Event-related potential correlates of illusory line motion

We recorded event-related potentials (ERPs) during an illusory line motion paradigm to determine whether involuntary crossmodal attention speeds perception. Behavioural responses indicated that participants experienced the line motion illusion. Specifically, they perceived most instantaneously presented lines and many quickly growing lines as growing away from the location of a preceding auditory cue. ERPs at electrode locations contralateral to the cued ends of instantaneously presented lines did not differ in latency from those contralateral to the uncued ends. However, there was an amplitude difference that was found most consistently in the time range of the N1. ERPs at lateral parietal-occipital electrode sites were more positive contralateral to the cued than to the uncued end of the line. This could reflect an attention-induced amplitude modulation of the visual signal, rather than earlier onset of the initial perceptual processing of that signal.