Fig. 4.

PDA extracted principal components of amplitude differences (as exemplified by fig. 3) for all participants. A–D and F clearly resemble single current dipole fields, E is less distinct. Computation was based on the participants’ 3 to 4 most successful training runs (54 to 72 trials). Dots indicate sensors, lines are isocontours of normalized field strength (actual field strength is indicated in fig. 7). Markers indicate which sensors enter into cursor feedback, and the signs of their respective weights in spatial filtering. (All topographies are viewed from the top.)