Interaction of brain areas of visual and vestibular simultaneous activity with fMRI.

Static body equilibrium is an essential requisite for human daily life. It is known that visual and vestibular systems must work together to support equilibrium. However, the relationship between these two systems is not fully understood. In this work, we present the results of a study which identify the interaction of brain areas that are involved with concurrent visual and vestibular inputs. The visual and the vestibular systems were individually and simultaneously stimulated, using flickering checkerboard (without movement stimulus) and galvanic current, during experiments of functional magnetic resonance imaging. Twenty-four right-handed and non-symptomatic subjects participated in this study. Single visual stimulation shows positive blood-oxygen-level-dependent (BOLD) responses (PBR) in the primary and associative visual cortices. Single vestibular stimulation shows PBR in the parieto-insular vestibular cortex, inferior parietal lobe, superior temporal gyrus, precentral gyrus and lobules V and VI of the cerebellar hemisphere. Simultaneous stimulation shows PBR in the middle and inferior frontal gyri and in the precentral gyrus. Vestibular- and somatosensory-related areas show negative BOLD responses (NBR) during simultaneous stimulation. NBR areas were also observed in the calcarine gyrus, lingual gyrus, cuneus and precuneus during simultaneous and single visual stimulations. For static visual and galvanic vestibular simultaneous stimulation, the reciprocal inhibitory visual-vestibular interaction pattern is observed in our results. The experimental results revealed interactions in frontal areas during concurrent visual-vestibular stimuli, which are affected by intermodal association areas in occipital, parietal, and temporal lobes.