Touch and Tactile Perception
Transcription
Touch and Tactile Perception
Touch and Tactile Perception Li Liu ☺ Skin Stimuli and Receptors ☺ Neural Responses ☺ Neural Pathway ☺ Tactile Perception Tactile sensory receptors Thermoreceptors change in skin temperature Mechanoreceptor pressure, vibration, slip Nocioreceptor pain Cross section of the skin Neutral Responses Receptor responds to stimulation Mechanical energy deforms the receptor cell Tiny holes at the membrane open, positive ions flow through the cell (Na+ in and K+ out). An action potential is generated. Electrical activity. Sensory adaption Receptors have different rates of adaption to stimuli: Slow adaption (SA): The fibers fire when stimulated, continue responding as long as the stimulus exits. Rapid adaption (RA): The fibers fire when stimulated, then drop rapidly to zero, even if the stimulus continues, i.e., wearing clothes Which receptors are rapidly adapting and which are slowly adapting? Receptors for touch Which receptor has the largest receptive field In the brain, the same response often signals very different sensations. How do we know what the stimulus is? How do we know what the stimulus is? A similar problem occurs on the internet On the internet, your message and those of many others, travel down a shared common line. To separate your message from that of others, each packet is giving a tag or label. At the end of the line a decoder separates your packet from that of others. How do we know what the stimulus is? Each type of skin receptor has its own private line, where the touch information is sent through spinal cord to the somatosensory cortex. There are lots of lines in our spinal cord, In this way, each message is separated and sent to its own location in the brain. Neural Pathways Neural pathways Maps of the body on the cortex Tactile Perception Measuring tactile activity: the two-point threshold Two-point threshold the smallest separation between two points on the skin that is perceived as two rather than one. Method Two pencils side by side, and they are 12 mm apart; Then touch both points to any part of the body; If you feel only one, increase the distance until you feel two; The distance is the threshold. Two - Point Threshold - measure of pressure acuity - varies greatly over different areas of the body Sensory humunculus What a person would look like if their sensory humunculus represented size rather than sensitivity Braille code Natural letters ABCDEFGHIJKLMN OPQRSTVUWXYZ Neural response to letters Braille alphabet Braille board Play cards Electronic book Picture perception by touch Picture perception by touch Touch pictures 2D or 3D graphics as output Receptive fields responds to movement across fingertip Active touch Exploratory procedures Tactile perception (1965)
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