# Environmental motion presented ahead of self-motion modulates heading direction estimation

## TL;DR

The study shows that visual motion seen before moving affects how people perceive their direction of movement, suggesting the brain uses past visual cues to better estimate self-motion.

## Contribution

The novel finding is that pre-movement environmental motion modulates heading perception, supported by a causal inference-based computational model.

## Key findings

- Environmental motion presented before self-motion significantly modulates perceived heading direction.
- A normative computational model explains how visual signals before and during movement are integrated for heading estimation.
- The brain uses temporal context from visual motion to resolve ambiguity in self-motion perception.

## Abstract

The ability of a moving observer to accurately perceive their heading direction is essential for effective locomotion and balance control. While previous studies have shown that observers integrate visual and vestibular signals collected during movement, it remains unclear whether and how observers use visual signals collected before their movement to perceive heading direction. Here we investigate the effect of environmental motion that occurred ahead of self-motion on the perception of self-motion. Human observers sat on a motion platform, viewed visual motion stimuli, and then reported their perceived heading after the platform moved. The results reveal that environmental motion presented before the observers’ movement significantly modulates their heading perception. We account for this effect using a normative computational model that takes into account the causal relationship between visual signals generated before and during the observers’ movement. Overall, our study highlights the crucial role of environmental motion presented before self-motion in heading perception, broadening the current perspective on the computational mechanisms behind heading estimation.

Perceiving our own movement, such as walking down the street or trying to keep our balance, requires the brain to interpret noisy and ambiguous signals from our senses. This becomes especially challenging when the environment is also in motion, because the movement we see might result from either our own movement or something in the surroundings. In this study, we asked whether the brain could use visual motion signals gathered before we start moving to help resolve this ambiguity. Using a novel experimental paradigm, we found that motion in the environment, presented just before the self-motion, can change the way we perceive the direction of our movement. To understand why this happens, we developed a computational model grounded in principles of causal inference. The model captures how an ideal observer would estimate self-motion from sensory signals collected over time, given their belief about whether motion in the environment has remained constant. Together, our results indicate that the brain does not rely only on what’s happening during movement but also incorporates visual temporal context to make optimal estimates of self-motion.