Theta activity in the RSC anchors space to the body cardinal axes

Understanding human navigation in moving conditions requires uncovering how the brain anchors directional representations to the body's orientation. Using high-density mobile electroencephalography and immersive virtual reality during whole-body rotations, we found that theta bursts reconstructed in the retrosplenial complex (RSC) encode both acceleration and alignment with the body's principal axes. Crucially, this body-axis-anchored neural signal emerged only during goal-directed rotations performed in the absence of landmarks, and its strength correlated with individual rotation performance, suggesting an adaptive mechanism that provides a stable egocentric scaffold for heading updating. These results provide evidence for a self-motion-gated, body-centered reference frame supporting directional coding, and bridge the gap between static neuroimaging findings in humans and rodent research on RSC geometry codes. Overall, our findings advance an embodied, mechanistic account of heading updating in humans, opening new avenues for investigating brain dynamics in naturalistic, movement-rich settings using non-invasive neural recordings.