Abstract
When navigating through an environment, we integrate visual and vestibular signals to estimate heading direction. To interpret the visual signals properly, the system must segregate visual signals caused by body motion from the visual signals by environmental motions. Existing studies have shown that the heading perception is biased by concurrent environmental motions. However, it remains unknown whether and how the system differentially processes visual signals before and during body motion. Here we examined whether the environmental motion before body motion modulates the heading perception. Seven subjects reported body motion direction after being passively moved on a motion platform for two seconds. The motion direction was one of ten directions: ±5°, ±15°, ±25°, ±35° or ±45° from the vertically upward. The peak velocity was 8.5°/s. A rigid translational environmental visual motion, which moved rightward or leftward, was presented through an aperture from two seconds before the onset of the body motion until the offset of the body motion. Critically, there were three different visual motion conditions. In Condition 1, visual motion velocity was ±5°/s or ±10°/s before and during body motion. In Condition 2, visual motion velocity was zero during two seconds before the onset of body motion and accelerated to ±5°/s or ±10°/s at the onset of body motion. In Condition 3, visual motion velocity was ±10°/s or ±20°/s and decelerated to ±5°/s or ±10°/s at the onset of body motion. Results show that environmental visual motion before the body motion strongly modulates heading perception, and the effect is statistically significant, F(2,54) = 35.64, p<0.0001, indicating that the system takes into account environmental motion presented before body motion while interpreting visual motion during body motion. However, results of Condition 1, where heading perception was modulated by constant environmental motion, F(2,18) = 13.08, p<0.001, directly show that the compensation is insufficient