Perception of longitudinal body axis in microgravity during parabolic flight

BACKGROUND: During large angles of self-tilt in the roll plane on Earth, measurements of the subjective visual vertical (SVV) in the dark show a bias towards the longitudinal body axis, reflecting a systematic underestimation of self-tilt. OBJECTIVE: This study tested the hypothesis that self-tilt is underestimated in partial gravity conditions, and more so at lower gravity levels. METHODS: The SVV was measured in parabolic flight at three partial gravity levels: 0.25, 0.50, and 0.75 g. Self-tilt was varied amongst 0, 15, 30, and 45 deg, using a tiltable seat. The participants indicated their SVV by setting a linear array of dots projected inside a head mounted display to the perceived vertical. The angles of participants’ body and head roll tilt relative to the gravito-inertial vertical were measured by two separate inertial measurement units. RESULTS: Data on six participants were collected. Per G-level, a regression analysis was performed with SVV setting as dependent variable and head tilt as independent variable. The latter was used instead of chair tilt, because not all the participants’ heads were aligned with their bodies. The estimated regression slopes significantly decreased with smaller G-levels, reflecting an increased bias of the SVV towards the longitudinal body axis. On average, the regression slopes were 0.95 (±0.38) at 0.75 g; 0.84 (±0.22) at 0.5 g; and 0.63 (±0.33) at 0.25 g. CONCLUSIONS: The results of this study show that reduced gravity conditions lead to increased underestimation of roll self-tilt.

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Antihysteresis of perceived longitudinal body axis during continuous quasi-static whole-body rotation in the earth-vertical roll plane

Experimental Brain Research ◽

10.1007/s00221-011-2572-8 ◽

2011 ◽

Vol 209 (3) ◽

pp. 443-454

Author(s):

M. Tatalias ◽

C. J. Bockisch ◽

G. Bertolini ◽

D. Straumann ◽

A. Palla

Keyword(s):

Body Axis ◽

Whole Body ◽

Body Rotation ◽

Longitudinal Body Axis ◽

Vertical Roll ◽

The Earth

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Method of Stimulus Presentation and Apparent Body Position under Lateral Body Tilt

Perceptual and Motor Skills ◽

10.2466/pms.1967.24.1.43 ◽

1967 ◽

Vol 24 (1) ◽

pp. 43-50 ◽

Cited By ~ 4

Author(s):

M. Bauermeister ◽

S. Wapner ◽

H. Werner

Keyword(s):

Reference System ◽

Body Position ◽

Body Schema ◽

Stimulus Presentation ◽

Body Axis ◽

Body Tilt ◽

Spatial Reference ◽

Longitudinal Body Axis ◽

Lateral Body ◽

Method Of Constant Stimuli

Eighty Ss, 40 male and 40 female, indicated by means of a luminescent rod the location of their longitudinal body axis (apparent body position) under body tilt ranging from 90° left (counterclockwise), through upright, to 90° right (clockwise). The luminescent rod was presented by two psychophysical methods: (a) the method of limits and (b) the method of constant stimuli. Deviations of apparent from objective body position showed significant differences between the two methods. The results were interpreted in terms of an organismic theory of perception, utilizing the notion of a dynamic body schema as spatial reference system which was subject to modifications due to the method of stimulus presentation.

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Gruesome twosome kukri rippers: Oligodon formosanus (Günther, 1872) and O. fasciolatus (Günther, 1864) eat Kaloula pulchra Gray, 1831 either by eviscerating or swallowing whole

Herpetozoa ◽

10.3897/herpetozoa.34.e62688 ◽

2021 ◽

Vol 34 ◽

pp. 49-55

Author(s):

Henrik Bringsøe ◽

Maneerat Suthanthangjai ◽

Winai Suthanthangjai ◽

Jo Lodder ◽

Navapol Komanasin

Keyword(s):

Hong Kong ◽

Prey Size ◽

Body Axis ◽

Anuran Species ◽

Longitudinal Body Axis

Predation on adult microhylid frogs Kaloula pulchra by two closely-related colubrid snakes is described, based on two observations of Oligodon formosanus in Hong Kong and one observation of O. fasciolatus in Thailand. In two instances, O. formosanus was observed cutting open the abdomen of this anuran species. In one case, it performed repeated rotations about its own longitudinal body axis (“death roll”) while its head was inserted into the frog’s abdomen. The purpose of this behaviour was probably to tear off organs and swallow them. Once O. fasciolatus was observed catching and swallowing K. pulchra whole. In that case, the snake also made a series of rotations while it maintained its firm grip in the frog’s belly. It is concluded that, for these two closely-related kukri snakes, prey size is crucial for determining whether the gape width allows large preys to be swallowed entire.

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Effects of prismatic adaptation on balance and postural disorders in patients with chronic right stroke: protocol for a multicentre double-blind randomised sham-controlled trial

BMJ Open ◽

10.1136/bmjopen-2021-052086 ◽

2021 ◽

Vol 11 (11) ◽

pp. e052086

Author(s):

Aurélien Hugues ◽

Amandine Guinet-Lacoste ◽

Sylvie Bin ◽

Laurent Villeneuve ◽

Marine Lunven ◽

...

Keyword(s):

Controlled Trial ◽

Weight Bearing ◽

Body Axis ◽

Double Blind ◽

Longitudinal Body Axis ◽

Stroke Lesion ◽

The Right ◽

Prismatic Adaptation ◽

Straight Ahead ◽

Postural Disorders

IntroductionPatients with right stroke lesion have postural and balance disorders, including weight-bearing asymmetry, more pronounced than patients with left stroke lesion. Spatial cognition disorders post-stroke, such as misperceptions of subjective straight-ahead and subjective longitudinal body axis, are suspected to be involved in these postural and balance disorders. Prismatic adaptation has showed beneficial effects to reduce visuomotor disorders but also an expansion of effects on cognitive functions, including spatial cognition. Preliminary studies with a low level of evidence have suggested positive effects of prismatic adaptation on weight-bearing asymmetry and balance after stroke. The objective is to investigate the effects of this intervention on balance but also on postural disorders, subjective straight-ahead, longitudinal body axis and autonomy in patients with chronic right stroke lesion.Methods and analysisIn this multicentre randomised double-blind sham-controlled trial, we will include 28 patients aged from 18 to 80 years, with a first right supratentorial stroke lesion at chronic stage (≥12 months) and having a bearing ≥60% of body weight on the right lower limb. Participants will be randomly assigned to the experimental group (performing pointing tasks while wearing glasses shifting optical axis of 10 degrees towards the right side) or to the control group (performing the same procedure while wearing neutral glasses without optical deviation). All participants will receive a 20 min daily session for 2 weeks in addition to conventional rehabilitation. The primary outcome will be the balance measured using the Berg Balance Scale. Secondary outcomes will include weight-bearing asymmetry and parameters of body sway during static posturographic assessments, as well as lateropulsion (measured using the Scale for Contraversive Pushing), subjective straight-ahead, longitudinal body axis and autonomy (measured using the Barthel Index).Ethics and disseminationThe study has been approved by the ethical review board in France. Findings will be submitted to peer-reviewed journals relative to rehabilitation or stroke.Trial registration numberNCT03154138.

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