Distinguishing the neural correlates of perceptual awareness and post-perceptual processing

Abstract

To identify the neural correlates of perceptual awareness, researchers often compare the differences in neural activation between conditions in which an observer is or is not aware of a target stimulus. While intuitive, this approach often contains a critical limitation: In order to link brain activity with perceptual awareness, observers traditionally report the contents of their perceptual experience. However, relying on observers' reports is problematic because it makes it difficult to know if the neural responses being measured are associated with conscious perception per se or with post-perceptual processes involved in the reporting task (i.e., working memory, decision-making, etc.). To address this issue, we combined a standard visual masking paradigm with a recently developed "no-report" paradigm. In the visual masking paradigm, observers saw images of animals and objects that were visible or invisible depending on their proximity to masks. Meanwhile, on half of the trials, observers reported the contents of their perceptual experience (i.e., report condition), while on the other half of trials they refrained from reporting about their experiences (i.e., no-report condition). We used electroencephalography (EEG) to examine how visibility interacts with reporting by measuring the P3b event related potential (ERP), one of the proposed canonical "signatures" of conscious processing. Overall, we found a robust P3b in the report condition, but no P3b whatsoever in the no-report condition. This finding suggests that the P3b itself is not a neural signature of conscious processing and highlights the importance of carefully distinguishing the neural correlates of perceptual awareness from postperceptual processing. Significance statementWhat are the neural signatures that differentiate conscious and unconscious processing in the brain? Perhaps the most well-established candidate signature is the P3b event-related potential (ERP), a late slow wave that appears when observers are aware of a stimulus, but disappears when a stimulus fails to reach awareness. Here, however, we found that the P3b does not track what observers are perceiving but instead tracks what observers are reporting. When observers are aware of simple visual stimuli, the P3b is nowhere to be found unless observers are reporting the contents of their experience. These results challenge the well-established notion of the P3b as a neural marker of awareness and highlight the need for new approaches to the neuroscience of consciousness. Figure 4. Results from cluster-based permutations analysis for both (a) the report and (b) the no-report condition. Each individual electrode is plotted as a row on the y-axis, while time (ms) is plotted on the x-axis. Only significant t-values are plotted in the figure.

Auditory Event-Related “Global Effect” Predicts Recovery of Overt Consciousness

“…This discussion is clearly beyond the scope of the present report, but the strong relation we discovered between the presence of a GE and the ability to report subjectively global deviance advocates for this second hypothesis (19). Moreover, scalp topography of the ERP GE corresponds to a P3b component (17), and a current scientific debate questions the meaning of P3b: is it a direct neural signature of conscious access, or rather a post-perceptual correlate of cognitive events that are posterior in time to conscious access (29)(30)(31)(32)(33)(34)(35)(36)(37)(38)? Interestingly, the single consensual point of this debate consists of considering that P3b presence does require conscious processing (even if it is not the neural signature of conscious access).…”

When effort matters: Expectations of reward and efficacy guide cognitive control allocation

“…With that said, we note that P3b amplitude was also associated with variability in performance, though to a somewhat lesser degree. It is therefore possible that control allocation was already being determined at this early stage of the trial but, in conjunction with past findings 67 , it is equally or perhaps more likely that the P3b indexed the initial evaluation of the motivational relevance of cued incentives, as we originally hypothesized. Consistent with our original interpretation, we found that the amplitude of the P3b (but not CNV) decreased over the course of the session, potentially reflecting decreased attentiveness to the cues.…”

The predictive global neuronal workspace: A formal active inference model of visual consciousness

“…Using a novel inattentional blindness paradigm, they showed that the P3, which was initially thought to discriminate information that did or did not enter the global workspace (see Dehaene, 2014, p.180), was driven by task relevance and not conscious access. This result was recently replicated in a standard masking paradigm (Cohen, et al, 2020) showing unequivocally that the P3 is related to task relevance and is not a necessary signature of conscious access.…”