The overall aim of this study is to elucidate the impact of a vestibular dysfunction on the cognitive and motor performance by means of an extensive test protocol, evaluating the vestibular, cognitive and motor function using single as well as dual-task paradigms.

The test protocol consists of five cognitive tasks, all assessing a different cognitive domain: executive function, working memory, processing speed, and visuospatial abilities (mental rotation and visuospatial memory). These cognitive tasks will be performed separately (in single task condition, while seated), as well as while performing different motor tasks (in dual-task condition). These motor tasks will also be performed in single task condition (without performing the cognitive tasks).

The study consists of the establishment of normative age-related data for the single as well as dual-task protocol in healthy adults, age ranging from 18 to 65 years old (objective 1). Subsequently, the test protocol will be validated in persons with bilateral vestibulopathy (objective 2). Finally, a cross-sectional study in persons with unilateral vestibular impairment will take place, and the results on the single as well as dual-task components will be compared to normative data, as well as to persons with bilateral vestibulopathy (objective 3).

For healthy controls:

Exclusion Criteria:

• Vestibular disorders or subjective dizziness complains (past or present)
• Hearing loss
• Mild Cognitive Impairment (Montreal Cognitive Assessment, MOCA)
• Visual impairment (Snellen Chart)
• Motor abnormalities (anamnestic questionnaire)

For bilateral vestibulopathy (BV):

Inclusion criteria:

• Bilaterally reduced vestibular function, as defined by the Bárány Criteria for BV(Michael Strupp 2017):
• the horizontal vestibulo-ocular reflex (VOR) gain should be <0.6 bilaterally and/or
• the sum of the maximal peak velocities of caloric response for stimulation with warm and cold water should be <6◦/s bilaterally and/or
• the horizontal angular VOR gain should be <0.1 upon sinusoidal stimulation on the rotation test

For unilateral vestibulopathy:

Inclusion criteria:

• the horizontal VOR gain should be <0.6 unilaterally and/or
• the slow component velocity of the caloric response should be below the age-dependent normative data unilaterally, established by Maes et al. (2010)

Healthy adults were used for establishing normative data of the dual-task protocol (convenience sampling).

Persons with bilateral vestibulopathy, established by vestibular assessment, were used for the validation of the study (recruited at the Ghent University Hospital, Antwerp University Hospital, and Maastricht University Medical Center).

Persons with unilateral vestibular impairment, established by vestibular assessment, were used for the cross-sectional study (recruited at the Ghent University Hospital).