EEG signs of vigilance fluctuations preceding perceptual flips in multistable illusionary motion

THIS EEG study was performed to clarify the time course of brain electrical events and possible vigilance changes associated with perceptual flips dur ing multistable perception. 13 healthy subjects (28.5 +/- 3.8 years) were r ecorded with a 21-channel digital EEG during a stroboscopic alternative mot ion paradigm implying illusionary motion with ambiguous direction. Perceptu al flips were preceded by a significant decrease of EEG frequencies, and fo llowed by a significant frequency increase with a trend to overshoot. EEG s lowing is a reliable sign of vigilance decrease and can be related to thala mic deactivation. This is consistent with a recent fMRI study, which showed thalamic deactivation associated with perceptual flips. The study added im portant chronological information about-this phenomenon and allows the conc lusion that reduced vigilance facilitates perceptual discontinuities during multistable perception. NeuroReport 10:3423-3427 (C) 1999 Lippincott Willi ams & Wilkins.