Integration of visual and extra-retinal self-motion during voluntary head movements in the human brain

Our phenomenological experience of the stable world is maintained due to continuous integration of visual self-motion with extra-retinal signals. This mechanism is not only essential for locomotion and navigation but also a crucial prerequisite for virtually any successful interaction with our environment. Constraints in fMRI acquisition methods previously prevented the study of neural processing associated to integration of visual signals with those related to head-movement. Here, we developed a novel and ecologically valid fMRI paradigm that enabled us to study integration of optic flow with extra-retinal heading signals while observers performed voluntary head movements. Our results provide first evidence for the multisensory integration of head-motion in human regions MST, VIP, the cingulate visual area (CSv) and a region in pecuneus (Pc) that are known to process visual self-motion signals. In addition, we found multisensory heading integration in posterior insular cortex (PIC) that we suggest to be homolog to monkey visual posterior sylvian (VPS). In contrast, no integration was found in parieto-insular-vestibular cortex (PIVC). These results identify for the first time head-movement related integration of visual heading signals in the human brain, and identify a clear functional segregation of the human posterior insular cortex