Temporal structure of stimuli in each of the three training conditions.

<p>Top: visual onset training; middle: auditory onset training; bottom: audio-visual onset training. Visual and auditory stimuli are represented as black and white curves respectively. Each stimulus condition is composed of two targets: left vs. right of fixation (visual onset condition); to left vs right ears (auditory onset condition); and visually vs. auditorily (audio-visual onset condition). Within each trial, target increment onsets (dotted curves) are delayed with respect to each other by “target onset asynchrony” (vertical shaded region) and are linearly summed with a pedestal presented throughout the trial (solid curves). As described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011283#s4" target="_blank">Methods</a>, each target/pedestal combination is amplitude modulated at 2.5 Hz throughout the trial, with a temporal phase difference of 180° applied to each.