Abstract
Given the higher chance to recognize attended compared to unattended stimuli, the specific neural correlates of these two processes, attention and awareness, tend to be intermingled in experimental designs. In this study, we dissociated the neural correlates of conscious face perception from the effects of visual attention. To do this, we presented faces at the threshold of awareness and manipulated attention through the use of exogenous prestimulus cues. We show that the N170 component, a scalp EEG marker of face perception, was modulated independently by attention and by awareness. An earlier P1 component was not modulated by either of the two effects and a later P3 component was indicative of awareness but not of attention. These claims are supported by converging evidence from (a) modulations observed in the average evoked potentials, (b) correlations between neural and behavioral data at the single-subject level, and (c) single-trial analyses. Overall, our results show a clear dissociation between the neural substrates of attention and awareness. Based on these results, we argue that conscious face perception is triggered by a boost in face-selective cortical ensembles that can be modulated by, but are still independent from, visual attention.
Highlights
When an image is flashed to an observer, retinal stimulation triggers a series of neural processes, a subset of which lead to conscious perception
We previously showed that the amplitude of a face-selective occipito-temporal EEG component, peaking ~170 ms after stimulus onset, was larger whenever subjects reported seeing a face, the stimuli eliciting the seen and unseen conditions, at the threshold of conscious perception, was exactly the same
For the P1 and N170, we selected time windows using the same procedure in Navajas et al (2013); we considered 40 ms windows centred in the peak of each component (110-150 ms for the P1, 170-210 ms for the N170)
Summary
When an image is flashed to an observer, retinal stimulation triggers a series of neural processes, a subset of which lead to conscious perception (C. Koch, 2004). When an image is flashed to an observer, retinal stimulation triggers a series of neural processes, a subset of which lead to conscious perception In order to identify these brain processes, a standard approach is to compare the brain responses elicited by “seen” and “unseen” visual stimuli. We previously showed that the amplitude of a face-selective occipito-temporal EEG component, peaking ~170 ms after stimulus onset (i.e., the N170), was larger whenever subjects reported seeing a face, the stimuli eliciting the seen and unseen conditions, at the threshold of conscious perception, was exactly the same Navajas, Ahmadi, & Quian Quiroga, 2013). With the peak amplitude of this signal it was possible to decode above chance the subjects’
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