{"id":3696,"date":"2019-02-05T22:14:35","date_gmt":"2019-02-05T21:14:35","guid":{"rendered":"http:\/\/junq.info\/?p=3696"},"modified":"2019-02-08T11:27:13","modified_gmt":"2019-02-08T10:27:13","slug":"wich-way-is-up","status":"publish","type":"post","link":"https:\/\/junq.info\/?p=3696","title":{"rendered":"Which way is up?"},"content":{"rendered":"\n

Imagine you are\non an airplane, ten thousand meters up in the sky. Now, if you close\nyour eyes you know exactly which way the airplane has started moving,\nwhether it has begun to manoeuvre to the right or to descend. This\nability we owe to our inner ear as a part the humans\u2019 vestibular\nsystem. \n<\/p>\n\n\n\n

The vestibular\nsystem is designed to send information about the position of the head\nto the brain\u2019s movement control centre, that is the cerebellum. It\nis made up of three semi-circular canals and two pockets called the\notolith organs (Fig. 1), which together provide constant feedback to\nthe cerebellum about head movement. Each of the semi-circular canals\nis orthogonal to the two others so that they detect the variety of\nmovements in three independent directions: rotation around the neck\n(horizontal canal), nodding (superior canal) and tilting to the sides\n(posterior canal). Movement of fluid inside these canals due to the\nhead movement stimulates tiny hairs that send signals via the\nvestibular nerve to the cerebellum. The two otolith organs (called\nthe saccule and utricle) signal to the brain about linear movements\n(backwards\/forwards or upwards\/downwards) and also about where the\nhead is in relation to gravity. These organs contain small crystals\nthat are displaced during linear movements and stimulate tiny hairs\ncommunicating via the vestibular, or balance nerve to the cerebellum.<\/p>\n\n\n\n

So why is that,\neven equipped with such a tool, sometimes we get a feeling sitting on\nan airplane that it is falling down when in fact it is not? Why is\nthat some people, particularly underwater divers, may lose direction\nand no longer know which way is up?[1] Surely, typical divers should\nstill have the inner ear, unless a shark has bitten their heads off.\nIs it all caused by stress? Actually, there is much more to it!<\/p>\n\n\n\n

Humans have\nevolved to maintain spatial orientation on the ground, whereas the\nthree-dimensional environment of flight or underwater is unfamiliar\nto the human body, creating sensory conflicts and illusions that make\nspatial orientation difficult. Normally, changes in linear and\nangular accelerations and gravity, detected by the vestibular system,\nand the relative position of parts of our own bodies, provided by\nmuscles and joints to the proprioceptive system, are compared in the\nbrain with visual information. In unusual conditions, these sensory\nstimuli vary in magnitude, direction, and frequency. Any differences\nor discrepancies between visual, vestibular, and proprioceptive\nsensory inputs result in a sensory mismatch that can produce\nillusions. Often the result of these various visual and nonvisual\nillusions is spatial disorientation.<\/p>\n\n\n\n

For example,\nfighter pilots who turn and climb at the same time (they call it\n“bank and yank”), feel a strong sensation of heaviness.\nThat feeling, caused by their acceleration, surpasses the pull of\ngravity. Now, if you asked them while blindfolded to tell which way\nwas down using only their vestibular organ, they would point to the\ncues provided by the turn, not to the cues provided by the earth’s\ngravity. [2] \n<\/p>\n\n\n\n

Furthermore, the\nvestibular system detects only changes in acceleration, thus a\nprolonged rotation of 15-20 seconds [3] results in a cessation of\nsemi-circular output. As a result, the brain adjusts and does not\nfeel the acceleration anymore which can even result in the perception\nof motion in the opposite direction. In other words, it is possible\nto gradually climb or descend without a noticeable change in pressure\nagainst the seat. Moreover, in some airplanes, it is even possible to\nexecute a loop without exerting negative G-forces so that, without\nvisual reference, the pilot could be upside down without being aware\nof it. \n<\/p>\n\n\n\n

Another\ninteresting example is the phenomenon of loopy walking. When lost in\na desert or a thick forest terrain without landmarks people tend to\nwalk in circles. Recent studies performed by researchers of Max\nPlanck Institute for Biological Cybernetics, Germany, revealed that\nblindfolded people show the same tendency. Lacking external reference\npoints, they curve around in loops as tight as 20 meters in diameter\nwhile believing they are walking in straight lines. [4] \n<\/p>\n\n\n\n

Seemingly the\nvestibular system is quite easy to trick by eliminating other sensory\ninputs. However, even when visual information is accessible, e.g.\nunderwater, spatial disorientation can still occur [any scuba diving\nforum \u2013 for the reference]. The obvious fact that water changes\nvisual and proprioceptive perception is crucial here: humans move\nslower, see differently and let\u2019s not forget the Archimedes’\nprinciple. It happened a lot, that a confused diver thought that the\nsurface was down, especially when the bottom seemed brighter because\nof reflections. This can be a dangerous mirage in such an unusual\ngravity. On top of it, water can affect the vestibular system\ndirectly through the outer ear. When the cold water penetrates and\nreaches the vestibular system, it can cause thermal effects on the\nwalls of the semi-circular canals, leading to slight movements of the\nfluid inside, which are enough to be detected by the brain.[5] Just\nlike in the situations described before this causes the symptoms of\nspatial disorientation and dizziness. \n<\/p>\n\n\n\n

\"\"


Fig. 1. Schematic structure of a humans\u2019 inner ear [6]. <\/figcaption><\/figure><\/div>\n\n\n\n

The vestibular\nsystem is indeed frightfully complicated. We can trick it for fun\nriding roller coasters in an adventure park, but when incorrect\ninterpretation of the signals coming from the vestibular system\noccurs at the wrong moment this can lead to serious consequences.\nLuckily, nowadays the airplanes and even divers are equipped with\nprecise instruments used to complement the awareness of the situation\nand thus avert dangerous situations.<\/p>\n\n\n\n

P.S. If you are interested, try riding an elevator while seated on a bike.<\/p>\n\n\n\n

— Mariia Filianina<\/p>\n\n\n\n

<\/p>\n\n\n\n

References:<\/p>\n\n\n\n

  1. \nThe\n\tEditors of Encyclopaedia Britannica, (2012). Spatial disorientation,\n\tEncyclop\u00e6dia Britannica, inc., \n\t\n\t<\/li>
  2. \nL.\n\tKing, (2017). The science of psychology: An appreciative view. (4th.\n\ted.) McGraw-Hill, New York.\n\t<\/li>
  3. \nPrevic,\n\tF. H., & Ercoline, W. R. (2004). Spatial disorientation in\n\taviation. Reston, VA: American Institute of Astronautics and\n\tAeronautics.\n\t<\/li>
  4. \nJ.\n\tL. Souman, I. Frissen, M. N. Sreenivasa and M. O. Ernst,Walking\n\tstraight into circles,\n\tCurrent Biology<\/em>\n\t19<\/strong>,\n\t1538 (2009).\n\t<\/li>
  5. \nhttp:\/\/www.videodive.ru\/diving\/vizov5.shtml<\/a>\n\t<\/li>
  6. \nhttp:\/\/www.nidcd.nih.gov\/health\/balance\/balance_disorders.asp<\/a>\n<\/li><\/ol>\n","protected":false},"excerpt":{"rendered":"

    Imagine you are on an airplane, ten thousand meters up in the sky. Now, if you close your eyes you know exactly which way the airplane has started moving, whether it has begun to manoeuvre to the right or to descend. This ability we owe to our inner ear as a part the humans\u2019 vestibular… Read More »Which way is up?<\/span><\/a><\/p>\n","protected":false},"author":12,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":true,"template":"","format":"standard","meta":{"neve_meta_sidebar":"","neve_meta_container":"","neve_meta_enable_content_width":"","neve_meta_content_width":0,"neve_meta_title_alignment":"","neve_meta_author_avatar":"","neve_post_elements_order":"","neve_meta_disable_header":"","neve_meta_disable_footer":"","neve_meta_disable_title":"","footnotes":""},"categories":[6],"tags":[86,85,87],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/junq.info\/index.php?rest_route=\/wp\/v2\/posts\/3696"}],"collection":[{"href":"https:\/\/junq.info\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/junq.info\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/junq.info\/index.php?rest_route=\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/junq.info\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3696"}],"version-history":[{"count":5,"href":"https:\/\/junq.info\/index.php?rest_route=\/wp\/v2\/posts\/3696\/revisions"}],"predecessor-version":[{"id":3705,"href":"https:\/\/junq.info\/index.php?rest_route=\/wp\/v2\/posts\/3696\/revisions\/3705"}],"wp:attachment":[{"href":"https:\/\/junq.info\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3696"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/junq.info\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3696"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/junq.info\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3696"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}