Although robust and accurate, these paradigms are less intuitive and comfortable for navigation compared to imagining limb movements (motor imagery, MI). However, the majority of BCI-based navigation studies adopt cue-based visual paradigms, and the evoked brain responses are encoded into navigation commands. As brain–computer interfaces (BCI)s rely on mental control, bypassing traditional neural pathways, they provide to paralyzed users an alternative way to navigate.
Navigation in virtual worlds is ubiquitous in games and other virtual reality (VR) applications and mainly relies on external controllers. Analysis of the online performance over time shows that users can reliably control the new BCI paradigm with stable performance over at least 30 minutes of continuous operation. We did not observe a strong relation between a subject’s offline and online performance. In online mode, the average classification accuracy reached 87.9☑1.4%, which resulted in an ITR of 23.8☖.75 bits/min. Offline analy- sis of the training data reveals an average classification accuracy of 96.9☑.64%, corre- sponding to an information transfer rate of 30.1☑.8 bits/min. We demonstrate the embedding of this novel SSVEP stimulation paradigm in the user interface of an online BCI for navigating a 2-dimensional computer game. It uses a single flicker stimulus that appears always in the extrafoveal field of view, yet it allows the user to control four control channels. The spatially coded SSVEP BCI we present in this article addresses this issue. However, traditional fre- quency-coded SSVEP BCIs require the user to gaze directly at the selected flicker stimulus, which is liable to cause fatigue or even photic epileptic seizures. Main advantages of these SSVEP BCIs are a simple and low-cost setup, little effort to adjust the system parameters to the user and comparatively high information transfer rates (ITR). A promising approach for brain-computer interfaces (BCIs) employs the steady-state visual evoked potential (SSVEP) for extracting control information.
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