In search of consciousness: Examining the temporal dynamics of conscious visual perception using MEG time-series data.

Visual information can be processed by the brain without reaching consciousness. Using multivariate pattern analysis and magnetoencephalography, brain activity was recorded while participants viewed stimuli at threshold contrast in a backward masking paradigm. Both conscious and non-conscious trials contained stimulus information, but the information was enhanced in conscious trials. Visual consciousness is characterized by enhanced neural activity representing the visual stimulus, an effect arising as early as 180 ms post-stimulus onset.

Study at a glance

Abstract

The mere presence of information in the brain does not always mean that this information is available to consciousness. Experiments using paradigms such as binocular rivalry, visual masking, and the attentional blink have shown that visual information can be processed and represented by the visual system without reaching consciousness. Using multivariate pattern analysis (MVPA) and magneto-encephalography (MEG), we investigated the temporal dynamics of information processing for unconscious and conscious stimuli. We decoded stimulus information from the brain recordings while manipulating visual consciousness by presenting stimuli at threshold contrast in a backward masking paradigm. Participants' consciousness was measured using both a forced-choice categorisation task and self-report. We show that brain activity during both conscious and non-conscious trials contained stimulus information and that this information was enhanced in conscious trials. Overall, our results indicate that visual consciousness is characterised by enhanced neural activity representing the visual stimulus and that this effect arises as early as 180 ms post-stimulus onset.