1 3 Exp Brain Res (2015) 233:237–252 DOI 10.1007/s00221-014-4107-6 RESEARCH ARTICLE Interaction of brain areas of visual and vestibular simultaneous activity with fMRI Hellen M. Della-Justina · Humberto R. Gamba · Katerina Lukasova · Mariana P. Nucci-da-Silva · Anderson M. Winkler · Edson Amaro Jr. Received: 2 September 2013 / Accepted: 18 September 2014 / Published online: 10 October 2014 © Springer-Verlag Berlin Heidelberg 2014 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 simulta- neous 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 interac- tions in frontal areas during concurrent visual–vestibular stimuli, which are affected by intermodal association areas in occipital, parietal, and temporal lobes. Keywords Visual system · Vestibular system · Simultaneous stimulation · Visual–vestibular interaction · fMRI Introduction Static body equilibrium is an essential requisite for daily life. It is known that equilibrium balance is controlled by three sensory systems: the vestibular system, which acts by tracking the position and the movements of the head; the visual system, which gives a spatial estimate of the position of objects relative to the body; and the proprioceptive sys- tem, which monitors the relative position of different parts of the body. The interactions among these three systems prevent the imbalance sensation. The visual and vestibu- lar systems can be individually or simultaneously studied, using unimodal or bimodal stimulations with functional magnetic resonance imaging (fMRI). A conventional static visual task consists of a flickering checkerboard (Fox and Raichle 1985; Singh et al. 2003). The vestibular stimulation is accomplished using transcutaneous bipolar sinusoidal Abstract Static body equilibrium is an essential requi- site for human daily life. It is known that visual and ves- tibular 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. Sin- gle 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 cer- ebellar hemisphere. Simultaneous stimulation shows PBR H. M. Della-Justina (*) · H. R. Gamba Graduate Program in Electrical and Computer Engineering, Federal University of Technology-Parana, Av. Sete de Setembro, 3165, Curitiba, PR 80230-901, Brazil e-mail: hellenjustina@gmail.com K. Lukasova · M. P. Nucci-da-Silva · E. Amaro Jr. Department of Radiology, University of Sao Paulo, Av. Dr. Enéas de Carvalho Aguiar, s/n, São Paulo, SP 05403-900, Brazil A. M. Winkler Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford OX3 9DU, UK A. M. Winkler Department of Psychiatry, Yale University School of Medicine, 300 George St, New Haven, CT 06511, USA