Presentation speeds for a N400-based BCI

The N400 is an ERP sensitive to the semantic content of a stimulus, in relation to the active mental context of a subject. By repeatedly presenting stimuli (i.e., probe words), we can thus infer information about this context through decoding of this relatedness response. This can form the basis of a, so called, semantic Brain Computer Interface, allowing us to directly identify the concept on a users mind without spelling out the letters. The usability of such a BCI depends on how much information can be extracted from a single presentation, but also on how fast stimuli can be presented. Here we report results from a pilot study of an experimental design that aims to determine the effect of the time between such probes on the amplitude of this N400. The preliminary results show that an N400 can still be detected across subjects, even with stimuli presented at nearly twice the rate (1.7x) used in one of our previous studies.