Vestibular Function Predicts Prefrontal and Sensorimotor Cortical Gray Matter Volumes in a Cross-Sectional Study of Healthy, Older Adults

The vestibular system is emerging as a pre-eminent contributor to alterations in the structure and function of the central nervous system. Yet, whether age-related vestibular loss is related to volume loss in the cerebral cortical areas that receive vestibular input remains unknown. In this cross-sectional study of 117 healthy, older adults from the Baltimore Longitudinal Study of Aging, we examine the relationships between age-related vestibular functions and the gray matter volumes of the prefrontal cortex and its subregions and of the sensorimotor cortex--regions known to process vestibular information. To measure the functions of three vestibular organs, the saccule, utricle, and horizontal semi-circular canal vestibulo-ocular reflex (VOR), we performed cervical vestibular-evoked reflex (cVEMP), ocular VEMP (oVEMP), and video-head impulse tests, respectively. Log-linear multiple regression was used to investigate the relationships between average regional volume and vestibular function, adjusting for age, sex, and intracranial volume. We found that age-related changes in vestibular end-organ function differentially alter gray matter volumes in the prefrontal and sensorimotor cortices, with many findings persisting when considering left (or right) side only. Lower canal function had a degenerative effect on the volume of the prefrontal cortex concomitant with ongoing, age-related, global brain atrophy. Lower saccular function preserved the volume of the sensorimotor cortex against age-related, global brain atrophy and had no relationship with the prefrontal cortical volume. Whereas lower utricular function showed a degenerative effect on the volume of the middle frontal gyrus accompanying age-related, global brain atrophy, it showed a protective effect on the volume of the pole of the superior frontal gyrus and showed no relationship with sensorimotor cortical volume. Together, these findings suggest that vestibular function may play a role in the resilience to or acceleration of global age effects on regional brain atrophy. Moreover, these findings enhance the understanding of the role of age-related vestibular function in the structural alterations of the cerebral cortex. Key PointsO_LIAge-related vestibular function is significantly associated with gray matter volumes in the prefrontal and sensorimotor cortices in adults. C_LIO_LILower canal function showed a degenerative effect on the volume of the prefrontal cortex in addition to ongoing age-related brain atrophy. Lower saccular function had a protective effect against age-related atrophy on sensorimotor cortical volume. Lower utricular function showed a degenerative effect on the relative volume of the middle frontal gyrus and a protective effect on the relative volume of the pole of the superior frontal gyrus. Canal and utricular function were not associated with the relative volumes of the sensorimotor cortex, and saccular function was not associated with the relative volumes of the prefrontal cortex. C_LIO_LILower canal and utricular function may play an important role in the acceleration of age-related brain atrophy in the prefrontal cortex and in the middle frontal gyrus, respectively. Lower utricular function may play a role in the resilience to age-related atrophy in the pole of the superior frontal gyrus. C_LI