In the elderly, major complaints include dizziness and an increasing number of falls, possibly related to an altered processing of vestibular sensory input. In this study, we therefore investigate age-related changes induced by processing of vestibular sensory stimulation. While previous functional imaging studies of healthy aging have investigated brain function during task performance or at rest, we used galvanic vestibular stimulation during functional MRI in a task-free sensory stimulation paradigm to study the effect of healthy aging on central vestibular processing, which might only become apparent during stimulation processing. Since aging may affect signatures of brain function beyond the BOLD-signal amplitude-such as functional connectivity or temporal signal variability--we employed independent component analysis and partial least squares analysis of temporal signal variability. We tested for age-associated changes unrelated to vestibular processing, using a motor paradigm, voxel-based morphometry and diffusion tensor imaging. This allows us to control for general age-related modifications, possibly originating from vascular, atrophic or structural connectivity changes. Age-correlated decreases of functional connectivity and increases of BOLD--signal variability were associated with multisensory vestibular networks. In contrast, no age-related functional connectivity changes were detected in somatosensory networks or during the motor paradigm. The functional connectivity decrease was not due to structural changes but to a decrease in response amplitude. In synopsis, our data suggest that both the age-dependent functional connectivity decrease and the variability increase may be due to deteriorating reciprocal cortico-cortical inhibition with age and related to multimodal vestibular integration of sensory inputs.
This report describes the objectives, design, and methods of the Munich Diagnostic and Predictor Study of Dizziness, a prospective study investigating diagnostic subgroups, correlates, and predictors of dizziness that is not sufficiently explained medically but clearly related to a psychiatric disorder. All patients presenting at the Integrated Centre for Research and Treatment of Vertigo, Balance and Ocular Motor Disorders at the University Hospital Großhadern in Munich, Germany, are investigated during their first-time visit. The study consists of a baseline and two follow-up assessment points at 6 and 12 months. At the baseline assessment point, all participants complete self-rated questionnaires concerning dizziness, depression, anxiety, dissociative and traumatic experiences, somatization, body sensations and perception, cognitions, attachment, personality, quality of life and experiences with the health care system. Additionally, a structured clinical interview is conducted to assess mental disorders. Then, the neurologists complete questionnaires regarding the subjective doctor-patient relationship and to document the somatic diagnoses and results. The follow-up measurements consist of self-rated questionnaires. This study aims to improve the diagnosis and treatment of patients who suffer from dizziness related to a psychiatric disorder and who are often severely impaired in their working and daily lives.
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