Verticality Perception Assessed by the Haptic Vertical

Study Overview
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Brief Summary
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The investigators previously shown that a rotating optokinetic stimulus results in shifts of the subjective visual vertical in healthy human subjects. However, the origin of these shifts is still poorly understood. Both torsional displacement of the eyes and a shift in the internal estimate of direction of gravity have been proposed as potential explanations. Here the investigators use a vision-independent setup to differentiate between these two hypotheses, predicting no impact of a rotating stimulus on the subjective haptic vertical if torsion triggers the shift.

Official Title
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Verticality Perception - Modulatory Effect of a Rotating Optokinetic Stimulus on the Haptic Vertical in Healthy Human Subjects

Conditions
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Healthy

Intervention / Treatment
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* Other: changes in whole-body roll position and visual/haptic stimuli presented


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: ages 18-65 years informed consent absence of exclusion criteria Exclusion Criteria: peripheral-vestibular deficit disturbed consciousness history of sensory deficits visual field deficits other neurological or systemic disorder which can cause dementia or cognitive dysfunction intake of antidepressants, sedatives, or neuroleptics pregnancy, unless excluded by a negative pregnancy test known neck pain or status post neck trauma

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: intervention arm<br>all participants will be assigned to the same arm. Interventions applied include presenting a visual line or a rod with or without a moving (rotating) background while being in different whole-body roll positions. Participants will be asked to adjust the line or the rod along perceived direction of gravity. | Other: changes in whole-body roll position and visual/haptic stimuli presented<br>* In different whole-body roll positions subjects will be presented a luminous line or a rod in combination with a moving or stationary background. Participants will be asked to align the line or the rod along perceived direction of gravity.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Adjustment errors of aligning a rod along perceived direction of gravity while an optokinetic stimulus is presented. | This outcome parameter focuses on the adjustment errors of the subjective haptic vertical while presenting a visual bias (i.e. an optokinetic rotatory stimulus). | 60 minutes | 
| Trial-to-trial variability of aligning a rod along perceived direction of gravity while an optokinetic stimulus is presented. | This outcome parameter focuses on the trial-to-trial variability of rod alignments along perceived direction of gravity when presenting a visual bias cue (i.e. an optokinetic rotatory stimulus). | 60 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Comparison of adjustment errors between the subjective haptic vertical and the subjective visual vertical |  | 60 minutes | 
| Comparison of adjustment errors of perceived vertical using the subjective haptic vertical with and without presenting an optokinetic stimulus |  | 60 minutes | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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vestibular, spatial orientation, vision, optokinetic