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{{short description|Sense of the relative position of one's own body parts and strength of effort employed in movement}}
[[File:Proprioception image-01.jpg|alt=|right|frameless|668x668px]]
'''Proprioception''' ({{IPAc-en|ˌ|p|r|oʊ|p|r|i|oʊ|ˈ|s|ɛ|p|ʃ|ən|,_|-|p|r|i|ə|-}}{{refn|{{MerriamWebsterDictionary|Proprioception}}}}{{refn|{{cite web |url=https://www.oxforddictionaries.com/definition/english/proprioceptive |title=proprioceptive – definition of proprioceptive in English from the Oxford dictionary |publisher=[[OxfordDictionaries.com]] |access-date=2016-01-20 }}}} {{respell|PROH|pree|o|SEP|shən}}) , also referred to as '''kinaesthesia''' (or '''kinesthesia''', in American English), is the sense of self-movement and body position.<ref name=":3">{{Cite journal|last=Tuthill|first=John C.|last2=Azim|first2=Eiman|date=March 2018|title=Proprioception|journal=Current Biology|volume=28|issue=5|pages=R194–R203|doi=10.1016/j.cub.2018.01.064|pmid=29510103}}</ref> It is sometimes described as the "sixth sense".<ref>{{cite magazine|magazine=The Scientist|title=Proprioception: The Sense Within|first1=Simon|last1=Gandevia|first2=Uwe| last2=Proske|date=1 September 2016|url=https://www.the-scientist.com/features/proprioception-the-sense-within-32940|accessdate=25 July 2018}}</ref>
Proprioception is mediated by proprioceptors, mechanosensory neurons located within muscles, tendons, and joints.<ref>{{cite journal|last1=Tuthill & Azim |title=Proprioception |journal=Current Biology |volume=28 |issue=5 |pages=R194–R203 |date=5 March 2018 |doi=10.1016/j.cub.2018.01.064|pmid=29510103 }}</ref> There are multiple types of proprioceptors which are activated during distinct behaviors and encode distinct types of information: limb velocity and movement, load on a limb, and limb limits. Vertebrates and invertebrates have distinct but similar modes of encoding this information.
The [[central nervous system]] integrates proprioception and other sensory systems, such as [[Visual perception|vision]] and the [[vestibular system]], to create an overall representation of body position, movement, and acceleration.
More recently proprioception has also been described in flowering land plants ([[Flowering plant|angiosperms]]).<ref name=":0">{{Cite journal|last=Bastien|first=Renaud|last2=Bohr|first2=Tomas|last3=Moulia|first3=Bruno|last4=Douady|first4=Stéphane|date=2013-01-08|title=Unifying model of shoot gravitropism reveals proprioception as a central feature of posture control in plants|journal=Proceedings of the National Academy of Sciences|volume=110|issue=2|pages=755–760|doi=10.1073/pnas.1214301109|issn=0027-8424|pmid=23236182|bibcode=2013PNAS..110..755B|pmc=3545775}}</ref><ref name=":1">{{Cite journal|last=Hamant|first=Olivier|last2=Moulia|first2=Bruno|date=2016-10-01|title=How do plants read their own shapes?|journal=New Phytologist|volume=212|issue=2|pages=333–337|doi=10.1111/nph.14143|pmid=27532273|issn=1469-8137}}</ref>
==System Overview==
In vertebrates, limb velocity and movement (muscle length and the rate of change) are encoded by one group of sensory neurons ([[Type Ia sensory fiber]]) and another type encode static muscle length ([[Type II sensory fiber|Group II neurons]]).<ref>{{cite journal |last1=Lundberg, Malmgren, & Schomburg |title=Role of joint afferents in motor control exemplified by effects on reflex pathways from Ib afferents |journal=The Journal of Physiology |volume=284 |pages=327–343 |date=Nov 1978 |doi=10.1113/jphysiol.1978.sp012543 |pmid=215758 |pmc=1282824 }}</ref> These two types of sensory neurons compose muscle spindles. There is a similar division of encoding in invertebrates; different subgroups of neurons of the [[Chordotonal organ]]<ref>{{cite journal|last1=Bush |title=Proprioception by the Coxo-Basal Chordotonal Organ, CB, in Legs of the Crab, Carcinus Maenas |journal=Journal of Experimental Biology |volume=42 |pages=285–97 |date=1965 |pmid=14323766 |url=http://jeb.biologists.org/content/42/2/285.long}}</ref> encode limb position and velocity.
To determine the load on a limb, vertebrates use sensory neurons in the Golgi tendon organs:<ref>{{cite journal |last1=Murphy, Wong, & Kwan |title=Afferent-efferent linkages in motor cortex for single forelimb muscles. |journal=Journal of Neurophysiology |volume=38 |issue=4 |pages=990–1014 |date=July 1975 |doi=10.1152/jn.1975.38.4.990 |pmid=125786}}</ref> type Ib afferents. These proprioceptors are activated at given muscle forces, which indicate the resistance that muscle is experiencing. Similarly, invertebrates have a mechanism to determine limb load: the [[Campaniform sensilla]].<ref>{{cite journal|last1=Chapman |title=Campaniform Sensilla on the tactile spines of the legs of the cockroach |journal=Journal of Experimental Biology |volume=42 |pages=191–203 |date=April 1965 |pmid=14323763}}</ref> These proprioceptors are active when a limb experiences resistance.
A third role for proprioceptors is to determine when a joint is at a specific position. In vertebrates, this is accomplished by [[Ruffini ending]]s and [[Pacinian corpuscles]]. These proprioceptors are activated when the joint is at a threshold, usually at the extremes of joint position. Invertebrates use [[hair plate]s<ref>{{cite journal |last1=Bräunig, Hustert, & Pflüger |title=Distribution and specific central projections of mechanoreceptors in the thorax and proximal leg joints of locusts. I. Morphology, location and innervation of internal proprioceptors of pro- and metathorax and their central projections |journal=Cell and Tissue Research |volume=216 |issue=1 |pages=57–77 |date=1981 |pmid=7226209|doi=10.1007/bf00234545 }}</ref> to accomplish this; a row of bristles located along joints detect when the limb moves.
===Reflexes===
The sense of proprioception is ubiquitous across mobile animals and is essential for the motor coordination of the body. Proprioceptors can form reflex circuits with motor neurons to provide rapid feedback about body and limb position. These mechanosensory circuits are important for flexibly maintaining posture and balance, especially during locomotion. For example, consider the stretch reflex, in which stretch across a muscle is detected by a sensory receptor (e.g., [[muscle spindle]], [[Chordotonal organ|chordotonal neurons]]), which activates a motor neuron to induce muscle contraction and oppose the stretch. During locomotion, sensory neurons can reverse their activity when stretched, to promote rather than oppose movement.<ref>{{Cite journal|last=Bässler|first=U.|last2=Büschges|first2=A.|date=June 1998|title=Pattern generation for stick insect walking movements--multisensory control of a locomotor program|journal=Brain Research. Brain Research Reviews|volume=27|issue=1|pages=65–88|pmid=9639677|doi=10.1016/S0165-0173(98)00006-X}}</ref><ref>{{Cite journal|last=Tuthill|first=John C.|last2=Wilson|first2=Rachel I.|date=October 2016|title=Mechanosensation and Adaptive Motor Control in Insects|journal=Current Biology|volume=26|issue=20|pages=R1022–R1038|doi=10.1016/j.cub.2016.06.070|pmid=27780045|pmc=5120761}}</ref>
===Conscious and non-conscious===
In humans, a distinction is made between ''conscious'' proprioception and ''non-conscious'' proprioception:
* Conscious proprioception is communicated by the [[dorsal column-medial lemniscus pathway]] to the [[cerebrum]].<ref name="isbn0-7817-2829-0">
{{cite book |author=Fix, James D. |title=Neuroanatomy |publisher=Lippincott Williams & Wilkins |location=Hagerstown, MD |year=2002 |pages=127 |isbn=978-0-7817-2829-4 |oclc= |doi=}}</ref>
* Non-conscious proprioception is communicated primarily via the [[dorsal spinocerebellar tract]]<ref name="titleChapter 7A: Somatosensory Systems">{{cite web |author=Swenson RS |location=(online version Dartmouth college) |url=http://www.dartmouth.edu/~rswenson/NeuroSci/chapter_7A.html#Unconscious_sensation |title=Review of Clinical and Functional Neuroscience, Chapter 7A: Somatosensory Systems |accessdate=2008-04-10 |archive-url=https://web.archive.org/web/20080405222242/http://www.dartmouth.edu/~rswenson/NeuroSci/chapter_7A.html#Unconscious_sensation#Unconscious_sensation |archive-date=2008-04-05 |url-status=live }}</ref> and [[ventral spinocerebellar tract]],<ref>{{cite book|last=Siegel|first=Allan|title=Essential Neuroscience|year=2010|publisher=Lippincott Williams & Wilkins|page=263}}</ref> to the [[cerebellum]].
* A non-conscious reaction is seen in the human proprioceptive reflex, or [[righting reflex]]—in the event that the body tilts in any direction, the person will cock their head back to level the eyes against the horizon.<ref>{{cite web|url=http://erikdalton.com/tmj-forward-head-posture-neck-pain/|title=TMJ, Forward Head Posture and Neck Pain|publisher=Freedom From Pain Institute|accessdate=3 October 2013|archive-url=https://web.archive.org/web/20131005114808/http://erikdalton.com/tmj-forward-head-posture-neck-pain/#|archive-date=2013-10-05|url-status=live}}</ref> This is seen even in infants as soon as they gain control of their neck muscles. This control comes from the [[cerebellum]], the part of the brain affecting balance.
== Mechanisms ==
Proprioception is mediated by mechanically sensitive '''proprioceptor neurons''' distributed throughout an animal's body. Most vertebrates possess three basic types of proprioceptors: [[muscle spindle]]s, which are embedded in [[Skeletal muscle|skeletal muscle fibers]], [[Golgi tendon organ]]s, which lie at the interface of muscles and tendons, and joint receptors, which are [[Mechanosensation#Cutaneous Mechanoreceptors|low-threshold mechanoreceptors]] embedded in [[joint capsule]]s. Many invertebrates, such as insects, also possess three basic proprioceptor types with analogous functional properties: [[Chordotonal organ|chordotonal neurons]], [[campaniform sensilla]], and hair plates.<ref name=":3" />
The initiation of proprioception is the activation of a proprioreceptor in the periphery.<ref>{{cite journal |author=Sherrington CS |title=On the proprioceptive system, especially in its reflex aspect |journal=Brain |volume=29 |issue=4 |pages=467–85 |year=1907 |url=http://brain.oxfordjournals.org/cgi/reprint/29/4/467 |doi=10.1093/brain/29.4.467 |access-date=2008-02-15 |archive-url=https://web.archive.org/web/20081206045426/http://brain.oxfordjournals.org/cgi/reprint/29/4/467# |archive-date=2008-12-06 |url-status=live }}</ref> The proprioceptive sense is believed to be composed of information from [[sensory neuron]]s located in the [[Labyrinth (inner ear)|inner ear]] (motion and orientation) and in the [[stretch receptor]]s located in the [[muscle spindle|muscles]] and the joint-supporting ligaments (stance). There are specific nerve receptors for this form of perception termed "proprioreceptors", just as there are specific receptors for pressure, light, temperature, sound, and other sensory experiences. Proprioreceptors are sometimes known as [[Adequate stimulus|adequate stimuli]] receptors. [[TRPN]], a member of the [[transient receptor potential]] family of [[ion channel]]s, has been found to be responsible for proprioception in [[Drosophila melanogaster|fruit flies]],<ref>{{Cite journal
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}}</ref> [[PIEZO2]], a nonselective cation channel, has been shown to underlie the mechanosensitivity of proprioceptors in mice.<ref>{{cite journal |vauthors=Woo SH, Lukacs V, de-Nooij JC, Zaytseva D, Criddle CR, Francisco A, Jessell TM, Wilkinson KA, Patapounian A |title=Piezo2 is the principal mechanotransduction channel for proprioception |journal=Nature Neuroscience |volume=18 |issue=12 |pages=1756–1762 |year=2015 |pmid=26551544 |pmc=4661126 |doi=10.1038/nn.4162}}</ref> The channel mediating human proprioceptive mechanosensation has yet to be discovered.
Proprioception of the head stems from the muscles innervated by the [[trigeminal nerve]], where the [[General somatic afferent fibers|GSA fibers]] pass without synapsing in the [[trigeminal ganglion]] (first-order sensory neuron), reaching the [[mesencephalic tract]] and the [[mesencephalic nucleus of trigeminal nerve]].
Although it was known that finger kinesthesia relies on skin sensation, recent research has found that kinesthesia-based [[haptic perception]] relies strongly on the forces experienced during touch.<ref>{{cite journal |vauthors=Robles-De-La-Torre G, Hayward V |title=Force can overcome object geometry in the perception of shape through active touch |journal=Nature |volume=412 |issue=6845 |pages=445–8 |year=2001 |pmid=11473320 |url=http://www.roblesdelatorre.com/gabriel/GR-VH-Nature2001.pdf |doi=10.1038/35086588 |access-date=2006-10-03 |archive-url=https://web.archive.org/web/20061003225801/http://www.roblesdelatorre.com/gabriel/GR-VH-Nature2001.pdf# |archive-date=2006-10-03 |url-status=live |bibcode=2001Natur.412..445R }}</ref> This research allows the creation of "virtual", illusory haptic shapes with different perceived qualities.<ref>[http://www.technologyreview.com/read_article.aspx?id=17363&ch=biotech&sc=&pg=1 the MIT Technology Review article "The Cutting Edge of Haptics"]</ref>
==Development==
In adult ''Drosophila'', each proprioceptor class arises from a specific [[cell lineage]] (i.e. each chordotonal neuron is from the chordotonal neuron lineage, although multiple lineages give rise to sensory bristles). After the last cell division, proprioceptors send out axons toward the central nervous system and are guided by hormonal gradients to reach stereotyped synapses.
<ref>Jan, Y. N. and Jan, L. Y. (1993). The peripheral nervous system. In: The Development of Drosophila
melanogaster (ed. Bate, M and Arias, A. M.), pp 1207-1244. New York, Cold Spring Harbor
Laboratory Press. </ref>
The mechanisms underlying [[axon guidance]] are similar across invertebrates and vertebrates.
In mammals with longer gestation periods, [[muscle spindles]] are fully formed at birth. Muscle spindles continue to grow throughout post-natal development as muscles grow.
<ref>Maier, A., 1997. Development and regeneration of muscle spindles in mammals and birds. The International journal of developmental biology, 41(1), pp.1-17.</ref>
==Clinical relevance==
===Impairment===
Temporary loss or impairment of proprioception may happen periodically during growth, mostly during adolescence. Growth that might also influence this would be large increases or drops in bodyweight/size due to fluctuations of fat ([[liposuction]], rapid [[Weight loss|fat loss]] or gain) and/or muscle content ([[bodybuilding]], [[anabolic steroid]]s, [[Catabolism|catabolisis]]/[[starvation]]). It can also occur in those that gain new levels of [[flexibility (anatomy)|flexibility]], [[stretching]], and [[contortion]]. A limb's being in a new range of motion never experienced (or at least, not for a long time since youth perhaps) can disrupt one's sense of location of that limb. Possible experiences include suddenly feeling that feet or legs are missing from one's mental self-image; needing to look down at one's limbs to be sure they are still there; and falling down while walking, especially when attention is focused upon something other than the act of walking.
Proprioception is occasionally impaired spontaneously, especially when one is tired. Similar effects can be felt during the [[Hypnagogia#Other sensations|hypnagogic state of consciousness]], during the onset of sleep. One's body may feel too large or too small, or parts of the body may feel distorted in size. Similar effects can sometimes occur during [[epilepsy]] or [[migraine]] [[aura (symptom)|auras]]. These effects are presumed to arise from abnormal stimulation of the part of the [[parietal cortex]] of the [[brain]] involved with integrating information from different parts of the body.<ref>{{cite journal |vauthors=Ehrsson H, Kito T, Sadato N, Passingham R, Naito E |title=Neural substrate of body size: illusory feeling of shrinking of the waist |journal=PLoS Biol. |volume=3 |issue=12 |pages=e412 |year=2005 |pmid=16336049 |doi=10.1371/journal.pbio.0030412 |pmc=1287503}}</ref>
Proprioceptive illusions can also be induced, such as the [[Pinocchio illusion]].
The proprioceptive sense is often unnoticed because humans will adapt to a continuously present stimulus; this is called [[habituation]], [[desensitization (psychology)|desensitization]], or [[adaptation]]. The effect is that proprioceptive sensory impressions disappear, just as a scent can disappear over time. One practical advantage of this is that unnoticed actions or sensation continue in the background while an individual's attention can move to another concern. The [[Alexander Technique]] addresses these unconscious elements by bringing attention to them and practicing a new movement with focus on how it feels to move in the new way.
People who have a limb [[amputation|amputated]] may still have a confused sense of that limb's existence on their body, known as [[Phantom limb|phantom limb syndrome]]. Phantom sensations can occur as passive proprioceptive sensations of the limb's presence, or more active sensations such as perceived movement, pressure, pain, itching, or temperature. There are a variety of theories concerning the etiology of [[phantom limb]] sensations and experience. One is the concept of "proprioceptive memory", which argues that the brain retains a memory of specific limb positions and that after amputation there is a conflict between the visual system, which actually sees that the limb is missing, and the memory system which remembers the limb as a functioning part of the body.<ref>{{cite journal | last1 = Weeks | first1 = S.R. | last2 = Anderson-Barnes | first2 = V.C. | last3 = Tsao | first3 = J. | year = 2010 | title = Phantom limb pain: Theories and therapies | url = http://people.usd.edu/~cliff/Courses/Advanced%20Seminars%20in%20Neuroendocrinology/Pain/Weeks10.pdf | journal = The Neurologist | volume = 16 | issue = 5 | pages = 277–286 | doi = 10.1097/nrl.0b013e3181edf128 | pmid = 20827116 | url-status = dead | archiveurl = https://web.archive.org/web/20110812204549/http://people.usd.edu/~cliff/Courses/Advanced%20Seminars%20in%20Neuroendocrinology/Pain/Weeks10.pdf | archivedate = 2011-08-12 }}</ref> Phantom sensations and phantom pain may also occur after the removal of body parts other than the limbs, such as after amputation of the breast, extraction of a tooth (phantom tooth pain), or removal of an eye ([[phantom eye syndrome]]).
Temporary impairment of proprioception has also been known to occur from an overdose of [[vitamin B6]] (pyridoxine and pyridoxamine). Most of the impaired function returns to normal shortly after the amount of the vitamin in the body returns to a level that is closer to that of the physiological norm. Impairment can also be caused by [[cytotoxicity|cytotoxic]] factors such as [[chemotherapy]].
It has been proposed that even common [[tinnitus]] and the attendant hearing frequency-gaps masked by the perceived sounds may cause erroneous proprioceptive information to the balance and comprehension centers of the brain, precipitating mild confusion.
Proprioception is permanently impaired in patients that suffer from joint hypermobility or [[Ehlers-Danlos syndrome]] (a genetic condition that results in weak connective tissue throughout the body).<ref name="Castori 2012">{{cite journal |author=Castori M |title=Ehlers-danlos syndrome, hypermobility type: an underdiagnosed hereditary connective tissue disorder with mucocutaneous, articular, and systemic manifestations |journal=ISRN Dermatol |volume=2012 |issue= |pages=1–22 |year=2012 |pmid=23227356 |pmc=3512326 |doi=10.5402/2012/751768 |url=}}</ref> It can also be permanently impaired from viral infections as reported by Sacks. The catastrophic effect of major proprioceptive loss is reviewed by Robles-De-La-Torre (2006).<ref>{{cite journal |author=Robles-De-La-Torre G |title=The Importance of the Sense of Touch in Virtual and Real Environments |journal=IEEE Multimedia |volume=13 |issue=3 |pages=24–30 |year=2006 |doi=10.1109/MMUL.2006.69 |url=http://www.roblesdelatorre.com/gabriel/GR-IEEE-MM-2006.pdf |access-date=2006-10-07 |archive-url=https://web.archive.org/web/20140124073640/http://www.roblesdelatorre.com/gabriel/GR-IEEE-MM-2006.pdf# |archive-date=2014-01-24 |url-status=live }}</ref>
Proprioception is also permanently impaired in physiological aging (presbypropria).<ref>{{cite journal|pmid=21850402|year=2012|last1=Boisgontier|first1=MP|last2=Olivier|first2=I|last3=Chenu|first3=O|last4=Nougier|first4=V|title=Presbypropria: The effects of physiological ageing on proprioceptive control|volume=34|issue=5|pages=1179–94|doi=10.1007/s11357-011-9300-y|pmc=3448996|journal=Age (Dordrecht, Netherlands)}}</ref>
[[Parkinson's disease]] is characterized by a decline in motor function as a result of neurodegeneration. It is likely that some of the symptoms of Parkinson's disease are in part related to disrupted proprioception.<ref>Konczak, J., Corcos, D.M., Horak, F., Poizner, H., Shapiro, M., Tuite, P., Volkmann, J. and Maschke, M., 2009. Proprioception and motor control in Parkinson's disease. Journal of motor behavior, 41(6), pp.543-552.</ref>. Whether this symptom is caused by degeneration of proprioceptors in the periphery or disrupted signaling in the brain or spinal cord is an open question.
===Diagnosis===
"Joint position matching" is an established protocol for measuring proprioception, and joint position sense specifically, without the aid of visual or vestibular information.<ref>{{cite journal|url=http://www.flexor.com/sites/default/files/media/memory_based_proprio.PDF|pmid=20600603|year=2010|last1=Goble|first1=DJ|last2=Noble|first2=BC|last3=Brown|first3=SH|title=Where was my arm again? Memory-based matching of proprioceptive targets is enhanced by increased target presentation time|volume=481|issue=1|pages=54–8|doi=10.1016/j.neulet.2010.06.053|journal=Neuroscience Letters|access-date=2013-03-15|archive-url=https://web.archive.org/web/20141219074335/http://www.flexor.com/sites/default/files/media/memory_based_proprio.PDF#|archive-date=2014-12-19|url-status=live}}</ref> During such tasks, individuals are blindfolded while a joint is moved to a specific angle for a given period of time, returned to neutral, and the subjects are asked to replicate the specified angle. Measured by constant and absolute errors, ability to accurately identify joint angles over a series of conditions is the most accurate means of determining proprioceptive acuity in isolation to date.
Recent investigations have shown that hand dominance, participant age, active versus passive matching, and presentation time of the angle can all affect performance on joint position matching tasks.<ref>{{cite journal|pmid=20522675|year=2010|last1=Goble|first1=DJ|title=Proprioceptive acuity assessment via joint position matching: From basic science to general practice|volume=90|issue=8|pages=1176–84|doi=10.2522/ptj.20090399|journal=Physical Therapy}}</ref> Joint position matching has been used in clinical settings in both the upper and lower extremities.
Proprioception is tested by American [[police officer]]s using the [[field sobriety testing]] to check for [[Effects of alcohol on the body#Excessive doses|alcohol intoxication]]. The subject is required to touch his or her nose with eyes closed; people with normal proprioception may make an error of no more than {{cvt|20|mm}}, while people suffering from impaired proprioception (a symptom of moderate to severe alcohol intoxication) fail this test due to difficulty locating their limbs in space relative to their noses.
===Training===
Proprioception is what allows someone to learn to walk in complete darkness without losing balance. During the learning of any new skill, sport, or art, it is usually necessary to become familiar with some proprioceptive tasks specific to that activity. Without the appropriate integration of proprioceptive input, an artist would not be able to brush paint onto a canvas without looking at the hand as it moved the brush over the canvas; it would be impossible to drive an automobile because a motorist would not be able to steer or use the pedals while looking at the road ahead; a person could not [[touch type]] or perform ballet; and people would not even be able to walk without watching where they put their feet.
[[Oliver Sacks]] reported the case of a young woman who lost her proprioception due to a viral infection of her [[spinal cord]].<ref>[[Oliver Sacks|Sacks, O.]]. "The Disembodied Lady", in ''[[The Man Who Mistook His Wife for a Hat]]'' and his autobiographical case study ''[[A Leg to Stand On]]''.</ref> At first she could not move properly at all or even control her tone of voice (as voice modulation is primarily proprioceptive). Later she relearned by using her sight (watching her feet) and [[inner ear]] only for movement while using hearing to judge voice modulation. She eventually acquired a stiff and slow movement and nearly normal speech, which is believed to be the best possible in the absence of this sense. She could not judge effort involved in picking up objects and would grip them painfully to be sure she did not drop them.
[[File:Trabajo propioceptivo en miembro inferior.webm|thumb|Lower limb proprioceptive work]]
The proprioceptive sense can be sharpened through study of many disciplines. Examples are the [[Feldenkrais method]]<ref>{{cite journal|doi=10.1093/ecam/nep055|pmid=19553385|title=Feldenkrais Method Balance Classes Improve Balance in Older Adults: A Controlled Trial|year=2011|last1=Connors|first1=Karol A.|last2=Galea|first2=Mary P.|last3=Said|first3=Catherine M.|journal=Evidence-Based Complementary and Alternative Medicine|volume=2011|pages=1–9|pmc=3137762}}</ref> and the Alexander Technique. [[Juggling]] trains reaction time, spatial location, and efficient movement.{{Citation needed|date=April 2012}} Standing on a [[Balance board|wobble board or balance board]] is often used to retrain or increase proprioception abilities, particularly as [[physical therapy]] for ankle or knee injuries. [[Slacklining]] is another method to increase proprioception.
Standing on one leg (stork standing) and various other body-position challenges are also used in such disciplines as [[yoga]], [[Wing Chun]] and [[tai chi]].<ref>{{cite book|last=cheng man ch'ing|title=T'ai Chi Ch'uan|publisher=Blue Snake Books usa|isbn=978-0-913028-85-8|pages=86, 88|year=1981}}</ref> The vestibular system of the inner ear, vision and proprioception are the main three requirements for balance.<ref>{{cite news|last1=Hanc|first1=John|title=Staying on Balance, With the Help of Exercises|url=https://www.nytimes.com/2010/09/16/business/retirementspecial/16BALANCE.html|work=The New York Times|accessdate=11 October 2017|archive-url=https://web.archive.org/web/20171011130322/http://www.nytimes.com/2010/09/16/business/retirementspecial/16BALANCE.html#|archive-date=2017-10-11|url-status=live}}</ref> Moreover, there are specific devices designed for proprioception training, such as the [[exercise ball]], which works on balancing the abdominal and back muscles.
==History of study==
The position-movement sensation was originally described in 1557 by [[Julius Caesar Scaliger]] as a "sense of locomotion".<ref>{{cite book
|last1=Jerosch
|first1=Jörg
|last2=Heisel
|first2=Jürgen
|title=Management der Arthrose: Innovative Therapiekonzepte
|url=https://books.google.com/books?id=p8-2j4d-hqwC&pg=PA107
|accessdate=8 April 2011
|date=May 2010
|publisher=Deutscher Ärzteverlag
|language=German
|isbn=978-3-7691-0599-5
|page=107}}</ref> Much later, in 1826, [[Charles Bell]] expounded the idea of a "muscle sense",<ref name="Singh1991">{{cite book
|last=Singh
|first=Arun Kumar
|title=The Comprehensive History of Psychology
|url=https://books.google.com/books?id=dXZnwvs6gYIC&pg=PA66
|accessdate=8 April 2011
|date=September 1991
|publisher=Motilal Banarsidass
|isbn=978-81-208-0804-1
|page=66}}</ref> which is credited as one of the first descriptions of physiologic feedback mechanisms.<ref name="Dickinson1976">{{cite book
|last=Dickinson
|first=John
|title=Proprioceptive control of human movement
|url=https://books.google.com/books?id=CI8XAQAAMAAJ
|accessdate=8 April 2011
|year=1976
|publisher=Princeton Book Co.
|page=4}}</ref> Bell's idea was that commands are carried from the brain to the muscles, and that reports on the muscle's condition would be sent in the reverse direction. In 1847 the London neurologist [[Robert Bentley Todd|Robert Todd]] highlighted important differences in the anterolateral and [[posterior column]]s of the spinal cord, and suggested that the latter were involved in the coordination of movement and balance.<ref>{{cite book|last1=Todd|first1=Robert Bentley|title=The Cyclopaedia of Anatomy and Physiology Vol. 4|date=1847|publisher=Longmans|location=London|pages=585–723}}</ref>
At around the same time, [[Moritz Heinrich Romberg]], a Berlin neurologist, was describing unsteadiness made worse by eye closure or darkness, now known as the eponymous [[Romberg's test|Romberg's sign]], once synonymous with [[tabes dorsalis]], that became recognised as common to all proprioceptive disorders of the legs. Later, in 1880, [[Henry Charlton Bastian]] suggested "kinaesthesia" instead of "muscle sense" on the basis that some of the [[afferent nerve fiber|afferent]] information (back to the brain) comes from other structures, including tendons, joints, and skin.<ref name="Foster2010">{{cite book
|last=Foster
|first=Susan Leigh
|title=Choreographing Empathy: Kinesthesia in Performance
|url=https://books.google.com/books?id=MDWuaqZiHZcC&pg=PA74
|accessdate=8 April 2011
|date=15 December 2010
|publisher=Taylor & Francis
|isbn=978-0-415-59655-8
|page=74}}</ref> In 1889, [[Alfred Goldscheider]] suggested a classification of kinaesthesia into three types: muscle, tendon, and articular sensitivity.<ref name="BrookhartMountcastle1984">{{cite book
|last1=Brookhart
|first1=John M.
|last2=Mountcastle
|first2=Vernon B. (Vernon Benjamin)
|last3=Geiger
|first3=Stephen R.
|title=The Nervous system: Sensory processes; volume editor: Ian Darian-Smith
|url=https://books.google.com/books?id=n7fwAAAAMAAJ
|accessdate=8 April 2011
|year=1984
|publisher=American Physiological Society
|isbn=978-0-683-01108-1
|page=784}}</ref>
In 1906, [[Charles Scott Sherrington]] published a landmark work that introduced the terms "proprioception", "[[interoception]]", and "exteroception".<ref>Sherrington, C.S.(1906). The Integrative Action of the Nervous System. NewHaven, CT:YaleUniversityPress.</ref> The "exteroceptors" are the organs that provide information originating outside the body, such as the eyes, ears, mouth, and skin. The [[interoceptor]]s provide information about the internal organs, and the "proprioceptors" provide information about movement derived from muscular, tendon, and articular sources. Using Sherrington's system, physiologists and anatomists search for specialised nerve endings that transmit mechanical data on joint capsule, tendon and muscle tension (such as [[Golgi tendon organ]]s and [[muscle spindles]]), which play a large role in proprioception.
Primary endings of muscle spindles "respond to the size of a muscle length change and its speed" and "contribute both to the sense of limb position and movement".<ref name="Proske">{{cite journal|pmc=2754351|year=2009|last1=Proske|first1=U|last2=Gandevia|first2=SC|title=The kinaesthetic senses|volume=587|issue=Pt 17|pages=4139–4146|doi=10.1113/jphysiol.2009.175372|journal=The Journal of Physiology|pmid=19581378}}</ref> Secondary endings of muscle spindles detect changes in muscle length, and thus supply information regarding only the sense of position.<ref name="Proske"/> Essentially, muscle spindles are stretch receptors.<ref>{{cite journal|pmid=16109730|year=2005|last1=Winter|first1=JA|last2=Allen|first2=TJ|last3=Proske|first3=U|title=Muscle spindle signals combine with the sense of effort to indicate limb position|volume=568|issue=Pt 3|pages=1035–46|doi=10.1113/jphysiol.2005.092619|pmc=1464181|journal=The Journal of Physiology}}</ref> It has been accepted that cutaneous receptors also contribute directly to proprioception by providing "accurate perceptual information about joint position and movement", and this knowledge is combined with information from the muscle spindles.<ref>{{cite journal|pmid=15917323|year=2005|last1=Collins|first1=DF|last2=Refshauge|first2=KM|last3=Todd|first3=G|last4=Gandevia|first4=SC|title=Cutaneous receptors contribute to kinesthesia at the index finger, elbow, and knee|volume=94|issue=3|pages=1699–706|doi=10.1152/jn.00191.2005|journal=Journal of Neurophysiology}}</ref>
===Etymology===
Proprioception is from [[Latin]] ''[[wikt:proprius#Latin|proprius]]'', meaning "one's own", "individual", and ''[[wikt:capio#Latin|capio]]'', ''capere'', to take or grasp. Thus to grasp one's own position in space, including the position of the limbs in relation to each other and the body as a whole.
The word '''''kinesthesia''''' or '''''kinæsthesia''''' ('''''kinesthetic sense''''') refers to movement sense, but has been used inconsistently to refer either to proprioception alone or to the brain's integration of proprioceptive and vestibular inputs. Kinesthesia is a modern medical term composed of elements from Greek; ''kinein'' "to set in motion; to move" (from PIE root *keie- "to set in motion") + ''aisthesis'' "perception, feeling" (from PIE root *au- "to perceive") + Greek abstract noun ending ''-ia'' (corresponds to English ''-hood'' e.g. motherhood).
== Plants ==
[[Terrestrial plant]]s control the orientation of their [[primary growth]] through the sensing of several vectorial [[stimulus (physiology)|stimuli]] such as the light gradient or the [[gravitational acceleration]]. This control has been called [[tropism]]. However, a quantitative study of [[shoot]] [[gravitropism]] demonstrated that, when a plant is tilted, it cannot recover a steady erected posture under the sole driving of the sensing of its angular deflection versus gravity. An additional control through the continuous sensing of its [[curvature]] by the organ and the subsequent driving an active straightening process are required.<ref name=":0" /><ref name=":1" /><ref>{{Cite web|url=http://talks.cam.ac.uk/talk/index/44690|title=From gravitropism to dynamical posture control: proprioception in plants|publisher=[[University of Cambridge]]|access-date=5 August 2017|archive-url=https://web.archive.org/web/20170805181808/http://talks.cam.ac.uk/talk/index/44690#|archive-date=2017-08-05|url-status=live}}</ref> Being a sensing by the plant of the relative configuration of its parts, it has been called proprioception. This dual sensing and control by gravisensing and proprioception has been formalized into a unifying [[mathematical model]] simulating the complete driving of the gravitropic movement. This model has been validated on 11 species sampling the [[Angiosperm Phylogeny Group III system|phylogeny of land angiosperms]], and on organs of very contrasted sizes, ranging from the small germination of [[wheat]] ([[coleoptile]]) to the trunk of [[Populus|poplar trees]].<ref name=":0" /><ref name=":1" /> This model also shows that the entire gravitropic dynamics is controlled by a single [[dimensionless quantity|dimensionless number]] called the "Balance Number", and defined as the ratio between the sensitivity to the inclination angle versus gravity and the proprioceptive sensitivity. This model has been extended to account for the effects of the passive bending of the organ under its self-weight, suggesting that proprioception is active even in very compliant stems, although they may not be able to efficiently straighten depending on their elastic deformation under the gravitational pull.<ref>{{Cite journal|last=Chelakkot|first=Raghunath|last2=Mahadevan|first2=L.|date=March 2017|title=On the growth and form of shoots|journal=Journal of the Royal Society Interface|volume=14|issue=128|pages=20170001|doi=10.1098/rsif.2017.0001|issn=1742-5689|pmid=28330990|pmc=5378141}}</ref>
Further studies have shown that the cellular mechanism of proprioception in plants involves [[myosin]] and [[actin]], and seems to occur in specialized cells.<ref>{{Cite journal|last=Okamoto|first=Keishi|last2=Ueda|first2=Haruko|last3=Shimada|first3=Tomoo|last4=Tamura|first4=Kentaro|last5=Kato|first5=Takehide|last6=Tasaka|first6=Masao|last7=Morita|first7=Miyo Terao|last8=Hara-Nishimura|first8=Ikuko|date=2015-03-23|title=Regulation of organ straightening and plant posture by an actin–myosin XI cytoskeleton|journal=Nature Plants|volume=1|issue=4|pages=15031|doi=10.1038/nplants.2015.31|pmid=27247032|issn=2055-0278|hdl=2433/197219}}</ref> Proprioception was then found to be involved in other tropisms and to be central also to the control of [[Nutation (botany)|nutation]] <ref>{{Cite journal|last=Bastien|first=Renaud|last2=Meroz|first2=Yasmine|date=2016-12-06|title=The Kinematics of Plant Nutation Reveals a Simple Relation between Curvature and the Orientation of Differential Growth|journal=PLOS Computational Biology|volume=12|issue=12|pages=e1005238|doi=10.1371/journal.pcbi.1005238|pmid=27923062|pmc=5140061|issn=1553-7358|bibcode=2016PLSCB..12E5238B|arxiv=1603.00459}}</ref>
These results change the view we have on plant sensitivity. They are also providing concepts and tools for the [[plant breeding|breeding]] of [[crop]]s that are [[ecological resilience|resilient]] to [[lodging (agriculture)|lodging]], and of trees with straight trunks and homogeneous wood quality.<ref>{{Cite journal|last=Gardiner|first=Barry|last2=Berry|first2=Peter|last3=Moulia|first3=Bruno|title=Review: Wind impacts on plant growth, mechanics and damage|journal=Plant Science|volume=245|pages=94–118|doi=10.1016/j.plantsci.2016.01.006|pmid=26940495|year=2016}}</ref>
The discovery of proprioception in plants has generated an interest in the popular science and generalist media.<ref>{{Cite web|url=http://www.bbc.com/earth/story/20170109-plants-can-see-hear-and-smell-and-respond|title=Plants can see, hear and smell – and respond|last=Gabbatiss|first=Josh|date=10 January 2017|access-date=5 August 2017|archive-url=https://web.archive.org/web/20170806010610/http://www.bbc.com/earth/story/20170109-plants-can-see-hear-and-smell-and-respond#|archive-date=2017-08-06|url-status=live}}</ref><ref name=":2">{{Cite web|url=https://www.howplantswork.com/2017/05/28/the-selfish-plant-4-plant-proprioception/|title=The Selfish Plant 4 – Plant Proprioception?|last=plantguy|date=28 May 2017|website=How Plants Work|access-date=5 August 2017}}</ref> This is because this discovery questions a long-lasting ''a priori'' that we have on plants. In some cases this has led to a shift between proprioception and [[self-awareness]] or [[self-consciousness]]. There is no scientific ground for such a semantic shift. Indeed, even in animals, proprioception can be unconscious; so it is thought to be in plants.<ref name=":1" /><ref name=":2" />
==See also==
{{col div}}
* {{annotated link|Balance disorder}}
* {{annotated link|Body image}}
* {{annotated link|Body schema}}
* {{annotated link|Broken escalator phenomenon}}
* {{annotated link|Dizziness}}
* {{annotated link|Equilibrioception}}
* {{annotated link|Eye-hand coordination}}
* {{annotated link|Ideomotor phenomenon}}
* {{annotated link|Illusions of self-motion}}
* {{annotated link|Instinctive aiming}}
* {{annotated link|Kinaesthetics}}
* {{annotated link|Kinesthetic learning}}
* {{annotated link|Motion sickness}}
* {{annotated link|Motor control}}
* {{annotated link|Multisensory integration}}
* {{annotated link|Seasickness}}
* {{annotated link|Spatial disorientation}}
* {{annotated link|Theory of multiple intelligences}}
* {{annotated link|Vertigo}}
{{colend}}
==References==
{{Reflist|30em}}
==External links==
* [http://www.eicollege.edu/neuroscience-tutorial/ Neuroscience Tutorial ] See "Basic somatosensory pathway", Eastern International College.
*[https://web.archive.org/web/20051103235935/http://www.reumatologia-dr-bravo.cl/para%20medicos/HIPERLAXITUD/www_jointandbone_org_RODGRAH.htm Joint & Bone – Ehlers-Danlos/Joint Hypermobility Syndrome – Proprioception]
* [http://www.everything2.com/index.pl?node_id=690040 Humans have six senses, why does everyone think we only have five?] at [[Everything2]]
*[http://www.artbrain.org/proprioception ''Proprioception''] this essay by Charles Wolfe takes its cue from such thinkers & artists as [[Charles Olson]], [[Merleau-Ponty]], [[James J. Gibson]], and [[Andy Clark]] to illustrate the view of the "priority of dynamic embodied activity over isolated 'mental' and 'physical' regions" to define this concept
*[http://www.radiolab.org/story/91524-where-am-i/ WNYC – Radio Lab: Where Am I? (May 05, 2006)] radio program looks at the relationship between the brain and the body
*[http://www.abc.net.au/rn/allinthemind/stories/2005/1323547.htm The Dancers Mind] ABC (Aust) podcast on the nature of proprioception.
* {{MeshName|Proprioception}}
{{Somatosensory system}}
{{Sensory system}}
[[Category:Proprioception]]
[[Category:Sensory systems]]
[[Category:Articles containing video clips]]
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