  A Theory <ul><li>Recall that the cortex is plastic and may reorganize. </li></ul><ul><li>Normally this invo...
Phantom Pain The cortical areas for the face annex the cortical areas for the arm and fingers. Some of those neurons were ...
Phantom Pain <ul><li>TENS  (transcutaneous electrical stimulation) uses tiny electrical pulses, delivered through the skin...
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12 touch

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12 touch

  1. 1. TOUCH, HAPTICS & PROPRIOCEPTION
  2. 2. Touch <ul><li>The oldest perceptual modality </li></ul><ul><li>The most social sense </li></ul><ul><li>The most closely linked to motion and action </li></ul>
  3. 3. Receptive Field <ul><li>Mechanoreceptors detect skin deformations Tactile acuity is determined by how close the mechanoreceptors are to each other and by the size of the receptive field </li></ul>
  4. 4. Receptive Field
  5. 5. Receptive Field The two-point threshold for any part of the body is determined by the size of the receptive fields and the extent of overlap
  6. 6. Receptive Field The two-point threshold for any part of the body is determined by the size of the receptive fields and the extent of overlap
  7. 7. Types of Fibers <ul><li>Rapidly Adapting (RA) -respond to changes in stimulation, but do not continue to respond to constant stimulation </li></ul><ul><li>Slowly Adapting (SA) -respond to constant stimulation </li></ul><ul><li>Punctate - small receptive fields with distinct boundaries </li></ul><ul><li>Diffuse - large receptive fields with non-distinct boundaries </li></ul>
  8. 8. The nerve fibers enervate four receptor types <ul><li>Receptors </li></ul><ul><li>Meissner Corpuscles (RA-punctate) responds best to active touch involved in object exploration </li></ul><ul><li>Pacinian Corpuscles (RA-diffuse) extremely sensitive over a large receptive field -- blow gently on the palm of your hand </li></ul><ul><li>Merkel Disks (SA-punctate) constant sources of stimulation over a small area, such as if you were carrying a pebble </li></ul><ul><li>Ruffini Endings (SA-diffuse)constant stimulation over a larger area - also detects skin stretch </li></ul><ul><li>Free nerve endings - pain fibers & thermal conductance fibers </li></ul>
  9. 9. Four Receptor Types <ul><li>Merkel Receptor SA Punctate </li></ul><ul><li>Meissner Corpuscle RA Punctate </li></ul><ul><li>Ruffini Ending SA Diffuse </li></ul><ul><li>Pacinian Corpuscle RA Diffuse </li></ul>
  10. 10. Cross Section of the Skin
  11. 11. Peripheral Pathways of Touch <ul><li>Proprioceptors </li></ul><ul><li>Mechanoreceptors </li></ul><ul><li>Two pathways for pain (both of which are independent from other tactile or proprioceptive pathways) – </li></ul><ul><ul><li>one fast pathway for sharp pain, </li></ul></ul><ul><ul><li>one slow pathway for dull pain </li></ul></ul>
  12. 12. Peripheral Pathways for Touch
  13. 13. Peripheral Pathways For Touch
  14. 14. Cortical Pathways of Touch
  15. 15. Sensation of Touch <ul><li>Adjacent portions of skin surface tend to be represented by adjacent portions of cortex </li></ul><ul><li>Cortical magnification for lips, nose and fingers </li></ul>
  16. 16. Cortical Magnification <ul><li>The receptive fields and cortical representations give more acuity to fingers, mouth, nose and tongue </li></ul>
  17. 17. Cortical Magnification corresponds to greater acuity
  18. 18. Cortical Plasticity for Touch
  19. 19. Faculties of Touch <ul><li>1) Object identification </li></ul><ul><li>2) Proprioception </li></ul><ul><li>3) Object localization </li></ul><ul><li>4) Detection of tissue damage </li></ul>
  20. 20. Object Identification <ul><li>Haptics provide abstract, 3-D information about object form </li></ul><ul><li>Spatial Frequency Analysis of Skin Deformations provides information about local form texture, density, mass and torque </li></ul><ul><li>Thermal conductance gives information about object material properties </li></ul>
  21. 21. Haptics <ul><li>Active touch is a mode of perceptual explorarion (c.f., visual search) </li></ul><ul><li>Haptics can detect gross features of objects form, mass, weight distribution, torque, </li></ul>
  22. 22. Haptics
  23. 23. Spatial Frequencies <ul><li>Spatial frequencies correspond to the rate of minute deformation which determine texture (i.e. coarse, smooth etc.) </li></ul><ul><li>Larger deformations correspond to object features </li></ul><ul><li>Active touch ( Haptics ) allows us to determine the position of tactile features on an object relative to each other </li></ul><ul><li>These features corresponds to visual information about texture, shape and form and relative position </li></ul><ul><li>Sensory Substitution --Braille </li></ul>
  24. 24. Proprioception <ul><li>All muscles have nerve fibers which detect the amount the muscle is stretched </li></ul><ul><li>All joints have fibers which detect the relative position of each bone </li></ul><ul><li>Together these allow you to determine the position of every part of your body. </li></ul>
  25. 25. Proprioception
  26. 26. Prioprioception Includes The Vestibular Sense Ocular Motor
  27. 27. Haptics, Proprioception and Object Location <ul><li>Prioprioceptors allow you to determine the position of every part of your body. </li></ul><ul><li>Haptic touch is the interaction of proprioceptive and mechanoreceptive information </li></ul><ul><li>Object location is determined (within a narrow range) by the position of the object relative to the body </li></ul>
  28. 28. Interactions of Touch & Vision
  29. 30. Thermal Conductance <ul><li>A uniquely tactile object property </li></ul><ul><li>The rate at which heat is gained or lost between the skin and an object - we do not detect absolute temperature </li></ul><ul><li>Metal objects, fluids etc. create a more extreme sensation of temperature than do other objects (despite no differences in absolute temperature) because heat energy is transferred more easily to and from them </li></ul><ul><li>If a metal and a wooden block are both 150°, the metal block will feel hotter than the wooden block.Likewise for the same blocks at 0° the metal block will feel colder </li></ul>
  30. 31. Pain <ul><li>Pain Pathway </li></ul>Somatosensory Cortex Thalamus Spinal Cord Dorsal Horn Nerve Free Nerve Ending
  31. 32. Pain <ul><li>Sharp Pain Reflex </li></ul><ul><li>Limb is pulled toward the body out of harms way </li></ul><ul><li>Normal pain information continues to brain for more considered action </li></ul>Somatosensory Cortex Thalamus Spinal Cord Dorsal Horn Nerve Muscle Free Nerve Ending
  32. 33. Pain: The Reflex Arc
  33. 34. Gaiting Pain <ul><li>Gate control theory of pain - pain is actively suppressed in emergency situations by messages sent from the brain to the </li></ul><ul><li>Dorsal Horn </li></ul><ul><li>This allows you to escape on a broken limb or with a gash </li></ul><ul><li>Pain resumes when emergency is over </li></ul>Cortex Thalamus Spinal Cord Dorsal Horn Nerve Free Nerve Ending
  34. 35. Gating Pain: Dorsal Horn (Root) Back Chest
  35. 36. Spino-Thalamic Pathway: Temperature & Pain
  36. 37. Medial Lemniscal Pathway: Mechanoreceptors & Proprioception
  37. 38. Phantom Pain <ul><li>After surgical removal of a limb, sensations resume in the limb </li></ul><ul><li>In 90% of patients, the sensations are very painful </li></ul><ul><li>In 60% the pain is excruciating: described sometimes as an arm on fire, being torn or punctured, great pressure </li></ul>
  38. 39. Phantom Pain: Strange Facts <ul><li>Stimulating certain areas of skin (e.g., face) may aggrevate phantom pain. </li></ul><ul><li>Severing the nerve doesn’t help. Blocking the nerve doesn’t help. Removing the portion of the thalamus that relays the information to the brain doesn’t help! </li></ul><ul><li>Stimulating the nerve does help. Electric or manual stimulation of the stump helps tremendously electric more so). </li></ul>
  39. 40. Phantom Pain: A Theory <ul><li>Recall that the cortex is plastic and may reorganize. </li></ul><ul><li>Normally this involves annexing juvenile or unused neurons (indicated by low activity level) </li></ul><ul><li>In amputation the entire area of say an arm is no longer active in the brain </li></ul><ul><li>Other areas attempt to annex these neurons </li></ul><ul><li>Because the neurons already had a specialization (e.g., sharp pain) and are no being stimulated by adjacent areas of cortex, the subject feels pain. </li></ul>
  40. 41. Phantom Pain The cortical areas for the face annex the cortical areas for the arm and fingers. Some of those neurons were previously specialized for pain.
  41. 42. Phantom Pain <ul><li>TENS (transcutaneous electrical stimulation) uses tiny electrical pulses, delivered through the skin to nerve fibers, to directly stimulate nerves in the stump that formerly enervated the limb. </li></ul><ul><li>Spinal cord stimulation uses electrodes surgically inserted within the epidural space of the spinal cord. </li></ul><ul><li>Deep brain or intracerebral stimulation is considered an extreme treatment and involves surgical stimulation of the brain. </li></ul><ul><li>These treatments all create activity in the cortical region associated with the former limb, which prevents adjacent neurons from annexing </li></ul>

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