Brain-Computer Interface: Comparison of two paradigms to freely navigate in a virtual environment through one mental task

A Brain-Computer Interface (BCI) is a system that enables communication and control that is not based on muscular movements, but on brain activity. Some of these systems are based on discrimination of different mental tasks; usually they match the number of mental tasks to the number of control commands. In this paper, we will present a BCI system focused on the control of a virtual wheelchair. Our aim is to test different navigation paradigms to train subjects in a safe environment, prior to using it under real conditions. Due to the danger associated to a misclassification of the user´s intention in a navigation system, the BCI system was developed using the optimum number of mental states regarding the classification accuracy, that is, only two. However, the system let the subjects choose among several navigation commands using only one active mental task (versus any other mental activity). Mapping one task into a higher number of commands was carried out with two different paradigms: i) the first one let the subjects move in a continuous way while they kept this task active, and ii) the subjects used the mental task to switch their state on /off: they stopped if they were moving (advances and turns) and vice versa. Sixteen healthy and untrained subjects, divided into two groups, participated in an experiment in which each group used one of the paradigms. Preliminary results show that both paradigms can be used to navigate through virtual environments, although with the first one the times needed to complete a path were notably lower.