Coherent EEG indicators of cognitive binding during ambiguous figure tasks

We tested the hypothesis that perception of an alternative image in ambiguo us figures would he manifest as high-frequency (gamma) components that beco me synchronized over multiple scalp sites as a "cognitive binding" process occurs. Far 171 combinations of data from 19 electrodes, obtained from 17 s ubjects and 10 replicate stimuli, we calculated the difference in correlati on between the response to first seeing an ambiguous figure and when the al ternative percept for that figure became consciously realized (cognitively bound). Numerous statistically significant correlation differences occurred in all frequency bands tested with ambiguous-figure stimulation, but not i n two kinds of control data (a reaction-time test to sound stimuli and a no -task, mind-wandering test). Statistically significant correlation changes were widespread, involving frontal, parietal, central, and occipital region s of both hemispheres. Correlation changes were evident at each of five fre quency bands, ranging up to 62.5 Hz. Most of the statistically significant correlation changes were not between adjacent sites but between sires relat ively distant, both ipsilateral and contralateral. Typically, these correla tion changes occurred in more than one frequency band. These results sugges t that cognitive binding is a distinct mental state that is reliably induce d by ambiguous-figure perception tasks. Coherent oscillations at multiple f requencies may re fleet the mechanism by which such binding occurs. Moreove r, different coherent frequencies may mediate different components of the t otal cognitive-binding process. (C) 2000 Academic Press.