September 9, 2026
Angus Leung, Yota Kawashima, Naotsugu Tsuchiya
preprint
Freud’s iceberg metaphor has long been used to describe (un)consciousness: a huge unconsciousness supports a tiny tip of consciousness. Inspired by this, research has assumed that unconscious discriminative processing persists into consciousness, employing contrastive analysis to isolate the neural correlates of consciousness (NCC). For example, in electroencephalography (EEG) studies, features...
August 16, 2026
Francesco Ellia, Naotsugu Tsuchiya
preprint
Consciousness science remains caught between a first-person approach that cannot independently corroborate its data and a third-person approach that excludes its target of explanation. We argue that this is a false dichotomy, and propose a third option, the first-person plural perspective (FPP): the position that the primary route of epistemic access to the structure of experience is the plural...
arXiv Preprint Archive
August 12, 2026
Kallum Robinson, Giulio Tononi, Naotsugu Tsuchiya et al.
The classical problem of Other Minds has dogged philosophers for millennia; asking if we have any way to truly understand the experience of another mind. We know our own intrinsic experience by acquaintance, but can only ever hope to possess an extrinsic description of another's, with the two separated by an acquaintance gap. Structural approaches aim to characterise experience in terms of a...
Mind and Matter
June 30, 2026
J. Díaz-Boils, Naotsugu Tsuchiya, CM. Signorelli
The article introduces a partial order structure to study the relations between levels and contents of conscious experience within a formal and mathematical model. Inspired by Husserl’s phenomenology, our account models structural aspects of experiences as layers that can be experienced in potentiality or in actuality, composing further experiences and imposing an order among them. From our...
F1000Research
June 25, 2026
Kyoko Kusano, Hayato Saigo, Naotsugu Tsuchiya
Abstract* Characterizing qualitative aspects of subjective experiences, qualia, remains a challenging open problem. The recent Qualia structure paradigm proposes capturing qualia through massive relations with other qualia. A concrete method for this involves measuring pairwise similarities. This approach has been successfully applied to reveal similarities and differences in qualia structures...
Entropy (Basel, Switzerland)
May 29, 2026
Zoe Lee-Youngzie, Naotsugu Tsuchiya, Michael Robinson et al.
4 citations
Recent work in the structural approach to consciousness has shown great promise as a research paradigm for the formal and empirical study of the phenomenal qualities of experience, i.e., qualia. In this paradigm, qualia are characterized by modeling the internal organization of parts within an experience, or by modeling external relations between instances of experience. A major next step for...
Trends in Cognitive Sciences
April 7, 2026
Francesco Ellia, Naotsugu Tsuchiya
Contemporary consciousness science faces an impasse: competing theoretical frameworks-structuralist versus functionalist, universal versus local, intrinsic versus extrinsic-appear to be inducing philosophical deadlocks and conceptual standstills. While these debates have generated valuable insights, they have proceeded in parallel, without a systematic framework for understanding their...
Zenodo (CERN European Organization for Nuclear Research)
March 2, 2026
Francesco Ellia, Naotsugu Tsuchiya
Recent advances in consciousness neuroscience have exposed a critical impasse: competing theoretical frameworks, structuralist vs. functionalist (Fleming & Shea 2024, 2024b; Song 2024, Ellia & Tsuchiya 2024; Kleiner 2024), universal vs. local (Albantakis et al. 2023; Kanai & Fujisawa 2024; Fleming 2024); intrinsic vs. extrinsic (Cohen and Dennett 2011; Doerig et al. 2019; Tsuchiya et al 2020;...
Philosophy and the Mind Sciences
January 31, 2026
Alexander F G Maier, Naotsugu Tsuchiya
Structural descriptions of qualitative aspects of conscious experience (qualia) offer a rigorous empirical approach to study consciousness. Mathematical structures describing qualia can be mapped to mathematical structures derived from brain activity and underlying neuronal connectivity. That is, rather than merely identifying the co-occurrence of specific neuronal activity patterns with...
2026
Naotsugu Tsuchiya
Consciousness has long been a focus of philosophical inquiry. Philosophers have employed thoughts supported by language and logic as a primary tool to examine the essence and structure of consciousness in mostly adult humans. Language elevates the abstraction of thought and has significantly contributed to the advancement of civilization. Within an individual, language plays a significant role...
Philosophy and the Mind Sciences
December 23, 2025
Tadahiro Taniguchi, Masafumi Oizumi, Noburo Saji et al.
1 citation
This perspective paper explores the bidirectional influence between language emergence and the relational structure of subjective experiences, termed qualia structure, and lays out a constructive approach to the intricate dependency between the two. We hypothesize that the emergence of languages with distributional semantics (e.g., syntactic-semantic structures) is linked to the coordination of...
bioRxiv Preprint Server
October 1, 2025
Kallum Robinson, Ariel Zeleznikow-Johnston, Jiahao Wu et al.
1 citation
preprint
What is a possible physical substrate of the qualitative aspects of consciousness (qualia)? Answering this question is a central goal of consciousness research. Due to their subjective and ineffable nature, finding a quantitative way to characterise qualia from verbal description has thus far proven elusive. To overcome the challenge of expressing subjective experience, recent structural and...
Communications Biology
September 30, 2025
Yun Zhao, Naotsugu Tsuchiya, Mario Boley et al.
Waking levels of human consciousness are known to be supported by the integrity of complex structures and processes in the brain, yet how they are exactly regulated by neurobiological mechanisms remains uncertain. Here a space-time-resolved inference-based framework is applied to estimate the neurophysiological variables of a whole-cortex model and analyze the neural mechanism correlates of...
Nature Communications
August 13, 2025
William Wong, Rubén Herzog, Kátia Cristine Andrade et al.
10 citations
Magneto/electroencephalography (M/EEG) studies of dreaming are an essential paradigm in the investigation of neurocognitive processes of human consciousness during sleep, but they are limited by the number of observations that can be collected per study. Dream research also involves substantial methodological and conceptual variability, which poses problems for the integration of results. To...
PLoS Biology
July 1, 2025
Angus Leung, Ahmed A Mahmoud, Travis Jeans et al.
3 citations
The neural mechanisms of consciousness remain elusive. Previous studies on both human and non-human animals, through manipulation of level of conscious arousal, have reported that specific time-series features correlate with level of consciousness, such as spectral power in certain frequency bands. However, such features often lack principled, theoretical justifications as to why they should be...
iScience
March 21, 2025
Genji Kawakita, Ariel Zeleznikow-Johnston, Ken Takeda et al.
Whether one person's subjective experience of the "redness" of red is equivalent to another's is a fundamental question in consciousness studies. Intersubjective comparison of the relational structures of sensory experiences, termed "qualia structures", can constrain the question. We propose an unsupervised alignment method, based on optimal transport, to find the optimal mapping between the...
Proceedings of the National Academy of Sciences of the United States of America
March 18, 2025
Yusuke Moriguchi, Ryoichi Watanabe, Chifumi Sakata et al.
13 citations
Examination of the subjective qualitative aspects of an experience, or "qualia" in short, is a fundamental and core aspect of consciousness research. How can we characterize the particular quality of redness, i.e. a red quale? Based on a recent proposal of the structural characterization of qualia, which did not rely on verbal descriptions, we developed a task that obtained pairwise similarity...
Scientific Data
March 6, 2025
Takahiro Hirao, Mitsuhiro Miyamae, Daisuke Matsuyoshi et al.
Recent neuroscientific research has advanced our understanding of consciousness, yet the connection between specific qualitative aspects of consciousness, known as "qualia," and particular brain regions or networks remains elusive. Traditional methods that rely on verbal descriptions from participants pose challenges in neuroimaging studies. To address this, our group has introduced a novel...
Neuroscience of Consciousness
2025
Francesco Ellia, Naotsugu Tsuchiya
2 citations
This commentary engages with recent work on computational functionalist theories of consciousness through a structural lens. We address three key aspects: the role of subjective experience in theory building, the hypothesis regarding local lateral connectivity in sensory areas, and the implications of "silent units" for consciousness. We argue that while their structural turn is welcome, many...
Neuroscience of Consciousness
2025
Anikó Kusztor, Nirmitee Mulay, Makiko Yamada et al.
During an acute episode of depersonalization/derealization (DP/DR), people report a complex and idiosyncratic change in their perceptual experience. Specifically, derealisation describes the experience of detachment from the external world and altered visual perception in which the surroundings look faded, foggy, or dream-like. Whilst some have argued that there may not be genuine perceptual...
Neuroscience of Consciousness
2025
Elise G Rowe, Ken Takeda, Masafumi Oizumi et al.
Top-down attentional amplification is often assumed to affect 'what' we see, that is, the contents of conscious experience. Previously, this claim has been examined by studies that manipulated attention and characterized conscious perception in binary categorical labels (e.g. seen versus unseen). However, these categorical judgments are not powerful enough to characterize the quality of...
arXiv Preprint Archive
December 13, 2024
Steven Phillips, Naotsugu Tsuchiya
Conscious (subjective) experience permeates our daily lives, yet general consensus on a theory of consciousness remains elusive. Integrated Information Theory (IIT) is a prominent approach that asserts the existence of subjective experience (0th axiom), from an intrinsic system of causally related units, and five essential properties (axioms 1-5): intrinsicality, information, integration,...
Cortex; a journal devoted to the study of the nervous system and behavior
May 1, 2024
Antonio Maffei, Filippo Gambarota, Mario Liotti et al.
Contrary to the extensive research on processing subliminal and/or unattended emotional facial expressions, only a minority of studies have investigated the neural correlates of consciousness (NCCs) of emotions conveyed by faces. In the present high-density electroencephalography (EEG) study, we first employed a staircase procedure to identify each participant's perceptual threshold of the...
Cortex; a journal devoted to the study of the nervous system and behavior
March 1, 2024
Elise G Rowe, Marta I. Garrido, Naotsugu Tsuchiya
Current theories of consciousness can be categorized to some extent by their predictions about the putative role of the prefrontal cortex (PFC) in conscious perception. One family of the theories proposes that the PFC is necessary for conscious perception. The other postulates that the PFC is not necessary and that other areas (e.g., posterior cortical areas) are more important for conscious...
Frontiers in Psychology
2024
Naotsugu Tsuchiya, Peter Bruza, Makiko Yamada et al.
8 citations
To arbitrate theories of consciousness, scientists need to understand mathematical structures of quality of consciousness, or qualia. The dominant view regards qualia as points in a dimensional space. This view implicitly assumes that qualia can be measured without any effect on them. This contrasts with intuitions and empirical findings to show that by means of internal attention qualia can...