Abstract
The event-related potential (ERP) P300 is an electroencephalographic correlate of target recognition in decision-making tasks. The P300 is used in several brain-computer interfaces (BCIs) as a non-motor signal of decisions, such as letter choice in the P300-Speller utility. Accuracy in choice specification depends on the difference in P300 amplitude evoked by target versus non-target stimuli. In this study, we describe two novel visual attention stimuli, motion-modulated and complexity-modulated, both of which enhance the difference in P300 magnitude between target and non-target stimuli for P300-based BCIs. In the motion-modulated stimulus condition, subjects were asked to focus on a subtarget randomly appearing between two positions inside the main target. In the complexity-modulated stimulus condition, the spatial frequency of a red-green checkered pattern was modulated (low vs. high). Eight healthy subjects viewed these stimuli while brain signals were recorded by electroencephalography. Under all stimulus conditions, P300 amplitudes were significantly larger in response to targets as measured at a single electrode site (Cz). The high-complexity modulated condition produced the greatest difference in P300 between target and non-target stimuli and significance was reached after only four trials. Stimulus arrays incorporating these stimulus forms may be used for the design of improved P300-based BCIs with greater choice accuracy and speed.
