Editing Stimulus modality (section)

==Pressure modality==

===Description===
The sense of touch, or tactile perception, is what allows organisms to feel the world around them.  The environment acts as an external stimulus, and tactile perception is the act of passively exploring the world to simply sense it.  To make sense of the stimuli, an organism will undergo active exploration, or [[haptic perception]], by moving their hands or other areas with environment-skin contact.<ref>{{cite journal |author1=Reuter E. |author2=Voelcker-Rehage C. |author3=Vieluf S. |author4=Godde B. | year = 2012 | title = Touch perception throughout working life: Effects of age and expertise | journal = Experimental Brain Research | volume = 216 | issue = 2| pages = 287–297 | doi = 10.1007/s00221-011-2931-5 |pmid=22080104 |s2cid=16712201 }}</ref>  This will give a sense of what is being perceived, and give information about size, shape, weight, temperature, and material.  Tactile stimulation can be direct in the form of bodily contact, or indirect through the use of a tool or probe.  Direct and indirect send different types messages to the brain, but both provide information regarding roughness, hardness, stickiness, and warmth.  The use of a probe elicits a response based on the vibrations in the instrument rather than direct environmental information.<ref>{{cite journal |author1=Yoshioka T. |author2=Bensmaïa S. |author3=Craig J. |author4=Hsiao S. | year = 2007 | title = Texture perception through direct and indirect touch: An analysis of perceptual space for tactile textures in two modes of exploration | journal = Somatosensory & Motor Research | volume = 24 | issue = 1–2| pages = 53–70 | doi = 10.1080/08990220701318163 |pmid=17558923 |pmc=2635116 }}</ref>  Tactual perception gives information regarding [[cutaneous]] stimuli (pressure, vibration, and temperature), [[kinaesthetic]] stimuli (limb movement), and [[proprioception|proprioceptive]] stimuli (position of the body).<ref>{{cite journal | author = Bergmann Tiest W | year = 2010 | title = Tactual perception of material properties | journal = Vision Research | volume = 50 | issue = 24| pages = 2775–2782 | doi = 10.1016/j.visres.2010.10.005 | pmid = 20937297 | doi-access = free }}</ref>   There are varying degrees of tactual sensitivity and thresholds, both between individuals and between different time periods in an individual's life.<ref>{{cite journal | author = Angier R | year = 1912 | title = Tactual and kinæsthetic space | url = https://zenodo.org/record/1429145| journal = Psychological Bulletin | volume = 9 | issue = 7| pages = 255–257 | doi = 10.1037/h0073444 }}</ref>  It has been observed that individuals have differing levels of tactile sensitivity between each hand.  This may be due to callouses forming on the skin of the most used hand, creating a buffer between the stimulus and the receptor.  Alternately, the difference in sensitivity may be due to a difference in the cerebral functions or ability of the [[left hemisphere|left]] and [[right hemisphere]].<ref>{{cite journal |author1=Weinstein S. |author2=Sersen E. | year = 1961 | title = Tactual sensitivity as a function of handedness and laterality | journal = Journal of Comparative and Physiological Psychology | volume = 54 | issue = 6| pages = 665–669 | doi = 10.1037/h0044145 |pmid=14005772 }}</ref>  Tests have also shown that deaf children have a greater degree of tactile sensitivity than that of children with normal hearing ability, and that girls generally have a greater degree of sensitivity than that of boys.<ref>{{cite journal | author = Chakravarty A | year = 1968 | title = Influence of tactual sensitivity on tactual localization, particularly of deaf children | journal = Journal of General Psychology | volume = 78 | issue = 2| pages = 219–221 | doi = 10.1080/00221309.1968.9710435 | pmid = 5656904 }}</ref>

Tactile information is often used as additional stimuli to resolve a sensory ambiguity.  For example, a surface can be seen as rough, but this inference can only be proven through touching the material.  When sensory information from each modality involved corresponds, the ambiguity is resolved.<ref>{{cite thesis |last1=Lovelace |first1=Christopher Terry |title=Feature binding across sense modalities: Visual and tactual interactions |date=October 2000 |id={{ProQuest|619577012}} }}</ref>

===Somatosensory information===
Touch messages, in comparison to other sensory stimuli, have a large distance to travel to get to the brain.  Tactile perception is achieved through the response of [[mechanoreceptor]]s ([[cutaneous receptor]]s) in the skin that detect physical stimuli.  The response from a mechanoreceptor detecting pressure can be experienced as a touch, discomfort, or pain.<ref>{{cite journal |last1=Xiong |first1=Shuping |last2=Goonetilleke |first2=Ravindra S. |last3=Jiang |first3=Zuhua |title=Pressure thresholds of the human foot: measurement reliability and effects of stimulus characteristics |journal=Ergonomics |date=March 2011 |volume=54 |issue=3 |pages=282–293 |doi=10.1080/00140139.2011.552736 |pmid=21390958 |s2cid=22152573 }}</ref>   Mechanoreceptors are situated in highly vascularized skin, and appear in both glabrous and hairy skin.  Each mechanoreceptor is tuned to a different sensitivity, and will fire its action potential only when there is enough energy.<ref>{{cite journal |last1=Pawson |first1=Lorraine |last2=Checkosky |first2=Christine M. |last3=Pack |first3=Adam K. |last4=Bolanowski |first4=Stanley J. |title=Mesenteric and tactile Pacinian corpuscles are anatomically and physiologically comparable |journal=Somatosensory & Motor Research |date=January 2008 |volume=25 |issue=3 |pages=194–206 |doi=10.1080/08990220802377571 |pmid=18821284 |s2cid=33152961 }}</ref>  The axons of these single tactile receptors will converge into a single nerve trunk, and the signal is then sent to the spinal cord where the message makes its way to the [[somatosensory system]] in the brain.

====Mechanoreceptors====

There are four types of mechanoreceptors: Meissner corpuscles and merkel cell neurite complexes, located between the epidermis and dermis, and [[Pacinian]] corpuscles and [[Ruffini ending]]s, located deep within the dermis and subcutaneous tissue.  Mechanoreceptors are classified in terms of their adaptation rate and the size of their receptive field.  Specific mechanoreceptors and their functions include:<ref name=Wolfe>Wolfe, J., Kluender, K., & Levi, D. (2009). Sensation and perception. (2 ed.). Sunderland: Sinauer Associates.{{pn|date=August 2020}}</ref>

* Thermoreceptors that detect changes in skin temperature.
* Kinesthetic receptors detect movements of the body, and the position of the limbs.
* Nociceptors that have bare nerve endings that detect tissue damage and give the sensation of pain.

===Tests===
A common test used to measure the sensitivity of a person to tactile stimuli is measuring their two-point touch threshold.  This is the smallest separation of two points at which two distinct points of contact can be sensed rather than one.  Different parts of the body have different degrees of tactile acuity, with extremities such as the fingers, face, and toes being the most sensitive.  When two distinct points are perceived, it means that your brain receives two different signals.  The differences of acuity for different parts of the body are the result of differences in the concentration of receptors.<ref name="Wolfe" />

===Use in clinical psychology===
Tactile stimulation is used in clinical psychology through the method of prompting.  Prompting is the use of a set of instructions designed to guide a participant through learning a behavior.  A physical prompt involves stimulation in the form of physically guided behavior in the appropriate situation and environment.  The physical stimulus perceived through prompting is similar to the physical stimulus that would be experienced in a real-world situation, and is makes the target behavior more likely in a real situation.<ref>Miltenberger, R. (2012). Behavior modification: principles and procedures. (5 ed.). Belmont, CA: Wadsworth.{{pn|date=August 2020}}</ref>