Processing vestibular impulses in the central nervous system. Study using positron emission tomography

Background and objective. Functional imaging methods have opened new perspe ctives for vestibular research. Many authors have investigated the central connections of the system, but the differences between the reports leave fu rther questions open. We investigated the cerebral projection of the vestib ular system, using positron emission tomography in right-handed subjects. Patients and methods. Bilateral caloric stimulation was used in every volun teer (n = 6). This can be considered a standard method, which will make it possible to compare the results from different laboratories in the future. A detailed ma p of activated and deactivated brain regions is included. Results. Changes caused by vestibular stimulation are portrayed. The activa ted regions partially correspond with previous results in the literature. W e would like to point out the Brodmann 6 region as the cortical manifestati on of involuntary isometric tightening of muscles. We have found many, prev iously unidentified regions showing decreased regional cerebral blood flow. Conclusions. We are the first to point out the functional connection betwee n the hippocampus and the vestibular system in this report.