View source for Proprioception

{{Short description|Sense of self-movement, force, and body position}}
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[[File:Proprioception image-01.jpg|thumb|upright=1.35|Schematics and images of types of limb proprioceptor neurons in mammals (top) and insects (bottom)<ref name=":3" />]]

'''Proprioception''' ({{IPAc-en|ˌ|p|r|oʊ|p|r|i|.|oʊ|ˈ|s|ɛ|p|ʃ|ən|,_|-|ə|-}}{{refn|{{cite Merriam-Webster|proprioception}}}}{{refn|{{cite web |url=https://www.oxforddictionaries.com/definition/english/proprioceptive |archive-url=https://web.archive.org/web/20120903092536/http://oxforddictionaries.com/definition/english/proprioceptive |url-status=dead |archive-date=September 3, 2012 |title=proprioceptive |publisher=[[Lexico|OxfordDictionaries.com]] |access-date=2016-01-20}}}} {{respell|PROH|pree|oh|SEP|shən|,_|-|ə|-}}) is the [[sense]] of self-movement, force, and body position.<ref name=":3">{{cite journal |vauthors=Tuthill JC, Azim E |title=Proprioception |journal=[[Current Biology]] |volume=28 |issue=5 |pages=R194–R203 |date=1 March 2018 | pmid=29510103 |doi=10.1016/j.cub.2018.01.064 |doi-access=free |bibcode=2018CBio...28.R194T }}</ref><ref>{{cite book | vauthors = Balasubramanian R, Santos V |title=The Human Hand as an Inspiration for Robot Hand Development |date=3 January 2014 |publisher=Springer |isbn=978-3-319-03017-3 |page=127 |url=https://books.google.com/books?id=h3u5BQAAQBAJ&pg=PA127 |quote= Proprioception also includes the ability to perceive force and heaviness, the history of which has been less controversial than the senses of limb position and movement. The sense of force refers to the ability to perceive the force that is generated by the muscles and its primary receptor is the Golgi tendon organ.}}</ref>

Proprioception is mediated by '''proprioceptors''', [[sensory receptor]]s, located within [[muscle]]s, [[tendon]]s, and [[joint]]s.<ref name=":3"/> Most animals possess multiple subtypes of proprioceptors, which detect distinct kinesthetic parameters, such as joint position, movement, and load. Although all mobile animals possess proprioceptors, the structure of the sensory organs can vary across species.

Proprioceptive signals are transmitted to the [[central nervous system]], where they are integrated with information from other [[Sensory nervous system|sensory systems]], such as [[Visual perception|the visual system]] and the [[vestibular system]], to create an overall representation of body position, movement, and acceleration. In many animals, sensory feedback from proprioceptors is essential for stabilizing body posture and coordinating body movement.

== System overview ==
In vertebrates, limb movement and velocity (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 | vauthors = Lundberg A, Malmgren K, Schomburg ED | 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 = 327–43 | date = November 1978 | pmid = 215758 | pmc = 1282824 | doi = 10.1113/jphysiol.1978.sp012543 }}</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 | vauthors = Bush BM | title = Proprioception by the Coxo-Basal Chordotonal Organ, Cb, in Legs of the Crab, Carcinus Maenas | journal = The Journal of Experimental Biology | volume = 42 | pages = 285–97 | date = April 1965 | issue = 2 | doi = 10.1242/jeb.42.2.285 | 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 | vauthors = Murphy JT, Wong YC, Kwan HC | 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 | pmid = 125786 | doi = 10.1152/jn.1975.38.4.990 | s2cid = 20111229 }}</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 | vauthors = Chapman KM | title = Campaniform Sensilla on the Tactile Spines of the Legs of the Cockroach | journal = The Journal of Experimental Biology | volume = 42 | pages = 191–203 | date = April 1965 | issue = 2 | doi = 10.1242/jeb.42.2.191 | pmid = 14323763 }}</ref> These proprioceptors are active when a limb experiences resistance.<ref name=":3" />

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 position, usually at the extremes of joint position. Invertebrates use [[hair plate]]s<ref>{{cite journal | vauthors = Bräunig P, Hustert R, Pflüger HJ | 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 | s2cid = 29439820 }}</ref> to accomplish this; a field of bristles located within joints that detects the relative movement of limb segments through the deflection of the associated cuticular hairs.

=== 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 [[mechanosensation]] 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 | vauthors = Bässler U, Büschges A | 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 | date = June 1998 | pmid = 9639677 | doi = 10.1016/S0165-0173(98)00006-X | s2cid = 16673654 }}</ref><ref>{{cite journal | vauthors = Tuthill JC, Wilson RI | title = Mechanosensation and Adaptive Motor Control in Insects | journal = Current Biology | volume = 26 | issue = 20 | pages = R1022–R1038 | date = October 2016 | pmid = 27780045 | pmc = 5120761 | doi = 10.1016/j.cub.2016.06.070 | bibcode = 2016CBio...26R1022T }}</ref>

=== Conscious and nonconscious ===
In humans, a distinction is made between ''conscious'' proprioception and ''nonconscious'' proprioception:
* Conscious proprioception is communicated by the [[dorsal column-medial lemniscus pathway]] to the [[cerebrum]].<ref name="isbn0-7817-2829-0">{{cite book | vauthors = Fix JD |title=Neuroanatomy |url=https://archive.org/details/neuroanatomy0003fixj |url-access=registration |publisher=Lippincott Williams & Wilkins |location=Hagerstown, MD |year=2002 |pages=[https://archive.org/details/neuroanatomy0003fixj/page/127 127] |isbn=978-0-7817-2829-4 }}</ref>
* Nonconscious proprioception is communicated primarily via the [[dorsal spinocerebellar tract]]<ref name="titleChapter 7A: Somatosensory Systems">{{cite web | vauthors = 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 |access-date=2008-04-10 |archive-url=https://web.archive.org/web/20080405222242/http://www.dartmouth.edu/~rswenson/NeuroSci/chapter_7A.html#Unconscious_sensation |archive-date=2008-04-05 |url-status=live }}</ref> and [[ventral spinocerebellar tract]],<ref>{{cite book| vauthors = Siegel A |title=Essential Neuroscience|year=2010|publisher=Lippincott Williams & Wilkins|page=263}}</ref> to the [[cerebellum]].
* A nonconscious 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|access-date=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.{{citation needed|date=May 2022}}

== 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]]s, [[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 plate]]s.<ref name=":3" />

The initiation of proprioception is the activation of a proprioceptor in the periphery.<ref>{{cite journal | vauthors = Sherrington CS |title=On the proprioceptive system, especially in its reflex aspect |journal=Brain |volume=29 |issue=4 |pages=467–85 |year=1907 |doi=10.1093/brain/29.4.467 }}</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 "proprioceptors", just as there are specific receptors for pressure, light, temperature, sound, and other sensory experiences. Proprioceptors are sometimes known as [[Adequate stimulus|adequate stimuli]] receptors.{{citation needed|date=May 2022}}

Members of the [[transient receptor potential]] family of [[ion channel]]s have been found to be important for proprioception in [[Drosophila melanogaster|fruit flies]],<ref>{{cite journal | vauthors = Walker RG, Willingham AT, Zuker CS | title = A Drosophila mechanosensory transduction channel | journal = Science | volume = 287 | issue = 5461 | pages = 2229–34 | date = March 2000 | pmid = 10744543 | doi = 10.1126/science.287.5461.2229 | citeseerx = 10.1.1.646.2497 | bibcode = 2000Sci...287.2229W }}</ref> [[Caenorhabditis elegans|nematode worms]],<ref>{{cite journal | vauthors = Li W, Feng Z, Sternberg PW, Xu XZ | title = A C. elegans stretch receptor neuron revealed by a mechanosensitive TRP channel homologue | journal = Nature | volume = 440 | issue = 7084 | pages = 684–87 | date = March 2006 | pmid = 16572173 | pmc = 2865900 | doi = 10.1038/nature04538 | bibcode = 2006Natur.440..684L }}</ref> [[African clawed frog]]s,<ref>{{cite journal | vauthors = Shin JB, Adams D, Paukert M, Siba M, Sidi S, Levin M, Gillespie PG, Gründer S | title = Xenopus TRPN1 (NOMPC) localizes to microtubule-based cilia in epithelial cells, including inner-ear hair cells | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 102 | issue = 35 | pages = 12572–77 | date = August 2005 | pmid = 16116094 | pmc = 1194908 | doi = 10.1073/pnas.0502403102 | bibcode = 2005PNAS..10212572S | doi-access = free }}</ref> and [[zebrafish]].<ref>{{cite journal | vauthors = Sidi S, Friedrich RW, Nicolson T | title = NompC TRP channel required for vertebrate sensory hair cell mechanotransduction | journal = Science | volume = 301 | issue = 5629 | pages = 96–99 | date = July 2003 | pmid = 12805553 | doi = 10.1126/science.1084370 | bibcode = 2003Sci...301...96S | s2cid = 23882972 | doi-access = free }}</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, Patapoutian A | title = Piezo2 is the principal mechanotransduction channel for proprioception | journal = Nature Neuroscience | volume = 18 | issue = 12 | pages = 1756–62 | date = December 2015 | pmid = 26551544 | pmc = 4661126 | doi = 10.1038/nn.4162 }}</ref> Humans with loss-of-function mutations in the ''PIEZO2'' gene exhibit specific deficits in joint proprioception,{{efn|name= piezoChannels|The Piezo channel receptors play key roles in the perception of pressure, touch, and proprioception (Piezo2 receptor).<ref  name= 4Oct2021>The Nobel Assembly at Karolinska Institutet [https://www.nobelprize.org/prizes/medicine/2021/press-release/ (4 Oct 2021) Press release: The Nobel Prize in Physiology or Medicine 2021 ] The Nobel Prize in Physiology or Medicine 2021: David Julius, and Ardem Patapoutian</ref>}} as well as vibration and touch discrimination, suggesting that the PIEZO2 channel is essential for mechanosensitivity in some proprioceptors and low-threshold mechanoreceptors.<ref>{{cite journal | vauthors = Chesler AT, Szczot M, Bharucha-Goebel D, Čeko M, Donkervoort S, Laubacher C, Hayes LH, Alter K, Zampieri C, Stanley C, Innes AM, Mah JK, Grosmann CM, Bradley N, Nguyen D, Foley AR, Le Pichon CE, Bönnemann CG | title = The Role of PIEZO2 in Human Mechanosensation | journal = The New England Journal of Medicine | volume = 375 | issue = 14 | pages = 1355–64 | date = October 2016 | pmid = 27653382 | pmc = 5911918 | doi = 10.1056/NEJMoa1602812 }}</ref>

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 = 445–48 | date = July 2001 | pmid = 11473320 | doi = 10.1038/35086588 | url = http://www.roblesdelatorre.com/gabriel/GR-VH-Nature2001.pdf | access-date = 2006-10-03 | url-status = dead | bibcode = 2001Natur.412..445R | s2cid = 4413295 | archive-url = https://web.archive.org/web/20061003225801/http://www.roblesdelatorre.com/gabriel/GR-VH-Nature2001.pdf | archive-date = 2006-10-03 }}</ref> This research allows the creation of "virtual", illusory haptic shapes with different perceived qualities.<ref>[https://www.technologyreview.com/2006/08/25/100586/the-cutting-edge-of-haptics/ the MIT Technology Review article "The Cutting Edge of Haptics"]</ref>

== Anatomy ==
Proprioception of the head stems from the muscles innervated by the [[trigeminal nerve]], where the [[general somatic afferent fibers]] pass without synapsing in the [[trigeminal ganglion]] (first-order sensory neuron), reaching the mesencephalic tract and the [[mesencephalic nucleus of trigeminal nerve]].<ref name="Arslan2014">{{cite book | vauthors = Arslan OE | date = 7 August 2014 | title = Neuroanatomical Basis of Clinical Neurology | edition = 2nd | publisher = CRC Press | pages = 432– | isbn = 978-1-4398-4834-0 | url = https://books.google.com/books?id=NCPOBQAAQBAJ&pg=PA432}}</ref> Proprioception of limbs often occurs due to receptors in [[connective tissue]] near joints.<ref>{{cite journal | vauthors = van der Wal J | title = The architecture of the connective tissue in the musculoskeletal system-an often overlooked functional parameter as to proprioception in the locomotor apparatus | journal = International Journal of Therapeutic Massage & Bodywork | volume = 2 | issue = 4 | pages = 9–23 | date = December 2009 | pmid = 21589740 | pmc = 3091473 | doi = 10.3822/ijtmb.v2i4.62 }}</ref>

== Function ==

=== Stability ===
An important role for proprioception is to allow an animal to stabilize itself against perturbations.<ref name="MageeZachazewskiQuillen2008">{{cite book | vauthors = Magee DJ, Zachazewski JE, Quillen WS | date = 18 September 2008 | title = Pathology and Intervention in Musculoskeletal Rehabilitation - E-Book | publisher = Elsevier Health Sciences | pages = 533– | isbn = 978-1-4160-6942-3 | oclc = 1017975705 | url = https://books.google.com/books?id=xUFqHSwrXiQC&pg=PA533}}</ref> For instance, for a person to walk or stand upright, they must continuously monitor their posture and adjust muscle activity as needed to provide balance. Similarly, when walking on unfamiliar terrain or even tripping, the person must adjust the output of their muscles quickly based on estimated limb position and velocity. [[#Reflexes|Proprioceptor reflex circuits]] are thought to play an important role to allow fast and unconscious execution of these behaviors, To make control of these behaviors efficient, proprioceptors are also thought to regulate reciprocal inhibition in muscles, leading to [[Anatomical terms of muscle#Agonist-antagonist pairs|agonist-antagonist muscle pairs]].<ref name="proske">{{cite journal |vauthors=Proske U, Gandevia SC |title=The proprioceptive senses: their roles in signaling body shape, body position and movement, and muscle force |journal=Physiological Reviews |volume=92 |issue=4 |pages=1651–97 |date=October 2012 |pmid=23073629 |doi=10.1152/physrev.00048.2011 |url=https://journals.physiology.org/doi/full/10.1152/physrev.00048.2011}}</ref>

=== Planning and refining movements ===
When planning complex movements such as reaching or [[Personal grooming|grooming]], an animal must consider the current position and velocity of its limb and use that information to adjust dynamics to target a final position. If the animal's estimate of its limb's initial position is wrong, then a deficiency in the movement can result. Furthermore, proprioception is crucial in refining the movement if it deviates from the trajectory.<ref name=proske/><ref>{{Cite journal |last=Blanke |first=Olaf |date=2012-07-18 |title=Multisensory brain mechanisms of bodily self-consciousness |url=https://pubmed.ncbi.nlm.nih.gov/22805909/ |journal=Nature Reviews. Neuroscience |volume=13 |issue=8 |pages=556–571 |doi=10.1038/nrn3292 |issn=1471-0048 |pmid=22805909}}</ref>

== Development ==
In adult fruit flies, 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>{{cite book | vauthors = Jan YN, Jan LY | date =  1993 | chapter = The peripheral nervous system. | title = The Development of ''Drosophila melanogaster'' | veditors = Bate M, Arias AM | pages = 1207–1244 | location = New York | publisher = Cold Spring Harbor Laboratory Press }}</ref>
The mechanisms underlying [[axon guidance]] are similar across invertebrates and vertebrates.<ref>{{cite journal | vauthors = Prokop A | title = Cytoskeletal organization of axons in vertebrates and invertebrates | journal = The Journal of Cell Biology | volume = 219 | issue = 7 | date = July 2020 | pmid = 32369543 | pmc = 7337489 | doi = 10.1083/jcb.201912081 }}</ref>

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 name="pmid9074933">{{cite journal | vauthors = Maier A | title = Development and regeneration of muscle spindles in mammals and birds | journal = The International Journal of Developmental Biology | volume = 41 | issue = 1 | pages = 1–17 | date = February 1997 | pmid = 9074933}}</ref>

== Mathematical models ==
Proprioceptors transfer the mechanical state of the body into patterns of neural activity. This transfer can be modeled mathematically, for example to better understand the internal workings of a proprioceptor<ref name=":4">{{cite journal | vauthors = Blum KP, Lamotte D'Incamps B, Zytnicki D, Ting LH | title = Force encoding in muscle spindles during stretch of passive muscle | journal = PLOS Computational Biology | volume = 13 | issue = 9 | pages = e1005767 | date = September 2017 | pmid = 28945740 | pmc = 5634630 | doi = 10.1371/journal.pcbi.1005767 | bibcode = 2017PLSCB..13E5767B | doi-access = free }}</ref><ref name=":5">{{cite journal | vauthors = Mileusnic MP, Brown IE, Lan N, Loeb GE | title = Mathematical models of proprioceptors. I. Control and transduction in the muscle spindle | journal = Journal of Neurophysiology | volume = 96 | issue = 4 | pages = 1772–88 | date = October 2006 | pmid = 16672301 | doi = 10.1152/jn.00868.2005 }}</ref><ref name=":6">{{cite journal | vauthors = Maltenfort MG, Burke RE | title = Spindle model responsive to mixed fusimotor inputs and testable predictions of beta feedback effects | journal = Journal of Neurophysiology | volume = 89 | issue = 5 | pages = 2797–809 | date = May 2003 | pmid = 12740414 | doi = 10.1152/jn.00942.2002 | s2cid = 18253128 }}</ref> or to provide more realistic feedback in neuromechanical simulations.<ref>{{cite journal | vauthors = Röhrle O, Yavuz UŞ, Klotz T, Negro F, Heidlauf T | title = Multiscale modeling of the neuromuscular system: Coupling neurophysiology and skeletal muscle mechanics | journal = Wiley Interdisciplinary Reviews. Systems Biology and Medicine | volume = 11 | issue = 6 | pages = e1457 | date = November 2019 | pmid = 31237041 | doi = 10.1002/wsbm.1457  | s2cid = 195354352 | url = https://ris.utwente.nl/ws/files/286393690/R_hrle_2019_multiscale.pdf }}</ref><ref>{{cite book | vauthors = Prilutsky BI, Klishko AN, Weber DJ, Lemay MA |chapter=Computing Motion Dependent Afferent Activity During Cat Locomotion Using a Forward Dynamics Musculoskeletal Model|date=2016 |title=Neuromechanical Modeling of Posture and Locomotion|pages=273–307| veditors = Prilutsky BI, Edwards DH |series=Springer Series in Computational Neuroscience|place=New York|publisher=Springer|language=en|doi=10.1007/978-1-4939-3267-2_10|isbn=978-1-4939-3267-2 }}</ref>

Various proprioceptor models of complexity have been developed. They range from simple phenomenological models to complex structural models, in which the mathematical elements correspond to anatomical features of the proprioceptor. The focus has been on [[muscle spindle]]s,<ref name=":4" /><ref name=":5" /><ref name=":6" /><ref>{{cite book | vauthors = Prochazka A |  chapter = Chapter 11 Quantifying Proprioception|date=1999| title =Progress in Brain Research|volume=123|pages=133–142| veditors = Binder MD |series=Peripheral and Spinal Mechanisms in the Neural Control of Movement|publisher=Elsevier }}</ref> but [[Golgi tendon organ]]s<ref>{{cite journal | vauthors = Mileusnic MP, Loeb GE | title = Mathematical models of proprioceptors. II. Structure and function of the Golgi tendon organ | journal = Journal of Neurophysiology | volume = 96 | issue = 4 | pages = 1789–802 | date = October 2006 | pmid = 16672300 | doi = 10.1152/jn.00869.2005 }}</ref><ref name=":7">{{cite journal | vauthors = Houk J, Simon W | title = Responses of Golgi tendon organs to forces applied to muscle tendon | journal = Journal of Neurophysiology | volume = 30 | issue = 6 | pages = 1466–81 | date = November 1967 | pmid = 6066449 | doi = 10.1152/jn.1967.30.6.1466 }}</ref> and insects' [[hair plate]]s<ref>{{cite journal | vauthors = Ache JM, Dürr V | title = A Computational Model of a Descending Mechanosensory Pathway Involved in Active Tactile Sensing | journal = PLOS Computational Biology | volume = 11 | issue = 7 | pages = e1004263 | date = July 2015 | pmid = 26158851 | pmc = 4497639 | doi = 10.1371/journal.pcbi.1004263 | bibcode = 2015PLSCB..11E4263A | doi-access = free }}</ref> have been modeled too.

=== Muscle spindles ===
Poppele and Bowman <ref>{{cite journal | vauthors = Poppele RE, Bowman RJ | title = Quantitative description of linear behavior of mammalian muscle spindles | journal = Journal of Neurophysiology | volume = 33 | issue = 1 | pages = 59–72 | date = January 1970 | pmid = 4243791 | doi = 10.1152/jn.1970.33.1.59 }}</ref> used [[Linear time-invariant system|linear system theory]] to model mammalian muscle spindles Ia and II afferents. They obtained a set of de-afferented muscle spindles, measured their response to a series of sinusoidal and step function stretches, and fit a transfer function to the spike rate. They found that the following [[Transfer function|Laplace transfer function]] describes the firing rate responses of the [[Type Ia sensory fiber|primary sensory fibers]] for a change in length:

<math>H(s) = K_1 \frac{s(s+0.44)(s+11.3)(s+44)}{(s + 0.04)(s+0.816)}</math>

The following equation describes the response of [[Type II sensory fiber|secondary sensory fibers]]:

<math>H(s) = K_2 \frac{(s+0.44)(s+11.3)}{s+0.816}</math>

More recently, Blum et al.<ref>{{cite journal | vauthors = Blum KP, Lamotte D'Incamps B, Zytnicki D, Ting LH | title = Force encoding in muscle spindles during stretch of passive muscle | journal = PLOS Computational Biology | volume = 13 | issue = 9 | pages = e1005767 | date = September 2017 | pmid = 28945740 | pmc = 5634630 | doi = 10.1371/journal.pcbi.1005767 | veditors = Ayers J | bibcode = 2017PLSCB..13E5767B | doi-access = free }}</ref> showed that the muscle spindle firing rate is modeled better as tracking the force of the muscle, rather than the length. Furthermore, muscle spindle firing rates show history dependence which cannot be modeled by a linear time-invariant system model.

=== Golgi tendon organs ===
Houk and Simon <ref name=":7" /> provided one of the first mathematical models of a Golgi tendon organ receptor, modeling the firing rate of the receptor as a function of the muscle tension force. Just as for muscle spindles, they find that, as the receptors respond linearly to sine waves of different frequencies and has little variance in response over time to the same stimulus, Golgi tendon organ receptors may be modeled as linear time-invariant systems. Specifically, they find that the firing rate of a Golgi tendon organ receptor may be modeled as a sum of 3 decaying exponentials:

<math>r(t) = K[1 + A\exp(-at) + B \exp(-b t) + C \exp(-c t)] u(t)</math>

where <math>r(t)</math> is the firing rate and <math>u(t)</math> is a step function of force.

The corresponding Laplace transfer function for this system is:

<math>H(s) = K\left(1 + \frac{A s }{s + a}  + \frac{Bs}{s+b} + \frac{Cs}{s + c} \right)</math>

For a [[Soleus muscle|soleus]] receptor, Houk and Simon obtain average values of K=57 pulses/sec/kg, A=0.31, a=0.22 sec<sup>−1</sup>, B=0.4, b=2.17 sec<sup>−1</sup>, C=2.5, c=36 sec<sup>−1</sup> .

When modeling a stretch reflex, Lin and Crago<ref>{{cite journal | vauthors = Lin CC, Crago PE | title = Neural and mechanical contributions to the stretch reflex: a model synthesis | journal = Annals of Biomedical Engineering | volume = 30 | issue = 1 | pages = 54–67 | date = January 2002 | pmid = 11874142 | doi = 10.1114/1.1432692 | s2cid = 13015209 }}</ref> improved upon this model by adding a logarithmic nonlinearity before the Houk and Simon model and a [[Rectifier (neural networks)|threshold nonlinearity]] after.

== Impairment ==
=== Chronic ===
Proprioception, a sense vital for rapid and proper body coordination,<ref>{{cite journal|vauthors=Robles-De-La-Torre G|year=2006|title=The Importance of the Sense of Touch in Virtual and Real Environments|url=http://www.roblesdelatorre.com/gabriel/GR-IEEE-MM-2006.pdf|url-status=dead|journal=IEEE MultiMedia|volume=13|issue=3|pages=24–30|doi=10.1109/MMUL.2006.69|archive-url=https://web.archive.org/web/20140124073640/http://www.roblesdelatorre.com/gabriel/GR-IEEE-MM-2006.pdf|archive-date=2014-01-24|access-date=2006-10-07|s2cid=16153497}}</ref> can be permanently lost or impaired as a result of genetic conditions, disease, viral infections, and injuries. For instance, patients with joint hypermobility or [[Ehlers–Danlos syndromes]], genetic conditions that result in weak connective tissue throughout the body, have chronic impairments to proprioception.<ref name="Castori 2012">{{cite journal|vauthors=Castori M|year=2012|title=Ehlers-danlos syndrome, hypermobility type: an underdiagnosed hereditary connective tissue disorder with mucocutaneous, articular, and systemic manifestations|journal=ISRN Dermatology|volume=2012|pages=751768|doi=10.5402/2012/751768|pmc=3512326|pmid=23227356 |doi-access=free }}</ref> [[Autism spectrum|Autism spectrum disorder]]<ref>{{cite journal | vauthors = Blanche EI, Reinoso G, Chang MC, Bodison S | title = Proprioceptive processing difficulties among children with autism spectrum disorders and developmental disabilities | journal = The American Journal of Occupational Therapy | volume = 66 | issue = 5 | pages = 621–624 | date = 1 September 2012 | pmid = 22917129 | pmc = 3754787 | doi = 10.5014/ajot.2012.004234 }}</ref> and [[Parkinson's disease]] can also cause chronic disorder of proprioception.<ref name="pmid19592360">{{cite journal|vauthors=Konczak J, Corcos DM, Horak F, Poizner H, Shapiro M, Tuite P, Volkmann J, Maschke M|date=November 2009|title=Proprioception and motor control in Parkinson's disease|journal=Journal of Motor Behavior|volume=41|issue=6|pages=543–52|doi=10.3200/35-09-002|pmid=19592360|s2cid=5775266}}</ref> In regards to Parkinson's disease, it remains unclear whether the proprioceptive-related decline in motor function occurs due to disrupted proprioceptors in the periphery or signaling in the spinal cord or brain.

In rare cases, viral infections result in a loss of proprioception. Ian Waterman and Charles Freed are two such people that lost their sense of proprioception from the neck down from supposed viral infections (i.e. gastric flu and a rare viral infection). After losing their sense of proprioception, Ian and Charles could move their lower body, but could not coordinate their movements. However, both individuals regained some control of their limbs and body by consciously planning their movements and relying solely on visual feedback. Interestingly, both individuals can still sense pain and temperature, indicating that they specifically lost proprioceptive feedback, but not tactile and nociceptive feedback. The impact of losing the sense of proprioception on daily life is perfectly illustrated when Ian Waterman stated, "What is an active brain without mobility".<ref>The Man Who Lost His Body (1997). BBC Documentary.</ref><ref>{{Citation |title=The Man Who Lost His Body |url=https://topdocumentaryfilms.com/the-man-who-lost-his-body/ |language=en |access-date=2023-02-21}}</ref>

Proprioception is also permanently lost in people who lose a limb or body part through injury or amputation. After the removal of a limb, people may 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|vauthors=Weeks SR, Anderson-Barnes VC, Tsao JW|date=September 2010|title=Phantom limb pain: theories and therapies|url=http://people.usd.edu/~cliff/Courses/Advanced%20Seminars%20in%20Neuroendocrinology/Pain/Weeks10.pdf|url-status=dead|journal=The Neurologist|volume=16|issue=5|pages=277–86|doi=10.1097/nrl.0b013e3181edf128|pmid=20827116|archive-url=https://web.archive.org/web/20110812204549/http://people.usd.edu/~cliff/Courses/Advanced%20Seminars%20in%20Neuroendocrinology/Pain/Weeks10.pdf|archive-date=2011-08-12|s2cid=205894711}}</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]]).

There is a decline in the sense of proprioception with [[ageing]]. This can often result in chronic lower back pain, and be the cause of falls in the elderly.<ref name="Sakai">{{cite journal |vauthors=Sakai Y, Watanabe T, Wakao N, Matsui H, Osada N, Sugiura T, Morita Y, Kawai K, Ito T, Yamazaki K |title=Proprioception and Geriatric Low Back Pain |journal=Spine Surg Relat Res |volume=6 |issue=5 |pages=422–432 |date=September 2022 |pmid=36348676 |pmc=9605761 |doi=10.22603/ssrr.2021-0269 |url=}}</ref>

=== Acute ===
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 HH, Kito T, Sadato N, Passingham RE, Naito E | title = Neural substrate of body size: illusory feeling of shrinking of the waist | journal = PLOS Biology | volume = 3 | issue = 12 | pages = e412 | date = December 2005 | pmid = 16336049 | pmc = 1287503 | doi = 10.1371/journal.pbio.0030412 | doi-access = free }}</ref> Proprioceptive illusions can also be induced, such as the "Pinocchio illusion", the illusion that one's nose is growing longer.{{cn|date=September 2024}}

Temporary impairment of proprioception has also been known to occur from an overdose of [[vitamin B6]] (pyridoxine and pyridoxamine). This is due to a reversible neuropathy.<ref>{{Cite journal |last=Smyth |first=Duncan |last2=Kramarz |first2=Caroline |last3=Carr |first3=Aisling S. |last4=Rossor |first4=Alexander M. |last5=Lunn |first5=Michael P. |date=2023-04-01 |title=Toxic neuropathies: a practical approach |url=https://pn.bmj.com/content/23/2/120 |journal=Practical Neurology |language=en |volume=23 |issue=2 |pages=120–130 |doi=10.1136/pn-2022-003444 |issn=1474-7758 |pmid=36697225}}</ref> 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.

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]]).<ref>Hirtz, Peter, and Wlodzimierz Starosta. "Sensitive and critical periods of motor co-ordination development and its relation to motor learning." ''Journal of human kinetics'' 7 (2002): 19-28.</ref> 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.

=== Diagnosis ===
Impaired proprioception may be diagnosed through a series of tests, each focusing on a different functional aspect of proprioception.

The [[Romberg's test]] is often used to assess balance. The subject must stand with feet together and eyes closed without support for 30 seconds. If the subject loses balance and falls, it is an indicator for impaired proprioception.

For evaluating proprioception's contribution to motor control, a common protocol is joint position matching.<ref>{{cite journal | vauthors = Goble DJ, Noble BC, Brown SH | title = Where was my arm again? Memory-based matching of proprioceptive targets is enhanced by increased target presentation time | journal = Neuroscience Letters | volume = 481 | issue = 1 | pages = 54–58 | date = August 2010 | pmid = 20600603 | doi = 10.1016/j.neulet.2010.06.053 | url = http://www.flexor.com/sites/default/files/media/memory_based_proprio.PDF | access-date = 2013-03-15 | url-status = dead | s2cid = 24385107 | 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 }}</ref> The patient is blindfolded while a joint is moved to a specific angle for a given period of time and then returned to neutral. The subject is then asked to move the joint back to the specified angle. 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 | vauthors = Dempsey-Jones H, Kritikos A | title = Handedness modulates proprioceptive drift in the rubber hand illusion | journal = Experimental Brain Research | volume = 237 | issue = 2 | pages = 351–361 | date = February 2019 | pmid = 30411222 | pmc = 6373180 | doi = 10.1007/s00221-018-5391-3 }}</ref><ref>{{Citation | vauthors = Carranza E, Franovic S, Boos A, Pirondini E |title=Understanding Age-Related Changes in Proprioception through Active and Passive Tasks |date=2023-11-06 |url=https://www.biorxiv.org/content/10.1101/2023.11.06.565689v1 |access-date=2024-07-04 |language=en |doi=10.1101/2023.11.06.565689 }}</ref>

For passive sensing of joint angles, recent studies have found that experiments to probe psychophysical thresholds produce more precise estimates of proprioceptive discrimination than the joint position matching task.<ref>{{cite journal | vauthors = Elangovan N, Herrmann A, Konczak J | title = Assessing proprioceptive function: evaluating joint position matching methods against psychophysical thresholds | journal = Physical Therapy | volume = 94 | issue = 4 | pages = 553–561 | date = April 2014 | pmid = 24262599 | pmc = 6281037 | doi = 10.2522/ptj.20130103 }}</ref> In these experiments, the subject holds on to an object (such as an armrest) that moves and stops at different positions. The subject must discriminate whether one position is closer to the body than another. From the subject's choices, the tester may determine the subject's discrimination thresholds.

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}}{{citation needed|date=December 2021}}, while people with 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.{{citation needed|date=May 2022}}

[[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. [[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 proprioceptive 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| vauthors = Cheng M |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| vauthors = Hanc J |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|date=15 September 2010 |access-date=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==
In 1557, the position-movement sensation was described by [[Julius Caesar Scaliger]] as a "sense of locomotion".<ref>{{cite book | vauthors = Jerosch J, Heisel J | title = Management der Arthrose: Innovative Therapiekonzepte | url = https://books.google.com/books?id=p8-2j4d-hqwC&pg=PA107 | access-date = 8 April 2011 | year=2010 | publisher = Deutscher Ärzteverlag | language = de | isbn = 978-3-7691-0599-5 | page = 107 }}</ref>

In 1826, [[Charles Bell]] expounded the idea of a "muscle sense",<ref name="Singh1991">{{cite book | vauthors = Singh AK | title = The Comprehensive History of Psychology | url = https://books.google.com/books?id=dXZnwvs6gYIC&pg=PA66 | access-date = 8 April 2011 | year= 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 | vauthors = Dickinson J | title = Proprioceptive control of human movement | url = https://books.google.com/books?id=CI8XAQAAMAAJ | access-date = 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| vauthors = Todd RB |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.{{citation needed|date=October 2022}}

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 | vauthors = Foster SL | title = Choreographing Empathy: Kinesthesia in Performance | url = https://books.google.com/books?id=MDWuaqZiHZcC&pg=PA74 | access-date = 8 April 2011 | year= 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 | vauthors = Brookhart JM, Mountcastle VB, Geiger SR | title = The Nervous system: Sensory processes; | veditors = Darian-Smith I | url = https://books.google.com/books?id=n7fwAAAAMAAJ | access-date = 8 April 2011 | year = 1984 | publisher = American Physiological Society | isbn = 978-0-683-01108-1 | page = 784 }}</ref>

In 1906, the term ''proprio-ception'' (and also ''[[interoception|intero-ception]]'' and ''extero-ception'') is attested in a publication by [[Charles Scott Sherrington]] involving [[Receptor (biochemistry)|receptors]].<ref>Sherrington, C.S. (1906). The Integrative Action of the Nervous System. NewHaven, CT: Yale University Press.</ref> He explains the terminology as follows:<ref>{{cite journal | vauthors = Sherrington CS |author-link1=Charles Scott Sherrington |title=On The Proprio-ceptive System, Especially In Its Reflex Aspect |journal=Brain |date=1907 |volume=29 |issue=4 |pages=467–482 |doi=10.1093/brain/29.4.467}}</ref>

{{Poem quote|The main fields of distribution of the [[Receptor (biochemistry)|receptor]] organs fundamentally distinguishable seem, therefore, to be two, namely, a ''surface'' field constituted by the surface layer of the organism, and a ''deep'' field constituted by the tissues of the organism beneath the surface sheet.
[...]
''the stimulations occurring in [the] deep field is that the stimuli are traceable to actions of the organism itself'', and are so in much greater measure than are the stimulations of the surface field of the organism. Since in the deep field the stimuli to the receptors are delivered by the organism ''itself'',{{efn|name=proprio|in [[Latin]]: ''[[wikt:proprius#Latin|propriō]]''}} the deep receptors may be termed ''proprio-ceptors'', and the deep field a field of proprio-ception.}}

Today, 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.{{citation needed|date=May 2022}}

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 | vauthors = Proske U, Gandevia SC | title = The kinaesthetic senses | journal = The Journal of Physiology | volume = 587 | issue = Pt 17 | pages = 4139–46 | date = September 2009 | pmid = 19581378 | pmc = 2754351 | doi = 10.1113/jphysiol.2009.175372 }}</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 | vauthors = Winter JA, Allen TJ, Proske U | title = Muscle spindle signals combine with the sense of effort to indicate limb position | journal = The Journal of Physiology | volume = 568 | issue = Pt 3 | pages = 1035–46 | date = November 2005 | pmid = 16109730 | pmc = 1464181 | doi = 10.1113/jphysiol.2005.092619 }}</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 | vauthors = Collins DF, Refshauge KM, Todd G, Gandevia SC | title = Cutaneous receptors contribute to kinesthesia at the index finger, elbow, and knee | journal = Journal of Neurophysiology | volume = 94 | issue = 3 | pages = 1699–706 | date = September 2005 | pmid = 15917323 | doi = 10.1152/jn.00191.2005 }}</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.{{citation needed|date=May 2022}}

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").

== Plants and bacteria ==
Although they lack neurons, systems responding to stimuli (analogous to the sensory system in animals with a nervous system, which includes the proprioception) have also been described in some plants ([[Flowering plant|angiosperms]]).<ref name=":0">{{cite journal | vauthors = Bastien R, Bohr T, Moulia B, Douady S | 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 of the United States of America | volume = 110 | issue = 2 | pages = 755–60 | date = January 2013 | pmid = 23236182 | pmc = 3545775 | doi = 10.1073/pnas.1214301109 | bibcode = 2013PNAS..110..755B | doi-access = free }}</ref><ref name=":1">{{cite journal | vauthors = Hamant O, Moulia B | title = How do plants read their own shapes? | journal = The New Phytologist | volume = 212 | issue = 2 | pages = 333–37 | date = October 2016 | pmid = 27532273 | doi = 10.1111/nph.14143 | doi-access = free }}</ref> [[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]]. A quantitative study of [[Shoot (botany)|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" />

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 | vauthors = Okamoto K, Ueda H, Shimada T, Tamura K, Kato T, Tasaka M, Morita MT, Hara-Nishimura I | title = Regulation of organ straightening and plant posture by an actin-myosin XI cytoskeleton | journal = Nature Plants | volume = 1 | issue = 4 | pages = 15031 | date = March 2015 | pmid = 27247032 | doi = 10.1038/nplants.2015.31 | hdl-access = free | hdl = 2433/197219 | s2cid = 22432635 }}</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 | vauthors = Bastien R, Meroz Y | 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 | date = December 2016 | pmid = 27923062 | pmc = 5140061 | doi = 10.1371/journal.pcbi.1005238 | arxiv = 1603.00459 | bibcode = 2016PLSCB..12E5238B | doi-access = free }}</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| vauthors = Gabbatiss J |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|archive-date=9 November 2018|archive-url=https://web.archive.org/web/20181109203947/https://www.howplantswork.com/2017/05/28/the-selfish-plant-4-plant-proprioception/|url-status=dead}}</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" />

Recent studies suggest that bacteria have control systems that may resemble proprioception.<ref>{{cite journal | vauthors = Antani JD, Gupta R, Lee AH, Rhee KY, Manson MD, Lele PP | title = Mechanosensitive recruitment of stator units promotes binding of the response regulator CheY-P to the flagellar motor | journal = Nature Communications | volume = 12 | issue = 1 | pages = 5442 | date = September 2021 | pmid = 34521846 | pmc = 8440544 | doi = 10.1038/s41467-021-25774-2 | bibcode = 2021NatCo..12.5442A }}</ref>

== 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|Hand–eye coordination}}
* {{annotated link|Ideomotor phenomenon}}
* {{annotated link|Illusions of self-motion}}
* {{annotated link|Instinctive aiming}}
* {{annotated link|Kinaesthetics}}
* {{annotated link|Kinesthetic learning}}
* {{annotated link|List of distinct cell types in the adult human body}}
* {{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}}

== Notes ==
{{Notelist}}

== References ==
{{reflist}}

== External links ==
* {{MeshName|Proprioception}}

{{Somatosensory system}}
{{Sensation and perception}}

[[Category:Proprioception| ]]
[[Category:Articles containing video clips]]
[[Category:Sensory systems]]