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Does gravity influence the visual line bisection task?
J Neurophysiol. 2016 08 01; 116(2):629-36.JN

Abstract

The visual line bisection task (LBT) is sensitive to perceptual biases of visuospatial attention, showing slight leftward (for horizontal lines) and upward (for vertical lines) errors in healthy subjects. It may be solved in an egocentric or allocentric reference frame, and there is no obvious need for graviceptive input. However, for other visual line adjustments, such as the subjective visual vertical, otolith input is integrated. We hypothesized that graviceptive input is incorporated when performing the LBT and predicted reduced accuracy and precision when roll-tilted. Twenty healthy right-handed subjects repetitively bisected Earth-horizontal and body-horizontal lines in darkness. Recordings were obtained before, during, and after roll-tilt (±45°, ±90°) for 5 min each. Additionally, bisections of Earth-vertical and oblique lines were obtained in 17 subjects. When roll-tilted ±90° ear-down, bisections of Earth-horizontal (i.e., body-vertical) lines were shifted toward the direction of the head (P < 0.001). However, after correction for vertical line-bisection errors when upright, shifts disappeared. Bisecting body-horizontal lines while roll-tilted did not cause any shifts. The precision of Earth-horizontal line bisections decreased (P ≤ 0.006) when roll-tilted, while no such changes were observed for body-horizontal lines. Regardless of the trial condition and paradigm, the scanning direction of the bisecting cursor (leftward vs. rightward) significantly (P ≤ 0.021) affected line bisections. Our findings reject our hypothesis and suggest that gravity does not modulate the LBT. Roll-tilt-dependent shifts are instead explained by the headward bias when bisecting lines oriented along a body-vertical axis. Increased variability when roll-tilted likely reflects larger variability when bisecting body-vertical than body-horizontal lines.

Authors+Show Affiliations

Department of Neurology, University Hospital Zurich and University of Zurich, Zurich, Switzerland;Department of Neurology, University Hospital Zurich and University of Zurich, Zurich, Switzerland; Department of Otorhinolaryngology, University Hospital Zurich and University of Zurich, Zurich, Switzerland; and Department of Ophthalmology, University Hospital Zurich and University of Zurich, Zurich, Switzerland.Department of Neurology, University Hospital Zurich and University of Zurich, Zurich, Switzerland; alexander.tarnutzer@access.uzh.ch.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

27226452

Citation

Drakul, A, et al. "Does Gravity Influence the Visual Line Bisection Task?" Journal of Neurophysiology, vol. 116, no. 2, 2016, pp. 629-36.
Drakul A, Bockisch CJ, Tarnutzer AA. Does gravity influence the visual line bisection task? J Neurophysiol. 2016;116(2):629-36.
Drakul, A., Bockisch, C. J., & Tarnutzer, A. A. (2016). Does gravity influence the visual line bisection task? Journal of Neurophysiology, 116(2), 629-36. https://doi.org/10.1152/jn.00312.2016
Drakul A, Bockisch CJ, Tarnutzer AA. Does Gravity Influence the Visual Line Bisection Task. J Neurophysiol. 2016 08 1;116(2):629-36. PubMed PMID: 27226452.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Does gravity influence the visual line bisection task? AU - Drakul,A, AU - Bockisch,C J, AU - Tarnutzer,A A, Y1 - 2016/05/25/ PY - 2016/04/19/received PY - 2016/05/23/accepted PY - 2016/5/27/entrez PY - 2016/5/27/pubmed PY - 2017/9/8/medline KW - otolith organs KW - perception KW - spatial orientation KW - vestibular signal SP - 629 EP - 36 JF - Journal of neurophysiology JO - J. Neurophysiol. VL - 116 IS - 2 N2 - The visual line bisection task (LBT) is sensitive to perceptual biases of visuospatial attention, showing slight leftward (for horizontal lines) and upward (for vertical lines) errors in healthy subjects. It may be solved in an egocentric or allocentric reference frame, and there is no obvious need for graviceptive input. However, for other visual line adjustments, such as the subjective visual vertical, otolith input is integrated. We hypothesized that graviceptive input is incorporated when performing the LBT and predicted reduced accuracy and precision when roll-tilted. Twenty healthy right-handed subjects repetitively bisected Earth-horizontal and body-horizontal lines in darkness. Recordings were obtained before, during, and after roll-tilt (±45°, ±90°) for 5 min each. Additionally, bisections of Earth-vertical and oblique lines were obtained in 17 subjects. When roll-tilted ±90° ear-down, bisections of Earth-horizontal (i.e., body-vertical) lines were shifted toward the direction of the head (P < 0.001). However, after correction for vertical line-bisection errors when upright, shifts disappeared. Bisecting body-horizontal lines while roll-tilted did not cause any shifts. The precision of Earth-horizontal line bisections decreased (P ≤ 0.006) when roll-tilted, while no such changes were observed for body-horizontal lines. Regardless of the trial condition and paradigm, the scanning direction of the bisecting cursor (leftward vs. rightward) significantly (P ≤ 0.021) affected line bisections. Our findings reject our hypothesis and suggest that gravity does not modulate the LBT. Roll-tilt-dependent shifts are instead explained by the headward bias when bisecting lines oriented along a body-vertical axis. Increased variability when roll-tilted likely reflects larger variability when bisecting body-vertical than body-horizontal lines. SN - 1522-1598 UR - https://www.unboundmedicine.com/medline/citation/27226452/Does_gravity_influence_the_visual_line_bisection_task L2 - http://journals.physiology.org/doi/full/10.1152/jn.00312.2016?url_ver=Z39.88-2003&amp;rfr_id=ori:rid:crossref.org&amp;rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -