Our aim is to investigate the effects of long-term stimulation with orientation information on humans. In order to do this, we constructed a belt which enables its user to feel his orientation in space via vibrotactile stimulation.
This belt is equipped with a set of vibrators controlled by an electronic compass: the element pointing north is always slightly vibrating. That way, the person wearing the belt gets permanent input about his heading relative to the earth's magnetic field.
In a pilot study conducted in 2005 we first tested whether subjects could integrate the information provided by the belt. Although promising, the results were not entirely conclusive. Therefore we're currently running a large-scale follow-up study: twelve subjects wear this belt for a six week training period. Through a battery of experiments before and after the training period, we are able to measure physiological, behavioural, perceptual and subjective changes induced by the feelSpace belt.
This study will contribute greatly to our understanding of how humans learn to use their "built-in" sensors and actuators: eyes and ears, fingers and legs - questions which could previously only be answered by studies with infants. And whats more: through sophisticated interview techniques we also gain insight into the subjective quality of this new sensory experience.
The person who can be seen as the father of sensory substitution is the physician Dr. Paul Bach-y-Rita. In the late sixties, he built the empirical foundation of the "substitution of the senses".
Bach-y-Rita was looking for a possibility to use machines for the compensation of sensory deficits. So, for instance, the use of a camera and transduction of the picture into systematical tactile stimulation can compensate a deficit in visual perception. This idea was first realized in the year 1963 in a "Tactile to Visual Sensory Substitution" device (TVSS).
The pictures taken by the camera are transduced into tactile stimulation at the back of blind persons. The use of the tactile sense for the human-machine interface was made possible through the enormous adaptability (plasticity) of the brain.
The Quality of Experience
A theoretical basis of our work and an explanation why the sensory substitution works is provided by the perception theory of Alva Noe and Kevin O'Regan. According to their approach, the special experience, which we associate with a certain sensory modality, is not established by the activation of certain brain areas. It will, however, be defined through the systematical change in the sensation as a result of an action. In this context, a modality becomes a certain way of actively exploring the environment and it is not bound to a certain sensory apparatus.
A comprehensive presentation of the theory can be found in the article published in 2001: "A sensorimotor account of vision and visual consciousness".