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FSU EXP 3202C - Somatosensation

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Not very great at this, we can if pattern is small enough to fit 1 fingertip; can’t “read” more than 1 finger at a time (narrow haptic field of view, the area of skin we can “take in” all at once)“Touch acts like blurred vision when the fingertip explores a raised pattern” do equally well and make same mistakes when identifying patterns with blurred vision of hectically.Somatosensation• What are are somatosensation, kinesthesis & proprioception? What are the types of kinesthesis receptors? Where are they and what kind of info do they convey?• Somatosensation: A collective term for sensory signals from the body• Kinesthesis: The perception of the position and movement of our limbs in space• Muscle spindles • Golgi tendons:• Proprioception: Perception mediated by kinesthetic and vestibular receptors. Position of your body in space. •• What is haptic perception? What is perception for action? What is action for perception? In the latter, what types of exploratory procedures do we use to give us info about an object, and what type of info do those procedures yield?• Haptic perception : Knowledge of the world that is derived from sensory receptors in skin, muscles, tendons, and joints, usually involving active exploration• This is an active process: Action for perception• Touch relies on action to get info (as opposed to vision or audition, which are more passive (in a moment))• We then use this perception to act: Perception for action… • Example of haptic perception: For instance, aligning the arrows and opening a child-proof aspirin bottle in the dark• Perception for action:• Using somatosensation to grasp & manipulate objects in a stable & coordinated manner, & to maintain proper balance and posture• Anesthetize skin (kinesthetic receptors work, touch receptors don’t) à subject can’tmaintain stable grasp of objects he/she must manipulate• Example: grabbing a baseball • Action for perception• Exploratory procedure: feel an object to learn about it• Different procedures tell you different things• If the skin is anesthetized, but proprioceptive/kinesthetic receptors are intact, can you still grasp/manipulate an object? Why or why not?• Not very great at this, we can if pattern is small enough to fit 1 fingertip; can’t “read” more than 1 finger at a time (narrow haptic field of view, the area of skin we can “take in” all at once)• “Touch acts like blurred vision when the fingertip explores a raised pattern” do equally well and make same mistakes when identifying patterns with blurred vision of hectically. •• What do you know about haptic search? What features of an object that you are touching “pop out” and what features do not?• You can detect before using selective attention to identify a particular feature…this is calledpreattentive feature detection.• No need to compare in order to detect; some features just “pop-out” • No need to think about it just jumps out on them. • You can rotate it so you can have different surfaces. • Works for texture (rough vs. smooth), temperature, hard/soft • Doesn’t work for horizontal vs. vertical lines• Haptic recognition relies on material properties, not object contours• Good for handling objects to identify them…• Bad for feeling raised contours of a drawing of the object• This is opposite visual system, which would be good at horizontal vs. vertical• We use this in the visual system too; red pops out with greens, for example. Also horizontal versus vertical.• Not good at understanding contours through the touch system. This is the reason that braille is dots not letter. Your fingers are only good at small limited patterns. • Can we perceive patterns with the skin? What are the limitations on this capability? How does this capability compare to looking w/ blurred vision?• We can do it if the pattern is small enough to fit on 1 fingertip.• Also, can’t “read” more than 1 finger at a time (suggests narrow haptic field of view (the area of skin we can “take in” all at once))• “Touch acts like blurred vision when the fingertip explores a raised pattern.”• Do equally well and make same mistakes when identifying patterns w/ blurred vision or haptically• What are the 4 main types of touch receptors? How do they differ in terms of adaptation & receptive field size? What tactile functions do they subserve? What does it mean that they are mechanoreceptors?• Generally in the lower layers of the epidermis and within the dermis. • Axons that are ending in the skin and go into the spinal cord. There is a fancy encapsulation that causes axons to be stimulated. • Merkel• Meissner• Ruffini• Pacinian• Differences:• 1. Type of stimulation to which the receptor responds (pressure, vibration, temperature, damage, etc)• Depends on anatomy of receptor• 2. Size of the receptive field (part/amount of body that activates that receptor)• How much of the skin can actually cause a change in the action potentials. • Depends on the location of touch receptor (deeper in the skin the larger the receptive fields• 3. Rate of adaptation (fast versus slow)• Depends on the anatomy of the receptor• Very sensitive area of body = small and densely packed receptive fields = more cortical areaprocessing touch from that area ( like finger tips or parts of the face)• Mechanoreceptor: stimulated by mechanical deformation. They are detecting a physical change• How do pacinian corpuscles work?• These are really deep in the skin and most ubiquitous you have them everywhere so they have larger receptive fields. They respond to vibration and are rapidly adapting. • Stimulated by touch they are deflected down through the membranes and deflect the membrane of the axon. The membrane then becomes leaky to sodium. • The • Force à neuron’s membrane is deflected à channels become leaky to sodium à receptor potential …mechanoreceptors • The greater the deflection, the greater the receptor potential… threshold à AP• Only sudden or vibrating force can deflect membrane• Onion-like outer membrane provides mechanical support so it is resistant to gradual or constant pressure…so rapidly adapting. BTW, the other rapidly adapting receptor, Meissner corpuscle, works in a similar way.•• What are thermoreceptors, and what kinds are there? What type of channel do they use? Understand that


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