  This paper discusses the use of the scalp electric field to decode
EEG-recorded brain processes. Instead of using bipolar measurements, the scalp
electric field is described as a 3-vector field whose orthogonal components are
obtained from the data through spline differentiation. The method was tested in
the context of brainwave recognition with experiments involving brain
representation of spoken phonemes, visual images, and mental images. The
practical effect of improvements in recognition rates was assessed by
estimating effect sizes and confidence intervals, the results suggesting a good
prospect for other applications.
