Traditionally, perceptual research has been compartmentalized into distinct and isolated categories according to individual modalities (i.e., visual, auditory, haptic, proprioceptive, vestibular, etc.).  This modular approach has treated individual sensory and motor processing as involving largely independent systems.  However, recently investigators are recognizing the importance of understanding cross-modal interactions and how they relate to perception and behaviour.

Much of the multisensory research up until this point has focused upon tasks involving discrete stimulus presentations in near body space. Such cue interactions of interest have included: visual-auditory integration, visual-proprioceptive integration, or visual-haptic integration. It is important, however, to investigate multisensory integration from the perspective of large-scale self-motion through action space. Unlike traditional approaches to examining the integration of two specific cues at a particular instance in time, navigating through one’s environment requires the dynamic integration of several cues across space and over time (i.e., visual flow, lower-limb proprioception, and vestibular information).  Understanding the principles underlying multimodal integration in this context of unfolding cue dynamics is very important as it provides insight into an important category of multisensory processing.

◘ Multi-sensory integration in the estimation of distance traveled
◘ Contribution of inertial information to the perception of walking speed
◘ Perception of visual speed while walking
◘ Adaptive treadmill control
◘ Vestibular perception is slow
◘ Perceived object stability
◘ Shape from shading

Adaptive treadmill control

Treadmills allow for unlimited walking through virtual worlds. This, however, is not as simple as it may seem. In order to create an immersive virtual environment, the user should ideally not be aware of the fact that he/she is walking on a treadmill, instead of a real environment. This creates conflicting demands on treadmill speed control: on the one hand, the user should be kept on the treadmill, meaning that the treadmill should change its speed rapidly enough to match that of the user, while on the other hand the user should stay unaware of changes in treadmill speed, because they might disrupt the immersiveness of the virtual environment.

Together with researchers of the University of Rome, we developed a control algorithm that meets these two demands and performed an evaluation study to fine tune its parameters. The algorithm is based on minimization of the differences between the position of the user and the centre of the treadmill and between the walking speed of the user and the speed of the treadmill. Evaluation showed that performance of the algorithm was very satisfactory, although the full length of our treadmill (almost 6 m.) was necessary. Further studies will evaluate the contribution of the visual environment.

FUNDED BY THE EU PROJECT
◘ Cyberwalk, sixth Framework Program of the European Commission FP6-511092