Proprioceptive system: Difference between revisions - VR & AR Wiki

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Both “proprioception” and “kinaesthesis” are terms that continue to be used in the scientific literature, sometimes with different interpretations according to the authors. Some researchers define proprioception as the sense of joint position only, while kinaesthesia as the conscious awareness of joint motion. Others consider kinaesthesia as one of the submodalities of proprioception. In this case, proprioception contains both joint position sense and the sensation of joint movement. This last definition is in accordance with the conceptualization of kinaesthesis that was originally coined by Bastian (1888): the ability to sense the position and movement of limbs and trunk. Dover and Powers (2003) include the joint position sense, kinaesthesia, and sense of tension or force as submodalities of proprioception. It has also been argued that “proprioception” and “kinaesthesis” can be synonymous <ref name=”1”></ref> <ref name=”5”></ref> <ref name=”7”></ref> <ref name=”9”> Collins, D. F., Refshauge, G. T. and Gandevia, S. C. (2005). Cutaneous receptors contribute to kinesthesia at the index finger, elbow, and knee. Journal of Neurophysiology, 94: 1699-1706</ref> <ref name=”10”> Proske, U. (2015). The role of muscle proprioceptors in human limb position sense: a hypothesis. Journal of Anatomy, 227: 178-183</ref> <ref name=”11”> Dover, G. and Powers, M. (2003). Reliability of joint position sense and force-reproduction measures during internal and external rotation of the shoulder. Journal of Athletic Training, 38(4): 304-310</ref>.

===The study of proprioception===

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Another factor that can impact proprioception is the increased exposure to relevant proprioceptive stimuli. This was observed in studies of visually guided reaching, where the accuracy of matching performance was improved <ref name=”8”></ref>.

==Muscle spindles==

As mentioned, muscle spindles afferents are considered to be mainly responsible for the sense of position and the perception of limb movement. They include both the primary and secondary endings of spindles. It is believed that the secondary endings signal only length changes, contributing to the sense of position since they do not have a pronounced velocity sensitivity <ref name=”5”></ref> <ref name=”7”></ref> <ref name=”10”></ref>. Proske and Gandevia (2009) referred that “The neural basis of limb position sense is the ability of receptors like muscle spindles to maintain static levels of discharge which increase in proportion to the increase in muscle length.” <ref name=”7”></ref>

Muscle spindles serves various roles in motor control, and although they are proprioceptors, they have other non-proprioceptive roles such has contributing to the reflex control of posture and locomotion <ref name=”10”></ref>.

===Evidence===

There is strong evidence in support of muscle spindles as the main proprioceptors. Their role has been studied through the illusory movement sensation paradigm, and it is based in two kinds of experiment that generate the illusion of limb displacement. First, and maybe the most important evidence, is the fact that using muscle vibration over the tendon or muscle – a selective stimulus for muscle spindles – generates illusions of limb movement and displacement, provided the muscle remains passive. This was first observed by Goodwin et al. (1972). The second piece of evidence comes from the thixotropic property of extrafusal and intrafusal muscle, meaning the dependence of passive tension in muscle on the previous history of contraction and length changes. This second method has the advantage of changing muscle spindle background activity without changing the muscle length <ref name=”2”></ref> <ref name=”5”></ref> <ref name=”7”></ref> <ref name=”10”></ref>.

Further evidence has been provided by studies that use other techniques such as skin and joint anesthesia, and the disengagement of muscles from joints. For example, the sense of position and movement persisted after joint replacement. In patients that had a total hip placement, the kinaesthetic sense remained intact, pointing to the importance of muscle receptors in proprioception. It also suggest that, at least at some joints, joint receptors do not play a significant role in kinaesthesia <ref name=”2”></ref> <ref name=”7”></ref>.

The central nervous system distinguishes between muscle spindle impulses generated by muscle stretch and by fusimotor activity, which may further indicate the prominent role of these receptors in kinaesthesia <ref name=”5”></ref>.

==References==