Nature of the Transition Between Two Modes of External Space Perception in Tilted Subjects

Tarnutzer AA, Bockisch CJ, Straumann D. Roll-dependent modulation of the subjective visual vertical: contributions of head-and trunk-based signals. J Neurophysiol 103: 934 -941, 2010. First published December 16, 2009 doi:10.1152/jn.00407.2009. Precision and accuracy of the subjective visual vertical (SVV) modulate in the roll plane. At large roll angles, systematic SVV errors are biased toward the subject's body-longitudinal axis and SVV precision is decreased. To explain this, SVV models typically implement a bias signal, or a prior, in a head-fixed reference frame and assume the sensory input to be optimally tuned along the head-longitudinal axis. We tested the pattern of SVV adjustments both in terms of accuracy and precision in experiments in which the head and the trunk reference frames were not aligned. Twelve subjects were placed on a turntable with the head rolled about 28°counterclockwise relative to the trunk by lateral tilt of the neck to dissociate the orientation of head-and trunk-fixed sensors relative to gravity. Subjects were brought to various positions (roll of head-or trunk-longitudinal axis relative to gravity: 0°, Ϯ75°) and aligned an arrow with perceived vertical. Both accuracy and precision of the SVV were significantly (P Ͻ 0.05) better when the headlongitudinal axis was aligned with gravity. Comparing absolute SVV errors for clockwise and counterclockwise roll tilts, statistical analysis yielded no significant differences (P Ͼ 0.05) when referenced relative to head upright, but differed significantly (P Ͻ 0.001) when referenced relative to trunk upright. These findings indicate that the bias signal, which drives the SVV toward the subject's body-longitudinal axis, operates in a head-fixed reference frame. Further analysis of SVV precision supports the hypothesis that head-based graviceptive signals provide the predominant input for internal estimates of visual vertical.

Section: Methodsmentioning

confidence: 99%

Section: Reference Frame Of the Graviceptive Sensory Systems And Of Tmentioning

confidence: 99%

Roll-Dependent Modulation of the Subjective Visual Vertical: Contributions of Head- and Trunk-Based Signals

Tarnutzer¹,

Bockisch

Straumann³

2010

“…Several earlier investigations showed that roll-tilted subjects may have a rather accurate estimate of body tilt but may yet show a large A-effect in their SVV settings (Kaptein and Van Gisbergen 2004;Mast and Jarchow 1996;Mittelstaedt 1983). Mittelstaedt (1983) attributes this apparent disparity to the tendency to use the body axis as a partial reference for verticality judgments in the context of the SVV task, but not in the perception of body tilt.…”

Section: Methodological Aspectsmentioning

confidence: 99%

“…However, many reports showed that stationary subjects, tilted sideways in darkness, make systematic errors when adjusting a luminous line parallel to the perceived direction of gravity. At large tilt angles, the subjective visual vertical (SVV) deviates toward the long-body axis [Aubert effect (A-effect)], as if tilt is underestimated, with errors amounting to 35°when the body is tilted 120° (Kaptein andVan Gisbergen 2004, 2005;Mittelstaedt 1983Mittelstaedt , 1989Schöne 1964;Udo de Haes 1970;Van Beuzekom and Van Gisbergen 2000). For small body tilts (Ͻ30°), these errors are generally much smaller and may even reverse sign [Müller effect (E-effect)].…”

mentioning

confidence: 99%

Verticality Perception During Off-Vertical Axis Rotation

Vingerhoets

Gisbergen²,

Medendorp³

2007

During prolonged rotation about a tilted yaw axis, often referred to as off-vertical axis rotation (OVAR), a percept of being translated along a conical path slowly emerges as the sense of rotation subsides. Recently, we found that these perceptual changes are consistent with a canal–otolith interaction model that attributes the illusory translation percept to improper interpretation of the ambiguous otolith signals. The model further predicts that the illusory translation percept must be accompanied by slowly worsening tilt underestimates. Here, we tested this prediction in six subjects by measuring the time course of the subjective visual vertical (SVV) during OVAR stimulation at three different tilt-rotation speed combinations, in complete darkness. Throughout the 2-min run, at each left-ear-down and right-ear-down position, the subject indicated whether a briefly flashed line deviated clockwise or counterclockwise from vertical to determine the SVV with an adaptive staircase procedure. Typically, SVV errors indicating tilt underestimation were already present at rotation onset and then increased exponentially to an asymptotic value, reached at about 60 s after rotation onset. The initial error in the SVV was highly correlated to the response error in a static tilt control experiment. The subsequent increase in error depended on both rotation speed and OVAR tilt angle, in a manner predicted by the canal–otolith interaction model. We conclude that verticality misjudgments during OVAR reflect a dynamic component linked to canal–otolith interaction, superimposed on a tilt-related component that is also expressed under stationary conditions.

“…It is very unlikely that G vis 1 because the full range of orientations (0 -360°) has to be coded, which is possible only when G vis ϭ 1. Further indications come from line-orientation estimates (Kaptein and Van Gisbergen 2005;Van Beuzekom et al 2001). Based on these FIG. 5.…”

Section: What Determines Spatial Orientation Constancy?mentioning

confidence: 99%

Canal and Otolith Contributions to Visual Orientation Constancy During Sinusoidal Roll Rotation

Kaptein¹,

Gisbergen²

2006

Self Cite

Kaptein, Ronald G. and Jan A.M. Van Gisbergen. Canal and otolith contributions to visual orientation constancy during sinusoidal roll rotation. J Neurophysiol 95: 1936 -1948, 2006. First published November 30, 2005 doi:10.1152/jn.00856.2005. Using vestibular sensors to maintain visual stability during changes in head tilt, crucial when panoramic cues are not available, presents a computational challenge. Reliance on the otoliths requires a neural strategy for resolving their tilt/translation ambiguity, such as canal-otolith interaction or frequency segregation. The canal signal is subject to bandwidth limitations. In this study, we assessed the relative contribution of canal and otolith signals and investigated how they might be processed and combined. The experimental approach was to explore conditions with and without otolith contributions in a frequency range with various degrees of canal activation. We tested the perceptual stability of visual line orientation in six human subjects during passive sinusoidal roll tilt in the dark at frequencies from 0.05 to 0.4 Hz (30°p eak to peak). Because subjects were constantly monitoring spatial motion of a visual line in the frontal plane, the paradigm required moment-to-moment updating for ongoing ego motion. Their task was to judge the total spatial sway of the line when it rotated sinusoidally at various amplitudes. From the responses we determined how the line had to be rotated to be perceived as stable in space. Tests were taken both with (subject upright) and without (subject supine) gravity cues. Analysis of these data showed that the compensation for body rotation in the computation of line orientation in space, although always incomplete, depended on vestibular rotation frequency and on the availability of gravity cues. In the supine condition, the compensation for ego motion showed a steep increase with frequency, compatible with an integrated canal signal. The improvement of performance in the upright condition, afforded by graviceptive cues from the otoliths, showed low-pass characteristics. Simulations showed that a linear combination of an integrated canal signal and a gravity-based signal can account for these results.