Exploring a world turned upside down: a shift to egocentric navigation.

Disorientation poses significant challenges for astronauts, scuba divers, and jet-fighter pilots, arising from mismatches among visual, vestibular, and proprioceptive cues and unstable frame of reference. To model how such disruptions affect navigation and exploration, we tested agile wild rats that were introduced into an unfamiliar square arena while suspended in an inverted posture. These upside-down rats displayed egocentric navigation, following circuitous meandering paths largely independent of corners and walls, resembling the disorientation observed in humans and rodents exploring featureless or dark environments. In contrast, control rats that were tested in an upright posture used an allocentric strategy, repeatedly returning to a home corner and predominantly traveling along the arena walls. Therefore, upside-down rats did not rely on available visual and tactile landmarks that upright rats effectively employed in structuring their spatial behavior. These findings demonstrate that distorted vestibular and gravitational input can override visual and tactile landmarks, forcing a shift from allocentric to egocentric navigation. This mechanistic insight advances our understanding of how vestibular and visual cues interact during disorientation, with direct relevance to wayfinding in altered gravity, sensory-conflicted environments and age-related balance decline.