Association between vestibular function and rotational spatial orientation perception in older adults.

BACKGROUND: Spatial orientation is a complex process involving vestibular sensory input and possibly cognitive ability. Previous research demonstrated that rotational spatial orientation was worse for individuals with profound bilateral vestibular dysfunction. OBJECTIVE: Determine whether rotational and linear vestibular function were independently associated with large amplitude rotational spatial orientation perception in healthy aging. METHODS: Tests of rotational spatial orientation accuracy and vestibular function [vestibulo-ocular reflex (VOR), ocular and cervical vestibular evoked myogenic potentials (VEMP)] were administered to 272 healthy community-dwelling adults participating in the Baltimore Longitudinal Study of Aging. Using a mixed model multiple linear regression we regressed spatial orientation errors on lateral semicircular canal function, utricular function (ocular VEMP), and saccular function (cervical VEMP) in a single model controlling for rotation size, age, and sex. RESULTS: After adjusting for age, and sex, individuals with bilaterally low VOR gain (ß= 20.9, p = 0.014) and those with bilaterally absent utricular function (ß= 9.32, p = 0.017) made significantly larger spatial orientation errors relative to individuals with normal vestibular function. CONCLUSIONS: The current results demonstrate for the first time that either bilateral lateral semicircular canal dysfunction or bilateral utricular dysfunction are associated with worse rotational spatial orientation. We also demonstrated in a healthy aging cohort that increased age also contributes to spatial orientation ability.

Saccular function is associated with both angular and distance errors on the triangle completion test.

OBJECTIVE: The present study was designed to determine whether healthy older adults with age-related vestibular loss have deficits in spatial navigation. METHODS: 154 adults participating in the Baltimore Longitudinal Study of Aging were tested for semicircular canal, saccular, and utricular function and spatial navigation ability using the blindfolded Triangle Completion Test (TCT). Multiple linear regression was used to investigate the relationships between each measure of vestibular function and performance on the TCT (angular error, end point error, and distance walked) while controlling for age and sex. RESULTS: Individuals with abnormal saccular function made larger angular errors (ß = 4.2°, p < 0.05) and larger end point errors (ß = 13.6 cm, p < 0.05). Independent of vestibular function, older age was associated with larger angular (ß's = 2.2-2.8°, p's < 0.005) and end point errors (ß's = 7.5-9.0 cm, p's < 0.005) for each decade increment in age. CONCLUSIONS: Saccular function appears to play a prominent role in accurate spatial navigation during a blindfolded navigation task. SIGNIFICANCE: We hypothesize that gravitational cues detected by the saccule may be integrated into estimation of place as well as heading direction.