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Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts
Perceived direction of gravity, as assessed by the subjective visual vertical (SVV), shows roll-angle dependent errors that drift over time and a bias upon return to upright. According to Bayesian observer theory, the estimated direction of gravity is derived from the posterior probability distribut...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Public Library of Science
2013
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3815095/ https://www.ncbi.nlm.nih.gov/pubmed/24205099 http://dx.doi.org/10.1371/journal.pone.0078079 |
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author | Tarnutzer, Alexander A. Bertolini, Giovanni Bockisch, Christopher J. Straumann, Dominik Marti, Sarah |
author_facet | Tarnutzer, Alexander A. Bertolini, Giovanni Bockisch, Christopher J. Straumann, Dominik Marti, Sarah |
author_sort | Tarnutzer, Alexander A. |
collection | PubMed |
description | Perceived direction of gravity, as assessed by the subjective visual vertical (SVV), shows roll-angle dependent errors that drift over time and a bias upon return to upright. According to Bayesian observer theory, the estimated direction of gravity is derived from the posterior probability distribution by combining sensory input and prior knowledge about earth-vertical in a statistically optimal fashion. Here we aimed to further characterize the stability of SVV during and after prolonged roll-tilts. Specifically we asked whether the post-tilt bias is related to the drift pattern while roll-tilted. Twenty-nine healthy human subjects (23-56yo) repetitively adjusted a luminous arrow to the SVV over periods of 5min while upright, roll-tilted (±45°, ±90°), and immediately after returning to upright. Significant (p<0.05) drifts (median absolute drift-amplitude: 10°/5min) were found in 71% (±45°) and 78% (±90°) of runs. At ±90° roll-tilt significant increases in absolute adjustment errors were more likely (76%), whereas significant increases (56%) and decreases (44%) were about equally frequent at ±45°. When returning to upright, an initial bias towards the previous roll-position followed by significant exponential decay (median time-constant: 71sec) was noted in 47% of all runs (all subjects pooled). No significant correlations were found between the drift pattern during and immediately after prolonged roll-tilt. We conclude that the SVV is not stable during and after prolonged roll-tilt and that the direction and magnitude of drift are individually distinct and roll-angle-dependent. Likely sensory and central adaptation and random-walk processes contribute to drift while roll-tilted. Lack of correlation between the drift and the post-tilt bias suggests that it is not the inaccuracy of the SVV estimate while tilted that determines post-tilt bias, but rather the previous head-roll orientation relative to gravity. We therefore favor central adaptation, most likely a shift in prior knowledge towards the previous roll orientation, to explain the post-tilt bias. |
format | Online Article Text |
id | pubmed-3815095 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2013 |
publisher | Public Library of Science |
record_format | MEDLINE/PubMed |
spelling | pubmed-38150952013-11-07 Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts Tarnutzer, Alexander A. Bertolini, Giovanni Bockisch, Christopher J. Straumann, Dominik Marti, Sarah PLoS One Research Article Perceived direction of gravity, as assessed by the subjective visual vertical (SVV), shows roll-angle dependent errors that drift over time and a bias upon return to upright. According to Bayesian observer theory, the estimated direction of gravity is derived from the posterior probability distribution by combining sensory input and prior knowledge about earth-vertical in a statistically optimal fashion. Here we aimed to further characterize the stability of SVV during and after prolonged roll-tilts. Specifically we asked whether the post-tilt bias is related to the drift pattern while roll-tilted. Twenty-nine healthy human subjects (23-56yo) repetitively adjusted a luminous arrow to the SVV over periods of 5min while upright, roll-tilted (±45°, ±90°), and immediately after returning to upright. Significant (p<0.05) drifts (median absolute drift-amplitude: 10°/5min) were found in 71% (±45°) and 78% (±90°) of runs. At ±90° roll-tilt significant increases in absolute adjustment errors were more likely (76%), whereas significant increases (56%) and decreases (44%) were about equally frequent at ±45°. When returning to upright, an initial bias towards the previous roll-position followed by significant exponential decay (median time-constant: 71sec) was noted in 47% of all runs (all subjects pooled). No significant correlations were found between the drift pattern during and immediately after prolonged roll-tilt. We conclude that the SVV is not stable during and after prolonged roll-tilt and that the direction and magnitude of drift are individually distinct and roll-angle-dependent. Likely sensory and central adaptation and random-walk processes contribute to drift while roll-tilted. Lack of correlation between the drift and the post-tilt bias suggests that it is not the inaccuracy of the SVV estimate while tilted that determines post-tilt bias, but rather the previous head-roll orientation relative to gravity. We therefore favor central adaptation, most likely a shift in prior knowledge towards the previous roll orientation, to explain the post-tilt bias. Public Library of Science 2013-10-10 /pmc/articles/PMC3815095/ /pubmed/24205099 http://dx.doi.org/10.1371/journal.pone.0078079 Text en © 2013 Tarnutzer et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited. |
spellingShingle | Research Article Tarnutzer, Alexander A. Bertolini, Giovanni Bockisch, Christopher J. Straumann, Dominik Marti, Sarah Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts |
title | Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts |
title_full | Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts |
title_fullStr | Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts |
title_full_unstemmed | Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts |
title_short | Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts |
title_sort | modulation of internal estimates of gravity during and after prolonged roll-tilts |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3815095/ https://www.ncbi.nlm.nih.gov/pubmed/24205099 http://dx.doi.org/10.1371/journal.pone.0078079 |
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