The right temporo parietal junction plays a causal role in maintaining the internal representation of verticality

Perception of the visual vertical is strongly based on our ability to match visual inflow with vestibular, proprioceptive, tactile and even visceral information which contributes to maintaining an internal representation of the vertical. An important cortical region implicated in multisensory integration is the right temporo-parietal junction (rTPJ), that is also involved in higher-order forms of body- and space-related cognition. To test whether this region integrates body related multisensory information necessary for establishing the subjective visual vertical, we combined a psychophysical task (the Rod-and-Frame test) with transient inhibition of the rTPJ via continuous theta burst stimulation (cTBS). A Gabor patch visual detection task was used as a control visual task. cTBS of early visual cortex (V1-V3) was used to test whether early visual cortices played any role in verticality estimation. We show that inhibition of rTPJ activity selectively impairs the ability to evaluate the rod's verticality when no contextual visual information, such as a frame surrounding the rod, is provided. Conversely, transient inhibition of V1-V3 selectively disrupts the ability to visually detect Gabor patch orientation. This anatomo-functional dissociation supports the idea that the rTPJ plays a causal role in integrating egocentric sensory information encoded in different reference systems (i.e. vestibular, and somatic) in order to maintain an internal representation of verticality.