ACTIVATION OF THE HIPPOCAMPAL-FORMATION BY VESTIBULAR STIMULATION - AFUNCTIONAL MAGNETIC-RESONANCE-IMAGING STUDY

Functional MRI (f-MRI) is a non-invasive technique developed to permit functional mapping of the brain with a better temporal and spatial re solution than that offered by PET techniques. in our study, f-MRI was performed using blood oxygenation level dependent (BOLD) contrast imag ing based on the magnetic properties of hemoglobin. This method relies on changes in the blood supply to the brain that accompany sensory st imulation or changes in cognitive state. All the images were obtained at 1.5 T on a Signa GEMS without ultrafast imaging, The vestibular sti mulation was cold irrigation of the external auditory meatus (caloric stimulation). A population of normal healthy volunteers without a hist ory of vestibular dysfunction was studied. The hippocampal formation a s well as the retrosplenial cortex and the subiculum were activated by vestibular stimulation, suggesting that this activation may be relate d to spatial disorientation and a sensation of self-rotation experienc ed by the subjects during vestibular stimulation. The other results ar e similar to those obtained using PET.