Cortex; a journal devoted to the study of the nervous system and behavior
May 1, 2024
Antonio Maffei, Filippo Gambarota, Mario Liotti et al.
Visual awareness of fear expressed on a face is associated with a frontal brain response occurring 150–300 milliseconds after seeing the face, beyond the earlier face-sensitive N170 component. Using high-density EEG and a staircase procedure to individually calibrate perceptual thresholds, the study compared brain activity when participants were aware versus unaware of the emotion on otherwise identical faces. A data-driven cluster analysis showed that awareness of fear specifically modulated a frontal event-related potential in that time window. The findings are discussed in relation to current theories of visual consciousness and proposed neural correlates of consciousness.
Nature communications
June 29, 2021
Thomas Andrillon, Angus Burns, Teigane Mackay et al.
Attentional lapses—moments when focus drifts to unrelated thoughts (mind wandering) or the stream of consciousness halts (mind blanking)—are linked to localized slow-wave brain activity resembling sleep. Healthy participants performed a task while high-density electroencephalography recorded their brain activity; random interruptions prompted them to report whether their mental state was task-focused, mind-wandering, or mind-blanking. Slow waves preceded reports of both mind wandering and mind blanking, and their location distinguished between sluggish and impulsive behaviors as well as between the two types of lapses. The findings suggest that attentional lapses share a common physiological origin: the emergence of local sleep-like activity within the awake brain.
Neuroscience of consciousness
January 1, 2020
Matthew J Davidson, Irene L Graafsma, Naotsugu Tsuchiya et al.
Perceptual filling-in (PFI) happens when a visible target disappears from conscious awareness and its location is filled in by the surrounding background. This study tracked brain activity using steady-state visually evoked potentials (SSVEPs) while participants reported when four peripheral targets disappeared or reappeared against a dynamically updating background. Background SSVEPs closely matched subjective reports and increased with more filled-in targets. Unexpectedly, as more targets filled in, the duration of disappearances grew, suggesting facilitatory interactions across visual quadrants. Distinct spatiotemporal correlates appeared: before genuine PFI, the second harmonic (40 Hz) increased before the first (20 Hz), possibly linked to attention, a pattern absent for physically removed stimuli. These findings show PFI can study multi-object perceptual suppression and reveal distinct neural correlates for endogenous versus exogenous changes in consciousness.
Entropy
December 1, 2019
G. Northoff, Naotsugu Tsuchiya, H. Saigo
A mathematical framework called category theory (CT) can formally define and study the relationship between consciousness and its neural substrates. CT uses concepts such as category, inclusion functor, expansion functor, and natural transformation, each mapped to specific features in the neural correlates of consciousness (NCC). Applying CT to integrated information theory (IIT) and the temporospatial theory of consciousness (TTC) shows that natural transformation reveals the need to go beyond NCC and raises questions that any future neuroscientific theory of consciousness must address.
bioRxiv Preprint Server
August 7, 2019
Matthew J Davidson, Irene Graafsma, Naotsugu Tsuchiya et al.
preprint
Perceptual filling-in (PFI) makes a visible target disappear from awareness while the background fills its location. In this experiment, participants viewed four peripheral targets on a background updating at 20 Hz. Brain activity tracked via steady-state visually evoked potentials (SSVEPs) showed that background signals closely matched participants' reports of target disappearances. More filled-in targets led to longer disappearances, suggesting interactions between targets in different visual quadrants. Distinct neural responses appeared at different harmonics: the second harmonic (40 Hz) increased before the first (20 Hz) prior to genuine PFI, possibly reflecting attention. No such difference occurred for physically removed stimuli. The results demonstrate PFI as a tool for studying multi-object perceptual suppression and the neural correlates of consciousness.
bioRxiv Preprint Server
May 27, 2019
William Wong, Valdas Noreika, Levente Móró et al.
preprint
A test called the Dream Catcher test was conducted for the first time in a simplified form to see if brain activity alone can reveal whether someone is dreaming. Data Team collected brain measurements (polysomnograms) during NREM sleep from 9 participants, producing 54 one-minute recordings—27 from dreamful sleep and 27 from dreamless sleep. A blinded Analysis Team tried to classify each recording as dreamful or dreamless using an unsupervised machine learning classifier based on EEG spectral power and electrode location. Over five iterations with gradually reduced blindness, the team never performed significantly better than chance. The results suggest that EEG spectral power does not carry signatures of phenomenal consciousness, and the study also failed to replicate key findings from earlier reports on dreaming consciousness.
Naotsugu Tsuchiya, Masafumi Oizumi, Makiko Yamada et al.
preprint
The mystery of consciousness—how subjective experience arises from physical and chemical brain processes—is one of modern science's greatest challenges. Approaches that define humans and animals solely by observable behavior cannot scientifically address the conscious experiences of patients with hallucinations or delusions, nor those of non-verbal patients, infants, or animals. Recently, researchers confronting consciousness directly have advanced empirical studies of the brain-consciousness relationship. This article reviews several promising frameworks for consciousness research and introduces the authors' own strategy: clarifying the structure of conscious experience, the structure of information generated by the brain, and the relationships between these structures. The mathematical tool of category theory is briefly introduced as a means to achieve this, along with future prospects.