Vestibular and Visual Responses in Human Posterior Insular 13 Cortex

36 The central hub of the cortical vestibular network in humans is likely localized in the region 37 of posterior lateral sulcus. An area characterized by responsiveness to visual motion has 38 previously been described at a similar location and named posterior insular cortex (PIC). 39 Currently it is not known whether PIC processes vestibular information as well. We localized 40 PIC using visual motion stimulation in functional magnetic resonance imaging (fMRI) and 41 investigated whether PIC also responds to vestibular stimuli. To this end, we designed an 42 MRI-compatible caloric stimulation device that allowed us to stimulate bi-thermally with hot 43 temperature in one ear and simultaneously cold temperature in the other or with warm 44 temperatures in both ears for baseline. During each trial participants indicated the presence or 45 absence of self-motion sensations. We found activation in PIC during periods of self motion 46 when vestibular stimulation was carried out with minimal visual input. In combined visual47 vestibular stimulation area PIC was activated in a similar fashion during congruent and 48 incongruent stimulation conditions. Our results show that PIC not only responds to visual 49 motion but also to vestibular stimuli related to the sensation of self motion. We suggest that 50 PIC is part of the cortical vestibular network and plays a role in the integration of visual and 51 vestibular stimuli for the perception of self motion. 52