Abstract
Continuous flash suppression (CFS) is an interocular suppression paradigm used to examine the extent that visual information is processed without visual awareness. Neuroimaging evidence demonstrates that neural signals associated with categorical processing are attenuated during CFS, but with the sensitivity of multivariate pattern analysis (MVPA), signatures of categorical processing in high-level cortex can be detected during interocular suppression (Sterzer, Haynes, & Rees, 2008). By applying MVPA to EEG, there is potential to elucidate the temporal characteristics of categorical processing during interocular suppression. However, results from a previous EEG study reveal that a pattern classifier could not decode the category of object images viewed during CFS (Kaunitz et al., 2011). The present study was conducted to further investigate whether temporal characteristics of categorical processing during interocular suppression can be revealed in the EEG time series using MVPA. In a first experiment, EEG data was recorded while participants viewed flickered object images during normal viewing or during CFS. The images were flickered to implement a frequency-tagging approach in an attempt to increase the signal-to-noise ratio for detecting neural signatures of categorical processing during CFS. Similar to previous findings, the performance of a pattern classifier was attenuated when decoding the category of the images viewed during CFS compared to that achieved for normally-viewed images. In another experiment, participants viewed a visible prime image that belonged to the same or a different category as a subsequently viewed target image that was temporarily suppressed from visual awareness by CFS. The participants indicated the moment the target image broke suppression (i.e., a semantic-priming/breaking-CFS (bCFS) paradigm). Using the same frequency-tagging approach implemented in the first experiment, the results reveal the evolution of decoding performance over time with respect to the behavioral report of bCFS as a function of the categorical relationship of the prime and target images.