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The Subjective Visual Vertical and the Subjective Haptic Vertical Access Different Gravity Estimates.

Fraser LE, Makooie B, Harris LR - PLoS ONE (2015)

Bottom Line: Experiment 1 compared SVV and SHV across three levels of whole-body tilt and found that SVV showed an A-effect at larger tilts while SHV was accurate.Experiment 2 found that tilting either the head or the trunk independently produced an A-effect in SVV while SHV remained accurate when the head was tilted on an upright body but showed an A-effect when the body was tilted below an upright head.Overall our results suggest that SVV and SHV access distinct underlying gravity percepts based primarily on head and body position information respectively, consistent with a model proposed by Clemens and colleagues.

View Article: PubMed Central - PubMed

Affiliation: Center for Vision Research, York University, Toronto, Ontario, Canada.

ABSTRACT
The subjective visual vertical (SVV) and the subjective haptic vertical (SHV) both claim to probe the underlying perception of gravity. However, when the body is roll tilted these two measures evoke different patterns of errors with SVV generally becoming biased towards the body (A-effect, named for its discoverer, Hermann Rudolph Aubert) and SHV remaining accurate or becoming biased away from the body (E-effect, short for Entgegengesetzt-effect, meaning "opposite", i.e., opposite to the A-effect). We compared the two methods in a series of five experiments and provide evidence that the two measures access two different but related estimates of gravitational vertical. Experiment 1 compared SVV and SHV across three levels of whole-body tilt and found that SVV showed an A-effect at larger tilts while SHV was accurate. Experiment 2 found that tilting either the head or the trunk independently produced an A-effect in SVV while SHV remained accurate when the head was tilted on an upright body but showed an A-effect when the body was tilted below an upright head. Experiment 3 repeated these head/body configurations in the presence of vestibular noise induced by using disruptive galvanic vestibular stimulation (dGVS). dGVS abolished both SVV and SHV A-effects while evoking a massive E-effect in the SHV head tilt condition. Experiments 4 and 5 show that SVV and SHV do not combine in an optimally statistical fashion, but when vibration is applied to the dorsal neck muscles, integration becomes optimal. Overall our results suggest that SVV and SHV access distinct underlying gravity percepts based primarily on head and body position information respectively, consistent with a model proposed by Clemens and colleagues.

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Results for experiments 4 and 5.A. Mean PSEs for SVV (with a blurry visual stimulus), SHV and bimodal measures for experiment 4 (dark grey bars), and experiment 5 (with neck vibration, light grey bars). PSEs predicted by the maximum likelihood estimate (MLE) model for each experiment are bolded. 0° corresponds to gravitational vertical. Asterisks indicate mean was significantly different from 0° at p<0.05. Error bars are 95% confidence intervals. B. Mean variance for all three modalities, with and without neck vibration. Error bars are 95% confidence intervals. MLE-predicted values are outlined in bold. C. Observed bimodal PSEs versus MLE predicted bimodal PSEs for each participant, for experiment 4 (open circles) and experiment 5 (filled circles). Solid line indicates a slope of 1. D. Observed variances of the bimodal measure versus predicted variances, for experiment 4 (open circles) and experiment 5 (filled circles). Solid line indicates a slope of 1.
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pone.0145528.g003: Results for experiments 4 and 5.A. Mean PSEs for SVV (with a blurry visual stimulus), SHV and bimodal measures for experiment 4 (dark grey bars), and experiment 5 (with neck vibration, light grey bars). PSEs predicted by the maximum likelihood estimate (MLE) model for each experiment are bolded. 0° corresponds to gravitational vertical. Asterisks indicate mean was significantly different from 0° at p<0.05. Error bars are 95% confidence intervals. B. Mean variance for all three modalities, with and without neck vibration. Error bars are 95% confidence intervals. MLE-predicted values are outlined in bold. C. Observed bimodal PSEs versus MLE predicted bimodal PSEs for each participant, for experiment 4 (open circles) and experiment 5 (filled circles). Solid line indicates a slope of 1. D. Observed variances of the bimodal measure versus predicted variances, for experiment 4 (open circles) and experiment 5 (filled circles). Solid line indicates a slope of 1.

Mentions: The mean PSEs for SHV, SVV, and the bimodal condition are plotted with 95% confidence intervals in light grey in Fig 3A. All experiments were done with the body tilted 45° to the left. A repeated-measures ANOVA comparing PSE across the three conditions found no main effect of condition (p = 0.64). There was no correlation between SVV and SHV PSEs (p = 0.88). Blurring the visual stimulus resulted in a bias away from the body in the unimodal SVV condition, t(15) = 2.66, p = 0.018, in contrast to the SVV results from experiments 1 and 2. The bimodal PSE was also significantly biased opposite to body tilt, t(15) = 3.02, p = 0.009. SHV PSEs did not statistically differ from 0°.


The Subjective Visual Vertical and the Subjective Haptic Vertical Access Different Gravity Estimates.

Fraser LE, Makooie B, Harris LR - PLoS ONE (2015)

Results for experiments 4 and 5.A. Mean PSEs for SVV (with a blurry visual stimulus), SHV and bimodal measures for experiment 4 (dark grey bars), and experiment 5 (with neck vibration, light grey bars). PSEs predicted by the maximum likelihood estimate (MLE) model for each experiment are bolded. 0° corresponds to gravitational vertical. Asterisks indicate mean was significantly different from 0° at p<0.05. Error bars are 95% confidence intervals. B. Mean variance for all three modalities, with and without neck vibration. Error bars are 95% confidence intervals. MLE-predicted values are outlined in bold. C. Observed bimodal PSEs versus MLE predicted bimodal PSEs for each participant, for experiment 4 (open circles) and experiment 5 (filled circles). Solid line indicates a slope of 1. D. Observed variances of the bimodal measure versus predicted variances, for experiment 4 (open circles) and experiment 5 (filled circles). Solid line indicates a slope of 1.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4696803&req=5

pone.0145528.g003: Results for experiments 4 and 5.A. Mean PSEs for SVV (with a blurry visual stimulus), SHV and bimodal measures for experiment 4 (dark grey bars), and experiment 5 (with neck vibration, light grey bars). PSEs predicted by the maximum likelihood estimate (MLE) model for each experiment are bolded. 0° corresponds to gravitational vertical. Asterisks indicate mean was significantly different from 0° at p<0.05. Error bars are 95% confidence intervals. B. Mean variance for all three modalities, with and without neck vibration. Error bars are 95% confidence intervals. MLE-predicted values are outlined in bold. C. Observed bimodal PSEs versus MLE predicted bimodal PSEs for each participant, for experiment 4 (open circles) and experiment 5 (filled circles). Solid line indicates a slope of 1. D. Observed variances of the bimodal measure versus predicted variances, for experiment 4 (open circles) and experiment 5 (filled circles). Solid line indicates a slope of 1.
Mentions: The mean PSEs for SHV, SVV, and the bimodal condition are plotted with 95% confidence intervals in light grey in Fig 3A. All experiments were done with the body tilted 45° to the left. A repeated-measures ANOVA comparing PSE across the three conditions found no main effect of condition (p = 0.64). There was no correlation between SVV and SHV PSEs (p = 0.88). Blurring the visual stimulus resulted in a bias away from the body in the unimodal SVV condition, t(15) = 2.66, p = 0.018, in contrast to the SVV results from experiments 1 and 2. The bimodal PSE was also significantly biased opposite to body tilt, t(15) = 3.02, p = 0.009. SHV PSEs did not statistically differ from 0°.

Bottom Line: Experiment 1 compared SVV and SHV across three levels of whole-body tilt and found that SVV showed an A-effect at larger tilts while SHV was accurate.Experiment 2 found that tilting either the head or the trunk independently produced an A-effect in SVV while SHV remained accurate when the head was tilted on an upright body but showed an A-effect when the body was tilted below an upright head.Overall our results suggest that SVV and SHV access distinct underlying gravity percepts based primarily on head and body position information respectively, consistent with a model proposed by Clemens and colleagues.

View Article: PubMed Central - PubMed

Affiliation: Center for Vision Research, York University, Toronto, Ontario, Canada.

ABSTRACT
The subjective visual vertical (SVV) and the subjective haptic vertical (SHV) both claim to probe the underlying perception of gravity. However, when the body is roll tilted these two measures evoke different patterns of errors with SVV generally becoming biased towards the body (A-effect, named for its discoverer, Hermann Rudolph Aubert) and SHV remaining accurate or becoming biased away from the body (E-effect, short for Entgegengesetzt-effect, meaning "opposite", i.e., opposite to the A-effect). We compared the two methods in a series of five experiments and provide evidence that the two measures access two different but related estimates of gravitational vertical. Experiment 1 compared SVV and SHV across three levels of whole-body tilt and found that SVV showed an A-effect at larger tilts while SHV was accurate. Experiment 2 found that tilting either the head or the trunk independently produced an A-effect in SVV while SHV remained accurate when the head was tilted on an upright body but showed an A-effect when the body was tilted below an upright head. Experiment 3 repeated these head/body configurations in the presence of vestibular noise induced by using disruptive galvanic vestibular stimulation (dGVS). dGVS abolished both SVV and SHV A-effects while evoking a massive E-effect in the SHV head tilt condition. Experiments 4 and 5 show that SVV and SHV do not combine in an optimally statistical fashion, but when vibration is applied to the dorsal neck muscles, integration becomes optimal. Overall our results suggest that SVV and SHV access distinct underlying gravity percepts based primarily on head and body position information respectively, consistent with a model proposed by Clemens and colleagues.

Show MeSH
Related in: MedlinePlus