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Abstract:
Vestibular models can predict many aspects of self-motion perception. However, it is still not completely understood how linear and angular cues combine to form the overall perception of 3D motion in space. Here, we investigated the perception of heading and travelled path during a circular trajectory. According to model predictions (Merfeld et al. 1993) we expected a bias in perceived heading (i.e., facing outward the curve) and a distorted travelled path when in darkness, but close to veridical perception when visual information was also provided. Participants were moved along a circular trajectory using the MPI CyberMotion Simulator (www.cyberneum.de), either blindfolded or viewing congruent visual motion (random dot cloud). The orientation of the body midline with respect to the motion path (heading) was varied using an adaptive procedure. Participants indicated whether they were facing inward or outward the travelled curve. In a separate session aiming at collecting continuous measures (darkness only), participants continuously pointed towards a distant imaginary earth-fixed target, or towards the direction of perceived motion. They also provided drawings of the perceived travelled trajectory. Results show that heading sensitivity in darkness for curved trajectories was significantly lower than generally found for straight paths. Most of the participants showed a heading bias, but its direction was opposite to the predictions of the Merfeld-model. Perceived heading based on continuous pointing and drawings were not always consistent. These results ask for changes of the current model and show that the various components of perception are not always consistent when investigated in isolation.
