Mechanoreceptors detect pressures, strains, and movements {touch, physiology}. Touch stimuli affect many touch-receptor types, which excite and inhibit each other to form intensity ratios. Receptors do not make equal contributions but have weights. Receptor sensitivity varies over touch spectrum and touch region [Katz, 1925] [McComas and Cupido, 1999] [Teuber et al., 1960] [Teuber, 1960].
Touch is more about weight, heat transfer, texture, and hardness {material property, touch} than about shape {geometric property, touch}. Weight discrimination is best if lifted-weight density is one gram per cubic centimeter. Touch receptors can detect mechanical vibrations up to 20 to 30 Hz.
Touch can detect body location. From one location, touch detects only one source. Touch can detect multiple sensations simultaneously. Touch has no fixed coordinate origin (egocenter), so coordinates change with task.
Pressure, pain, and touch receptor activity increases muscle flexor activity and decrease muscle extensor activity.
Mechanoreceptors detect pressures/stresses (compression, tension, torsion), strains, motions, and vibrations [Bolanowski et al., 1998] [Hollins, 2002] [Johnson, 2002]:
Free nerve ending: smooth or rough surface texture
Hair cell: motion
Meissner corpuscle: vibration
Merkel cell: light compression and vibration
Pacinian corpuscle: deep compression and vibration
Palisade cell: light compression
Ruffini endorgan: slip, stretch, and vibratio
pressure
Skin encapsulated tactile receptors are for steady pressure and light touch.
Skin free-nerve-ending mechanoreceptors respond to all skin-stimulation types.
Merkel cells detect continuous pressures and deformations as small as one micrometer. Merkel cells detect 0.4-Hz to 3-Hz low-frequency vibrations. Merkel cells are slow-adapting.
Pacinian corpuscles detect deep pressure. Pacinian corpuscles are fast-adapting.
Palisade cells respond to different deformations.
Ruffini endorgans respond to skin slip, stretch, and deformation, with sensitivity less than that of SA I receptors. Ruffini's endorgans are slow-adapting.
Nerve signals differ for pain, itch, heat, and pressure [Bialek et al., 1991]. Pain is irregular and high intensity and has rapid increase. Itch is regular and fast. Heat rises higher. Pressure has high intensity that fades away.
People can distinguish 10 stress levels. Maximum touch is when high pressure causes tissues to have inelastic strain, which stretches surface tissues past point to which they can completely return and which typically causes pain.
vibration
Skin encapsulated tactile receptors are for vibration.
Skin free-nerve-ending mechanoreceptors respond to all skin-stimulation types.
Meissner's corpuscles respond to vibration, to detect changing stimuli. Maximum sensitivity is at 20 to 40 Hz. Range is from 1 Hz to 400 Hz. Meissner corpuscles are fast-adapting.
Pacinian corpuscles respond to vibration with maximum sensitivity at 200 to 300 Hz. Range is 20 to 1500 Hz. Pacinian corpuscles can detect movements smaller than one micrometer. Pacinian-corpuscle lamellae act as high-pass filters to prevent steadily maintained pressure from making signals. Pacinian corpuscles are fast-adapting.
Palisade cells respond to vibration frequencies from 1 to 1500 Hz.
Ruffini endorgans respond to 100 Hz to 500 Hz. Ruffini's endorgans are slow-adapting.
People can distinguish 10 vibration levels. Age reduces vibration sensitivity.
movement
Skin hair-cell mechanoreceptors detect movement.
Skin free-nerve-ending mechanoreceptors respond to all skin-stimulation types.
The touch system can detect whether objects are stationary. Touch can tell whether surface is sliding under stationary skin, or skin is sliding over stationary surface.
Most objects connect to the ground and are stationary. Their connection to the ground makes them have high inertia and no acceleration when pushed or pulled.
Objects that slide past stationary skin have inertia similar to or less than the body. (If large object slides by skin, the collision affects the whole body, not just the skin.) They have measurable deceleration when pushed or pulled.
The touch system measures accelerations and decelerations in the skin. Large decelerations in skin result from sliding by stationary objects. Small decelerations in skin result from objects sliding by skin.
People can distinguish 10 motion levels.
space
Skin touches objects, and touch receptors receive information about objects adjacent to body. As body moves around in space, mental space expands by adding adjacency information. Sensations impinge on body surface in repeated patterns at touch receptors. From receptor activity patterns, nervous system builds a three-dimensional sensory surface.
Foot motions stop at ground. Touch and kinesthetic receptors define a horizontal plane in space.
People can distinguish inside-body stimuli, as self. Tightening muscles actively compresses, to affect proprioception receptors that define body points. When people move, other objects do not move, so correlated body movements belong to self.
People can distinguish outside-body stimuli, as non-self. During movements or under pressure, body surfaces passively extend, to affect touch receptors that define external-space points. When people move, correlated non-movements belong to non-self.
Because distance equals rate times time, motion provides information about distances. Nervous system correlates body motions and touch and kinesthetic receptors to extract reference points and three-dimensional space. Repeated body movements define perception metrics. Such ratios build standard length, angle, time, and mass units that model physical-space lengths, angles, times, and masses. As body, head, and eyes move, they trace geometric structures and motions.
material properties
Touch can identify {what system}.
Holding in hand determines weight.
Touching with no moving determines temperature. Material properties determine heat flow, which determines temperature, which ranges from cold to warm to pain. Temperature perceptual processes compare thermoreceptor inputs. People can distinguish 10 temperature levels.
Applying pressure determines hardness.
Sliding touch back and forth determines texture.
Wrapping around determines shape and volume. Following contours determines shape.
Touch is more about weight, heat transfer, texture, and hardness than about shape. Weight discrimination is best if lifted-weight density is one gram per cubic centimeter.
qualities
Emotions generate brain-gut hormones that cause abdominal feelings. Maximum touch is when high pressure causes tissues to have inelastic strain, which stretches surface tissues past point to which they can completely return and which typically causes pain.
neuron
Nerve signals differ for pain, itch, heat, and pressure [Bialek et al., 1991]. Pain is irregular and high intensity and has rapid increase. Itch is regular and fast. Heat rises higher. Pressure has high intensity that fades away.
EEG
In NREM sleep, anesthesia, and waking, short touch causes P1 cortical response 25 milliseconds later. In waking, short touch causes N1 cortical response 100 milliseconds later, lasting hundreds of milliseconds.
temperature
Coolness and warmth are relative and depend on body-tissue relative average random molecule speed. Very cold objects can feel hot at first. Skin is normally 30 C to 36 C. If objects are colder than 30 C, cold fibers provide information about material as heat flows from skin to object. If skin is above normal temperature, warmth fibers provide information about material as heat flows from skin to object. Warmth fibers also provide information about body state, such as fever or warm-weather overheating.
Consciousness>Consciousness>Sense>Touch>Physiology
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Date Modified: 2022.0224