Abstract
As we move we generate changes in the internal and external sensory signals, and the coupling between the two types of signals calibrates our actions. The calibration is stored and can be used to update an accurate egocentric representation of space when external sensory information is absent. We recently showed that the calibration established in the real world is inoperative in novel immersive virtual environments (VR). In that experiment, subjects walked without vision to a target in a VR scene. The only external source capable of providing feedback was a beep emitted at the end of a trial, implicitly signaling target distance. Initially, paths varied with the changing scene context, indicating a reliance on the memory of non-motion-generated visual information to define an egocentric position. Over time, men's paths were less affected by scene context. We postulate that the men used the implicit auditory cue to calibrate their action system. Here we test this hypothesis by varying the distance at which a beep is emitted. Using VR, 5 men and 5 women saw a 1-s display of a scene with a ball in a doorway located 6 m away. The ball was 3° left or right of starting position, and the task was to walk to the ball. A beep, indicating end of trial, was emitted when the subject passed a certain distance. Distance of beep (4 or 8 m) was tested in blocks of 18 trials, and data were analyzed in 3 time epochs. If subjects used the auditory cue for calibration, their angular path to target should scale with beep distance. Predicted scaling of the actual 3° target angle is 4.5° for a 4m beep and 2.3° for an 8m beep. The results showed an interaction between beep distance, epoch, and gender. Only men had significant differences in path angle between the 4 and 8 m beep distances (4.8° vs 2.9°), occurring as early as the 2nd epoch. Women's angles were 5.2° vs 5.5°. Our findings demonstrate that implicit auditory cues can calibrate men's action system and scale their egocentric representation of space.