eLife
May 28, 2025
Johannes Jacobus Fahrenfort, Philippa A Johnson, Niels A Kloosterman et al.
10 citations
Conservative response criterion placement unexpectedly inflates effect sizes in neural measures of both conscious and unconscious processing, while liberal criterion placement reduces them. Simulations and electroencephalography decoding analyses from two studies using common subjective awareness indicators confirm these confounding effects. The widely used Perceptual Awareness Scale (PAS) does not protect against criterion confounds. Follow-up simulations show that the experimental context determines whether the confounding effect is larger for conscious or unconscious neural measures. Criterion placement threatens the construct validity of neural measures of consciousness.
Cognitive neuroscience
January 1, 2021
Yair Pinto, Timo Stein
7 citations
The paper argues that the approach of setting aside the hard problem of consciousness—the question of why and how physical processes give rise to subjective experience—to focus only on measuring neural and functional correlates is not feasible. While some researchers advocate 'shut up and measure' as a pragmatic strategy, the authors contend that any data collection about consciousness necessarily involves an implicit or explicit stance on the hard problem itself. Thus, the hard problem cannot be bypassed through purely empirical methods.
eLife
June 18, 2025
Samuel Noorman, Timo Stein, Jasper Zantvoord et al.
2 citations
Perceptual inference—how the brain integrates visual features into a coherent whole—depends on recurrent processing, the back-and-forth communication between higher and lower cortical regions. Animal studies have implicated NMDA receptors in this process, but human evidence was lacking. In two double-blind, placebo-controlled experiments with healthy participants, the NMDA receptor antagonist memantine selectively improved the brain's ability to decode complex visual illusions (Kanizsa triangles) that require recurrent processing, while leaving simpler visual processing (contrast and collinearity) unaffected. This enhancement occurred only when stimuli were attended and consciously perceived. The findings suggest that blocking NMDA receptors can enhance recurrent processing for attended objects, linking animal and human research on the neural basis of conscious perception.
bioRxiv (Cold Spring Harbor Laboratory)
April 22, 2026
Sabine Gnodde, Vlada Aslanov, Jolien C. Francken et al.
Perceptual awareness is linked to early, posterior brain activity rather than later frontal processes. Using electroencephalography with a cross-decoding method that minimized report-related confounds, participants viewed gratings in backward-masking and no-report tasks. Classifiers trained on stimulus location in the no-report task were tested on masked trials sorted by subjective visibility. Decoding revealed a reliable difference between subjectively visible and invisible stimuli from 130 to 170 milliseconds, driven by posterior sensors over occipital, temporal, and parietal regions. No corresponding effects were observed over frontal sensors, suggesting frontal activity in report-based paradigms reflects post-perceptual processing rather than awareness itself.
Neuroscience of consciousness
January 1, 2025
Joaquim Streicher, Sascha Meyen, Volker H Franz et al.
A common method for studying unconscious processing compares participants' ability to consciously detect a stimulus with an indirect measure of processing, such as reaction time or brain activity. If the direct measure shows no awareness but the indirect measure shows a significant effect, researchers conclude the stimulus was processed unconsciously. However, this reasoning rests on a statistical fallacy: the sensitivities of the two measures are never directly compared. Reanalyzing 80 experimental conditions from 16 fMRI studies, only eight provided evidence for unconscious processing when sensitivities were properly compared. This suggests that the scope of unconscious processing—both its capacity and the brain areas involved—has been overestimated.
bioRxiv Preprint Server
February 22, 2024
Johannes J. Fahrenfort, Philippa A. Johnson, Niels A. Kloosterman et al.
preprint
Conservative criterion placement in subjective awareness judgments inflates neural effect sizes for both conscious and unconscious processing, while liberal placement reduces them. Simulations and two EEG studies show that the commonly used Perceptual Awareness Scale does not protect against this confound. The findings indicate that response criterion placement threatens the construct validity of neural measures of consciousness.
PLoS biology
May 1, 2021
Timo Stein, Daniel Kaiser, Johannes J Fahrenfort et al.
How unconscious processing is measured—either by asking participants what they saw (subjective) or by testing whether they can discriminate stimuli (objective)—affects conclusions about the brain's representation of unseen information. Using fMRI in 43 people viewing masked faces and houses that were either subjectively or objectively invisible, category information was found in early and higher visual cortex even for objectively invisible stimuli, though representations in anterior ventrotemporal areas were weaker. For subjectively invisible stimuli, a clear posterior-to-anterior gradient appeared, with stronger category information in ventrotemporal cortex. For objectively invisible stimuli, category information remained similar across visual areas. The measurement approach thus influences the extent of unconscious processing and the neural correlates of consciousness.