Importantly, they have been extensively used to measure the focus of attention without overt responses 14, 15, as well as the contents of consciousness 1– 3. SSVEPs have a high signal-to-noise ratio (SNR), and as a result have been widely adopted in the basic visual, cognitive, and clinical neurosciences 12, 13. EEG measures consisted of steady-state visually evoked potentials (SSVEPs), which are periodic cortical responses that entrain to rhythmic visual stimuli. To obtain large-scale entrained neural measures of stimulus disappearance and reappearance we employed EEG in a novel multi-target multi-response PFI paradigm 11. Existing theories propose that a combination of activity in retinotopic visual cortex 6, 7, and higher-level association areas 5, 8, 9 initiate and maintain these periods of invisibility 10.
The conscious awareness of target-presence is therefore negatively correlated with attention in this paradigm. During PFI, the disappearing stimuli are perceptually replaced by the surrounding visual background, despite their continued physical presence. For example, attending to shared colours 4, or forms 5 among targets increases their reported rates of disappearance. being filled-in) increases, rather than decreases, with attention 4, 5. To break the common correlation between attention and visibility we employed a perceptual filling-in (PFI) paradigm, in which the probability of a stimulus disappearing (i.e.
We argue that it is not conscious perception that has traditionally been correlated with these neural measures, but attention, and that neural activity and conscious perception will only positively correlate when increases in attention lead to increased visibility. This, in turn, casts doubt on the direct relationship that has been observed between neural activity and conscious perception, at least when measured with current neuroimaging tools such as EEG. Here we show using electroencephalography (EEG), that the disappearance of a stimulus can positively correlate with increases in neural activity. These findings go together with an often implicit assumption that the disappearance of a stimulus, and awareness of its absence, should lead to weaker neural responses. This research has a long history in showing that becoming aware of a stimulus leads to increases in neural responses (e.g., 1– 3).
Research on the neural basis of conscious perception has almost exclusively focused on an awareness of a stimulus that is present.
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