Slide 1The Cutaneous sensationsSlide 3SkinSlide 5Mechanoreceptors: pick up the movement of skinMechanoreceptorsSlide 8Slide 9Pathways from skin to cortexCortical mapPerceiving details (tactile acuity)Slide 13Perceiving vibrationPerceiving texturePerceiving objectsPerceiving Objects - continuedThe Physiology of Tactile Object Perception - continuedSlide 19Slide 20Pain perceptionPain PerceptionTypes of PainSlide 24Brain areas for pain perceptionSlide 26What does this tell?Cognitive and Experiential Aspects of PainCognitive and Experiential Aspects of Pain - continuedSlide 30ch 14 1Sensation & PerceptionCh. 14: The Cutaneous Senses© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)Main topicsMechanoreceptorsTemporal, spatial, & frequency responsesCortical mapTactile acuityPerceiving texturePain perceptionch 14 2The Cutaneous sensations•Sensations based on the stimulation of receptors in the skin.–Pressure, vibration, heating, cooling, and tissue damage.•It is served by the somatosensory system.•It also creates–Proprioception (the body sense – e.g., balancing the body)–Kinesthesis (the sense of the position and movement)ch 14 3•Ian Waterman (a 17 year old butcher)–Contracted flu. –Damaged somatosensory cortex–Couldn’t–As a result, he lost the ability to•feel skin sensation below his neck.•feel his body,•adjust his body position•grasp objects properly.ch 14 4Skin•“monumental façade of the human body”–(Cornel, 1953)ch 14 5SkinFunctions of Skin:Keeps the body warmProtects the body from bacteriaHelp maintains the integrity inside the body.2 LayersEpidermisdermisch 14 6Mechanoreceptors: pick up the movement of skinMerkel receptorMeissner corpuscleRuffin cylinderPacinian corpusclech 14 7Mechanoreceptors•Mechanoreceptors respond to –mechanical stimulation such as pressure, stretching, and vibration.•Transduction (Pacinian corpuscle)–When the corpuscle is bent relative to the axon, the tip of the nerve ending opens ion channels in the membrane.–The opening permits the entry of molecules with positive charge, which depolarize the membrane potential. –(from N. R. Carlson “Physiology of Behavior”, 7th ed)ch 14 8Fig. 14-1, p. 331ch 14 9Fig. 14-2, p. 332ch 14 10Pathways from skin to cortex•2 pathways•Medial lemniscal pathway–Proprioception & touch perception•Spinothalamic pathway–Temperature and painSkin  spinal cord  thalamus  cortexch 14 11Cortical map•Somatosensory cortex–Corresponds to body locations•Cortical magnification factor–Sensitive areas occupy large cortical areas (e.g., fingers)•These cortical areas are plastic (can be changed by experience) e.g., trained pianists have larger cortical representations of fingers.ch 14 12Perceiving details (tactile acuity)•Measuring tactile acuity–Two-point threshold - minimum separation needed between two points to perceive them as two units–Grating acuity - placing a grooved stimulus on the skin and asking the participant to indicate the orientation of the gratingch 14 13•The density of Merkel receptors and tactile acuity is highly correlated.–The areas that have more Merkel receptors are more sensitiveMerkel receptorsch 14 14Perceiving vibration•The Pacianian corpuscle is responsible.–Sustained stimuluation  no response–Rapid on-off stimulation  responseMerkel receptorMeissner corpuscleRuffin cylinderPacianian corpusclech 14 15Perceiving texture•Temporal cues–The movement of a surface generates vibration, which gives the perception of texture (rough vs. fine texture)ch 14 16Perceiving objects•Haptic perception–Perception, in which 3D objects are explored with the hand.–Involves sensory, motor, and cognitive systems.•Demonstration–Identifying objects–The person sitting next to you close his / her eye. –Pick up an object (e.g., an eraser)–Let him / her touch the object and identify the object.–Swap the role.ch 14 17Perceiving Objects - continued•Psychophysical research shows that people can identify objects haptically in 1 to 2 sec•people use exploratory procedures (EPs)–Lateral motion–Pressure–Enclosure–Contour followingch 14 18The Physiology of Tactile Object Perception - continued•Monkey’s somatosensory cortex also shows neurons that respond best to:–Grasping specific objects –Paying attention to the task•Neurons may respond to stimulation of the receptors, but attending to the task increases the responsech 14 19Figure 14.19 Receptive fields of neurons in the monkey’s somatosensory cortex. (a) This neuron responds best when a horizontally oriented edge is presented to the monkey’s hand. (b) This neuron responds best when a stimulus moves across the fingertip from right to left. (From “Movement-Sensitive and Direction and Orientation Selective Cutaneous Receptive Fields in the Hand Area of the Postcentral Gyrus in Monkeys,” by L. Hyvarinen and A. Poranen, 1978, Journal of Physiology, 283,523-537, figure 3. Copyright © 1978 by The Physiological Society, UK. Reprinted by permission.)ch 14 20Figure 14.20 The response of a neuron in a monkey’s parietal cortex that fires when the monkey grasps a ruler but that does not fire when the monkey grasps a cylinder. (From “Cortical Processing of Tactile Information in the First Somatosensory and Parietal Association Areas in the Monkey,” by H. Sakata and Y. Iwamura, 1978. In G. Gordon (Ed.), Active Touch, p. 61. Copyright © 1978 by Pergamon Press, Ltd. Reprinted by permission.)ch 14 21Pain perceptionch 14 22Pain Perception•Pain comes from– a sensory component and an emotional component.•Three types of pain:–Nociceptive - signals impending damage to the skin•Types of nociceptors respond to heat, chemicals, severe pressure, and coldch 14 23Types of Pain–Inflammatory pain • caused by damage to tissues and joints that releases chemicals that activate nociceptors–Neuropathic pain •caused by damage to the central nervous system, such as:–Brain damage caused by stroke–Repetitive movements which cause conditions like carpal tunnel syndromech 14 24Figure 14.22 Pain can be created in a number of different ways. See text for details. (Adapted from Scholz & Woolf, 2002.)Nociceptive (skin-oriented)Inflammatory (tissue & joints-oriented)Neuropathic (nervous- system-oriented)ch 14 25Brain areas for pain perception–Subcortical areas •hypothalamus, limbic system, and the thalamus–Cortical areas •S1 and S2 in