Abstract
The Rubin’s vase illusion evokes a bistable perception that alters between a pair of faces or a vase. In this study we looked at the oscillatory and network level effects that could differentiate between these two perceptions. Thus, tackling the issue of what leads to conscious access and, thus resulting in perceptual dominance between two competing signals. We conducted a study within the MEG, during which participants observed a brief presentation (150msec) of the Rubin’s vase illusion, and subsequently reported the dominant percept. Behavioral results indicated a stochastic trial-by-trial report of the vase or faces. Contrasts in the prestimulus period yielded significant results between the perceptual reports, whereby there was an increase in low-frequency power (12-17Hz) for the report of faces. Source analysis revealed the main locus of this effect to be in the “object-sensitive” right lateral occipital area (LO). In the evoked response a stronger late-processing (350msec-375msec) effect was observed for the face report, with source analysis indicating a locus of this effect in the right “face-sensitive” occipital face area (OFA). Using these two source effects (i.e. LO and OFA) as seeds we conducted a connectivity analysis within source space using the imaginary coherence measure. Connectivity analysis revealed a variant connectivity to right inferior frontal gyrus (IFG), whereby for the LO seed there was greater connectivity for vase vs. faces reports, conversely for the OFA seed there was greater connectivity for face vs. vase reports. This connectivity effect is an important finding within the theory of consciousness, and adds more support to a recent framework (WIN2CON) that predicts that not only is it the local effects that are sufficient for conscious access (e.g. LO and OFA) but it is the state of open connections to frontal regions (IFG) that results in the perceptual dominance.
Meeting abstract presented at VSS 2015