Temporal constancy of perceived direction of gravity assessed by visual line adjustments

Tarnutzer, Alexander A.; Fernando, Duván; Kheradmand, Amir; Lasker, Adrian G.; Zee, David S.

doi:10.3233/ves-2011-0436

Cited by 20 publications

(22 citation statements)

References 61 publications

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“…Previous approaches to characterize SVV drifts and post-tilt biases generally assumed that the drift patterns are similar across subjects and did not address individual differences. However, in a recent study focusing on SVV stability while upright, we noted distinct individual drift patterns [17]. The mechanism leading to these differences in drift patterns remains to be determined.…”

Section: Introductionmentioning

confidence: 74%

“…Previously, serial SVV adjustments were found to be dependent [17]. Drift in SVV may potentially be related to the self-similarity of consecutive adjustments as reviewed by Torre and Wagenmakers [45].…”

Section: Resultsmentioning

confidence: 99%

“…We have previously demonstrated that under optimal conditions (i.e. with a structured and illuminated background and when providing a visual reference along earth-vertical) this task can be completed with an at least twofold higher precision than the SVV task in darkness [17]. This makes a relevant contribution of direct motor effects unlikely.…”

Section: Discussionmentioning

confidence: 99%

“…Previously, we observed that serial SVV or subjective visual horizontal adjustments are not independent [17]. Drifts and fluctuations in SVV estimates may therefore also be related to the self-similarity of consecutive adjustments, that is, consecutive adjustments are dependent and therefore yield similar values, as reviewed by [45].…”

Section: Methodsmentioning

confidence: 95%

“…For modelling effects of prolonged roll-tilt on SVV, knowledge of the drift dynamics and their individual range is required, and for simulating the post-tilt bias the decay dynamics (and their inter-individual variability) are essential. Based on the heterogeneity of drift observed in upright position, with mostly increasing adjustment errors over time [17], drifts while roll-tilted may also differ in drift direction and amplitude between individual subjects. We therefore aimed to characterize the stability of internal estimates of the direction of gravity during prolonged roll-tilt positions and upon return to upright position using a psychophysical task.…”

Section: Introductionmentioning

confidence: 99%

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Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts

et al. 2013

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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.

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Section: Introductionmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts

et al. 2013

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How stable is perceived direction of gravity over extended periods in darkness?

et al. 2012

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Previous studies reported linear drift of perceived vertical for brief (≤10 min) observation periods. Here, we repeated estimates of direction of gravity up to 60 min to evaluate whether the drift is sustained, shows saturation or even reverses over time. Fifteen healthy human subjects repetitively adjusted a luminous line along subjective visual vertical (SVV) and horizontal (SVH) over periods of 5 min (constituting one block). We obtained seven blocks within 60 min in each subject for SVV and SVH. In between the first six blocks, subjects remained in darkness for 5 min each, whereas the lights were briefly turned on before block 7. We noted significantly (p < 0.05) increased errors in perceived direction of gravity by block 2 (SVV) and 3 (SVH). These increases disappeared after turning on the lights before block 7. Focusing on blocks 2-6, significant drift started from similar offset positions and pointed to the same direction in a majority of runs in 9/15 (SVV) and 11/15 (SVH) subjects. When pooling data from all blocks, orthogonality of errors was lost in all subjects. Trial-to-trial variability remained stable over the seven runs for SVV and SVH. Only when pooling all runs, precision was significantly (p < 0.05) higher for the SVH. Our findings suggest that perceived direction of gravity continues to fluctuate over extended recording periods with individuals showing unique patterns of direction-specific drift while variability remains stable. As subjects were upright during the entire experiment and as drift persisted over several blocks, sensory adaptation seems unlikely. We therefore favor a central origin of this kind of drift.

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Spatial orientation in patients with chronic unilateral vestibular hypofunction is ipsilesionally distorted

Müller

Bockisch

Tarnutzer

2016

Clinical Neurophysiology

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OBJECTIVE Acute unilateral peripheral-vestibular hypofunction (UVH) shifts the subjective visual vertical (SVV) ipsilesionally, triggering central compensation that usually eliminates shifts when upright. We hypothesized that compensation is worse when roll-tilted. METHODS We quantified SVV errors and variability in different roll-tilted positions (0°, ±45°, ±90°) in patients with chronic UVH affecting the superior branch (SVN; n=4) or the entire (CVN; n=9) vestibular nerve. RESULTS Errors in SVN and CVN were not different. When roll-tilted ipsilesionally 45°(9.6±5.4°vs. -0.2±6.4°, patients vs. controls, p<0.001) and 90°(23.5±5.7°vs. 16.8±8.8°, p=0.003), the patient's SVV was shifted significantly towards the lesioned ear. When upright, only a trend was noted (3.6±2.2°vs. 0.0±1.2°, p=0.099); for contralesional roll-tilts shifts were not different from controls. Variability was larger for CVN than SVN (p=0.046). With increasing disease-duration, adjustment errors decayed for ipsilesional roll-tilt and upright (p0.025). CONCLUSIONS The reason verticality perception was distorted for ipsilesional roll-tilts, may be the insufficient integration of contralesional otolith-input. Similar errors in SVN and CVN suggest a dominant utricular role in verticality perception, albeit the sacculus may improve precision of SVV estimates. SIGNIFICANCE With deficiencies in central compensation being roll-angle dependent, extending SVV-testing to roll-tilted positions may improve identifying patients with chronic UVH. Highlights:• Visual vertical (VV) was measured in 13 patients with chronic unilateral vestibular hypofunction.• VV shifts in the patients were significant only when rolled ipsilesionally.• Thus VV testing in roll-tilted positions is recommended to identify more subtle vestibular deficits. 3 AbstractObjective: Acute unilateral peripheral-vestibular hypofunction (UVH) shifts the subjective visual vertical (SVV) ipsilesionally, triggering central compensation that usually eliminates shifts when upright. We hypothesized that compensation is worse when roll-tilted. Methods

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Temporal constancy of perceived direction of gravity assessed by visual line adjustments

Cited by 20 publications

References 61 publications

Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts

Modulation of Internal Estimates of Gravity during and after Prolonged Roll-Tilts

How stable is perceived direction of gravity over extended periods in darkness?

Spatial orientation in patients with chronic unilateral vestibular hypofunction is ipsilesionally distorted

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