Electrophysiological correlates of perceptual reversals for three different types of multistable images.

Electrophysiological recordings were made in 21 observers to investigate whether differences in signature components (P1, N1, selection negativity [SN]) would be revealed during perceptual reversals of three different multistable figures. Using a lattice of Necker cubes as a stimulus, J. Kornmeier and M. Bach (2004, 2005) reported differences in P1 amplitudes as well a broad reversal-related negativity occurring 200-400 ms poststimulus. The current study investigated whether these event-related potentials of Necker cube reversals represent general "perceptual switching" mechanisms and would, therefore, be common to other types of multistable figures. Three different types of multistable stimuli were utilized: a modified Rubin's face/vase, a modified Schröder's staircase, and a novel natural stimulus, Lemmo's cheetahs. Results revealed the broad reversal-related negativity for the face/vase and the reversible staircase but not for the cheetahs. This component is comparable to the SN in polarity, latency, and scalp topography. An effect of early visual spatial attention on figure reversals was suggested by an analysis of the occipital P1 and N1 components. The P1, N1, or both were enhanced for trials in which the observer reported perceptual reversals compared with trials in which no reversals were reported for the face/vase and reversible staircase stimuli. These results support a model of multistable perception in which changes in early spatial attention (indicated by P1 and N1 enhancement) modulate perceptual reversals (indicated by the reversal negativity or SN).